AN ALTERNATIVE DYSTROPHIN TRANSCRIPT SPECIFIC TO PERIPHERAL-NERVE

Transcription of the 2.5 megabase dystrophin gene gives rise to multip le isoforms. We describe a 5.2 kilobase transcript, expressed specific ally in peripheral nerve, that initiates at a previously unrecognized exon located approximately 850 basepairs upstream of dystrophin exon 5 6. The likely product of this transcript (Dp116) is detected by C-term inal dystrophin antibodies exclusively in peripheral nerve and culture d Schwann cells. Dp116 is located along the Schwann cell membrane but is not present in the compact myelin lamellae or in axons. Dp116 lacks actin-binding and spectrin-like rod domains, arguing that it function s differently in the Schwann cell than does the major dystrophin trans cript in muscle.