HAND1 and heart disorder: These included: (1) Hrt2/Hey2, a member of the Hairy family of transcriptional repressors that mediates Notch signalling, which can itself cause heart disease [64]; and (2) Hand1, a bHLH transcription factor involved in ventricular development and septation that, in combination with Hand2 (a paralog of Hand1), is known to regulate expansion of the embryonic cardiac ventricles in a gene dosage-dependent manner [65].