CHRM1 and myeloid sarcoma: Next, we quantified and compared the percentage of M1R-expressing OPCs (M1+/NG2+) in non-MS tissue, in MS lesions classified as “active,” and in lesions classified as “inactive.” The results show that M1R-expressing OPCs are particularly abundant in active MS lesions, implicate M1R as a mechanism for differentiation block, and provide impetus for the development of an M1R antagonist for MS (Fig. 2C).