CCND2 and polydactyly: Individuals with elevated cyclin D2 as a result of cyclin D2 mutation rather than activating mutations in the PI3 K–AKT–GSK3β pathway have an increased incidence of polydactyly, suggesting that characteristics of the cyclin D2 overexpression phenotype might also result from a potential role in regulating a programme of gene expression as well as promoting the aberrant expansion of neural precursors.