Ears, crop

Phene ID

578

Name

Ears, crop

Phene Name

Notched ears; Nicked ears

OMIA ID

317

Species ID

9913

Characterised

Yes

Characterised Year

2013

Koch et al. (2013) suggested the following nomenclature: CE-0 for homozygous wild type; CE-1 for heterozygotes; and CE-2 for homozygous duplication.

In the original report, Yamane (1915) provided pedigree evidence that implied Mendelian inheritance. Later reports (Wriedt, 1925; MacDonald, 1957; Scheider et al., 1994) were consistent with autosomal dominance with variable expressivity (suggestive of a multifactorial underlying trait, with one gene of large effect). Koch et al. (2013) reached the same conclusion from a pedigree analysis, and were able to trace all cases back to a single bull born in 1943.

Among the 64 genes in the mapped region (see Mapping section), Koch et al. (2013) reported that HMX1 (which encodes a transcription factor) stood out as a "striking functional [comparative] candidate" (based on known mutations in humans, mice and rats). Whole-genome sequencing of a severely affected cow (assumed to be homozygous) revealed "6 non-synonymous DNA variants within the two coding exons of HMX1 and two structural variants within the downstream highly conserved region". Genotyping by sequencing in other animals excluded all but one of the structural variants, namely a 76bp duplication (Copy Number Variant; CNV), which was confirmed as the causal mutation by subsequent genotyping in 40 affecteds and 80 control Highland cattle, as well as in 144 cattle from a range of other breeds. As reported by Koch et al. (2013), "The affected ultra-conserved enhancer is located 148 kb apart of the coding region of HMX1 . . . . The sequence of the 76 bp duplication is highly conserved . . . . In silico prediction revealed several transcription factor binding sites indicating the potential functional relevance of this region".