An alternative dystrophin transcript specific to peripheral nerve.

Transcription of the 2.5 megabase dystrophin gene gives rise to multiple isoforms. We describe a 5.2 kilobase transcript, expressed specifically in peripheral nerve, that initiates at a previously unrecognized exon located approximately 850 basepairs upstream of dystrophin exon 56. The likely product of this transcript (Dp116) is detected by C-terminal dystrophin antibodies exclusively in peripheral nerve and cultured 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 functions differently in the Schwann cell than does the major dystrophin transcript in muscle.