GRB2 and Huntington disease: Of these only 6 were known to be differentially expressed in HD [12,13] and only 3 have binding sites within 1Kb DNA sequence upstream to Grb2. Combining these two selection criteria, only Foxd3 and HNF-3beta/Foxa2 came out to be two probable candidates for the regulation, of which Foxd3was chosen for our study.