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#testis determination

2 public questions tagged with this topic.

sex determination-ll

Which pathway suppresses testis determination?

Testis determination is suppressed primarily by ovarian Wnt4/β-catenin/Rspo1 canonical pathway in mammals. In XX gonads secreted Wnt4 binds Frizzled and Lrp5/6, signals via Disheveled inhibiting destruction complex of β-catenin. Accumulated β-catenin represses Sox9 enhancer and Fgf9 proliferative loop, prevents Sertoli specification and blocks formation of male-specific coelomic vessel dependent on Fgf9. It also induces Follistatin to inhibit coelomic vessel formation and steroidogenesis. When pathway disrupted in XX embryos, testes-like structures develop with Sertoli cells, illustrating active repressive function of β-catenin/Wnt4 axis.

Ref: NCBI Bookshelf, Developmental Biology, Chapter: Antagonistic sex determination - Wnt4 suppression of testis.

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sex determination-ll

Which gene is crucial for testis determination pathway in mammals?

Testis determination in mammals absolutely requires Sox9, an HMG-box transcription factor functioning downstream of Sry. Sry expressed briefly in XY supporting precursors binds testis-specific enhancer TESCO together with Sf1 to trigger Sox9 transcriptional surge. Sox9 then establishes feed-forward loops with Fgf9 and prostaglandin D2, autoregulates, represses ovarian Wnt4/β-catenin pathway, activates Dhh, Amh, Sox8 and extracellular matrix genes driving testis cord formation. Loss-of-function XY gonads develop as ovaries, while ectopic Sox9 in XX gonads induces complete testes without Sry, proving central indispensability.

Ref: Gilbert, Developmental Biology, 12th ed., Chapter 6: Sox9 and Sry in testis differentiation.

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