Phenotypes

To date, all cases of this lethal disorder in cattle appear to be due to the same mutation, namely a nonsense mutation in the 5th of 9 exons of the ASS gene. Normal bovine ASS is a peptide containing 412 amino acids; the mutation occurs in the 86th codon.

Exome sequencing by Sasaki et al. (2016) within the candidate region (see Mapping section) revealed a likely causal missense variant: g.62382825G > A, p.Pro372Leu) in exon 10 of solute carrier family 12, member 1 (SLC12A1).

By cloning and sequencing a very likely comparative candidate gene (based on the same disorder in humans), Shuster et al. (1992; PNAS) showed that this disorder in Holstein cattle is due to a missense mutation (c.383A>G) in the CD18 gene, now known as ITGB2. This mutation was confirmed in Daetwyler et al. (2014)'s analysis of whole-genome sequence data from 234 cattle, including key ancestors of the Holstein-Friesian, Fleckvieh and Jersey b...

Building on the mapping results of Kobayashi et al. (2000) (see Mapping section above), Hirano et al. (2000) did some further fine mapping, and then constructed a cosmid library of the fine-mapped region of BTA1, and then used the best cosmid clone as a probe of kidney cDNA from normal and affected animals, identifying a single cDNA, which, when sequenced, turned out to be the bovine paracellin-1 gene, which they called Claudin-16, and which l...

By sequencing a strong positional candidate gene, namely TWIST1, Capitan et al. (2011) identified a small duplication (c.148_157dup (p.A56RfsX87)) that inactivates the gene. This frameshift mutation segregates perfectly with type 2 scurs.