Nuclear envelope breakdown was independently confirmed by labeling fixed gonads with nuclear pore antibodies (Fig

Nuclear envelope breakdown was independently confirmed by labeling fixed gonads with nuclear pore antibodies (Fig.?6I,J). to Rabbit Polyclonal to Cofilin an absence of functional sperm, as depleted animals produce arrested primary spermatocytes rather than haploid sperm. These spermatocytes arrest in prometaphase I and fail to either progress to anaphase or attempt spermatid-residual body partitioning. They make sperm-specific membranous organelles but fail to assemble their major sperm protein into fibrous bodies. NHR-23/NR1F1 appears to function independently of the known SPE-44 gene regulatory network, revealing the presence of an NHR-23/NR1F1-mediated module that regulates the spermatogenesis program. was to study events in meiosis required for gametogenesis (Zhang et al., 2015). During gametogenesis, stem cell precursors enact a developmental program producing highly specialized haploid sperm or oocytes. is usually a powerful model for studying gametogenesis as hermaphrodites produce a limited number of sperm before switching exclusively to producing oocytes, whereas males produce sperm constantly (Ellis and Schedl, 2007) (Fig.?1A,B). Extensive studies of sex determination (Barton and Kimble, 1990; Ellis and Schedl, 2007) identified the transcription factor TRA-1, a homolog of GLI and cubitus interruptus, as the key regulator of somatic sex determination and the spermatocyte/oocyte decision (Hodgkin, 1987; Schedl et al., 1989; Zarkower and Hodgkin, 1992). Within the germline, TRA-1 Docosahexaenoic Acid methyl ester promotes oogenesis and inhibits spermatogenesis by repressing expression of two germline-specific, RNA-binding proteins (FOG-1 and FOG-3) (Chen and Ellis, 2000; Jin et al., 2001). A different RNA-binding translational repressor, PUF-8, maintains sperm fate (Subramaniam and Seydoux, 2003). Open in a separate window Fig. 1. Overview of spermatogenesis. (A,B) Cartoons depicting a young adult hermaphrodite (A) and male (B), and their respective germlines. The hermaphrodite germline (A) is usually transitioning from spermatogenesis to oogenesis. The enlarged views highlight the linear arrangement of the primary spermatocytes (1), residual bodies (RBs) (2) and mature haploid spermatids (3). (C) Stylized cartoon of a surface view of the male germline highlighting its overall linear organization. Mitotic proliferation of the germline stem cells is usually maintained by two somatic distal tip cells (DTCs) that form the germ cell niche. The early events of meiotic prophase, including homolog pairing and formation of the synaptonemal complex, Docosahexaenoic Acid methyl ester occur in the transition zone. Following an extended pachytene stage, spermatocytes enter a karyosome stage before mature spermatocytes detach from the syncytial germline and divide meiotically. The first meiotic division is usually often incomplete, leaving secondary spermatocytes linked by a cytoplasmic connection. Following anaphase II, the spermatocytes morph into budding figures that split into residual bodies and haploid spermatids. (D) Details of the meiotic divisions and post-meiotic partitioning event. Once spermatocytes detach from the germline syncytium, they pass through a brief diakinesis stage before undergoing nuclear envelope breakdown and initiating meiotic divisions. During the post-meiotic partitioning event, microtubules become acentrosomal and localize to the developing residual body (Winter et al., 2017). Components retained in the spermatids include fibrous body-membranous organelles (FB-MO), mitochondria, chromatin and centrioles. Components discarded within the RB include the tubulin, actin, endoplasmic reticulum and ribosomes of the cell; mature sperm are thus both transcriptionally and translationally inactive. Following separation from the RB, FBs disassemble and release unpolymerized MSP and the MOs dock with the plasma membrane. Males store sperm in this inactive spermatid state. During spermatid activation, MOs fuse with the plasma membrane and unpolymerized MSP Docosahexaenoic Acid methyl ester localizes to the pseudopod, where it forms fibers that are required for spermatozoon motility. Beyond the initial sperm fate decision, the subsequent control of sperm differentiation remains poorly comprehended. Understanding the gene networks that regulate sperm differentiation offers an inroad into this question. Many germline expressed genes primarily rely on mRNA 3 untranslated regions (UTRs), not promoters, to ensure expression at the correct time and location during germline development (Merritt et al., 2008). In contrast, spermatocyte promoters provide spatiotemporal control of gene expression, making transcription factors direct regulators of sperm differentiation (Merritt et al., 2008). The transcription factor SPE-44 is usually widely distributed on autosomes of developing spermatocytes and directly regulates other transcription factors, e.g. spermatogenesis and to what degree they control comparable or disparate sets of genes remains unknown. Spermatogenesis is usually a complex cellular process involving a host of dynamic subcellular events coordinated by a large number of genes. Because of its linear organization, the full developmental sequence of spermatogenesis can be analyzed in individual gonads (Fig.?1C, Chu and Shakes, 2013). Undifferentiated germ cells proliferate mitotically at the distal end while mature primary spermatocytes divide meiotically at the proximal end (Fig.?1C,D). The commitment to sperm fate occurs as undifferentiated germ cells exit mitosis and initiate meiotic homolog pairing. Transcription of genes required for spermatogenesis and translation of most sperm proteins occurs within an extended pachytene zone. During the subsequent karyosome stage, global transcription ceases as chromosomes detach from the nuclear envelope and coalesce into a central mass (Shakes et al., 2009)..