Evaluation of the Stag3 gene and the synaptonemal complex in a rat model (as/as) for male infertility

Affected males (as/as) from the mutant TT rat strain are sterile due to spe rmatogenesis impairment with meiotic arrest at the pachytene stage. The as locus is on rat chromosome 12, in a region that shows conserved synteny to cM 74-94 on mouse chromosome 5. Stag3, a new member of the stromalin protei n family, is expressed specifically in testis and associates to the synapto nemal complex. Mouse Stag3 gene has been assigned to cM 78 on chromosome 5. In this study, we have characterized the rat Stag3 gene and examined it as a candidate for male infertility in asl as rats. The rat Stag3 cDNA is 418 1 nucleotides long, contains a highly polymorphic hexanucleotide repeat in the coding region, and encodes a 1256 amino acid protein with 93 and 77% se quence identity to mouse and human Stag3 proteins, respectively. No mutatio ns or differences in size or abundance of Stag3 mRNA were detected between as/as and control rats, suggesting that Stag3 is not responsible for the as permic phenotype. In addition, immunohistochemistry with antibodies against SCP1 and SPC3 proteins suggest that the synaptonemal complex structures ar e not primarily affected in these rats. (C) 2001 Wiley-Liss, Inc.