Nonsense variant in COL7A1 causes recessive dystrophic epidermolysis bullosa in Central Asian Shepherd dogs

Abstract

A rare hereditary mechanobullous disorder called epidermolysis bullosa (EB) causes blistering in the skin and the mucosal membranes. To date, nineteen EB-related genes have been discovered in human and other species. We describe here a novel EB variant in dogs. Two newborn littermates of Central Asian Shepherd dogs with severe signs of skin blistering were brought to a veterinary clinic and euthanized due to poor prognosis. In post-mortem examination, the puppies were shown to have findings in the skin and the mucosal membranes characteristic of EB. A whole-genome sequencing of one of the affected puppies was performed to identify the genetic cause. The resequencing data were filtered under a recessive model against variants from 31 other dog genomes, revealing a homozygous case-specific nonsense variant in one of the known EB-causing genes, COL7A1 (c.4579C>T, p.R1527*). The variant results in a premature stop codon and likely absence of the functional protein in the basement membrane of the skin in the affected dogs. This was confirmed by immunohistochemistry using a COL7A1 antibody. Additional screening of the variant indicated full penetrance and breed specificity at ~28% carrier frequency. In summary, this study reveals a novel COL7A1 variant causing recessive dystrophic EB and provides a genetic test for the eradication of the disease from the breed.

Clinically Relevant Correction of Recessive Dystrophic Epidermolysis Bullosa by Dual sgRNA CRISPR/Cas9-Mediated Gene Editing

“…Immunoperoxidase detection of C7 in paraffin-embedded, formalin-fixed sections was carried out with proteinase K antigen retrieval as described. 36 Immunoperoxidase staining for human involucrin and p63 was performed using rabbit SY5 monoclonal antibody (Sigma) and 4A4 monoclonal antibody, respectively, on paraffin sections without antigen retrieval. The ABC peroxidase kit (Vector Laboratories) was used for immunohistochemical detection.…”

A COL7A1 Variant in a Litter of Neonatal Basset Hounds with Dystrophic Epidermolysis Bullosa

“…Thus, we suspect that the collagen VII alpha 1 chain, the protein product of COL7A1, is not produced in affected puppies. While this specific variant appears to be unique to this family of puppies, a nonsense variant that resulted in PTC and absence of functional collagen VII alpha 1 chains caused similar lesions in Central Asian Shepherd dogs diagnosed with recessive DEB [14].…”

“…Given the constellation of gross and microscopic lesions, age of onset, and multiple instances of inbreeding in the pedigree, EB was our top differential diagnosis. Our finding of a homozygous, candidate-causative variant in COL7A1 likely leading to a lack of collagen VII production in all three puppies is compatible with DEB, as this gene has multiple documented variants known to cause human DEB [1][2][3][4][5][6][7][8], and is found in two other canine cases of DEB [14][15][16].…”

“…In dogs, cases of putative EBS, JEB, and DEB have been described, although fewer subtypes and genetic variants than in humans have been recognized [9][10][11][12][13][14][15][16][17][18]. A recent case report of recessive DEB in two neonatal Central Asian Shepherd siblings found a homozygous nonsense variant of COL7A1 that resulted in a premature stop codon, likely preventing the production of functional protein [14] (OMIA 000341-9615). A mild, recessive form of DEB in a family of Golden Retrievers was identified, and genetic analysis found a homozygous missense variant, p.Gly1906Ser, in COL7A1 [15,16].…”

A de novo mutation in KRT5 in a crossbred calf with epidermolysis bullosa simplex

“…4 In human medicine, EB is associated with more than 1000 variants in at least 18 genes encoding structural proteins. 1,5 Four EB-related causative recessive variants are known in cattle, [6][7][8][9] 3 in dogs, [10][11][12][13] 2 in sheep, 14,15 and 2 in horses, [16][17][18][19] and 1 dominant variant is known in cattle 20 (Table S1). For cattle, a dominant form of EBS is associated with a keratin 5 (KRT5) missense variant (OMIA 002081-9913), 20 and recessive forms of JEB are associated with deleterious variants in ITGB4 (OMIA 001948-9913), LAMA3…”