BBS Proteins Affect Ciliogenesis and Are Essential for Hedgehog Signaling, but Not for Formation of iPSC-Derived RPE-65 Expressing RPE-Like Cells.

Bardet-Biedl syndrome (BBS) is a ciliopathy characterized by retinal dystrophy, renal cysts, obesity and polydactyly. BBS genes have been implicated in ciliogenesis, hedgehog signaling and retinal pigment epithelium maturation. BBS1 and BBS5 are members of the BBSome, implicated in cilia transport of proteins, and BBS10 is a member of the chaperonin-complex, mediating BBSome assembly. In this study, involvement of BBS1, BBS5 and BBS10 in ciliogenesis and hedgehog signaling were investigated in BBS-defective patient fibroblasts as well as in RPE-hTERT cells following siRNA-mediated knockdown of the BBS genes. Furthermore, the ability of BBS1-defective induced pluripotent stem-cells (iPSCs) to differentiate into RPE cells was assessed. We report that cells lacking functional BBS5 or BBS10 have a reduced number of primary cilia, whereas cells lacking functional BBS1 display shorter primary cilia compared to wild-type cells. Hedgehog signaling was substantially impaired and Smoothened, a component of hedgehog signaling, was trapped inside the cilia of the BBS-defective cells, even in the absence of Smoothened agonist. Preliminary results demonstrated the ability of BBS1-defective iPSC to differentiate into RPE-65 expressing RPE-like cells. The BBS1-/--defective RPE-like cells were less pigmented, compared to RPE-like cells differentiated from control iPSCs, indicating an impact of BBS1 on RPE maturation.

Mutational analysis of TSC1 and TSC2 in Danish patients with tuberous sclerosis complex.

Tuberous sclerosis complex (TSC) is an autosomal dominant disorder characterized by hamartomas in the skin and other organs, including brain, heart, lung, kidney and bones. TSC is caused by mutations in TSC1 and TSC2. Here, we present the TSC1 and TSC2 variants identified in 168 Danish individuals out of a cohort of 327 individuals suspected of TSC. A total of 137 predicted pathogenic or likely pathogenic variants were identified: 33 different TSC1 variants in 42 patients, and 104 different TSC2 variants in 126 patients. In 40 cases (24%), the identified predicted pathogenic variant had not been described previously. In total, 33 novel variants in TSC2 and 7 novel variants in TSC1 were identified. To assist in the classification of 11 TSC2 variants, we investigated the effects of these variants in an in vitro functional assay. Based on the functional results, as well as population and genetic data, we classified 8 variants as likely to be pathogenic and 3 as likely to be benign.

Generation and characterization of three isogenic induced pluripotent stem cell lines from a patient with Bardet-Biedl syndrome and homozygous for the BBS5 variant.

Bardet-Biedl syndrome (BBS), an autosomal recessive disease, is associated with non-functional primary cilia. BBS5 is part of the protein complex termed the BBSome. The BBSome associates with intra flagellar transport (IFT) particles and mediates trafficking of membrane proteins in the cilium, a process important for cilia-mediated signal transduction. Here we describe the generation of three induced pluripotent stem cell (iPSC) lines, KCi003-A, KCi003-B and KCi003-C from a patient with BBS and homozygous for the disease causing variant c.214G>A, p.(Gly72Ser) in BBS5. The iPSC lines can be used for investigation of IFT in different cell types differentiated from the iPSC line.

Generation of induced pluripotent stem cells, KCi002-A derived from a patient with Bardet-Biedl syndrome homozygous for the BBS10 variant c.271insT.

Bardet-Biedl syndrome (BBS) is genetically heterogeneous with at least 21 genes involved, and BBS10 encodes, together with BBS6 and BBS12, chaperonin-like proteins which are important for the assembly of the multiprotein complex, the BBSome encoded by other BBS genes. Here we describe the successful generation of an induced pluripotent stem cell (iPSC) line KCi002-A from a male with BBS, homozygous for the disease causing variant c.271insT, p.(Cys91fsX95) in BBS10. Resource table.

Generation of induced pluripotent stem cells, KCi001-A derived from a Bardet-Biedl syndrome patient compound heterozygous for the BBS1 variants c.1169T>G/c.1135G>C.

Bardet-Biedl syndrome (BBS) is an autosomal recessive ciliopathy with a wide range of symptoms including obesity, retinal dystrophy, polycystic kidney disease, polydactyly, hypogonadism and learning difficulties. Here we describe the successful generation of an induced pluripotent stem cell (iPSC) KCi001-A from a BBS patient compound heterozygous for two disease causing BBS1 variants c.1169T>G, p. (Met390Arg)/c.1135G>C, p.(Gly370Arg). Resource table.