Fig 1.
Congenital neuromuscular disorder in a Sphynx kitten.
Picture of the four-month-old Sphynx female kitten presented at the Neurology clinics located at the Alfort School of Veterinary Medicine campus, in Maisons-Alfort, France. The kitten displayed a peculiar gait while walking, with ventroflexion of her neck. Note the marked dorsal protrusion of scapulae. No significant muscle atrophy was noticed.
Fig 2.
Histological and histochemical features of the disease.
Cryosections (6 μm) of cervical muscle from a four-month-old affected Sphynx kitten (A-C) and from her healthy littermate (D-F). Haematoxylin-eosin staining (A, D) showed a wide range of fibre size with more rounded fibres surrounded by a thicker endomysium in the affected kitten (A) compared to the healthy control (D). No internal nuclei were present on both sections. Myosin adenosine triphosphatase isoforms (ATPase activity at pH 9.4, B and E) showed a slight increase in pale type-1 fibres in the affected kitten (B) compared to the healthy control (E) but no fibre-type aggregation. Motor end-plates were labelled with alpha-bungarotoxin (for acetylcholine receptors AchR; C and F insets; green) and esterase activity (for AchE; C, F; brown stain). Muscle nuclei were stained with Dapi (C and F insets; blue). Sections from the healthy littermate (F) showed a perfect colocalization of compacted AchR (green) and AchE (brown). In contrast, sections from the affected cat showed a faint, abnormally dispersed AchE staining in myofibres with normal clusters of AchR (C).
Fig 3.
Pedigree-tree of a Sphynx cat family segregating a neuromuscular disorder.
Circles represent females, squares represent males. Affected kittens are depicted with fully filled symbols and the proband shown with an arrow. Healthy carriers are depicted with two-toned symbols. Red symbols represent the seven cats from the nuclear family used to map the disease locus; blue symbols represent the four healthy siblings of the proband and the 16 healthy cats directly related to the sire; black symbols represent cats from the extended family. When available, result of the genotyping assay for the c.1190G>A variant is mentioned. The Devon Rex female born in 1990 and known by breeders to have several myopathy healthy carriers in her pedigree is shown (Devon Rex).
Fig 4.
Genotypes for chromosome C2 candidate region.
SNP genotypes for each cat were manually inspected in Excel to identify homozygous regions shared by the two affected cats. Only one region from chromosome C2 spanning from position 137108027 bp to position 140984522 bp (according to the updated felCat5 SNP manifest for the Illumina Feline 63k SNP genotyping array, [20]) was consistent with the highly-probable heterozygous status of the sire and dam, the non-homozygously mutated status of the proband’s healthy littermate and the inferred heterozygous status of the paternal grandmother. This region encompassed 3.9 Mb. Homozygosity for the allele shared by the affected sib-pair is shown in light green. Heterozygosity or homozygosity for the opposite allele is shown in yellow. Missing genotypes are noticed 0. Chr: chromosome. bp: base pairs.
Table 1.
Genotypes for the c.1190G>A variant in affected cats and unaffected relatives.
Table 2.
Genotypes for the c.1190G>A variant in 14 breeds of cats.
Fig 5.
Wild-type and mutant C-terminal domains of COLQ proteins.
Alignment of partial protein sequences of COLQ, translated from the c.[1190G>A] mutated allele identified in affected Sphynx and Rex Devon cats (Felis MUT) or wild-type alleles reported in human (Homo), mouse (Mus), cow (Bos), chicken (Gallus), xenopus (Xenopus), zebrafish (Danio), fugu (Taxifugu) and cat (Felis WT). The cysteine-rich domain of the C-terminal end of the protein starts with amino acid number 375 in human and cat proteins and ends with amino acid number 451 (according to [10]). Human COLQ sequence was used as the reference sequence. Conserved residues are written in red within the reference sequence and represented by red dots in other sequences. Dashes represent deletions. Arrows point out the ten conserved cysteine residues. Cysteine 397, mutated in affected cats (C397Y), is surrounded in blue.