DEVELOPMENTAL REGULATION OF ACETYLCHOLINESTERASE TRANSCRIPTS IN THE MOUSE DIAPHRAGM - ALTERNATIVE SPLICING AND FOCALIZATION

We studied the splicing and compartmentalization of acetylcholinestera se (AChE) mRNAs during muscle differentiation in the mouse, both in vi tro and in vivo. We used the polymerase chain reaction (PCR) to analys e AChE mRNAs in cultures of the myogenic C-2 and So18 cell lines, and in the developing diaphragm, from embryonic day 14 (E14). We character ized three types of alternatively spliced AChE mRNAs, encoding catalyt ic subunits that differ by their C-terminal regions (R, H and T). The T transcript is predominant in all cases and represents the only AChE mRNA in the adult muscle. We detected the presence of the minor R and H transcripts in the myogenic cell lines, both as myoblasts and differ entiated myotubes, and also in the diaphragm from E14 until birth. At E14 the R transcript represents similar to 1% of AChE mRNA and the lev el of the H transcript is still lower. By in situ hybridization, we fo und that the T AChE mRNAs begin to preferentially accumulate at the le vel of the first neuromuscular contacts in the mouse diaphragm and oth er muscles as early as E14, e.g. concomitantly with mRNAs encoding the receptor subunits. This suggests that a common control mechanism ensu res the synaptic focalization of mRNAs encoding the cholinergic protei ns AChE and acetylcholine receptor during muscle development.