Awasthi Mishra et al. (2017) reported a likely causal variant for this classic phene: "The belt-associated variant was a copy number variant (CNV) involving the quadruplication of a 6 kb non-coding sequence located approximately 16 kb upstream of the TWIST2 gene. Increased copy numbers at this CNV were strongly associated with the belt phenotype in a cohort of 333 cases and 1322 controls. We hypothesized that the CNV causes aberrant expression of TWIST2 during neural crest development, which might negatively affect melanoblasts. Functional studies showed that ectopic expression of bovine TWIST2 in neural crest in transgenic zebrafish led to a decrease in melanocyte numbers." In the first reported use of long-read (Oxford Nanopore) sequencing for investigating a single-locus trait in domestic animals, Rothammer et al. (2018) confirmed the quadruplication variant reported by Awasthi Mishra et al. (2017), and extended the number of breeds in which this variant occurs.
