MURINE A-MYB - EVIDENCE FOR DIFFERENTIAL SPLICING AND TISSUE-SPECIFICEXPRESSION

The myb gene family consists of three members, A-myb, B-myb and c-myb. The proteins encoded by these genes bind DNA in a sequence-specific m anner and regulate transcription of target genes. In this communicatio n, we report the nucleotide sequence of murine A-myb cDNA. This gene e ncodes a protein of 751 amino acids with an estimated molecular weight of 83 kDa. cDNA sequence analysis of multiple independent cDNA clones reveals the presence of alternatively spliced mRNAs that encode small er proteins. Northern blot analysis of adult mouse tissue RNAs reveals A-myb expression predominantly in the testis, with very low levels of expression in the ovaries, spleen and brain. In situ hybridization an alysis of adult mouse testis shows that this gene is expressed at high levels in type A spermatogonia (stem cells), and preleptotene and pac hytene spermatocytes, with concomitant downregulation of expression up on terminal differentiation of these cells into mature spermatozoa. Th is pattern of expression suggests that A-myb is involved in the contro l of proliferation and differentiation of spermatogonia. This potentia l function of A-myb in spermatogenesis is reminiscent of the role of c -myb in hematopoiesis.