preaxial polydactyly type 2
Wednesday 21 July 2010
Pre-axial polydactyly type 2 (PPD2, MIM.174500), Werner mesomelic syndrome (MIM.188770) and Haas polysyndactyly (MIM #186200) are a group of closely related conditions caused by mutations in a long-range Sonic hedgehog (SHH, MIM.600725) regulator called ZRS.
To 2010, 19 point mutations, 10 duplications and 1 triplication of the ZRS associated with those pre-axial polydactylies have been reported in humans, mice, cats and chickens.
Some of these have been shown to cause ectopic expression of SHH in the limb bud in mice, leading to a polydactylous phenotype, but the precise mechanism by which ZRS mutations generate this phenotype remains unknown.