Fig 1.
The macroscopic changes of epidermolysis bullosa in the affected puppy.
(A) Large erupted blisters were present on the nasal plane, lips and dorsal skin of the front paws. (B) Large intact and erupted blisters were also present in the inner ear lobe. (C) Numerous intact bullae were found on the digital pads and the erupted blisters of metacarpal and carpal pads resulted in the formation of large ulcers.
Fig 2.
Histological stainings of the haired skin of the inner ear lobe by periodic acid–Schiff (PAS).
(A) Small vacuoles at the basement membrane (arrowheads) (63X). (B) Larger, confluent vacuoles result in a split along the basement membrane zone (arrowheads) (63X). (C) Large subepidermal cleft with PAS-positive material, suggestive of basement membrane, on the roof and floor of the cleft and strands crossing the bulla (arrows) (20X). Epidermis is denoted with “E” and dermis with “D”.
Fig 3.
A pedigree of the affected puppies with a suspected recessive mode of inheritance.
The COL7A1 variant genotype is denoted for individuals that were tested. White symbol denotes wild type (C/C), half-filled heterozygous carrier (C/T) and black symbol homozygous mutant (T/T), while grey denotes that no sample was available for testing. The whole genome was sequenced from the affected dog surrounded with a square.
Fig 4.
Chromatograms of the COL7A1 c.4579C>T variant and a schematic representation of the collagen VII protein.
(A) Three genotypes are present in the Central Asian Shepherd Dog cohort: wild type C/C, heterozygous carrier C/T and homozygous mutant T/T. The mutation causes a change from arginine (CGA) to a stop codon (TGA). (B) The domain structure of collagen VII. The substitution site p.R1527* is located near the beginning of the characteristic triple-helical domain. (C) A schematic presentation of the dimerization of collagen VII homotrimers. If the abnormal COL7A1 is translated the p.R1527* substitution results in severe truncation of the protein, preventing the dimerization of collagen VII at the C-terminal end.
Table 1.
Summary of the unaffected control dogs used in the whole-genome variant filtering study.
Table 2.
Summary of study cohorts used in the COL7A1 c.4579C>T variant screening.
Fig 5.
Immunohistochemical staining for collagen VII.
(A) The basement membrane zone between the epidermis and dermis is positive for collagen VII in the haired skin of the flank of an unaffected control. (100X) (B) The basement membrane zone between the intact epidermis and dermis and the roof and floor of the vacuoles during early cleft formation are negative for collagen VII in the haired skin of the inner ear lobe of an affected puppy (100X). Epidermis is denoted with “E” and dermis with “D”.