Background: The cat has one common blood group with two major serotypes, blood type A that is dominant to type B. A rare type AB may also be allelic and is suspected to be recessive to A and dominant to B. Cat blood type antigens are defined, N-glycolylneuraminic acid (NeuGc) is associated with type A and N-acetylneuraminic acid (NeuAc) with type B. The enzymecytidine monophospho-N-acetylneuraminic acid hydroxylase(CMAH) determines the sugar bound to the red cell by converting NeuAc to NeuGc. Thus, mutations inCMAHmay cause the A and B blood types.Results: Genomic sequence ofCMAHfrom eight cats and the cDNA of four cats representing all blood types were analyzed to identify causative mutations. DNA variants consistent with the blood types were genotyped in over 200 cats. Five SNPs and an indel formed haplotypes that were consistent with each blood type.Conclusion: Mutations in type B cats likely disrupt the gene function ofCMAH, leading to a predominance of NeuAc. Type AB concordant variants were not identified, however, cDNA species suggest an alternative allele that activates a downstream start site, leading to a CMAH protein that would be altered at the 5' region. The cat AB blood group system is proposed to be designated by three alleles,A>a^ab>b. TheAandb CMAHalleles described herein can distinguish type A and type B cats without blood sample collections.CMAHrepresents the first blood group gene identified outside of non-human primates and humans.

The reduced cost and improved efficiency of whole genome sequencing (WGS) is drastically improving the development of cats as biomedical models. Persian cats are models for Leber’s congenital amaurosis (LCA), the most severe and earliest onset form of visual impairment in humans. Cats with innocuous breed-defining traits, such as a bobbed tail, can also be models for somite segmentation and vertebral column development. The first WGS in cats was conducted on a trio segregating for LCA and the bobbed tail abnormality. Variants were identified using FreeBayes and effects predicted using SnpEff. Variants within a known haplotype block for cat LCA and specific candidate genes for both phenotypes were prioritized by the predicted variant effect on the proteins and concordant segregation within the trio. The efficiency of WGS of a single trio of domestic cats was evaluated. A stop gain was identified at position c.577C > T in cat AIPL1, a predicted p.Arg193*. A c.5A > G variant causing a p.V2A was identified in HES7. The variants segregated concordantly in a Persian – Japanese bobtail pedigree. Over 1700 cats from 40 different breeds and populations were genotyped for the AIPL1 variant, defining an allelic frequency in only Persian –related breeds of 1.15 %. A sub-set of cats was genotyped for the HES7 variant, supporting the variant as private to the Japanese bobtail breed. Approximately 18 million SNPs were identified for application in cat research. The cat AIPL1 variant would have been considered a high priority variant for evaluation, regardless of a priori knowledge from previous genetic studies. This study represents the first effort of the 99 Lives Cat Genome Sequencing Initiative to identify disease - causing variants in the domestic cat using WGS. The current cat reference assembly is efficient for gene and variant identification. However, as the feline variant database improves, development of cats as biomedical models for human disease will be more efficient, providing an alternative, large animal model for drug and gene therapy trials. Undiagnosed human patients with early-onset blindness should be screened for this AIPL1 variant. The HES7 variant should further calibrate the somite segmentation clock.

Dogs exhibit a wide variety of coat color types, and many genes have been identified that control pigment production, appearance, and distribution. Some breeds, such as the Nova Scotia Duck Tolling Retriever (NSDTR), exhibit variation in pheomelanin pigment intensity that is not explained by known genetic variants. A genome-wide association study comparing light red to dark red in the NSDTR identified a significantly associated region on canine chromosome 15 (CFA 15:23 Mb–38 Mb). Coverage analysis of whole genome sequence data from eight dogs identified a 6 kb copy number variant (CNV) 152 kb upstream of KITLG. Genotyping with digital droplet PCR (ddPCR) confirmed a significant association between an increased copy number with the dark-red coat color in NSDTR (p = 6.1 × 10⁻⁷). The copy number of the CNV was also significantly associated with coat color variation in both eumelanin and pheomelanin-based Poodles (p = 1.5 × 10⁻⁸, 4.0 × 10⁻⁹) and across other breeds. Moreover, the copy number correlated with pigment intensity along the hair shaft in both pheomelanin and eumelanin coats. KITLG plays an important role in melanogenesis, and variants upstream of KITLG have been associated with coat color variation in mice as well as hair color in humans consistent with its role in the domestic dog.

A 12-week-old domestic cat presented at a local veterinary clinic with hypocalcemia and skeletal abnormalities suggestive of rickets. Osteomalacia (rickets) is a disease caused by impaired bone mineralization leading to an increased prevalence of fractures and deformity. Described in a variety of species, rickets is most commonly caused by vitamin D or calcium deficiencies owing to both environmental and or genetic abnormalities. Vitamin D-dependent rickets type 1A (VDDR-1A) is a result of the enzymatic pathway defect caused by mutations in the 25-hydroxyvitamin D ₃ -1-alpha-hydroxylase gene [ cytochrome P27 B1 ( CYP27B1 )]. Calcitriol, the active form of vitamin D ₃ , regulates calcium homeostasis, which requires sufficient dietary calcium availability and correct hormonal function for proper bone growth and maintenance. Patient calcitriol concentrations were low while calcidiol levels were normal suggestive of VDDR-1A. The entire DNA coding sequencing of CYP27B1 was evaluated. The affected cat was wild type for previously identified VDDR-1A causative mutations. However, six novel mutations were identified, one of which was a nonsense mutation at G637T in exon 4. The exon 4 G637T nonsense mutation results in a premature protein truncation, changing a glutamic acid to a stop codon, E213X, likely causing the clinical presentation of rickets. The previously documented genetic mutation resulting in feline VDDR-1A rickets, as well as the case presented in this research, result from novel exon 4 CYP27B1 mutations, thus exon 4 should be the initial focus of future sequencing efforts.

Altered melanosome transport in melanocytes, resulting from variants in the melanophilin (MLPH) gene, are associated with inherited forms of coat color dilution in many species. In dogs, the MLPH gene corresponds to the D locus and two variants, c.−22G > A (d¹) and c.705G > C (d²), leading to the dilution of coat color, as described. Here, we describe the independent investigations of dogs whose coat color dilution could not be explained by known variants, and who report a third MLPH variant, (c.667_668insC) (d³), which leads to a frameshift and premature stop codon (p.His223Profs*41). The d³ allele is found at low frequency in multiple dog breeds, as well as in wolves, wolf-dog hybrids, and indigenous dogs. Canids in which the d³ allele contributed to the grey (dilute) phenotype were d¹/d³ compound heterozygotes or d³ homozygotes, and all non-dilute related dogs had one or two D alleles, consistent with a recessive inheritance. Similar to other loci responsible for coat colors in dogs, this, alongside likely additional allelic heterogeneity at the D locus, or other loci, must be considered when performing and interpreting genetic testing.

Erythrocyte pyruvate kinase deficiency (PK deficiency) is an inherited hemolytic anemia that has been documented in the Abyssinian and Somali breeds as well as random bred domestic shorthair cats. The disease results from mutations in PKLR, the gene encoding the regulatory glycolytic enzyme pyruvate kinase (PK). Multiple isozymes are produced by tissue-specific differential processing of PKLR mRNA. Perturbation of PK decreases erythrocyte longevity resulting in anemia. Additional signs include: severe lethargy, weakness, weight loss, jaundice, and abdominal enlargement. In domestic cats, PK deficiency has an autosomal recessive mode of inheritance with high variability in onset and severity of clinical symptoms.