ABSTRACT
CCDC28B (coiled-coil domain-containing protein 28B) was identified as a modifier in the ciliopathy Bardet-Biedl syndrome (BBS). Our previous work in cells and zebrafish showed that CCDC28B plays a role regulating cilia length in a mechanism that is not completely understood. Here we report the generation of a Ccdc28b mutant mouse using CRISPR/Cas9 (Ccdc28b mut). Depletion of CCDC28B resulted in a mild phenotype. Ccdc28b mut animals i) do not present clear structural cilia affectation, although we did observe mild defects in cilia density and cilia length in some tissues, ii) reproduce normally, and iii) do not develop retinal degeneration or obesity, two hallmark features of reported BBS murine models. In contrast, Ccdc28b mut mice did show clear social interaction defects as well as stereotypical behaviors. This finding is indeed relevant regarding CCDC28B as a modifier of BBS since behavioral phenotypes have been documented in BBS. Overall, this work reports a novel mouse model that will be key to continue evaluating genetic interactions in BBS, deciphering the contribution of CCDC28B to modulate the presentation of BBS phenotypes. In addition, our data underscores a novel link between CCDC28B and behavioral defects, providing a novel opportunity to further our understanding of the genetic, cellular, and molecular basis of these complex phenotypes.
Subject(s)
Bardet-Biedl Syndrome , Retinal Degeneration , Animals , Bardet-Biedl Syndrome/genetics , Bardet-Biedl Syndrome/metabolism , Cilia/metabolism , Mice , Phenotype , Retinal Degeneration/genetics , Zebrafish/geneticsABSTRACT
Proteins associated with primary cilia and basal bodies mediate numerous signaling pathways, but little is known about their role in Notch signaling. Here, we report that loss of the Bardet-Biedl syndrome proteins BBS1 or BBS4 produces increased Notch-directed transcription in a zebrafish reporter line and in human cell lines. Pathway overactivation is accompanied by reduced localization of Notch receptor at both the plasma membrane and the cilium. In Drosophila mutants, overactivation of Notch can result from receptor accumulation in endosomes, and recent studies implicate ciliary proteins in endosomal trafficking, suggesting a possible mechanism by which overactivation occurs in BBS mutants. Consistent with this, we observe genetic interaction of BBS1 and BBS4 with the endosomal sorting complexes required for transport (ESCRT) gene TSG101 and accumulation of receptor in late endosomes, reduced endosomal recycling and reduced receptor degradation in lysosomes. We observe similar defects with disruption of BBS3. Loss of another basal body protein, ALMS1, also enhances Notch activation and the accumulation of receptor in late endosomes, but does not disrupt recycling. These findings suggest a role for these proteins in the regulation of Notch through endosomal trafficking of the receptor.
Subject(s)
Basal Bodies/physiology , Cell Membrane/metabolism , Cilia/physiology , Endosomes/metabolism , Microtubule-Associated Proteins/metabolism , Proteins/metabolism , Receptors, Notch/metabolism , ADP-Ribosylation Factors/genetics , ADP-Ribosylation Factors/metabolism , Animals , Cell Cycle Proteins , Cell Line , DNA-Binding Proteins/genetics , DNA-Binding Proteins/metabolism , Drosophila , Endosomal Sorting Complexes Required for Transport/genetics , Endosomal Sorting Complexes Required for Transport/metabolism , Humans , Microtubule-Associated Proteins/genetics , Mutation/genetics , Protein Transport/genetics , Proteins/genetics , Signal Transduction/genetics , Transcription Factors/genetics , Transcription Factors/metabolism , ZebrafishABSTRACT
CCDC28B encodes a coiled coil domain-containing protein involved in ciliogenesis that was originally identified as a second site modifier of the ciliopathy Bardet-Biedl syndrome. We have previously shown that the depletion of CCDC28B leads to shortened cilia; however, the mechanism underlying how this protein controls ciliary length is unknown. Here, we show that CCDC28B interacts with SIN1, a component of the mTOR complex 2 (mTORC2), and that this interaction is important both in the context of mTOR signaling and in a hitherto unknown, mTORC-independent role of SIN1 in cilia biology. We show that CCDC28B is a positive regulator of mTORC2, participating in its assembly/stability and modulating its activity, while not affecting mTORC1 function. Further, we show that Ccdc28b regulates cilia length in vivo, at least in part, through its interaction with Sin1. Importantly, depletion of Rictor, another core component of mTORC2, does not result in shortened cilia. Taken together, our findings implicate CCDC28B in the regulation of mTORC2, and uncover a novel function of SIN1 regulating cilia length that is likely independent of mTOR signaling.
