Spermatogenesis is an ongoing differentiation procedure that wake up in the seminiferous epithelium in the testis in males to produce spermatozoa (sperm) and is continual by a tissue-specific stem cabinet termed the “spermatogonial stem cell.”

From: Encyclopedia the Reproduction (Second Edition), 2018

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R. Renkawitz-Pohl, ... M.A. Schäfer, in substantial Molecular Insect Science, 2005

1.4.1 Introduction

Spermatogenesis is a highly specialized process of to move differentiation causing the development of useful spermatozoa for effective reproduction. In principle, the process of spermatogenesis is well conserved in every sexually proliferating organisms, back the size and shape that the maturation sperm differ considerably amongst different species. Many details space comparable between mammals and also Drosophila make the paris a very good model device to research fertility defects. Drosophila germ cells, prefer those of mammals, are collection aside early in embryonic advancement and move through the primordium the the hindgut into the internal of the embryo where they sign up with the somatic components of the embryonic gonads (review: Zhao and also Garbers, 2002). In ~ the finish of the 3rd larval instar and the start of pupariation, the first germ cells enter meiosis (Figure 1).

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Figure 1. Stages of spermatogenesis in testes that late 3rd instar larvae and also adult males. (a) Testis anlage that a larva mirroring the hub and stem cell region at the apex (asterisk), a cyst v spermatogonia (white arrow), and a cyst with primary spermatocytes (black arrowhead). (b) Testis of an adult male reflecting the apical pointer with hub and stem cells (asterisk), spermatogonia (white arrow), spermatocytes (arrowhead), and also elongated spermatids (black arrow). (c) The cyst shows synchronous meiotic divisions. (d) The left cyst reflects a Nebenkern stage shortly after the 2nd meiotic division. In the phase comparison optics the nucleus (n) shows up light, the Nebenkern (nk) dark. The right cyst includes young spermatids with a round nucleus (n) and an elongating flagellum (F). (e) β1-LacZ reporter gene expression in the masculine reproductive street (Wβ1K-carrying transgenic line; Buttgereit and also Renkawitz-Pohl, 1993). Within the testes (T), stem cells and also spermatogonia refer β-galactosidase. In addition, β-galactosidase expression is likewise observed in the vas deferens (V), in accessory glands (G), and in the ejaculatory duct (AD). (f) β2-LacZ reporter gene expression in the masculine reproductive tract (Michiels et al., 1989).

Spermatogenesis is a consistent process during adult life and, thus, the adult testes contain all stages from stem cell to mature sperm (Figure 1). Together in mammals, the germ cells develop in close contact with somatic cells, in this instance the cyst cells, which are of mesodermal origin. At the an extremely tip the the testis tube, the so-called hub is developed by somatic support cells (asterisk in figure 1) to which the germline stem cell (GSCs) and the cyst cabinet progenitors (somatic stem cells, SSCs) are physically connected. In close call to the hub, both stem cell species divide asymmetrically relying on the JAK-STAT signaling pathway (see ar for details). One daughter cabinet remains associated to the hub and also maintains stem cabinet characteristics. The various other daughter cell becomes disconnected from the hub and also enters the differentiation process. This germ cell, now called spermatogonium, is surrounding by two cyst cells, thus creating a cyst in i beg your pardon the germ cabinet undergoes four mitotic divisions, meiosis, and sperm morphogenesis till individualization (see figure 3 because that an overview).

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The ultrastructure and also cytology the Drosophila melanogaster spermatogenesis has actually been extensively reviewed by Fuller (1993). This complex differentiation process from round cells to the highly specialized structure that spermatozoa is regulated by a big number of genes (up to 1500) influence spermatogenesis, i beg your pardon is reflect in the huge number of male sterile mutants (reviews: Lindsley and Tokuyasu, 1980; Hackstein et al., 2000). The emphasis here is ~ above the recent advancements in understanding the molecule basis because that the dramatic alters in cabinet morphology during germ cabinet development starting with the asymmetric division of stem cells right into a stem cell and a spermatogonium as the entry suggest to germ cell differentiation. Manage of mitotic proliferation and also entry right into meiosis space discussed and also various facets of sperm morphogenesis highlighted, such as the development of the axoneme and the mitochondrial derivative, the Nebenkern. Then the prominence of cell interactions during the procedure is debated (Figure 4), and also finally transcriptional and translational control mechanisms during meiotic prophase, and also their relevance for sperm morphogenesis (Figure 3).