Imprinting Status Examination of the PLAGL1 Locus on Human Chromosome 6 Expressed in the Placenta

Abstract

One of the most critical health issues facing women and children is pre-term birth. A major cause of pre-term birth is poor placentation, which results in inadequate blood flow and nutrient transfer to the developing fetus. Genomic imprinting is an epigenetic mechanism that results in allele-specific expression (ASE) that is dependent on the parent of origin. Imprinted genes are critical for placental development and Loss of imprinting (LOI) is associated with aberrant placentation and adverse pregnancy outcomes, such as preterm birth, preeclampsia, and intrauterine growth restriction. LOI refers to re-expression of the silenced allele, which appears to occur in a developmental stage-specific manner in human placenta. Our goal is to better define the set of imprinted genes in the placenta, which would provide the framework for identifying epigenetic mechanisms that are important in human placental development. Imprinted genes are frequently located in clusters on chromosomes. This project will test whether several genes located near two known imprinted genes, PLAGL1 and HYMAI (non-coding RNA), on chromosome 6 are imprinted in the human placenta. The genes that will be examined are PHACTR2, STX11, LTV1, C6orf94, and SF5B3. Our past approaches involved real-time qPCR and high resolution melt (HRM) analysis for genotyping and determining the relative expression of the maternal and paternal alleles in heterozygous placentas. Currently, our approach includes using the Sequenom mass array to find the ASE of the heterozygote placentas. We have identified several informative single nucleotide polymorphisms (SNPs) with minor allele frequencies >0.1 that are located in the transcribed region of PLAGL1, rs36120645 and rs2076684; HYMAI, rs28364590 and rs12524155; PHACTR2, rs10447447 and rs3734226; and STX1, rs3734227. Past efforts resulted in designed and optimized PCR assays for HRM and qPCR assays. Current endeavors examine ASE from each gene, and test the parent-of-origin expression.