title: Spermatogenesis-specific features of the meiotic program in Caenorhabditis elegans.
abstract: In most sexually reproducing organisms, the fundamental process of meiosis is implemented concurrently with two differentiation programs that occur at different rates and generate distinct cell types, sperm and oocytes. However, little is known about how the meiotic program is influenced by such contrasting developmental programs. Here we present a detailed timeline of late meiotic prophase during spermatogenesis in Caenorhabditis elegans using cytological and molecular landmarks to interrelate changes in chromosome dynamics with germ cell cellularization, spindle formation, and cell cycle transitions. This analysis expands our understanding C. elegans spermatogenesis, as it identifies multiple spermatogenesis-specific features of the meiotic program and provides a framework for comparative studies. Post-pachytene chromatin of spermatocytes is distinct from that of oocytes in both composition and morphology. Strikingly, C. elegans spermatogenesis includes a previously undescribed karyosome stage, a common but poorly understood feature of meiosis in many organisms. We find that karyosome formation, in which chromosomes form a constricted mass within an intact nuclear envelope, follows desynapsis, involves a global down-regulation of transcription, and may support the sequential activation of multiple kinases that prepare spermatocytes for meiotic divisions. In spermatocytes, the presence of centrioles alters both the relative timing of meiotic spindle assembly and its ultimate structure. These microtubule differences are accompanied by differences in kinetochores, which connect microtubules to chromosomes. The sperm-specific features of meiosis revealed here illuminate how the underlying molecular machinery required for meiosis is differentially regulated in each sex.
authors.affiliation: Department of Biology, College of William and Mary, Williamsburg, Virginia, USA. dcshak@wm.edu
authors.forename: Diane C
authors.initials: DC
authors.lastname: Shakes
authors.forename: Jui-Ching
authors.initials: JC
authors.lastname: Wu
authors.forename: Penny L
authors.initials: PL
authors.lastname: Sadler
authors.forename: Kristen
authors.initials: K
authors.lastname: Laprade
authors.forename: Landon L
authors.initials: LL
authors.lastname: Moore
authors.forename: Alana
authors.initials: A
authors.lastname: Noritake
authors.forename: Diana S
authors.initials: DS
authors.lastname: Chu
mesh_terms: D000818:Animals; D017173:Caenorhabditis elegans / Q000166:cytology* / Q000235:genetics / Q000254:growth & development / Q000378:metabolism; D029742:Caenorhabditis elegans Proteins / Q000235:genetics / Q000378:metabolism; D018507:Gene Expression Regulation, Developmental; D008297:Male; D008540:Meiosis; D013091:Spermatogenesis; D013094:Spermatozoa / Q000166:cytology / Q000254:growth & development / Q000378:metabolism
chemical_list: D029742:Caenorhabditis elegans Proteins
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