Post-transcriptional regulation of the peripheral myelin protein gene PMP22/Gas3

The peripheral myelin protein PMP22 gene has been described as a growth arrest-specific gene gas3 and has been identified as disease gene of various demyelinating neuropathies. The gene consists of two highly conserved alternative noncoding 5'-exons la (CD25) and 1b (SR13), respectively. Differential expression patterns of these transcripts in vivo and in vitro suggest a very complex mode of PMP22 gene regulation, which cannot be explained merely by transcriptional control. In fact, the PMP22 gene is regulated on different post-transcriptional levels. While reverse transcriptase polymerase chain reaction (RT-PCR) analyses revealed no alterations in stability for both PMP22 transcripts in randomly growing Schwann cell cultures of rat sciatic nerve for at least 8 hours, in serum-induced synchronized cultures of resting cells we observed a specific cell cycle-regulated degradation of both transcripts. We further prepared diverse PMP22/CAT fusion genes to study the influence of the alternative 5'UTRs on PMP22 translation. Transient transfection of NIH3T3-fibroblasts and rat Schwann cells demonstrated that the alternative 5'UTRs (CD25 and SR13) and the 3'UTR exert differential regulatory influences on the translation efficiency.