C2CD3 and Down syndrome: The C2CD3 ortholog in humans is in the HSA11q13.4 chromosomal region, in close proximity to the critical regions for other human ciliopathies, including Meckel-Gruber syndrome 2 (MKS; 603194), Joubert syndrome 2 (JBTS2; 608091) and Nephronophthisis 15 (NPHP15; 614845) (Roume et al., 1998; Hoover et al., 2008; Valente et al., 2010).