Achaete Scute Complex Like Protein 1 (ASCL1)

Mash1 is expressed during development of rat retina and interacts specifically with an E-box identified in the promoter for the opsin gene during rod photoreceptor differentiation. It encodes a predicted protein of 238 amino acids that shares 95% identity with the mammalian achaete-scute homolog-1 (Mash1), a rodent basic helix-loop-helix factor.

The proximal coding region of the cDNA contains a striking 14-copy repeat of the triplet CAG that exhibits polymorphism in human genomic DNA; thus, ASCL1 is a candidate locus. Northern blot analysis revealed ASCL1 transcripts in RNA from a human MTC cell line, 2 fresh MTC tumors, fetal brain, and 3 lines of human SCLC. In contrast, cultured lines of non-SCLC lung cancers and a panel of normal adult human tissues showed no detectable ASCL1 transcripts.