The variant leading to PPD I may be associated with enhancing SHH expression mediated by HnRNP K. This study adds to the ZRS-associated syndromes classification system for PPD and clarifies the underlying molecular mechanisms.
The etiology of this PPD family still remains unclear and the question whether another limb-specific regulatory element of shh gene exists in the noncoding region in this 1.7 cM interval remains open for future research.
Point mutations in the long-range, limb-specific regulatory element of the SHH gene are responsible for the human limb abnormality called preaxial polydactyly (PPD).