Impact of missense mutations in recessive Mendelian disease: insight from ciliopathies (360G-Wellcome-210585_C_18_Z)

Background: Over 1,800 autosomal recessive (AR) Mendelian-disease genes have been identified. Missense mutations account for 59% of protein coding region mutations, yet their precise functional effects remain largely uncharacterized. Two important questions in human genetics aim to explain interindividual variation in phenotypic severity and assign pathogenic mechanisms to different disease phenotypes (including independent phenotypes within the same syndrome). For AR disorders, it is thought that many missense mutations cause protein instability. For these hypomorphic mutations, disease phenotypes are defined according to quantitative genetic threshold effects within a protein interaction network. Project: We will focus on a subset of AR ciliopathies which are strongly enriched for missense mutations, where complete gene knockout is thought to be lethal (see Rationale-below). We will use gene-editing and quantitative protein-protein interaction analyses to systematically compare the phenotypic effects of frameshift (likely knockout/null) and missense mutations. We will test our hypothesis that these missense mutations disrupt only a subset of gene functions/protein interactions, using phenomics algorithms we have developed and unbiased phenotyping in cell lines and mouse models, allowing us to assign pathogenic mechanisms to disease phenotypes. In future, this approach could be extended to the estimated 10-20% of > 3,000 Mendelian-disorders enriched for missense mutations.