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Why do sperm have centrioles and do female eggs cells even have centrioles?

Why do sperm have centrioles and do female eggs cells even have centrioles?


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I was just wondering why it is that sperm have centrioles underneath the acrosome, but that also prompted a thought as to whether eggs have them too?


Oocytes do not have centrioles. During fertilization, the centrioles of the sperm become the centrioles of the zygote. Only one pair is needed, as there is only one cell (i.e. zygote) right after fertilization.


During fertilization the centrosme inter the ooplasm with the sperm nucleus, if the oocyte still keep its centrosme there will result 2 centrosme in zygote with 4 centriole. Each one will migrate to pole of cell and produce 4 poles not two and the 4 daughter cells of one division will have one centriole in this case through mitosis will shut off.


Beyond genes: Are centrioles carriers of biological information?

An electron micrograph of a centriole. Credit: Pierre Gönczy/EPFL

Centrioles are barrel-shaped structures inside cells, made up of multiple proteins. They are currently the focus of much research, since mutations in the proteins that make them up can cause a broad range of diseases, including developmental abnormalities, respiratory conditions, male sterility and cancer. Publishing in Cell Research, EPFL scientists show that the original centrioles of a fertilized egg, which only come from the father, persist across tens of cell divisions in the developing embryo. The surprising finding raises the possibility that centrioles may actually be carriers of information, with profound implications for biology and disease treatment.

Perhaps best known for their role in cell division, centrioles ensure that chromosomes are properly passed on to the new daughter cells. However, they are also found in cilia, the long eyelash-like structures that allow many cells in the body to signal to their neighbors and other cells to exhibit motility, e.g. in cells that line the respiratory tracts. During reproduction, both parents equally contribute genetic material, while the female egg donates most of the cell organelles, such as mitochondria. However, the centrioles of the newly fertilized embryo come exclusively from the male's sperm, bringing with them any malfunctions to the first embryo cells.

Passing information across generations

The lab of Pierre Gönczy at EPFL's Swiss Institute for Experimental Cancer Research has found that centrioles can carry such information beyond the first cells to many of a developing embryo to several cell generations. The study focused on the worm C. elegans, which is commonly used as a model organism for embryonic development and human genetic diseases. As in other species, including humans, centrioles in C. elegans are only contributed by sperm cells. Gönczy's team wanted to know how far do these "original" centrioles last across the cell divisions that turn a fertilized egg into a fully formed embryo.

In order to track the fate of the centrioles, the scientists used genetically modified versions of C. elegans, in which they could tag three different centriole proteins with a fluorescent signal. Tagged male worms were mated to untagged females, so that the scientists could specifically track centriole components that were contributed from the father during the course of embryogenesis.

Gönczy's team imaged the fluorescent signals at different cell divisions of the developing embryos, and discovered that paternally contributed centriole proteins can actually persist up to ten cell generations. The data show for the first time that centrioles are remarkably persistent in the developing embryo.

Even more intriguing are the implications the study has for biology at large, as it raises the possibility that centrioles, persisting across several cell cycles, could effectively be a non-genetic information carrier. If this were confirmed, it could represent a paradigm shift in the way we think and understand the biology of an organelle that has been present across eukaryotic evolution.

Nonetheless, this does not detract from the value this study holds for medicine. Considering the number of diseases associated with centrioles, this could open the way for innovative treatment approaches. In particular, the study demonstrates how malfunctioning centrioles can pass directly from the father and well into the life of the embryo. This can have serious implications for the way we understand centriole diseases.

"Centrioles have always been seen as something that just jump-starts the development of the embryo," says Pierre Gönczy. "Here we show that centrioles could be the means of a unidirectional inheritance of information, with considerable impact in early development." His team will next investigate if the exceptional persistence of centrioles extends to other systems, including human cells.


Sperm matters

There&rsquos no delicate way to put this: Things can go wrong with the family jewels. Experts estimate that up to 50 percent of couples&rsquo infertility cases stem from the men. But the problem, say the experts, is that the reasons for male infertility are largely unknown.

Although some genetic and lifestyle factors have been shown to affect sperm cells, &ldquowe have a very poor understanding of the basic mechanisms that regulate sperm production by the testes, the maturation and transit of the sperm through the male and female genital tracts, and events required for fertilization and early embryonic development,&rdquo says Dolores Lamb at the Baylor College of Medicine, the immediate past president of the American Society for Reproductive Medicine. &ldquoBecause we don&rsquot understand these molecular processes, we can&rsquot diagnose&rdquo the causes of male infertility.

One would think that not understanding male infertility would drum up support for more research. After all, the future of the human race depends on it. But researchers say that is not the case. Male infertility research is largely in the hands of a small cohort of academic investigators backed by programs such as those at the U.S.&rsquos Eunice Kennedy Shriver National Institute of Child Health and Human Development and REPROTRAIN, a program funded by the European Commission to prepare researchers to study male reproductive biology. In recent years, the pharmaceutical players in contraceptive and fertility treatments, such as Schering Plough, Organon and Wyeth, have withdrawn from reproductive biology research and development.

Experts say that much of the pharmaceutical industry&rsquos lack of interest stems from the fact that in the past two decades assisted-reproduction clinics have been using a method that bypasses the need for functional sperm. Called intracytoplasmic sperm injection, or ICSI (pronounced ick-see), it now constitutes 68 percent of all assisted reproductive cycles done worldwide, according to ASRM. Because ICSI is effective in overcoming most forms of male infertility, Sheena Lewis at Queen&rsquos University Belfast says, &ldquoThere has been no impetus over the last 20 years to do any research on the basic molecular structures and functions of spermatozoa.&rdquo

Single-cell life

Because it is the only cell in the human body designed to leave the confines of the body, sperm genes echo those of unicellular life forms. An example is the sperm adenylate cyclase that produces cAMP. The sperm adenylate cyclase gene in homology studies bears the most resemblance to the adenylate cyclase found in cyanobacteria. &ldquoOne way to think about the human genome is that it contains the memory of unicellular life. When the gametes are made, that genetic memory becomes expressed, and genes that are actually most similar to genes found in other unicellular organisms begin to be expressed in the testes,&rdquo says John Herr at the University of Virginia. &ldquoWe call this the ancestral gene program that is activated&rdquo during sperm production. (Herr has developed two commercial home tests for male infertility, Sperm Check Fertility and Sperm Check Vasectomy, using biomarkers that are unique to the final stage of sperm development in the testes.)

Electron micrograph of a human sperm head at 30,000×. The (*) is a vacuole in the middle of the nucleus, which is an abnormality and may be related to DNA fragmentation. The (**) are vesicles formed from a premature acrosome reaction. Image courtesy of Charles H. Muller at the University of Washington.

Sperm cells up close

So what do we know about sperm cells? There are certainly a lot of them. A fertile male usually churns out between 5 million to 250 million sperm cells per milliliter of ejaculate (the average human ejaculate is between 0.75 mL and 2.5 mL). Out of the millions, fewer than a hundred sperm cells actually arrive at the oocyte. And out of those, only one can fertilize the oocyte. It&rsquos the sperm version of the TV show &ldquoSurvivor.&rdquo

Human sperm are produced in several steps. Testicular stem cells undergo mitotic and then meiotic cell division over the course of about 70 days. The result is spermatids, which then proceed onto terminal differentiation. These round haploid cells undergo a series of dramatic morphological changes into the long, polarized sperm cells known also as spermatozoa.

In an ideal human sperm, there is a smooth, oval-shaped 5-micrometer head free of indentations, bulges or tapers. In it sits a sacklike organelle, called the acrosome, with various lytic enzymes that help to break down the glycoprotein shell around the oocyte. The paternal genetic material of 23 chromosomes is crammed in the nucleus next to the acrosome. About 90 percent of the genetic material is condensed by small, arginine-rich proteins called protamines the remaining 10 percent is wrapped around histones. Next to the head is the midpiece, which houses mitochondria. And then there&rsquos the tail, which propels the sperm to the egg. The work of the tail is done by a complex microtubule structure known as the flagellum or axoneme. At the axoneme&rsquos base are the centrioles. A structure called the fibrous sheath is wrapped around the axoneme.

Sperm cells are carried out of the man in the semen, which is produced in the seminal vesicles, prostate gland and urethral glands. Once the sperm are inside the female genital tract, they undergo a subsequent maturation process called capacitation that gears them up for fertilization. (See sidebar.)

Molecular mysteries

From biochemical and molecular biology standpoints, sperm cells are puzzling. As spermatids go on to become spermatozoa, &ldquothey shed a lot of cytoplasm and the normal molecular biology machinery,&rdquo says Joseph Tash at the Kansas University Medical Center. This is in stark contrast with what happens to somatic cells, which are filled with the cytoplasm, a fluid that provides signaling molecules a medium through which to move. Indeed, several experts refer to the sperm interior as being a solid state. Charles Muller, director of the Male Fertility Laboratory at the University of Washington, explains, &ldquoIn sperm, the membranes of one organelle are pretty much placed up against the membranes of another.&rdquo

The sperm cell uses second messengers, such as cyclic AMP and GMP, which are soluble messengers in the somatic-cell book. &ldquoDo those second messengers function in the same way as a soluble second messenger in a sperm cell that has virtually no cytoplasm? Or do they function as second messengers more in a solid-state environment? Those are really interesting questions to ask,&rdquo says Gregory S. Kopf, also at KUMC and the former director of the preclinical male contraceptive research and development program at Wyeth, which is now part of Pfizer.

That conventional signaling molecules may work differently in sperm cells is indicated during capacitation, when some proteins undergo tyrosine phosphorylation. If these tyrosine phosphorylation events do not occur, a sperm cell cannot complete capacitation and fertilize an egg. &ldquoThe conundrum is that cAMP is important for these changes, but cAMP in every other cell type does not directly trigger tyrosine phosphorylation. cAMP triggers threonine and serine amino acid residues to be phosphorylated,&rdquo says Tash. &ldquoThe question of how cAMP triggers tyrosine phosphorylations in sperm is still unanswered.&rdquo

The highly segmented character of the sperm cells raises other questions. How does biochemical information get from one compartment to another? &ldquoMany people have argued over the years that there&rsquos actually no clear path for cytoplasmic molecules to move from the head into the midpiece or tail. There do seem to be constrictions and boundaries there that might form a structural barrier to any interchange,&rdquo says Muller. A case in point is ATP.

To do all that swimming and fertilizing, sperm cells need a lot of energy. How exactly does a sperm cell meet its energy requirements? The mitochondria in the sperm midpiece churn out ATP by oxidative phosphorylation. &ldquoHow does that ATP get down to the dynein ATPases that are along the axoneme in the middle of the tail? That&rsquos a long distance,&rdquo says Muller.

It turns out that the ATP in the tail comes from glycolysis, a topic in which Deborah O&rsquoBrien at the University of North Carolina in Chapel Hill is an expert. &ldquoWe learn about glycolysis in college as this kind of boring, immutable metabolic pathway, right?&rdquo she says. &ldquoWell, sperm cells have modified nearly every step of that pathway.&rdquo

Several glycolytic enzymes are distinct in sperm and may illustrate how sperm cells have adapted a metabolic pathway to occur essentially in the solid state. Multiple glycolytic enzymes are pinned to the fibrous sheath so firmly that O&rsquoBrien says attempts to strip them off the sheath, even with 6 M urea, potassium thiocyanate and detergents, fail. If any of these three glycolytic genes are knocked out in mice, the males are infertile. Thus, this sperm-specific glycolytic pathway is &ldquoa pathway that&rsquos essential for sperm function,&rdquo sums up O&rsquoBrien.

Besides oxidative phosphorylation and glycolysis, which derive ATP from sugars, sperm also can get their ATP from fatty acids metabolized in mitochondrial and peroxisomal pathways. In a paper published in Molecular & Cellular Proteomics earlier this year, a team led by Rafael Oliva, REPROTRAIN&rsquos project coordinator, and Alexandra Amaral at the University of Barcelona discovered a number of peroxisomal proteins in the tails of healthy human sperm. This came as a surprise, because the conventional wisdom was that sperm didn&rsquot have peroxisomes. Some peroxisomal proteins are involved in the oxidation of very long-chain fatty acids. The implications, Amaral says, are that &ldquosperm might be able to use fatty acids as fuel, and lipidic beta oxidation may contribute to sperm motility.&rdquo

Even if the sperm make it to the oocyte, the state of the sperm DNA can greatly influence male fertility. Experts say the tightly wrapped DNA in the sperm head gives the impression that the genetic material is protected. But that&rsquos not the case. Because much of the molecular machinery is taken out of the cell toward the end of making terminally differentiated sperm, the final cells don&rsquot have the tools for repairing damaged DNA. With the mitochondria in the midpiece, the DNA sits right next to organelles that spew out reactive oxygen species that damage DNA. With the loss of transcriptional machinery during differentiation, sperm have lost the primary surveillance system for identifying ROS-induced damage. ROS aren&rsquot the only things to damage DNA. Environmental toxins, lifestyle choices such as smoking, and stresses all damage DNA.

