YARS2 Missense Variant in Belgian Shepherd Dogs with Cardiomyopathy and Juvenile Mortality

Abstract

Dog puppy loss by the age of six to eight weeks after normal development is relatively uncommon. Necropsy findings in two spontaneously deceased Belgian Shepherd puppies indicated an abnormal accumulation of material in several organs. A third deceased puppy exhibited mild signs of an inflammation in the central nervous system and an enteritis. The puppies were closely related, raising the suspicion of a genetic cause. Pedigree analysis suggested a monogenic autosomal recessive inheritance. Combined linkage and homozygosity mapping assigned the most likely position of a potential genetic defect to 13 genome segments totaling 82 Mb. The genome of an affected puppy was sequenced and compared to 645 control genomes. Three private protein changing variants were found in the linked and homozygous regions. Targeted genotyping in 96 Belgian Shepherd dogs excluded two of these variants. The remaining variant, YARS2:1054G>A or p.Glu352Lys, was perfectly associated with the phenotype in a cohort of 474 Belgian Shepherd dogs.YARS2 encodes the mitochondrial tyrosyl-tRNA synthetase 2 and the predicted amino acid change replaces a negatively charged and evolutionary conserved glutamate at the surface of the tRNA binding domain of YARS2 with a positively charged lysine. Human patients with loss-of-function variants in YARS2 suffer from myopathy, lactic acidosis, and sideroblastic anemia 2, a disease with clinical similarities to the phenotype of the studied dogs. The carrier frequency was 27.2% in the tested Belgian Shepherd dogs. Our data suggest YARS2:1054G>A as the candidate causative variant for the observed juvenile mortality.

Keywords: Canis lupus familiaris; Groenendael; Laekenois; Malinois; Tervueren; animal model; mitochondrium; precision medicine; translation; whole genome sequence.

Figure 1

Histopathology of the heart. (A) Cardiomyocytes of an affected puppy are swollen and pale, and the sarcoplasm around the nucleus is dispersed (arrow) by finely granular material, hematoxylin and eosin (HE) stain. (B) Normal, smaller, and more intense staining of cardiomyocytes of a 5-week-old control puppy, HE stain.

Figure 2

Pedigree of the three investigated cases. Filled symbols represent puppies deceased by the age of six to eight weeks. Open symbols represent unaffected animals. Genotypes at YARS2:c1054G>A are indicated for all dogs, from which a DNA sample was available. The grey rectangle indicates the five dogs included in linkage and homozygosity analysis.

Figure 3

Details of the YARS2:p.Glu352Lys variant. (A) Representative Sanger electropherograms of a control, a carrier, and an affected dog illustrate the c.1054G>A variant. The amino acid translations are shown. (B) Evolutionary conservation. The glutamate at position 352 is highly conserved across all eukaryotes. (C) Three-dimensional structure of the human YARS2 protein in complex with an adenylate homolog [16,17,18]. The position of Glu352 is indicated in the right monomer. (D) Enlarged details of the structure in a space-filling model. The negatively charged carboxyl group of Glu352 is located at the surface of the tRNA binding domain.