SHH and holoprosencephaly: We next investigated the potential influence of GAS1-mediated Hedgehog signaling during human dental development by examining the permanent dentition of 3 subjects identified with pathogenic mutations at the GAS1 (n = 2) or SHH/GAS1 loci (n = 1) and features within the clinical spectrum of Holoprosencephaly (HPE), comparing them to population-matched controls (n = 4) (Ribeiro et al. 2010).