Even with damaged DNA, sperm can fertilize eggs. The oocyte&rsquos DNA repair machinery can fix most single-strand breaks in the paternal DNA. However, researchers have observed that there are a notable number of double-strand breaks in the sperm DNA. &ldquoThere is no way those can be put back in the right places,&rdquo says Muller. &ldquoWe don&rsquot know of a mechanism of DNA repair that can handle that. There is no template.&rdquo This has implications for older men, because age has been suggested to be a factor in creating more paternal DNA damage. For older men attempting to conceive babies, the highly damaged paternal DNA could stop fertilization from happening or, even if fertilization does happen, cause problems with fetal development.

For a long while, conventional wisdom held that sperm cells didn&rsquot have any RNA because the DNA was transcriptionally silent. In recent years, work by David Miller at the University of Leeds in the U.K. and others demonstrated that there are messenger and noncoding RNAs in sperm. But their role is unclear. Miller says that there are hints that the sperm RNA is responsible for embryonic gene activation. He also speculates that the RNA acts as a compatibility signal to the egg, telling it that the invading sperm cell is not a pathogen.

Human sperm exhibiting many different, and almost all abnormal, shapes (morphologies). In the human, it is typical for as few as 4 percent of the sperm to be of normal shape, having a smooth oval head and normal midpiece and tail, and other characteristics. Original magnification 1,000×. Image courtesy of Charles H. Muller at the University of Washington.

The first demonstration of assisted reproduction was in vitro fertilization and the birth of Louise Brown in 1978. Robert Edwards, the emeritus professor at the University of Cambridge who died last month, won the Nobel Prize in 2010 for developing IVF, a process in which sperm cells and eggs are incubated in cell culture dishes for fertilization to take place.

But IVF can&rsquot tackle all fertility problems. If a man&rsquos sperm cells are few in number, have poor motility or carry morphological defects, they are not going to fertilize an oocyte even in a cell-culture dish. Until ICSI came along in the1990s, &ldquothere used to be no hope for these men,&rdquo says Muller.

The technique, which bypassed the need for culture-dish fertilization, was developed by Gianpiero Palermo, currently at the Weill Cornell Medical College, while on sabbatical in Belgium. The first ICSI baby was born in January 1992 in Belgium. Approximately 4 million have been born by IVF in the past 35 years 2 million babies have been born worldwide by ICSI in the past two decades.

For ICSI, a technician scans a semen sample under an optical microscope and picks out a single sperm cell that appears to be normal. Then the technician moves that sperm cell with micromanipulators and directly injects it into the cytoplasm of a waiting egg.

ICSI works not only with terminally differentiated sperm cells but also with immature sperm cells plucked from a man&rsquos testes. Lewis says because ICSI allows technicians to use sperm that normally wouldn&rsquot be able to fertilize oocytes on their own, it provides a way &ldquoto bypass all the laws of nature.&rdquo

Experts say the method&rsquos success has killed the pharmaceutical industry&rsquos interest in understanding the fundamental biology of sperm and developing male infertility treatments. &ldquoThey think ICSI is the great panacea,&rdquo says Miller. &ldquoThere are two arguments which factor against those of us who are working in the male reproductive field. Because of the advent of ICSI, they think that it has solved the problem of male infertility. The second thing is that even if we do discover what causes male infertility, they think there is nothing we can do about it. There is no translational benefit &hellip They would turn around and say, &lsquoThere&rsquos nothing you can do about it. Just do ICSI and be done with it.&rsquo&rdquo

But Miller and others say that those arguments are fallacious because there may be other factors that lead to infertility that ICSI can&rsquot help. ICSI is based on sperm that seem morphologically fine under a microscope. &ldquoPeople have always made the assumption that the really nice looking sperm must be the best,&rdquo says Muller. &ldquoThat&rsquos a completely unsupported assumption.&rdquo

Muller describes a couple he encountered who had visited a clinic that &ldquobelieved ICSI was the answer to everything,&rdquo he says. &ldquoThey got zero fertilization. They spent $10,000 and got nothing out of it.&rdquo

After the failed attempt, the couple went to Muller, who recounts seeing under the microscope that the man&rsquos sperm cells were devoid of acrosomes. One component in or near the acrosomes is phospholipase C&zeta, which is postulated to be an activating factor that helps the fertilized oocyte initiate the first cell division. The enzyme triggers a calcium signaling cascade, so Muller&rsquos group attempted to trigger the calcium cascade with an ionophore. &ldquoLo and behold, they got five out of six embryos developing, and the couple is currently pregnant!&rdquo Muller says.

This example and others like it point to the fact that sperm cells are not mere donors of paternal genes. Besides phospholipase C&zeta, sperm also must donate their centrioles to the fertilized egg, a discovery made by Palermo and colleagues in 1994 using ICSI. Miller&rsquos work on RNA points to the possibility that sperm cells that don&rsquot contain the right RNA molecules may be ineffective for fertilization. There is probably a host of other molecules that sperm contributes to the fertilization process that haven&rsquot yet been identified.

Supporting reproductive biology

Given the heartache of infertility and the cost of treatments, experts argue that sperm biology needs to be investigated more thoroughly. One in five couples requires reproductive assistance, and a single round of IVF can cost up to $17,000. Data from the European Human Society of Reproduction and Embryology show that IVF and other assisted-reproduction technologies have had the same success rate over the past 30 years, somewhere between 25 and 30 percent. &ldquoWe haven&rsquot really made a lot of progress,&rdquo says Lewis. &ldquoA lot of things have been done to tweak superovulation regimens and things like that. But little has been done about the sperm.&rdquo

Then there is the health aspect. Men who resort to ICSI usually don&rsquot get an actual diagnosis to understand why they are not producing healthy sperm in the first place, say Lamb and Oliva. Often, the lack of sperm can point to a more general health problem. For example, men with DNA-repair problems don&rsquot produce functional sperm, and there are associations between poor sperm counts and cancer in later life. Oliva also points out that, because the men are not diagnosed, if there are any genetic issues with their sperm, ICSI just passes those issues to the next generation.

So the current situation with male infertility is worrying, say experts who are working hard to understand the molecular and biochemical basis for sperm malfunction. &ldquoWe cannot be treating infertility the way we are treating it now, by just taking one single sperm cell and injecting into an oocyte,&rdquo says Oliva. &ldquoIt seems to solve the problem, but it&rsquos temporary. The next generation is going to have the same problems as we have now.&rdquo


2 The Egg Cell Contributes Instructional Proteins

The egg stores many gene products from the mother. These gene products are called mRNA, or messenger RNA. These mRNAs as passed on from the egg to the zygote. Within the zygote, the mRNAs are instructions for making specific proteins that tell the zygote how to divide into the many cells that make up the embryo. In mammals, which includes humans, two of these important instruction proteins are named beta-catenin or glycogen synthase kinase.


Centrioles Could Carry Disease-Unlocking Billogical Data

EPFL scientists discover that certain cell structures, the centrioles, could act as information carriers throughout cell generations. The discovery raises the possibility that transmission of biological information could involve more than just genes.

Centrioles are barrel-shaped structures inside cells, made up of multiple proteins. They are currently the focus of much research, since mutations in the proteins that make them up can cause a broad range of diseases, including developmental abnormalities, respiratory conditions, male sterility and cancer. Publishing in the Nature journal Cell Research, EPFL scientists show that the original centrioles of a fertilized egg, which only come from the father, persist across tens of cell divisions in the developing embryo. The surprising finding raises the possibility that centrioles may actually be carriers of information, with profound implications for biology and disease treatment.

Perhaps best known for their role in cell division, centrioles ensure that chromosomes are properly passed on to the new daughter cells. However, they are also found in cilia, the long eyelash-like structures that allow many cells in the body to signal to their neighbors and other cells to exhibit motility, e.g. in cells that line the respiratory tracts. During reproduction, both parents equally contribute genetic material, while the female egg donates most of the cell organelles, such as mitochondria. However, the centrioles of the newly fertilized embryo come exclusively from the male's sperm, bringing with them any malfunctions to the first embryo cells.

The lab of Pierre Gönczy at EPFL's Swiss Institute for Experimental Cancer Research has found that centrioles can carry such information beyond the first cells to many of a developing embryo to several cell generations. The study focused on the worm C. elegans, which is commonly used as a model organism for embryonic development and human genetic diseases. As in other species, including humans, centrioles in C. elegans are only contributed by sperm cells. Gönczy's team wanted to know how far do these "original" centrioles last across the cell divisions that turn a fertilized egg into a fully formed embryo.

In order to track the fate of the centrioles, the scientists used genetically modified versions of C. elegans, in which they could tag three different centriole proteins with a fluorescent signal. Tagged male worms were mated to untagged females, so that the scientists could specifically track centriole components that were contributed from the father during the course of embryogenesis.

