Genotype–phenotype correlations have been proposed for ciliopathy genes such as TMEM67, in which two loss-of-function mutations were found to cause MKS while the presence of at least one hypomorphic mutation resulted in non-lethal phenotypes.43 However, this is not obvious for CEP120, as the MKS fetus (MKS-2930) was homozygous for a missense mutation, while at least one JS patient (MTI-991) carried a splice-site mutation that was shown to introduce a premature stop codon in part of the product. The gene discussed is TMEM67; the disease is Meckel syndrome, type 1.