Extensive parent-of-origin genetic effects on fetal growth

Background

Epigenetic effects have recently been recognized as playing a very significant role in several normal and pathological phenotypes. Imprinting, the silencing of either the paternally or maternally inherited allele, is one of the most pervasive and consistent epigenetic mechanisms across species and individuals. The majority of imprinted loci are involved in fetal growth regulation, and several defects in the epigenetic regulation of these genes are associated with extremes of fetal growth.

Materials and methods

We surveyed 62 SNPs across 17 genes (Table 1) in a cohort of African-American mother-newborn pairs selected using stringent inclusion/exclusion criteria intended to enrich for the genetic component of fetal growth regulation. All association analyses were adjusted for admixture using a suite of ancestry informative SNP markers. By inferring haplotypes within the imprinted loci in mothers and newborns, we could unambiguously infer the parental origin of haplotypes and associated alleles in the majority of newborns.

Table 1 SNPs Genotyped

Results and conclusion

We found very significant parent-of-origin effects in the insulin, H19 and GNAS genes that were completely consistent with their known patterns of imprinting. In the case of the insulin polymorphisms, a consistent trend was also observed for newborn IGF-II levels with respect to parental origin of haplotypes.