Comparative genomic imprinting and expression analysis of six cattle genes

¹ Department of Dairy Science, University of Wisconsin-Madison 1675 Observatory Dr., Madison, WI 53706 USA

^* To whom correspondence should be addressed. E-mail: hkhatib{at}wisc.edu.

	Abstract

Imprinted genes are monoallelically expressed in a parent-of-origin-specific manner under epigenetic regulation. Although it is generally believed that genomic imprinting is conserved among mammalian species, there is accumulating evidence that suggests such an assumption is false. Identification of species-specific imprinted genes is necessary to understand the evolution of genomic imprinting and to elucidate mechanisms leading to allele-specific expression. In this study, we analyzed the imprinting status of the CD81, TSSC4, and OBPH1 genes clustered on bovine chromosome 29; the PEG10 and ASB4 genes clustered on bovine chromosome 4; and the HTR2A microdomain gene on bovine chromosome 12 using a sequencing-based approach. CD81 and OBPH1 showed biallelic expression in all cattle tissues examined, while TSSC4 showed monoallelic expression in placental tissues, like its mouse orthologue. Comparative expression analysis showed that the imprinting pattern of the CD81, TSSC4, and OBPH1 cluster was not conserved among mouse, human, and cattle. None of these genes was imprinted in all three species. The PEG10 gene was imprinted in all three species, while ASB4, reported to be imprinted in mouse, was not imprinted in cattle. The HTR2A gene was not imprinted in cattle, and human imprinting data has shown conflicting results. It is more likely that imprinting in the genes examined in this study is species-specific. In addition, we studied the expression and tissue distribution of transcripts of these genes in 174 fetal and adult cattle tissues.

Key Words: cattle, comparative analysis, gene expression, imprinting