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Expression of Stimulated by Retinoic Acid Gene 8 (Stra8) and Maturation of Murine Gonocytes and Spermatogonia Induced by Retinoic Acid In Vitro¹

School of Molecular Biosciences,³ Washington State University, Pullman, Washington 99164 Department of Biology,⁴ University of Texas, San Antonio, Texas 78249

ABSTRACT

Vitamin A deficiency in the mouse results in an arrest in the progression of undifferentiated spermatogonia to differentiating spermatogonia. The supplement of retinol to vitamin-A-deficient mice reinitiates spermatogenesis in a synchronous manner throughout the testes. It is unclear whether the effects of retinoids are the result of a direct action on germ cells or are indirectly mediated through Sertoli cells. The expression of Stimulated by retinoic acid gene 8 (Stra8), which is required for spermatogenesis, is directly related to the availability of retinoic acid (RA). Analysis of gene expression by microarrays revealed moderate levels of Stra8 transcript in gonocytes and high levels in A and B spermatogonia. Stra8 mRNA levels were greatly reduced or absent in germ cells once they entered meiosis. This study examined the effect of retinoic acid on cultured neonatal testes and isolated gonocytes/spermatogonia in vitro. THY1⁺ and KIT⁺ germ cells were isolated by magnetic-activated cell sorting from the testes of mice of different ages. Isolated germ cells were cultured and treated with either vehicle (ethanol) or RA without feeder cells. We found that 1) Stra8 is predominantly expressed in premeiotic germ cells, 2) RA stimulates gonocyte DNA replication and differentiation in cultured neonatal testes, 3) in the absence of feeder cells, RA directly induces the transition of undifferentiated spermatogonia to differentiating spermatogonia by stimulating Stra8 and Kit gene expression, 4) RA dramatically stimulates Stra8 expression in undifferentiated spermatogonia but has a lesser impact in differentiating spermatogonia, 5) endogenous Stra8 gene expression is higher in differentiating spermatogonia than in undifferentiated spermatogonia and could mediate the RA effects on spermatogonial maturation, and 6) RA stimulates a group of genes involved in the metabolism, storage, transport, and signaling of retinoids.

differentiation, gonocytes, in vitro, retinoic acid, spermatogenesis, spermatogonia, spermatogonial differentiation, Stra8

¹Supported by NIH grants R01 HD 10808 and U54 HD 042454. The microarray data have been deposited in the National Center for Biotechnology Information Gene Expression Omnibus database (series no. GSE9521).

Correspondence: ²Michael D. Griswold, 531 Fulmer Hall, School of Molecular Biosciences, Washington State University, Pullman, WA 99164-4660. FAX: 509 335 9688; e-mail: mgriswold{at}wsu.edu

This article has been cited by other articles:

				Q. Zhou, R. Nie, Y. Li, P. Friel, D. Mitchell, R. A Hess, C. Small, and M. D Griswold Expression of Stimulated by Retinoic Acid Gene 8 (Stra8) in Spermatogenic Cells Induced by Retinoic Acid: An In Vivo Study in Vitamin A-Sufficient Postnatal Murine Testes Biol Reprod, July 1, 2008; 79(1): 35 - 42. [Abstract] [Full Text] [PDF]