E7 (1057ΔTA) mutation of the acidic α-glucosidase gene causes Pompe's disease in Droughtmaster cattle

To determine whether known loss-of-function alleles of the acidic α-glucosidase gene (GAA) are present in the Droughtmaster breed and, if so, whether the clinical signs and pathology of generalised glycogenosis (Pompe's disease) previously reported in other affected cattle are also seen in homozygous Droughtmasters.

Existing genomic and other diagnostic tests developed for generalised glycogenosis in cattle were used to test for the presence of the three known loss-of-function alleles of GAA in a herd of Droughtmaster cattle. Two calves with clinical signs of generalised glycogenosis were submitted for necropsy.

One loss-of-function GAA mutation (1057ΔTA or E7 allele) was identified using SNP chip technology and confirmed using conventional diagnostic DNA tests. Further testing demonstrated that the mutation was common within this herd and that two ill-thrift calves were homozygous for the E7 allele. Parentage analysis confirmed both sire and dam as heterozygous carriers. Pathology consistent with generalised glycogenosis was found in the skeletal and cardiac muscle and spinal cord of both of the affected calves. The 1783C>T (E13) or 2454ΔCA (E18) mutations associated with generalised glycogenosis in the Brahman and Shorthorn breeds, respectively, were not detected.

The lethal mutation 1057ΔTA of GAA is present in the Droughtmaster breed, with pathology identical to that reported in pure Brahman animals. Droughtmaster breeders should take action to prevent any increase in the prevalence of this lethal allele in the breed as it could cause both welfare issues and production losses if ignored.