Restoration of renal function in zebrafish models of ciliopathies

Abstract

The ciliopathies are a class of rare human genetic disease whose aetioligies lie in defective primary cilia. Typical ciliopathies include Bardet-Biedl syndrome (BBS), nephronophthisis (NPHP), Jeune, Joubert, oro-facial-digital (OFD1) and Meckel (MKS) syndromes. All ciliopathies have the common denominator of renal disease, often including tubular cysts. In this study, we have modelled a range of ciliopathies in zebrafish and shown in all cases that knocking down these genes causes cystic lesions in the kidney. We have identified two drugs, rapamycin and roscovitine, which ameliorate the renal phenotype, both morphologically and functionally. This is the first study in which zebrafish has been used to identify potential therapeutic modalities for ciliopathic renal disease, and the results pave the way for further investigations in mammalian models.

Mechanistic insights into Bardet-Biedl syndrome, a model ciliopathy

“…From a pharmacological perspective, one would predict that an organspecific approach might prove useful. Indeed, the rapamycin treatment of the zebrafish cystic BBS model (98) suggests that mTOR targeting might be of therapeutic benefit. However, it is unclear whether, and probably unlikely that, this approach will be useful in postmitotic tissues, such as the brain and the retina.…”

“…Compelling evidence implicating BBS proteins in kidney phenotypes was exhibited with the formation of kidney cysts in bbs zebrafish morphants (98). Interestingly, the cyst phenotype could be rescued by culturing embryos in a solution containing the mTOR signaling inhibitor rapamycin (98). These findings provide support for a possible role for pathways upstream of mTOR in the kidney phenotype, most notably the noncanonical Wnt planar cell polarity (PCP) pathway.…”

“…Bbs4-null mice display shorter renal tubule cilia initially, and these become longer over time, indicating a defect of either cilia assembly (97) or maintenance/regulation of ciliary length. Compelling evidence implicating BBS proteins in kidney phenotypes was exhibited with the formation of kidney cysts in bbs zebrafish morphants (98). Interestingly, the cyst phenotype could be rescued by culturing embryos in a solution containing the mTOR signaling inhibitor rapamycin (98).…”

Bardet–Biedl syndrome

“…56 The mTOR signalling inhibitor rapamycin rescues the renal cysts found in BBS zebrafish morphants, implicating the signalling pathways upstream of mTOR in BBS renal pathology. 57 Hyposmia/anosmia may be attributed to defective ciliated olfactory epithelium and subfertility in part to defective cilia in sperm cells/oviducts.…”

CaMK-II is a PKD2 target that promotes pronephric kidney development and stabilizes cilia

“…Renal filtration assays used tetramethylrhodamine dextran (70,000 MW; Invitrogen) injected into the pericardial sac of transiently anesthetized [0.003% Tricaine (MS-222); Sigma] 56 hpf zebrafish embryos as previously described (Tobin and Beales, 2008). Embryos were imaged within 20 minutes of injection and then again at 72 hpf.…”