Subject(s)
Adaptor Proteins, Signal Transducing/metabolism , Bardet-Biedl Syndrome/metabolism , Carrier Proteins/metabolism , Cell Cycle Proteins/metabolism , Cilia/metabolism , Multiprotein Complexes/metabolism , TOR Serine-Threonine Kinases/metabolism , Animals , Cytoskeletal Proteins , Gene Expression Regulation , Gene Knockdown Techniques , HEK293 Cells , HeLa Cells , Humans , Mechanistic Target of Rapamycin Complex 2 , Mice , Microtubule-Associated Proteins , NIH 3T3 Cells , Rapamycin-Insensitive Companion of mTOR Protein , Signal Transduction/physiology , Zebrafish/embryology , Zebrafish/metabolism , Zebrafish Proteins/metabolismABSTRACT
Bardet-Biedl syndrome (BBS) is a genetically heterogeneous ciliopathy. Although nine BBS genes have been cloned, they explain only 40-50% of the total mutational load. Here we report a major new BBS locus, BBS10, that encodes a previously unknown, rapidly evolving vertebrate-specific chaperonin-like protein. We found BBS10 to be mutated in about 20% of an unselected cohort of families of various ethnic origins, including some families with mutations in other BBS genes, consistent with oligogenic inheritance. In zebrafish, mild suppression of bbs10 exacerbated the phenotypes of other bbs morphants.
Subject(s)
Bardet-Biedl Syndrome/genetics , Proteins/genetics , Cohort Studies , Humans , Mutation , Proteins/metabolismABSTRACT
BACKGROUND: DZIP1 (DAZ-interacting protein 1) has been described as a component of the Hh signaling pathway with a putative regulatory role in ciliogenesis. DZIP1 interacts with DAZ RNA binding proteins in embryonic stem cells and human germ cells suggesting a role in mRNA regulation. RESULTS: We investigated DZIP1 function in HeLa cells and its involvement in ribonucleoprotein complexes. DZIP1 was predominantly located in granules in the cytoplasm. Under oxidative stress conditions, DZIP1 re-localized to stress granules. DZIP appears to be important for the formation of stress granules during the stress response. We used immunoprecipitation assays with antibodies against DZIP1 and microarray hybridization to identify mRNAs associated with DZIP1. The genetic networks formed by the DZIP1-associated mRNAs were involved in cell cycle and gene expression regulation. DZIP1 is involved in the Hedgehog signaling pathway. We used cyclopamine, a specific inhibitor of this pathway, to analyze the expression of DZIP1 and its associated mRNAs. The abundance of DZIP1-associated mRNAs increased with treatment; however, the silencing or overexpression of DZIP1 in HeLa cells had no effect on the accumulation of the associated mRNAs. Polysomal profile analysis by sucrose gradient centrifugation demonstrated the presence of DZIP1 in the polysomal fraction. CONCLUSIONS: Our results suggest that DZIP1 is part of an RNP complex that occupies various subcellular locations. The diversity of the mRNAs associated with DZIP1 suggests that this protein is a component of different RNPs associated with translating polysomes and with RNA granules.
