Genome-wide assessment of imprinted expression in human cells

Parent-of-origin dependent expression of alleles, imprinting, has been suggested to impact a substantial proportion of mammalian genes. Its discovery requires allele-specific detection of expressed transcripts, but in some cases detected allelic expression (AE) bias has been interpreted as imprinting without demonstrating compatible transmission patterns and excluding heritable variation. Therefore, we utilized a genome-wide tool exploiting high density genotyping arrays in parallel measurements of genotypes in RNA and DNA to determine AE across the transcriptome in lymphoblastoid cell lines (LCLs) and skin fibroblasts derived from families. To investigate imprinting, transmission patterns were analyzed in 2 LCL trios, 1 LCL 3-generation pedigree and 9 FB trios. To investigate random monoallelic expression, 2 cell lines were treated with three concentrations of 5-azadeoxycytidine (AZA), and one cell line was treated for two time periods.