The Different Expression Of Alternatively Spliced Transcripts And Imprinting Status Of Cattle Meg9Gene

Genomic imprinting is an epigenetic phenomenon that results in an allele-specificexpression from a single in a parent-of-origin-dependent manner. Imprinted genes aregenes that preferentially expressed from either the maternally allele or the paternally allele.Dlk1-Dio3imprinted domain is conserved among mammals, and involved in embryonic,placental and muscle growth. Dlk1-Dio3imprinted domain has been widely studied inmouse and human. But due to the lack of sequence and polymorphism information incoding regions, few imprinted genes have been reported in cattle.In this study, we cloned the cDNA sequence and analyzed the expression andimprinted status of Meg9gene, which is identified as a maternally expressed gene inmouse. Comparison the ovis Meg9cDNA sequence （GenBank accession no.AF354168.3）with bovine genomic sequence, the region with high similarity was selected as the putativebovine Meg9cDNA sequence. When aligned the putative sequence in NCBI/Blast （bovineESTs, http://blast.ncbi.nlm.nih.gov/）,17similar ESTs with three different5’ end and a3’end were found. The cattle Meg9gene is composed of3exons and3alternative splingspredicted. The DNA and cDNA sequences were about5kb and2248bp, respectively.Sequence homology analysis vevealed that cattle Meg9-c1variant shares highidentity（92%） to sheep （GenBank: AF354168） and shares46%to the human （GenBank：NR₀47664） and35%to mouse （GenBank：EU616813） homologies, respectively. Thevariants of cattle Meg9contain multiple small open reading frames （ORFs）, but have noKozak consensus sequences for initiation of translation, implying that Meg9may functionas a non-coding RNA, which in accordance with the findings in mouse Meg9gene.In this study, we found3alternative splicing variants occurred in cattle Meg9geneand every splicing variant exhibited different expression pattern in cattle tissues, includingheart, liver, spleen, lung, kidney, muscle and subcutaneous fat, which may be associatedwith its function.A single nucleotide polymorphisms （SNP） site was identified in exon3of cattle Meg9and used to distinguish between monoallelic and biallelic expression. Our results showedthat Meg9exhibited monoallelic expression in all examined cattle tissues by comparing sequencing results between at genomic DNA and cDNA levels on the SNP sites, suggestedthat Meg9is imprinted in cattle.