Differences in expression of acetylcholinesterase and collagen Q control the distribution and oligomerization of the collagen-tailed forms in fast and slow muscles.

The collagen-tailed forms of acetylcholinesterase (AChE) are accumulated at mammalian neuromuscular junctions. The A(4), A(8), and A(12) forms are expressed differently in the rat fast and slow muscles; the sternomastoid muscle contains essentially the A(12) form at end plates, whereas the soleus muscle also contains extrajunctional A(4) and A(8) forms. We show that collagen Q (ColQ) transcripts become exclusively junctional in the adult sternomastoid but remain uniformly expressed in the soleus. By coinjecting Xenopus oocytes with AChE(T) and ColQ mRNAs, we reproduced the muscle patterns of collagen-tailed forms. The soleus contains transcripts ColQ1 and ColQ1a, whereas the sternomastoid only contains ColQ1a. Collagen-tailed AChE represents the first evidence that synaptic components involved in cholinergic transmission may be differently regulated in fast and slow muscles.