Sexual differences of imprinted genes' expression levels

Abstract

In mammals, genomic imprinting has evolved as a dosage-controlling mechanism for a subset of genes that play critical roles in their unusual reproduction scheme involving viviparity and placentation. As such, many imprinted genes are highly expressed in sex-specific reproductive organs. In the current study, we sought to test whether imprinted genes are differentially expressed between the two sexes. According to the results, the expression levels of the following genes differ between the two sexes of mice: Peg3, Zim1, Igf2, H19 and Zac1. The expression levels of these imprinted genes are usually greater in males than in females. This bias is most obvious in the developing brains of 14.5-dpc embryos, but also detected in the brains of postnatal-stage mice. However, this sexual bias is not obvious in 10.5-dpc embryos, a developmental stage before the sexual differentiation. Thus, the sexual bias observed in the imprinted genes is most likely attributable by gonadal hormones rather than by sex chromosome complement. Overall, the results indicate that several imprinted genes are sexually different in terms of their expression levels, and further suggest that the transcriptional regulation of these imprinted genes may be influenced by unknown mechanisms associated with sexual differentiation.

Keywords: A disintegrin and metalloproteinase with thrombospondin motifs 2 isoform 1 preproprotein; Adamts2; Dlk1; Esr1; Genomic imprinting; Grb10; Gtl2; H19; H19 mRNA; Igf2; Mest; Ndn; Nnat; Peg3; Prlr; Rasgrf1; Sexual dimorphism; Snrpn; Ube3a; Usp29; Zac1; Zim1; estrogen receptor 1; gene target locus 2; growth factor receptor-bound protein 10; insulin-like growth factor 2; mesoderm-specific transcript protein; necdin; neuronatin isoform alpha; paternally expressed gene 3; prolactin receptor precursor; protein delta homolog 1 isoform 1 precursor; ras-specific guanine nucleotide-releasing factor; small nuclear ribonucleoprotein-associated; ubiquitin carboxyl-terminal hydrolase 29; ubiquitin-protein ligase E3A isoform 2; zinc finger protein 1 regulating apoptosis and cell cycle arrest; zinc finger, imprinted 1.