Methylation and Transcripts Expression at the Imprinted GNAS Locus in Human Embryonic and Induced Pluripotent Stem Cells and Their Derivatives

Data from the literature indicate that genomic imprint marks are disturbed in human pluripotent stem cells (PSCs). GNAS is an imprinted locus that produces one biallelic (Gsα) and four monoallelic (NESP55, GNAS-AS1, XLsα, and A/B) transcripts due to differential methylation of their promoters (DMR). To document imprinting at the GNAS locus in PSCs, we studied GNAS locus DMR methylation and transcript (NESP55, XLsα, and A/B) expression in human embryonic stem cells (hESCs) and human induced pluripotent stem cells (hiPSCs) derived from two human fibroblasts and their progenies. Results showed that (1) methylation at the GNAS locus DMRs is DMR and cell line specific, (2) changes in allelic transcript expression can be independent of a change in allele-specific DNA methylation, and (3) interestingly, methylation at A/B DMR is correlated with A/B transcript expression. These results indicate that these models are valuable to study the mechanisms controlling GNAS methylation, factors involved in transcript expression, and possibly mechanisms involved in the pathophysiology of pseudohypoparathyroidism type 1B.