Peg1/Mest in obese adipose tissue is expressed from the paternal allele in an isoform-specific manner

Paternally expressed 1 (Peg1)/mesoderm specific transcript (Mest) is an imprinted gene, which is only transcribed from the paternal (father's) allele. In some human cancer tissues, an alternatively spliced variant of PEG1/MEST mRNA using a different promoter of a distinct first exon is expressed from both paternal and maternal alleles. We previously reported that Peg11 Mest expression was markedly up-regulated in obese adipose tissue in mice. Moreover, transgenic overexpression of Peg11Mest in the adipose tissue resulted in the enlargement of adipocytes in size. Given the potential pathophysiologic relevance in obesity, we examined the nature of increased expression of Peg11Mest in obese adipose tissue. In obese adipose tissue, expression of Peg11Mest was increased, but not that of other imprinted genes tested. The transcription rate of Peg11Mest was increased in obese adipose tissue. We found at least four isoforms of mouse Peg11Mest generated by use of the alternative first exons. We also demonstrated that the abundantly expressed Peg11Mest in obese adipose tissue retained monoallelic expression. This is the first report of monoallelic induction of Peg11Mest in adult tissues. (c) 2006 Federation of European Biochemical Societies. Published by Elsevier B.V. All rights reserved.