A Mutation of the GFRΑ1 Gene is Responsible for Forelimb-Girdle Muscular Anomaly (FMA) of Japanese Black Cattle

Forelimb-girdle muscular anomaly (FMA) is an autosomal recessive hereditary disorder reported in a particular local population of Japanese Black cattle. Affected calves show tremors and astasia at birth. The most characteristic feature of this disorder is an abnormal shape of shoulders and swelling of scapula, caused by hypoplasia of the latissimus dorsi musculus limited to the forelimb-girdle muscles region. In this study, we mapped the FMA locus to a 2.4-Mb interval between microsatellite marker MOK2611 and MOK2603 on the bovine chromosome 26. To identify the causal mutations, we obtained whole genome sequence of a sire of FMA carrier by using a Genome Analyzer IIx (Illumina), and compared the nucleotide sequences of the 2.5-Mb region containing the FMA locus with that of reference sequences. As a result, the FMA locus of the carrier contained 1,226 SNPs that are specific for the carrier. Examination of a peculiarity of these SNPs in the affected animals revealed that a nucleotide substitution of C to T in exon 4 of the glial cell line derived neurotrophic factor family receptor alpha 1 (GFRΑ1) gene results in a Q144X mutation. GFRα1 serves as a receptor for GDNF signaling, which is involved in the innervation in the cutaneous maximus and latissimus dorsi muscles. The PCR-RFLP analysis for this nucleotide substitution in affected and normal animals revealed that the FMA phenotype was completely consistent with the genotype of the GFRΑ1 gene, indicating that the nonsense mutation of the GFRΑ1 gene is responsible for the FMA.