This family of proteins is domain of unknown function, which is found in eukaryotes. However, mutations in the gene lead to Joubert's Syndrome, indicating that the protein that the gene encodes for is vital for correct ciliogenesis[1].

1: Mutations in C5ORF42 cause Joubert syndrome in the French Canadian population. Srour M, Schwartzentruber J, Hamdan FF, Ospina LH, Patry L, Labuda D, Massicotte C, Dobrzeniecka S, Capo-Chichi JM, Papillon-Cavanagh S, Samuels ME, Boycott KM, Shevell MI, Laframboise R, Desilets V, Maranda B, Rouleau GA, Majewski J, Michaud JL; Am J Hum Genet. 2012;90:693-700. PMID:22425360