Gönczy's team imaged the fluorescent signals at different cell divisions of the developing embryos, and discovered that paternally contributed centriole proteins can actually persist up to ten cell generations. The data show for the first time that centrioles are remarkably persistent in the developing embryo.

Even more intriguing are the implications the study has for biology at large, as it raises the possibility that centrioles, persisting across several cell cycles, could effectively be a non-genetic information carrier. If this were confirmed, it could represent a paradigm shift in the way we think and understand the biology of an organelle that has been present across eukaryotic evolution.

Nonetheless, this does not detract from the value this study holds for medicine. Considering the number of diseases associated with centrioles, this could open the way for innovative treatment approaches. In particular, the study demonstrates how malfunctioning centrioles can pass directly from the father and well into the life of the embryo. This can have serious implications for the way we understand centriole diseases.

"Centrioles have always been seen as something that just jumpstarts the development of the embryo," says Pierre Gönczy. "Here we show that centrioles could be the means of a unidirectional inheritance of information, with considerable impact in early development." His team will next investigate if the exceptional persistence of centrioles extends to other systems, including human cells.


Difference Between Spermatids and Sperm Cells

Definition

Spermatids: Spermatids are immature male gametes, formed from spermatogonia during meiosis.

Sperm Cells: Sperm cells are mature male reproductive cells that are capable of fertilizing an egg cell.

Formation

Spermatids: Spermatids are formed during meiosis of germ cells.

Sperm Cells: Sperm cells are formed from spermatids in a process known as spermiogenesis.

Found in

Spermatids: Spermatids can be found near the walls of the seminiferous tubules.

Sperm Cells: Sperm cells can be found in the middle of the seminiferous tubules.

Differentiation

Spermatids: Spermatids are undifferentiated cells.

Sperm Cells: Sperm cells are differentiated cells.

Maturity

Spermatids: Spermatids are immature forms of male gametes.

Sperm Cells: Sperm cells are mature forms of male gametes.

Structure

Spermatids: Spermatids are large cells with a rounded-shape.

Sperm Cells: Sperm cells have mostly an elongated shape with flagella.

Nucleus

Spermatids: Spermatids have a large, rounded nucleus.

Sperm Cells: Sperm cells have a small, elongated nucleus.

Arrangement of Mitochondria

Spermatids: Mitochondria are scattered throughout the spermatid.

Sperm Cells: Mitochondria are concentrated near the flagellum in sperm cells.

Golgi Apparatus

Spermatids: Spermatids have Golgi apparatus.

Sperm Cells: Sperm cells lack Golgi apparatus.

Centrioles

Spermatids: The centrioles of the spermatids occur near the nucleus.

Sperm Cells: The centrioles of sperm cells serve as the basal body of the flagellum.

Mobility

Spermatids: Spermatids are immotile as they lack flagella.

Sperm Cells: Sperm cells are motile as they have flagella.

Capacity to Fertilize

Spermatids: Spermatids are incapable of fertilizing an egg cell.

Sperm Cells: Sperm cells have the capacity to fertilize an egg cell.

Conclusion

Spermatids and sperm cells are two stages of the male gametes. Both spermatids and sperm cells are haploid. Sperm cells are the morphologically and functionally differentiated cells that are mature. They are capable of fertilizing an egg cell. Spermatids are immature forms of sperm cells formed during the meiosis. Spermatids differentiate into sperm cells during spermiogenesis. The main difference between spermatids and sperm cells is the structure and the ability to fertilize an egg.

Reference:

1. Gilbert, Scott F. “Spermatogenesis.” Developmental Biology. 6th edition., U.S. National Library of Medicine, 1 Jan. 1970, Available here.

Image Courtesy:

1. “Figure 28 01 04” By OpenStax College – Anatomy & Physiology, Connexions Web site, Jun 19, 2013. (CC BY 3.0) via Commons Wikimedia
2. “Simplified spermatozoon diagram” By Mariana Ruiz – based on “Gray’s Anatomy” 36th edit Williams and Warwick, 1980 (Public Domain) via Commons Wikimedia

About the Author: Lakna

Lakna, a graduate in Molecular Biology & Biochemistry, is a Molecular Biologist and has a broad and keen interest in the discovery of nature related things


PCL, proximal centriole-like PCM, pericentriolar material GC, giant centriole.

