Genetic basis of Lipomatous Myopathy in Piedmontese beef cattle

In Piedmontese cattle breed, the sporadic detection of Lipomatous Myopathy (LM) has been reported. The phenotypic disease expression consists in degeneration and infiltration of the muscular tissue characterized by replacement of myofibers with adipose tissue. The aim of this study was to investigate the existence of genetic loci associated with lipomatous myopathy in Piedmontese cattle breed through a genome wide association study based on a DNA pooling design. The samples used for the study were collected from a meat cutting plant, pairing cases and controls within farms. Samples of different muscles (diaphragm, superficial and deep pectoral, intercostal, sternocleidomastoid group and vastus lateralis) were histopathologically and enzymatically classified as cases and controls. DNA pools of cases and controls were constructed. Equal amounts of DNA were pooled from individuals for the constitution of 4 pools (2 independent biological replicates for cases and 2 for controls). Technical duplicates were also built and all pools genotyped with the Illumina BovineHD BeadChip three time each, for a total of 24 chip array positions. SNPs positions were based on the UMB 3.1 bovine assembly. The B-allele frequencies (BAF) for each array replicate were used in a specific pipeline in R software to perform multiple marker tests after excluding the 5% of SNPs showing the highest BAF variability from the replicate arrays within tail, as well as the monomorphic SNPs. A total of 41 QTLRs were identified on the 29 bovine autosomes, and 4 on the X chromosome. A subset of the identified markers fall inside or nearby genes involved in myogenesis, adipogenesis and cell to cell adhesions. The biological role of these genes in the onset of lipomatous myopathy has been identified looking at the known functions of the encoded proteins on the GeneCards database. Gene networks have been identified using STRING.