A novel imprinted locus on bovine chromosome 18 homologous with human Chromosome 16q24.1

Genomic imprinting is an epigenetic regulation mechanism in mammals resulting in the parentally dependent monoallelic expression of genes. Imprinting disorders in humans are associated with several congenital syndromes and cancers and remain the focus of many medical studies. Imprinted genes usually cluster on chromosomes and are regulated by different methylation regions (DMRs) located in imprinting control regions (ICRs) that control gene expression in cis. There is an imprinted locus on human chromosome 16q24.1 associated with congenital lethal developmental lung disease in newborns. Cattle is a better model organism for investigating human embryo development than mice. However, genomic imprinting on bovine chromosome 18, which is homologous with human chromosome 16 has not been systematically studied. In this study, we analyzed the allelic expressions of eight genes ( CDH13 , ATP2C2 , TLDC1 , COTL1 , CRISPLD2 , ZDHHC7 , KIAA0513, and GSE1 ) on bovine chromosome 18. Three transcript variants of the ZDHHC7 gene (X1, X2, and X5) showed maternal imprinting in bovine placentas. In addition, the monoallelic expression of X2 and X5 was tissue-specific. Five transcripts of the KIAA0513 gene showed tissue- and isoform-specific monoallelic expression. The CDH13 , ATP2C2, and TLDC1 genes exhibited tissue-specific imprinting, however, COTL1 , CRISLPLD2, and GSE1 escaped imprinting. Four DMRs, established after fertilization, were found in this region. Two DMRs were located between the ZDHHC7 and KIAA0513 genes, and two were in exon 1 of the CDH13 and ATP2C2 genes, respectively. The results from this study support future studies on the physiological roles of candidate genes on bovine chromosome 18.