Distribution of alternatively spliced chicken c-myb exon 9A among hematopoietic tissues.

The role of the c-myb proto-oncogene in cellular differentiation may be regulated in part by alternative splicing of its mRNAs. Previously, two forms of alternative splicing of the chicken c-myb gene between exons 9 and 10 were described: one form utilizes the entire 360 base pair (bp) exon 9A while a second form utilizes exon 9A' which consists of the 3' 150 bp of exon 9A. In this study the distribution among chicken hematopoietic tissues of these two forms of alternative splicing was determined by Northern blot analysis using a probe specific for exon 9A. RNA species of 4.2 kilobases (kb) and 4.4 kb which contain exon 9A' or exon 9A, respectively, were detected in each tissue tested. Quantitative analysis of the major 4.0 kb c-myb species and the c-myb species containing exon 9A and exon 9A' revealed that cells from yolk sac contained both the highest absolute and the highest relative levels of alternatively spliced c-myb mRNA, presumably because of the preponderance of immature erythroid cells in these preparations.