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Keywords: centriole, centrosome, cilium, reproduction, fertilization, zygote, microtubules, sperm

Citation: Avidor-Reiss T, Khire A, Fishman EL and Jo KH (2015) Atypical centrioles during sexual reproduction. Front. Cell Dev. Biol. 3:21. doi: 10.3389/fcell.2015.00021

Received: 24 February 2015 Accepted: 13 March 2015
Published: 01 April 2015.

Eiman Aleem, Phoenix Children's Hospital and University of Arizona College of Medicine – Phoenix, USA

Valerio Donato, New York University Langone Medical Center, USA
Junmin Pan, University of Freiburg, Germany

Copyright © 2015 Avidor-Reiss, Khire, Fishman and Jo. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) or licensor are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.


Are centrosomes ever important for cell division?

Centrosomes are important for specialized cell divisions. For example, in Drosophila, adult males with no centrosomes show highly abnormal meiotic divisions [26]. Moreover, eggs from mothers that are mutant for centriole proteins arrest very early in embryonic development after only a few abnormal mitoses, showing that centrioles are necessary for syncytial mitoses [26, 27]. Moreover, asymmetric cell divisions can also be abnormal in the absence of centrosomes (reviewed in [16]). In summary, whereas centrioles may be dispensable for cell division in some tissues of the fly, they are absolutely essential in others, perhaps due to tissue specificity constraints, such as weaker checkpoints, different cell size and/or sharing of common cytoplasm in the context of a syncytium. The same is true in other organisms, such as the Caenorhabditis elegans embryo and fission yeast, where the centrosome and its equivalent, the spindle pole body, are essential for bipolar spindle assembly and cytokinesis, respectively (reviewed in [16, 26]).


We would like to thank Alyssa Sherman, Keith Hoying, Ruben Samroo, Ahmed Hussein, Andrew Gerts, and Rebecca Wynn for their technical help. We would like to thank Gerald Schatten and Calvin Simerly for providing information that was instrumental in initiating this research. We would like to thank Medical Student Research Program (MSRP) of the University of Toledo for sponsoring the work of MA, BO, and PD on this project.

Supplementary Table 1 | Patient information. Excel file containing fertility and semen analysis information of all patients.


Contents: Difference between Human Sperm and Ovum

Comparison Chart

Basis Sperm Ovum
Definition Sperm is a male gamete produced only in men in humans. An egg is a female gamete produced only in women in human beings.
Size Sperm is small in size. The egg is large in size.
Mobility Sperms can move inside the female genital tract. Eggs are not able to move.
Morphology Morphologically, sperms are divided into the middle piece, tail, head, and neck. Eggs are not further divided into parts morphologically.
Mitochondria Mitochondria are spirally arranged in the middle piece of the sperm. In the egg, mitochondria are dispersed in the cytoplasm.
Cytoplasm Sperms have a small amount of cytoplasm because of small size. Eggs have abundant cytoplasm because of large size. The nucleoplasm of the egg is called a germinal vesicle.
Types of chromosomes Its nucleus may contain X or Y chromosome. Its nucleus contains only X chromosomes.
Centrioles Centrioles are present in sperms. Centrioles are absent in eggs.
Generated in Sperms are generated in testis . Eggs are matured and released from ovaries.
Production from One spermatogonium divides to form four sperms. One oogonium matures to form one egg.
Surrounded by Sperms are surrounded by cell membrane only. Eggs are surrounded by additional egg envelops.
Nature of production Sperm production process cyclic in nature. Eggs production and release are cyclic in nature.

What are sperms?

Sperm is taken from the Greek word “sperm” which is meant for seed. Sperm is a male gamete which is produced in the testis of males. The size of human sperm is 60-micron meter approximately. The shape of human sperm is elongated. It is morphologically divided into head, middle piece, neck, and tail. In men, millions of sperms are released in one ejaculate. Sperms are mixed with the secretions of glands to form semen which is then released via ejaculation. The human sperm is the smallest known cell in the anatomy, and that is why it contains a small amount of cytoplasm. Sperms can move in the female genital tract, and finally, one sperm fertilizes the ovum. Sperms contain two types of chromosomes in its nucleus, i.e., X and Y chromosomes. If an X containing sperm fertilizes the egg, the zygote to be formed will be a baby girl. If a Y chromosome containing sperm fertilizes the egg, the zygote to be formed will be a baby boy.

What is Ovum?

Eggs are the female gametes which are produced in the ovaries of the females. Oogonia are formed in the ovaries even before the birth of a baby girl. After puberty, one oogonium matures to form one egg in one month. Ovum or egg is matured in the middle of the menstrual cycle of the female. Thus a female is fertile only for 12 to 24 hours a month when her egg is matured, and after 24 hours, this egg is either fertilized or regressed. The human egg is a large-sized cell, and thus it has abundant cytoplasm. Egg also has additional coverings.

