Roles of TYRO3 Family Receptors in Germ Cell Development During Mouse Testis Formation

Abstract

Objective: To investigate the role of a potential SOX9 target gene, Tyro3, along with its family members, Axl and Mertk (TAM family) in mouse testis development. Design: Experimental laboratory study. Setting: Research institute units. Subject(s): Embryonic day (E)11.5 Swiss mouse gonads for ex vivo gonad culture; Tyro3 knockout mouse embryos. Intervention(s): E11.5 Swiss mouse gonads were cultured in hanging droplets of 30 μL DMEM medium supplemented with 10% FBS and 1% antibiotic-antimycotic. A pair of gonads were treated with 20 μM of BMS-777607 or 30 μM of LDC1267 and an equivalent volume of the vehicle control DMSO. Main Outcome Measure(s): Immunofluorescence to measure morphological changes of ex vivo cultured gonads and in vivo Tyro3 mouse testes; qRT-PCR to measure gene expressions. Result(s): Inhibition of the TAM family in E11.5 ex vivo cultured male mouse gonads led to reduced germ cell numbers caused by reduced proliferation and increased apoptosis of the germ cells. Tyro3 knockout mice exhibited reduced expression levels of the germ cell genes Ddx4, Dazl and Pou5f1 and increased expression levels of the Sertoli cell genes Sox9 and Amh at E12.5. However, by E14.5, the expression of Ddx4, Dazl, Sox9 and Amh had returned to normal levels in Tyro3 knockout testes. Tyro3 knockout testes displayed normal morphology and structures during fetal testis development. Conclusion(s): TAM family members have redundant roles in regulating germ cell development during early testis development.