Assessment of genomic imprinting of SLC38A4, NNAT, NAP1L5, and H19 in cattle

Background: At present, few imprinted genes have been reported in cattle compared to human and mouse. Comparative expression analysis and imprinting status are powerful tools for investigating the biological significance of genomic imprinting and studying the regulation mechanisms of imprinted genes. The objective of this study was to assess the imprinting status and pattern of expression of the SLC38A4, NNAT, NAPIL5, and H19 genes in bovine tissues. Results: A polymorphism-based approach was used to assess the imprinting status of four bovine genes in a total of 75 tissue types obtained from 12 fetuses and their dams. In contrast to mouse Slc38a4, which is imprinted in a tissue-specific manner, we found that SLC38A4 is not imprinted in cattle, and we found it expressed in all adult tissues examined. Two single nucleotide polymorphisms (SNPs) were identified in NNAT and used to distinguish between monoallelic and biallelic expression in fetal and adult tissues. The two transcripts of NNAT showed paternal expression like their orthologues in human and mouse. However, in contrast to human and mouse, NNAT was expressed in a wide range of tissues, both fetal and adult. Expression analysis of NAP1L5 in five heterozygous fetuses showed that the gene was paternally expressed in all examined tissues, in contrast to mouse where imprinting is tissue-specific. H19 was found to be maternally expressed like its orthologues in human, sheep, and mouse. Conclusion: This is the first report on the imprinting status of SLC38A4, NAPIL5, and on the expression patterns of the two transcripts of NNAT in cattle. It is of interest that the imprinting of NAPIL5, NNAT, and H19 appears to be conserved between mouse and cow, although the tissue distribution of expression differs. In contrast, the imprinting of SLC38A4 appears to be species-specific.