Bardet-Biedl syndrome (BBS) is an archetypal ciliopathy caused by dysfunction of primary cilia. BBS affects multiple tissues, including the kidney, eye and hypothalamic satiety response. Understanding pan-tissue mechanisms of pathogenesis versus those which are tissue-specific, as well as gauging their associated inter-individual variation owing to genetic background and stochastic processes, is of paramount importance in syndromology. The BBSome is a membrane-trafficking and intraflagellar transport (IFT) adaptor protein complex formed by eight BBS proteins, including BBS1, which is the most commonly mutated gene in BBS. To investigate disease pathogenesis, we generated a series of clonal renal collecting duct IMCD3 cell lines carrying defined biallelic nonsense or frameshift mutations in Bbs1, as well as a panel of matching wild-type CRISPR control clones. Using a phenotypic screen and an unbiased multi-omics approach, we note significant clonal variability for all assays, emphasising the importance of analysing panels of genetically defined clones. Our results suggest that BBS1 is required for the suppression of mesenchymal cell identities as the IMCD3 cell passage number increases. This was associated with a failure to express epithelial cell markers and tight junction formation, which was variable amongst clones. Transcriptomic analysis of hypothalamic preparations from BBS mutant mice, as well as BBS patient fibroblasts, suggested that dysregulation of epithelial-to-mesenchymal transition (EMT) genes is a general predisposing feature of BBS across tissues. Collectively, this work suggests that the dynamic stability of the BBSome is essential for the suppression of mesenchymal cell identities as epithelial cells differentiate.

• Klíčová slova
• Bardet–Biedl syndrome, Wnt signalling, collecting duct cells, epithelial-to-mesenchymal transition, fibrosis, kidney, primary cilia,
• MeSH
• Bardetův-Biedlův syndrom * genetika   metabolismus   patologie   MeSH
• cilie metabolismus   MeSH
• lidé MeSH
• myši knockoutované MeSH
• myši MeSH
• proteiny asociované s mikrotubuly metabolismus   MeSH
• proteiny metabolismus   MeSH
• zvířata MeSH
• Check Tag
• lidé MeSH
• myši MeSH
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Názvy látek
• Bbs1 protein, human MeSH Prohlížeč
• Bbs1 protein, mouse MeSH Prohlížeč
• proteiny asociované s mikrotubuly MeSH
• proteiny MeSH

The primary cilium, a microtubule-based organelle found in most cells, is a centre for mechano-sensing fluid movement and cellular signalling, notably through the Hedgehog pathway. We recently found that each lens fibre cell has an apically situated primary cilium that is polarised to the side of the cell facing the anterior pole of the lens. The direction of polarity is similar in neighbouring cells so that in the global view, lens fibres exhibit planar cell polarity (PCP) along the equatorial-anterior polar axis. Ciliogenesis has been associated with the establishment of PCP, although the exact relationship between PCP and the role of cilia is still controversial. To test the hypothesis that the primary cilia have a role in coordinating the precise alignment/orientation of the fibre cells, IFT88, a key component of the intraflagellar transport (IFT) complex, was removed specifically from the lens at different developmental stages using several lens-specific Cre-expressing mouse lines (MLR10- and LR-Cre). Irrespective of which Cre-line was adopted, both demonstrated that in IFT88-depleted cells, the ciliary axoneme was absent or substantially shortened, confirming the disruption of primary cilia formation. However no obvious histological defects were detected even when IFT88 was removed from the lens placode as early as E9.5. Specifically, the lens fibres aligned/oriented towards the poles to form the characteristic Y-shaped sutures as normal. Consistent with this, in primary lens epithelial explants prepared from these conditional knockout mouse lenses, the basal bodies still showed polarised localisation at the apical surface of elongating cells upon FGF-induced fibre differentiation. We further investigated the lens phenotype in knockouts of Bardet-Biedl Syndrome (BBS) proteins 4 and 8, the components of the BBSome complex which modulate ciliary function. In these BBS4 and 8 knockout lenses, again we found the pattern of the anterior sutures formed by the apical tips of elongating/migrating fibres were comparable to the control lenses. Taken together, these results indicate that primary cilia do not play an essential role in the precise cellular alignment/orientation of fibre cells. Thus, it appears that in the lens cilia are not required to establish PCP.

• Klíčová slova
• Bardet–Biedl Syndrome (BBS), IFT88, Lens, Planar cell polarity (PCP), Primary cilium,
• MeSH
• cilie fyziologie   MeSH
• cytoskeletální proteiny MeSH
• epitelové buňky ultrastruktura   MeSH
• kultivované buňky MeSH
• myši knockoutované MeSH
• nádorové supresorové proteiny genetika   MeSH
• oční čočka ultrastruktura   MeSH
• polarita buněk MeSH
• proteiny asociované s mikrotubuly genetika   MeSH
• zvířata MeSH
• Check Tag
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Research Support, N.I.H., Extramural MeSH
• Názvy látek
• BBS4 protein, mouse MeSH Prohlížeč
• cytoskeletální proteiny MeSH
• nádorové supresorové proteiny MeSH
• proteiny asociované s mikrotubuly MeSH
• Tg737Rpw protein, mouse MeSH Prohlížeč
• Ttc8 protein, mouse MeSH Prohlížeč

Lenz-Majewski syndrome (LMS) is a syndrome of intellectual disability and multiple congenital anomalies that features generalized craniotubular hyperostosis. By using whole-exome sequencing and selecting variants consistent with the predicted dominant de novo etiology of LMS, we identified causative heterozygous missense mutations in PTDSS1, which encodes phosphatidylserine synthase 1 (PSS1). PSS1 is one of two enzymes involved in the production of phosphatidylserine. Phosphatidylserine synthesis was increased in intact fibroblasts from affected individuals, and end-product inhibition of PSS1 by phosphatidylserine was markedly reduced. Therefore, these mutations cause a gain-of-function effect associated with regulatory dysfunction of PSS1. We have identified LMS as the first human disease, to our knowledge, caused by disrupted phosphatidylserine metabolism. Our results point to an unexplored link between phosphatidylserine synthesis and bone metabolism.

• MeSH
• dánio pruhované embryologie   genetika   MeSH
• dítě MeSH
• embryo nesavčí MeSH
• fibroblasty metabolismus   MeSH
• fosfatidylseriny biosyntéza   genetika   MeSH
• hyperostóza MeSH
• kultivované buňky MeSH
• lidé MeSH
• mladiství MeSH
• mnohočetné abnormality genetika   MeSH
• molekulární sekvence - údaje MeSH
• mutace * MeSH
• nanismus MeSH
• syndrom MeSH
• transferasy dusíkatých skupin genetika   metabolismus   MeSH
• zvířata MeSH
• Check Tag
• dítě MeSH
• lidé MeSH
• mladiství MeSH
• mužské pohlaví MeSH
• ženské pohlaví MeSH
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Research Support, N.I.H., Extramural MeSH
• Názvy látek
• fosfatidylseriny MeSH
• phospholipid serine base exchange enzyme MeSH Prohlížeč
• transferasy dusíkatých skupin MeSH