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Early gonadogenesis in mammals: Significance of long and narrow gonadal structure
Author(s) -
Harikae Kyoko,
Miura Kento,
Kanai Yoshiakira
Publication year - 2013
Publication title -
developmental dynamics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.634
H-Index - 141
eISSN - 1097-0177
pISSN - 1058-8388
DOI - 10.1002/dvdy.23872
Subject(s) - testis determining factor , biology , sox9 , microbiology and biotechnology , sertoli cell , fgf9 , primordium , sexual differentiation , cell fate determination , blastula , transcription factor , developmental biology , morphogenesis , development of the gonads , anatomy , gonad , embryo , genetics , endocrinology , gene , embryogenesis , spermatogenesis , gastrulation , y chromosome
In mammalian embryogenesis, the gonadal primordium arises from the thickening of the coelomic epithelium, which results in a pair of extremely long and narrow gonadal structures along the anteroposterior axis. These gonadal structures are conserved in various mammalian species, suggesting a great advantage in properly receiving migrating primordial germ cells (PGCs) that are widely scattered throughout the hindgut tube. Soon after the PGCs settle, the bipotential gonads undergo sex determination into testes or ovaries by the sex‐determining gene, Sry , which is expressed in supporting cell precursors in a center‐to‐pole manner. Such a long, narrow gonadal structure bestows a considerable time lag on Sry expression between the center and pole regions, but testiculogenesis with cord formation and Leydig cell differentiation occurs synchronously throughout the whole organ. This synchronous testiculogenesis could be explained by a positive‐feedback mechanism between SOX9 (another SRY‐related transcription factor) and FGF9 downstream of Sry . FGF signals are likely secreted from the center region, rapidly diffuse into the poles, and then induce the establishment of SOX9 expression in Sertoli cells in the pole domains. This work focuses on recent knowledge of the molecular and cellular events of PGC migration, gonadogenesis, and testiculogenesis, and their biological significance in mammalian embryogenesis. Developmental Dynamics 242:330–338, 2013 . © 2012 Wiley Periodicals, Inc.