In other species: domestic cat , sheep

Categories: Nervous system phene

Possibly relevant human trait(s) and/or gene(s) (MIM number): 612768 (gene)

Links to MONDO diseases: No links.

Mendelian trait/disorder: yes

Mode of inheritance: Autosomal recessive

Considered a defect: yes

Key variant known: yes

Year key variant first reported: 2014

Mapping: By conducting a GWAS on 84 Weimaraner dogs "(40 males and 44 females) of whom 14 were affecteds, 19 were known carriers, and 51 were unaffecteds", each genotyped with the Illumina CanineHD BeadChip (yielding 95,990 informative autosomal SNPs), Pemberton et al. (2014) mapped this disorder to a 5Mb region (57.3 to 62.3) on chromosome CFA15. Subsequent homozygosity mapping narrowed this to a 3.7Mb region (573. to 61.0).

Molecular basis: After sequencing the most obvious candidate gene in the candidate region (see Mapping section) and discovering no mutations, Pemberton et al. (2014) sequenced all 199 exons of the remaining 16 genes in that region, yielding 54 variants, only one of which had the potential to be deleterious. This variant turned out to be the causal mutation: "a deletion of a single A nucleotide within exon 9 of the gene encoding folliculin-interacting protein 2 (FNIP2). This mutation at nucleotide 880 of the coding sequence (c.880delA, XM_532705) causes a frameshift, and the amino acid sequence is altered beginning at codon 294, with a premature translation stop signal introduced at codon 296 . . . . A highly truncated protein of 295 amino acids compared with the wild-type protein of 1,106 amino acids is predicted to result from this p.Ile294fsX296 mutation"

Clinical features: Affected animals present with generalised tremors at about 2 to 3 weeks of age (Kornegay et al., 1987; Pemberton et al., 2014). Clinical signs gradually resolve in most dogs by 3 to 4 months of age (Kornegay et al., 1987; Pemberton et al., 2014), "though some dogs retained a persistent fine tremor of the hind limbs" (Pemberton et al., 2014). Pemberton et al. (2014) suggest that hyppomyelination previously described in Chow Chow dogs (Vandevelde and Braund, 1981; Vandevelde et al., 1978) is identical to the disease in Weimaraner dogs.

Pathology: Kornegay et al., (1987) "Many axons in the brain and spinal cord were either thinly myelinated or nonmyelinated in the affected dogs relative to the controls, while the peripheral nervous system was normally myelinated. The degree of hypomyelination seemed particularly severe at the periphery of the lateral and ventral funiculi of the spinal cord. In all areas of white matter evaluated, astrocytes subjectively outnumbered oligodendrocytes in the [affeted] Weimaraners ..."

Associated gene: