Categories: Skeleton phene (incl. short stature & teeth)

Links to possible relevant human trait(s) and/or gene(s) in OMIM: 262500 (trait) , 604271 (trait) , 600946 (gene)

Mendelian trait/disorder: yes

Mode of inheritance: Z-linked recessive

Disease-related: yes

Key variant known: yes

Year key variant first reported: 1994

Species-specific symbol: dw

Species-specific description: Unlike the other forms of dwarfism that occur in chickens, this form appears to have commercial value. It is due to a range of mutations in the gene for the growth-hormone receptor, which is on the Z chromosome. In at least one strain of broilers, the mutation is a deletion. In one strain of Leghorn layers, a deletion is not the cause. Several broiler-breeder lines homozygous for dw have been developed. These dw lines are used as a source of female parents which are mated to males from a normal broiler strain. Mainly because of reduced feed consumption and a smaller space requirement, dw broiler-breeder lines are more economical than normal broiler lines.

Molecular basis: By cloning and sequencing a very likely comparative candidate gene (based on the homologous human disorder), Agarwal et al. (1994) discovered a deletion of 1773 bp in the 3' end of the coding region of the growth hormone receptor gene in the Connecticut (CT) strain of dwdw chickens. The region included in the deletion encodes 27 highly conserved amino acids and the stop codon. In the dw allele, the sequence of bases 3' of the deletion is such that the open reading frame extends to encode 27 new amino acids plus a further 26 amino acids, before reaching the transcription termination site. This mutant allele produces a novel peptide which is unable to fulfil the role of normal growth hormone receptor.

Associated gene: