Spermatogenesis in fish.
Spermatogenesis is a developmental process during which a small number of diploid spermatogonial stem cells produce a large number of highly differentiated spermatozoa carrying a haploid, recombined genome. We characterise morphologically the different germ cell stages with particular attention for the spermatogonial generations, including the stem cells and their specific capacity to colonise a recipient's testis after transplantation. We propose a nomenclature for fish germ cells to improve the comparability among different teleost fish but also to higher vertebrates. Survival and development of germ cells depends on their continuous and close contact to Sertoli cells, and we review their multiple roles in the cystic mode of spermatogenesis seen in fish. We then discuss gene expression patterns associated with testis maturation. The endocrine system of vertebrates has evolved as master control system over spermatogenesis. In fish, both pituitary gonadotropins LH and FSH stimulate gonadal sex steroid hormone production directly by activating Leydig cells. Information is reviewed on the effects of progestin, androgens, and estrogens on global testicular gene expression patterns (microarray analysis), and on the molecular mechanisms by which steroids regulate specific candidate genes (identified by subtractive hybridization approaches) during early stages of testis maturation. Moreover, progestin and androgen effects on spermiation and milt hydration are discussed. Sex steroids mainly act via receptors expressed by Sertoli cells. One type of response is that Sertoli cells change growth factor expression, which subsequently modulates germ cell proliferation/differentiation via mechanisms yet to be characterised. Finally, we review data on germ cell autonomous processes, mainly derived from loss-of-function mutant fish lines, before identifying a number of focus areas for future research activities.
Utrecht University, Science Faculty, Department Biology, Padualaan 8, NL-3584 CH Utrecht, The Netherlands. r.w.schulz@uu.nl
Rüdiger W
RW
Schulz
Luiz Renato
LR
de França
Jean-Jacques
JJ
Lareyre
Florence
F
Le Gac
Florence
F
LeGac
Helio
H
Chiarini-Garcia
Rafael Henrique
RH
Nobrega
Takeshi
T
Miura
D000818:Animals; D002454:Cell Differentiation / Q000502:physiology; D005399:Fishes / Q000235:genetics / Q000502:physiology*; D020869:Gene Expression Profiling; D006728:Hormones / Q000502:physiology; D036341:Intercellular Signaling Peptides and Proteins / Q000502:physiology; D007985:Leydig Cells / Q000502:physiology / Q000648:ultrastructure; D008297:Male; D008540:Meiosis / Q000235:genetics / Q000502:physiology; D012708:Sertoli Cells / Q000502:physiology / Q000648:ultrastructure; D013091:Spermatogenesis / Q000235:genetics / Q000502:physiology*; D013094:Spermatozoa / Q000502:physiology / Q000648:ultrastructure; D013737:Testis / Q000378:metabolism / Q000502:physiology* / Q000648:ultrastructure
D006728:Hormones; D036341:Intercellular Signaling Peptides and Proteins