Subject(s)
Adaptor Proteins, Signal Transducing/genetics , Cytoplasmic Granules/genetics , Oxidative Stress/genetics , Ribonucleoproteins/genetics , Cell Cycle/genetics , Cell Line, Tumor , Gene Expression Regulation/genetics , HeLa Cells , Hedgehog Proteins/genetics , Humans , RNA, Messenger/genetics , RNA-Binding Proteins/genetics , Signal Transduction/geneticsABSTRACT
Primary cilia are conserved organelles that play crucial roles as mechano- and chemosensors, as well as transducing signaling cascades. Consequently, ciliary dysfunction results in a broad range of phenotypes: the ciliopathies. Bardet-Biedl syndrome (BBS), a model ciliopathy, is caused by mutations in 16 known genes. However, the biochemical functions of the BBS proteins are not fully understood. Here we show that the BBS7 protein (localized in the centrosomes, basal bodies and cilia) probably has a nuclear role by virtue of the presence of a biologically confirmed nuclear export signal. Consistent with this observation, we show that BBS7 interacts physically with the polycomb group (PcG) member RNF2 and regulate its protein levels, probably through a proteasome-mediated mechanism. In addition, our data supports a similar role for other BBS proteins. Importantly, the interaction with this PcG member is biologically relevant because loss of BBS proteins leads to the aberrant expression of endogenous RNF2 targets in vivo, including several genes that are crucial for development and for cellular and tissue homeostasis. Our data indicate a hitherto unappreciated, direct role for the BBS proteins in transcriptional regulation and potentially expand the mechanistic spectrum that underpins the development of ciliary phenotypes in patients.
Subject(s)
Gene Expression Regulation , Proteins/physiology , Transcription, Genetic , Adaptor Proteins, Signal Transducing , Animals , Cell Nucleus/metabolism , Computer Simulation , Cytoskeletal Proteins , HEK293 Cells , HeLa Cells , Humans , Mice , NIH 3T3 Cells , Nuclear Export Signals , Polycomb Repressive Complex 1/metabolism , Protein Transport , Proteins/metabolism , Zebrafish/geneticsABSTRACT
Obesity poses significant challenges, necessitating comprehensive strategies for effective intervention. Bariatric Surgery (BS) has emerged as a crucial therapeutic approach, demonstrating success in weight loss and comorbidity improvement. This study aimed to evaluate the outcomes of BS in a cohort of 48 Uruguayan patients and investigate the interplay between BS and clinical and metabolic features, with a specific focus on FSTL1, an emerging biomarker associated with obesity and inflammation. We quantitatively analyzed BS outcomes and constructed linear models to identify variables impacting BS success. The study revealed the effectiveness of BS in improving metabolic and clinical parameters. Importantly, variables correlating with BS success were identified, with higher pre-surgical FSTL1 levels associated with an increased effect of BS on BMI reduction. FSTL1 levels were measured from patient plasma using an ELISA kit pre-surgery and six months after. This research, despite limitations of a small sample size and limited follow-up time, contributes valuable insights into understanding and predicting the success of BS, highlighting the potential role of FSTL1 as a useful biomarker in obesity.
Subject(s)
Bariatric Surgery , Biomarkers , Follistatin-Related Proteins , Obesity , Humans , Follistatin-Related Proteins/blood , Follistatin-Related Proteins/metabolism , Female , Male , Bariatric Surgery/methods , Adult , Middle Aged , Biomarkers/blood , Obesity/surgery , Obesity/metabolism , Uruguay/epidemiology , Cohort Studies , Weight Loss , Treatment Outcome , Body Mass IndexABSTRACT
Bardet-Biedl syndrome (BBS) is a genetically heterogeneous disorder that is generally inherited in an autosomal recessive fashion. However, in some families, trans mutant alleles interact with the primary causal locus to modulate the penetrance and/or the expressivity of the phenotype. CCDC28B (MGC1203) was identified as a second site modifier of BBS encoding a protein of unknown function. Here we report the first functional characterization of this protein and show it affects ciliogenesis both in cultured cells and in vivo in zebrafish. Consistent with this biological role, our in silico analysis shows that the presence of CCDC28B homologous sequences is restricted to ciliated metazoa. Depletion of Ccdc28b in zebrafish results in defective ciliogenesis and consequently causes a number of phenotypes that are characteristic of BBS and other ciliopathy mutants including hydrocephalus, left-right axis determination defects and renal function impairment. Thus, this work reports CCDC28B as a novel protein involved in the process of ciliogenesis whilst providing functional insight into the cellular basis of its modifier effect in BBS patients.
