CENPF and Bardet-Biedl syndrome: We did not detect recessive CENPF mutations in any of the MKS, NPHP, JBTS or BBS families, and because of the small sample size, we were unable to conclude that the heterozygous mutations in CENPF detected in BBS pedigrees act as phenotypical modifiers as has been described for other ciliopathy disease genes (see online supplementary table S5).