MEMBERS OF THE RAF GENE FAMILY EXHIBIT SEGMENT-SPECIFIC PATTERNS OF EXPRESSION IN MOUSE EPIDIDYMIS

The proto-oncogene c-raf-1 and the related genes A-raf and B-raf encod e serine/threonine protein kinases thought to be involved in regulatin g gene expression by acting as part of second-messenger signaling path ways within the cell. Among the tissues in which A-raf and c-raf-1 hav e been shown to be expressed was mouse epididymis. The present studies were undertaken to determine if the raf family genes exhibited specif icity in their pattern of expression that might be indicative of speci fic function in the epididymis. Northern and in situ hybridization ana lyses demonstrated that c-raf-1 mRNA was expressed as a 3.1 kb transcr ipt at uniform levels throughout the length of the epididymis in all t ypes of epididymal epithelial cells. Neither the germ cell-specific te sticular transcripts nor the somatic transcripts of B-raf were detecte d by either Northern or in situ hybridization analysis in any region o f the epididymis. A-raf, expressed as two transcripts of 2.6 and 4.3 k b, was the only gene examined which exhibited a segment-specific patte rn of expression, being highest in the principal epithelial cells of t he proximal caput epididymis and decreasing progressively in more dist al regions of the tubule. These studies indicate that each raf gene ex hibits a characteristic pattern of expression in the epididymis; A-raf in particular may play a unique regulatory role in the regionalized f unctions of the epididymis.