The RUSH transcription factors 1 alpha and 1 beta bind to the Rabbit Uterog
lobin promoter and are members of the SWI/SNF complex that facilitates tran
scription by remodeling chromatin (Helicase). To characterize gonadal expre
ssion of RUSH, a cRNA probe that recognizes both isoforms was used for in s
itu hybridization studies. We found RUSH mRNA to be abundant in Sertoli cel
ls from embryonic, neonatal, prepubertal, and pubertal rabbit testes. In ad
ults, RUSH mRNA was detected in tubules with preleptotene spermatocytes and
mature spermatids lining the lumen. However, RUSH was undetectable in tubu
les that contained leptotene spermatocytes and that lacked mature spermatid
s, In females, RUSH was expressed in presumptive granulosa cells of embryon
ic and neonatal ovaries before follicle organization, abundant RUSH mRNA wa
s detected in granulosa and theca cells surrounding preantral follicles of
prepubertal and adult ovaries. Expression of RUSH remained high in granulos
a cells of antral follicles in mature ovaries but was negligible in late-st
age atretic follicles and in corpora lutea. Western blot analysis confirmed
the RUSH-1a isoform predominated in both testicular and ovarian tissues. T
he expression pattern of RUSH indicates transcriptional activity in Sertoli
cells and during multiple stages of differentiating granulosa cells, espec
ially those of primordial follicles, which heretofore were considered to be
dormant.