Annotation of novel transcripts putatively relevant for bovine fat metabolism

Two bovine transcripts encoded by the interleukin-1 receptor-associated kinase 1 (IRAK1) gene and the locus LOC618944 predicted as similar to human chromosome 6 open reading frame 52 (C6orf52) gene had indicated divergent expression in bovine skeletal muscle containing different amount of intramuscular fat in a pilot screening experiment. However, for both loci any role in the regulation of energy or fat metabolism is not yet described. In this study, we validated and refined gene structure, screened for mRNA splice variants and analyzed the tissue-specific gene expression patterns of both loci as a prerequisite to elucidate their potential physiological function. Based on comparative sequence analysis, a new full-length gene model for the bovine IRAK1 gene was developed and confirmed experimentally. Expression of IRAK1 mRNA was found in a variety of tissues, and a splice variant was identified in skeletal muscle caused by an in-frame deleted segment of 210 bp affecting regions of intrinsic disorder in the respective protein. For the locus LOC618944, our data contributed to a revised gene model and its assignment to BTA23 (bovine chromosome 23) on the current bovine genome assembly supported by comparative similarity analysis between the bovine and human genomes and experimental data. Furthermore, we identified several splice variants in mammary gland, fat and skeletal muscle tissue and detected a highly similar processed pseudogene on BTA26. All transcript variants of LOC618944 detected in the analyzed tissues represent noncoding RNAs. For both loci, our results suggest yet undetected physiological functions in tissues relevant for fat or energy metabolism in cattle.