Subject(s)
Bardet-Biedl Syndrome/genetics , Cell Cycle Proteins/genetics , Cilia/genetics , Zebrafish Proteins/genetics , Zebrafish/embryology , Zebrafish/genetics , Amino Acid Sequence , Animals , Bardet-Biedl Syndrome/physiopathology , Cell Cycle Proteins/physiology , Cell Line , Cilia/physiology , Conserved Sequence , Cytoskeletal Proteins , Gene Knockdown Techniques , Humans , In Situ Hybridization , Molecular Sequence Data , Protein Structure, Tertiary , Sequence Homology, Amino Acid , Species Specificity , Zebrafish/physiology , Zebrafish Proteins/antagonists & inhibitors , Zebrafish Proteins/chemistry , Zebrafish Proteins/physiologyABSTRACT
Technological advances hold the promise of rapidly catalyzing the discovery of pathogenic variants for genetic disease. However, this possibility is tempered by limitations in interpreting the functional consequences of genetic variation at candidate loci. Here, we present a systematic approach, grounded on physiologically relevant assays, to evaluate the mutational content (125 alleles) of the 14 genes associated with Bardet-Biedl syndrome (BBS). A combination of in vivo assays with subsequent in vitro validation suggests that a significant fraction of BBS-associated mutations have a dominant-negative mode of action. Moreover, we find that a subset of common alleles, previously considered to be benign, are, in fact, detrimental to protein function and can interact with strong rare alleles to modulate disease presentation. These data represent a comprehensive evaluation of genetic load in a multilocus disease. Importantly, superimposition of these results to human genetics data suggests a previously underappreciated complexity in disease architecture that might be shared among diverse clinical phenotypes.
Subject(s)
Bardet-Biedl Syndrome/genetics , Mutation , Alleles , Animals , Female , Gene Expression Regulation , Humans , Male , Models, Animal , Pedigree , Phenotype , Zebrafish/embryology , Zebrafish/geneticsABSTRACT
BBS4 is one of several proteins that cause Bardet-Biedl syndrome (BBS), a multisystemic disorder of genetic and clinical complexity. Here we show that BBS4 localizes to the centriolar satellites of centrosomes and basal bodies of primary cilia, where it functions as an adaptor of the p150(glued) subunit of the dynein transport machinery to recruit PCM1 (pericentriolar material 1 protein) and its associated cargo to the satellites. Silencing of BBS4 induces PCM1 mislocalization and concomitant deanchoring of centrosomal microtubules, arrest in cell division and apoptotic cell death. Expression of two truncated forms of BBS4 that are similar to those found in some individuals with BBS had a similar effect on PCM1 and microtubules. Our findings indicate that defective targeting or anchoring of pericentriolar proteins and microtubule disorganization contribute to the BBS phenotype and provide new insights into possible causes of familial obesity, diabetes and retinal degeneration.
