Variegated monoallelic expression of a gene on proximal region of mouse chromosome 6

Abstract

Vme1, located near an imprinted region containing Peg1/Mest, Copg2 and Mit1/Lb9 on mouse chromosome 6, was identified and characterized to be under novel epigenetic regulations mediating non-imprinted monoallelic expression. The gene was transcribed independently from at least four promoters and alternatively spliced. Variable expression of the gene was found among individuals and was not affected by genetic backgrounds in contrast to relatively consistent expression of unlinked Peg3 under different genetic backgrounds. Monoallelic expression of the gene was confirmed in several tissues of hybrid F1s between a domesticus and a molossinus subspecies. However, the nature of monoallelic expression was different from those of its neighbors with respect to the allelic preference for the expression. The observed variable expression and monoallelic expression propose a mechanism that operates to variegate the Vme1 transcription acting asynchronously on parental alleles. In addition, we observed that some biallelically-expressed tissues exhibited allele-specific splicing such that expression from one parental allele yields elongated splice variants whereas the other allele is spliced into a short version. This unusual finding suggests that the epigenotype of a promoter can determine the splicing fate of the transcript.