Exploring the genetics of nephronophthisis and Joubert Syndrome…more than monogenic cystic renal diseases?!

摘要

BackgroundUnderstanding the pathogenesis of the autosomal recessivecystic kidney disease, nephronophthisis (NPHP) remains achallenge. NPHP is associated with extra-renal disease in10-15%, including abnormal eye and cerebellar development,this combination of problems is called Joubert Syndrome,JS. NPHP and JS are ciliopathies because theencoded proteins of all mutated genes are found in primarycilia/associated architecture. NPHP and JS are geneticallyheterogenous, with mutations in a single gene such asNPHP6, AHI1 or CC2D2A being sufficient to cause disease.Although homozygous mutations are identified in mostcases, some patients have an additional heterozygous mutationin another gene, leading to hypotheses of epistasismodifying the clinical phenotype.ObjectivesWe aim to use zebrafish, in whom nphp6, ahi1 and cc2d2aare highly conserved, as a model organism, to evaluatepotential genetic interactions and the influence this mayhave on the development of NPHP and JS.MethodsSplice blocking antisense morpholino oligonucleotides(MOs) directed towards nphp6, ahi1 and cc2d2a wereinjected individually, and in combination, into 1-4 cellstage wild type zebrafish embryos. Embryos were phenotypedusing light microscopy at 72 hours post fertilisation(hpf).ResultsEach MO individually induces a morphant phenotypeincluding curly tail, cardiac oedema, hydrocephalus,pronephric cysts, abnormal eye and ear development.Co-injection of low dose ahi1 and nphp6 MOs or ahi1 andcc2d2a MOs leads to synergy of the morphant phenotypes.ConclusionThe synergistic increase in the morphant phenotype followingcombined knockdown of ahi1 and nphp6 or ahi1and cc2d2a in zebrafish implicates a genetic interaction.