In other species: chicken

Possibly relevant human trait(s) and/or gene(s)s (MIM numbers): 119800 (trait) , 186550 (trait) , 602149 (gene)

Mendelian trait/disorder: yes

Considered a defect: no

Key variant known: yes

Year key variant first reported: 2016

Inheritance: As summarised by Domyan et al. (2016), "Classical studies in pigeon suggest two major-effect loci – grouse (gr) and Slipper (Sl) – are responsible for most of the variation in foot feathering (Doncaster, 1912; Wexelsen, 1934; Hollander, 1937; Levi, 1986). Through a combination of genetic, genomic, and developmental approaches, our data implicate regulatory mutations in the limb outgrowth and identity genes Pitx1 and Tbx5 as the molecular identities of the gr and Sl locus, respectively".

Mapping: Domyan et al. (2016) "identified [2 major QTL] in two linkage groups (LG11 and LG20) that had significant effects on three different aspects of foot feathering". In addition, using "probabilistic whole-genome scans of allele frequency differentiation across a genetically and phenotypically diverse panel of breeds by comparing 15 feather-footed birds (4 groused and 11 muffed) to 28 scale-footed birds", the same authors showed that the region corresponding to LG11 includes a 44kb deletion adjacent to the Pitx1 gene, and that the LG20 region includes the Tbx5 gene. As these authors noted, "These regions were especially intriguing because these two genes encode key transcriptional regulators of forelimb (Tbx5) and hindlimb (Pitx1) identity and development".

Molecular basis: Domyan et al. (2016) "found that feathered feet in pigeons result from a partial transformation from hindlimb to forelimb identity mediated by cis-regulatory changes in the genes encoding the hindlimb-specific transcription factor Pitx1 (this entry) and forelimb-specific transcription factor Tbx5" (see OMIA 000839-8932). These same authors reported that the QTL in LG20 (in which the gene Pitx1 resides) "contained a 44-kb deletion (from 6.719–6.763 Mb) that was homozygous in 10, and heterozygous in 2 of the 15 feather-footed birds". In other words, Domyan et al. (2016) reported a deletion variant for feathered shank that is very near to the gene Pitx1.

Associated gene: