ARSB gene variants causing Mucopolysaccharidosis VI in Miniature Pinscher and Miniature Schnauzer dogs

Summary Mucopolysaccharidosis (MPS) VI is a lysosomal storage disease caused by a deficiency of N‐acetylgalactosamine‐4‐sulfatase, also called arylsulfatase B (ARSB, EC 3.1.6.12). Dogs with MPS VI show progressive predominantly oculoskeletal signs homologous to those in human and feline patients. We report herein two pathogenic ARSB gene variants in Miniature Pinscher and Miniature Schnauzer dogs with MPS VI and a genotyping survey in these breeds. All exons and adjacent regions of the ARSB gene were sequenced from three affected Miniature Pinschers and three affected Miniature Schnauzers. Allelic discrimination assays were used for genotyping. A missense variant (NM_001048133.1:c.910G>A) was found in exon 5 of MPS VI‐affected Miniature Pinschers that is predicted to result in a deleterious amino acid substitution of a highly conserved glycine to arginine (NP_001041598.1:p.Gly304Arg). In MPS VI‐affected Miniature Schnauzers, a 56 bp deletion (NM_001048133.1:c.‐24_32del) was found at the junction of exon 1 and its upstream region, predicting no enzyme synthesis. All clinically affected Miniature Pinschers and Miniature Schnauzers were homozygous for the respective variants, and screened healthy dogs in each breed were either heterozygous or homozygous for the wt allele. Whereas the Miniature Pinscher variant seemed to occur commonly (0.133 allele frequency), the Miniature Schnauzer variant was presumed to be rare. In conclusion, two breed‐specific pathogenic ARSB gene variants were identified in Miniature Pinscher and Miniature Schnauzer dogs with MPS VI, allowing for genotyping and informed breeding to prevent the production of affected offspring.