Early Development of the Gonads: Origin and Differentiation of the Somatic Cells of the Genital Ridges.
The earliest manifestation of gonadogenesis in vertebrates is the formation of the genital ridges. The genital ridges form through the transformation of monolayer coelomic epithelium into a cluster of somatic cells. This process depends on increased proliferation of coelomic epithelium and disintegration of its basement membrane, which is foreshadowed by the expression of series of regulatory genes. The earliest expressed gene is Gata4, followed by Sf1, Lhx9, Emx2, and Cbx2. The early genital ridge is a mass of somatic SF1-positive cells (gonadal precursor cells) that derive from proliferating coelomic epithelium. Primordial germ cells (PGCs) immigrate to the coelomic epithelium even in the absence of genital ridges, e.g., in mouse null mutants for Gata4. And conversely, the PGCs are not required for the formation of the genital ridges. After reaching genital ridges, the PGCs become enclosed by somatic cells derived from coelomic epithelium. Subsequently, the expression of sex-determining genes begins and the bipotential gonads differentiate into either testes or ovaries. Gonadal precursor cells, derived from coelomic epithelium, give rise to the somatic supporting cells such as Sertoli cells, follicular cells, and probably also peritubular myoid and steroidogenic cells.
Department of Comparative Anatomy, Institute of Zoology, Jagiellonian University, Gronostajowa 9, 30-387, Krakow, Poland. rafal.piprek@uj.edu.pl.
Rafal P
RP
Piprek
Department of Surgery, The Houston Methodist Hospital, Houston, TX, USA.|The Houston Methodist Research Institute, Houston, TX, USA.
Malgorzata
M
Kloc
CNRS, UMR 6290, Institute of Genetics and Development of Rennes, Cell Cycle Group, 35043, Rennes, France.|Université Rennes 1, UEB, UMS Biosit, Faculty of Medicine, 35043, Rennes, France.
Jacek Z
JZ
Kubiak
D000818:Animals; D002454:Cell Differentiation; D005260:Female; D018507:Gene Expression Regulation, Developmental; D006066:Gonads / Q000166:cytology / Q000254:growth & development*; D008297:Male; D051379:Mice; D010053:Ovary / Q000166:cytology* / Q000254:growth & development; D013737:Testis / Q000166:cytology* / Q000254:growth & development
Bipotential gonads; Genital ridges; Ovary; Sertoli cells; Testis