Imprint status of M6P/IGF2R and IGF2 in chickens

Genomic imprinting is a method of gene regulation whereby a gene is express ed in a parent-of-origin-dependent fashion; however, it is hypothesized tha t imprinting should not occur in oviparous taxa such as birds. Therefore, w e examined the allelic expression of two genes in the chicken that are reci procally imprinted in most mammals, mannose 6-phosphate/insulin-like growth fnctor 2 receptor (M6P/IGF2R) and insulin-like growth fnctor 2 (IGF2). Sin gle nucleotide polymorphisms were identified in these genes, and cDNA was p repared from several tissues of embryos heterozygous for these polymorphism s. Both alleles of M6P/IGF2R and IGF2 were expressed in all tissues examine d by RT-PCR. Since the expression of these genes was independent of the par ent from which they were inherited, we conclude that neither M6P/IGF2R nor IGF2 are imprinted in the chicken.