In the nucleus of the egg, only X chromosomes are present. That is why the egg does not have gender determining the ability of the next progeny.

Key differences

  1. Sperms are the male gametes produced in the testes while eggs are female gametes produced in the ovaries of the females.
  2. Sperms are elongated in shape, and small-sized while eggs are rounded in shape and large sized.
  3. Sperms are motile. They can move while eggs do not have the ability to move.
  4. Sperm may contain X or Y chromosome in its nucleus while an egg contains an only X chromosome.
  5. Sperm production and release is not a cyclic process while eggs production and release is a cyclic process.

Eggs and sperms both are gamete cells in human beings. Sperms are male gametes while eggs are female gametes. Although both are gametes, both have many differences in morphology, types of chromosomes, nature of production, size and other properties. It is compulsive to know the differences between sperms and eggs. In the above article, we learned the clear differences between sperms and eggs.


Beyond genes: are centrioles carriers of biological information?

EPFL scientists discover that certain cell structures, the centrioles, could act as information carriers throughout cell generations. The discovery raises the possibility that transmission of biological information could involve more than just genes.

Centrioles are barrel-shaped structures inside cells, made up of multiple proteins. They are currently the focus of much research, since mutations in the proteins that make them up can cause a broad range of diseases, including developmental abnormalities, respiratory conditions, male sterility and cancer. Publishing in the Nature journal Cell Research, EPFL scientists show that the original centrioles of a fertilized egg, which only come from the father, persist across tens of cell divisions in the developing embryo. The surprising finding raises the possibility that centrioles may actually be carriers of information, with profound implications for biology and disease treatment.

Perhaps best known for their role in cell division, centrioles ensure that chromosomes are properly passed on to the new daughter cells. However, they are also found in cilia, the long eyelash-like structures that allow many cells in the body to signal to their neighbors and other cells to exhibit motility, e.g. in cells that line the respiratory tracts. During reproduction, both parents equally contribute genetic material, while the female egg donates most of the cell organelles, such as mitochondria. However, the centrioles of the newly fertilized embryo come exclusively from the male’s sperm, bringing with them any malfunctions to the first embryo cells.

Passing information across generations

The lab of Pierre Gönczy at EPFL’s Swiss Institute for Experimental Cancer Research has found that centrioles can carry such information beyond the first cells to many of a developing embryo to several cell generations. The study focused on the worm C. elegans, which is commonly used as a model organism for embryonic development and human genetic diseases. As in other species, including humans, centrioles in C. elegans are only contributed by sperm cells. Gönczy’s team wanted to know how far do these “original” centrioles last across the cell divisions that turn a fertilized egg into a fully formed embryo.

In order to track the fate of the centrioles, the scientists used genetically modified versions of C. elegans, in which they could tag three different centriole proteins with a fluorescent signal. Tagged male worms were mated to untagged females, so that the scientists could specifically track centriole components that were contributed from the father during the course of embryogenesis.

Gönczy’s team imaged the fluorescent signals at different cell divisions of the developing embryos, and discovered that paternally contributed centriole proteins can actually persist up to ten cell generations. The data show for the first time that centrioles are remarkably persistent in the developing embryo.

Even more intriguing are the implications the study has for biology at large, as it raises the possibility that centrioles, persisting across several cell cycles, could effectively be a non-genetic information carrier. If this were confirmed, it could represent a paradigm shift in the way we think and understand the biology of an organelle that has been present across eukaryotic evolution.

Nonetheless, this does not detract from the value this study holds for medicine. Considering the number of diseases associated with centrioles, this could open the way for innovative treatment approaches. In particular, the study demonstrates how malfunctioning centrioles can pass directly from the father and well into the life of the embryo. This can have serious implications for the way we understand centriole diseases.

“Centrioles have always been seen as something that just jumpstarts the development of the embryo,” says Pierre Gönczy. “Here we show that centrioles could be the means of a unidirectional inheritance of information, with considerable impact in early development.” His team will next investigate if the exceptional persistence of centrioles extends to other systems, including human cells.

Balestra FR, von Tobel L, Gönczy P. Paternally contributed centrioles exhibit exceptional persistence in C. elegans embryos.Cell Research 24 April 2015. DOI: 10.1038/cr.2015.49


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