PROTOONCOGENE C-SKI IS EXPRESSED IN BOTH PROLIFERATING AND POSTMITOTIC NEURONAL POPULATIONS

The cellular protooncogene, c-ski, is expressed in all cells of the de veloping mouse at low but detectable levels. In situ hybridization and Northern blot analyses reveal that some cells and tissues express thi s gene at higher levels at certain stages of embryonic and postnatal d evelopment. RT-PCR results indicate that alternative splicing of exon 2, known to occur in chickens (Sutrave and Hughes [1989] Mel. Cell. Bi ol, 9:4046-4051; Grimes et al. [1993] Oncogene 8:2863-2868) does not o ccur in adult mouse tissues. In the embryo, neural crest cells express the c-ski gene during migration at 8.5 to 9.5 days post coitum (p.c.) . Neural crest derivatives such as dorsal root ganglia and melanocytes stain positively with an antibody to the ski protein. At 9 days p.c., the entire neural tube has high levels of c-ski gene expression. By 1 2-13.5 days only the ependymal layer expresses c-ski above background levels. At 14-16 days p.c., c-ski mRNAs are detected at high levels in the cortical layers of the brain and in the olfactory bulb, In 2 week and 6 week postnatal brains, c-ski gene transcripts are also detected in the hippocampus and in the granule cell layer of the cerebellum. T he allantois and placenta exhibit high levels of c-ski mRNAs. Neonatal lung tissue increases c-ski gene expression approximately two-fold co mpared to prenatal levels. These results suggest that ski plays a role in both the proliferation and differentiation of specific cell popula tions of the central and peripheral nervous systems and of other tissu es. (C) 1994 Wiley-Liss, Inc.