Random monoallelic expression of three genes clustered within 60 kb of mouse t complex genomic DNA

Mammals achieve gene dosage control by (1) random X-chromosome inactivation in females, (2) parental origin-specific imprinting of selected autosomal genes, and (3) random autosomal inactivation. Genes belonging to the third category of epigenetic phenomenon are just now emerging, with only six iden tified so far. Here we report three additional genes, Nubp2, Igfals, and Js ap1, that show 50%-methylated CpG sites by Southern blot analyses and prima rily monoallelic expression in single-cell allele-specific RT-PCP analysis of bone marrow stromal cells and hepatocytes. Furthermore, we show that, in contrast to X inactivation, alleles can switch between active and inactive states during the formation of daughter cells. These three genes are the f irst in their category to exist as a tight cluster, in the proximal region of mouse chromosome 17, providing a thus far unique example of a region of autosomal random monoallelic expression.