Categories: Pigmentation phene

Mendelian trait/disorder: yes

Mode of inheritance: Autosomal recessive

Disease-related: no

Key variant known: no

Mapping: Via a GWAS involving 172 control and 18 affected Holstein-Friesians, each genotyped with the Illumina BovineSNP50 BeadChip (yielding 44,952 informative SNPs), Hollman et al. (2017) mapped this disorder to a region of "bovine chromosome 8 (BTA8) spanning from 57.3 to 65.3 Mb", and "The SNP with the highest -log10(p) = 9.17 (BTB-00352779) was located at position 60,990,733 (NCBI UMD3.1.1)". The absence of any sign of association with loci on BTA29 (plus strategic sequencing) ruled out variants of the RAG38 gene, which is causal for a very similar trait in Angus and Simmental (see OMIA 002101-9913).

Markers: In an analysis including an additional 316 Holstein Friesian cattle, Hollman et al. (2017) "showed that allele A at position 60,990,733 on BTA8 (P = 4.0e–08, odds ratio = 6.3, 95% confidence interval 3.02–13.17) significantly increased the chance of iridal hypopigmentation". This variant appears to not be located within any known coding sequence.

Clinical features: Hollman et al. (2017): "Summarizing the clinical analysis of the examined animals, a bilateral hypopigmentation caused by a hitherto unknown genetic variation strictly affecting iridal coloration was suspected. As the affected animals did not show any other anomalies, syndromes like Chediak-Higashi or Tietz were excluded."

Breed: Holstein Friesian (Cattle) (VBO_0000239).
Breeds in which the phene has been documented. (If a likely causal variant has been documented for the phene, see the variant table breeds in which the variant has been reported).