Sperm | EPFL Graph Search

Sperm (: sperm or sperms) is the male reproductive cell, or gamete, in anisogamous forms of sexual reproduction (forms in which there is a larger, female reproductive cell and a smaller, male one). Animals produce motile sperm with a tail known as a flagellum, which are known as spermatozoa, while some red algae and fungi produce non-motile sperm cells, known as spermatia. Flowering plants contain non-motile sperm inside pollen, while some more basal plants like ferns and some gymnosperms have motile sperm. Sperm cells form during the process known as spermatogenesis, which in amniotes (reptiles and mammals) takes place in the seminiferous tubules of the testes. This process involves the production of several successive sperm cell precursors, starting with spermatogonia, which differentiate into spermatocytes. The spermatocytes then undergo meiosis, reducing their chromosome number by half, which produces spermatids. The spermatids then mature and, in animals, construct a tail, or f

Oocyte CD9 is enriched on the microvillar membrane and required for normal microvillar shape and distribution

Surabhi Gupta, Henning Paul-Julius Stahlberg

Microvilli are found on the surface of many cell types, including the mammalian oocyte, where they are thought to act in initial contact of sperm and oocyte plasma membranes. CD9 is currently the only oocyte protein known to be required for sperm-oocyte fusion. We found CD9 is localized to the oocyte microvillar membrane using transmission electron microscopy (TEM). Scanning electron microscopy (SEM) showed that CD9 null oocytes, which are unable to fuse with sperm, have an altered length, thickness and density of their microvilli. One aspect of this change in morphology was quantified using TEM by measuring the radius of curvature at the microvillar tips. A small radius of curvature is thought to promote fusibility and the radius of curvature of microvillar tips on CD9 wild-type oocytes was found to be half that of the CD9 null oocytes. We found that oocyte CD9 co-immunoprecipitates with two Ig superfamily cis partners, EWI-2 and EWI-F, which could have a role in linking CD9 to the oocyte microvillar actin core. We also examined latrunculin B-treated oocytes, which are known to have reduced fusion ability, and found altered microvillar morphology by SEM and TEM. Our data suggest that microvilli may participate in sperm-oocyte fusion. Microvilli could act as a platform to concentrate adhesion/fusion proteins and/or provide a membrane protrusion with a low radius of curvature. They may also have a dynamic interaction with the sperm that serves to capture the sperm cell and bring it into close contact with the oocyte plasma membrane. (c) 2006 Elsevier Inc. All rights reserved.

Elsevier BV2007

Mechanisms of differential centriole inheritance in C. elegans

Lukas von Tobel

Centrosomes are the principal microtubule organizing center (MTOC) of animal cells and comprise a pair of centrioles surrounded by pericentriolar material (PCM). Centriole number must be carefully regulated to ensure bipolar spindle formation and thus faithful chromosome segregation. In the germ line of most metazoan species, centrioles are maintained during spermatogenesis, but eliminated during oogenesis. Such differential behavior ensures that the appropriate number of centrioles is present in the newly fertilized zygote. In this doctoral thesis work, I describe our investigation of centriole elimination during oogenesis in C. elegans and I characterize sas-1, a factor important for maintaining centriole integrity, especially during spermatogenesis, to ensure that two centrioles are present in the zygote. Despite being a fundamental feature of sexual reproduction in metazoans, themechanisms governing centriole elimination during oogenesis are poorly understood. We investigate this question using antibodies directed against centriolar components and serial-section electron microscopy and we establish that centrioles are eliminated during the diplotene stage of the meiotic cell cycle. Moreover, we show that centriole elimination is compromised upon depletion of the helicase CGH-1. We also find that somatic cellsmake a minor contribution to this process, and demonstrate that the germcell karyotype is important for timely centriole elimination. These findings set the stage for a mechanistic dissection of centriole elimination in ametazoan organism. How centriole integrity is ensured after organelle assembly is poorly understood, including in sperm cells, where such integrity is particularly critical. In a genetic screen in C. elegans, sas-1 was identified as a locus important for the maintenance of centrioles in the early embryo. Our analysis reveals that sperm-derived sas-1 mutant centrioles lose their integrity shortly after fertilization, and that a related defect occurs when maternal sas-1 function is absent. We establish that sas-1 encodes a C2 domain containing protein that localizes to centrioles once they are assembled. Futhermore, we demonstrate that SAS-1 can bind and stabilize microtubules when expressed in human cells. We also identify C2CD3, a protein required for proper centriole formation, as a putative mammalian SAS-1 homolog. Together, we uncover an important component required for maintaining centrioles in sperm cells to ensure that two centrioles are present after fertilization and thus guarantee the continuity of the species.

EPFL2014

SAS-1 Is a C2 Domain Protein Critical for Centriole Integrity in C. elegans

Simon Blanchoud, Pierre Gönczy, Graham Knott, Tamara Mikeladze-Dvali, Lukas von Tobel

Centrioles are microtubule-based organelles important for the formation of cilia, flagella and centrosomes. Despite progress in understanding the underlying assembly mechanisms, how centriole integrity is ensured is incompletely understood, including in sperm cells, where such integrity is particularly critical. We identified C. elegans sas-1 in a genetic screen as a locus required for bipolar spindle assembly in the early embryo. Our analysis reveals that sperm-derived sas-1 mutant centrioles lose their integrity shortly after fertilization, and that a related defect occurs when maternal sas-1 function is lacking. We establish that sas-1 encodes a C2 domain containing protein that localizes to centrioles in C. elegans, and which can bind and stabilize microtubules when expressed in human cells. Moreover, we uncover that SAS-1 is related to C2CD3, a protein required for complete centriole formation in human cells and affected in a type of oral-facial-digital (OFD) syndrome.

Public Library of Science2014

Mechanisms of differential centriole inheritance in C. elegans

Lukas von Tobel

EPFL2014