Subject(s)
Bardet-Biedl Syndrome/metabolism , Cell Cycle , Centrosome/metabolism , Microtubules/metabolism , Proteins/metabolism , Animals , Apoptosis , Autoantigens , Bardet-Biedl Syndrome/pathology , COS Cells , Cell Cycle Proteins/metabolism , Centrosome/pathology , Chlorocebus aethiops , Dyneins/metabolism , Gene Silencing , HeLa Cells , Humans , In Situ Nick-End Labeling , Microtubule-Associated Proteins , Peptide Fragments/immunology , Phenotype , Protein Binding , Protein Subunits , Protein Transport , Proteins/antagonists & inhibitors , Proteins/genetics , RNA, Small Interfering/pharmacology , Rabbits , Saccharomyces cerevisiae , Two-Hybrid System TechniquesABSTRACT
Defects in cilia are associated with several human disorders, including Kartagener syndrome, polycystic kidney disease, nephronophthisis and hydrocephalus. We proposed that the pleiotropic phenotype of Bardet-Biedl syndrome (BBS), which encompasses retinal degeneration, truncal obesity, renal and limb malformations and developmental delay, is due to dysfunction of basal bodies and cilia. Here we show that individuals with BBS have partial or complete anosmia. To test whether this phenotype is caused by ciliary defects of olfactory sensory neurons, we examined mice with deletions of Bbs1 or Bbs4. Loss of function of either BBS protein affected the olfactory, but not the respiratory, epithelium, causing severe reduction of the ciliated border, disorganization of the dendritic microtubule network and trapping of olfactory ciliary proteins in dendrites and cell bodies. Our data indicate that BBS proteins have a role in the microtubule organization of mammalian ciliated cells and that anosmia might be a useful determinant of other pleiotropic disorders with a suspected ciliary involvement.
Subject(s)
Bardet-Biedl Syndrome/genetics , Mutation , Olfaction Disorders/genetics , Proteins/genetics , Animals , Cilia/ultrastructure , Humans , Mice , Microtubule-Associated Proteins , Microtubules/ultrastructure , Mutagenesis, Site-Directed , Nasal Mucosa/metabolism , Nasal Mucosa/ultrastructure , Proteins/metabolismABSTRACT
RAB, ADP-ribosylation factors (ARFs) and ARF-like (ARL) proteins belong to the Ras superfamily of small GTP-binding proteins and are essential for various membrane-associated intracellular trafficking processes. None of the approximately 50 known members of this family are linked to human disease. Using a bioinformatic screen for ciliary genes in combination with mutational analyses, we identified ARL6 as the gene underlying Bardet-Biedl syndrome type 3, a multisystemic disorder characterized by obesity, blindness, polydactyly, renal abnormalities and cognitive impairment. We uncovered four different homozygous substitutions in ARL6 in four unrelated families affected with Bardet-Biedl syndrome, two of which disrupt a threonine residue important for GTP binding and function of several related small GTP-binding proteins. Analysis of the Caenorhabditis elegans ARL6 homolog indicates that it is specifically expressed in ciliated cells, and that, in addition to the postulated cytoplasmic functions of ARL proteins, it undergoes intraflagellar transport. These findings implicate a small GTP-binding protein in ciliary transport and the pathogenesis of a pleiotropic disorder.
Subject(s)
ADP-Ribosylation Factors/genetics , Bardet-Biedl Syndrome/genetics , Genes, ras , Membrane Proteins/genetics , Mutation , Base Sequence , Cilia/metabolism , GTP-Binding Proteins/genetics , Humans , Models, Molecular , Molecular Sequence Data , Neurons/cytology , PedigreeABSTRACT
Epistatic interactions have an important role in phenotypic variability, yet the genetic dissection of such phenomena remains challenging. Here we report the identification of a novel locus, MGC1203, that contributes epistatic alleles to Bardet-Biedl syndrome (BBS), a pleiotropic, oligogenic disorder. MGC1203 encodes a pericentriolar protein that interacts and colocalizes with the BBS proteins. Sequencing of two independent BBS cohorts revealed a significant enrichment of a heterozygous C430T mutation in patients, and a transmission disequilibrium test (TDT) showed strong over-transmission of this variant. Further analyses showed that the 430T allele enhances the use of a cryptic splice acceptor site, causing the introduction of a premature termination codon (PTC) and the reduction of steady-state MGC1203 messenger RNA levels. Finally, recapitulation of the human genotypes in zebrafish shows that modest suppression of mgc1203 exerts an epistatic effect on the developmental phenotype of BBS morphants. Our data demonstrate how the combined use of biochemical, genetic and in vivo tools can facilitate the dissection of epistatic phenomena, and enhance our appreciation of the genetic basis of phenotypic variability.
Subject(s)
Bardet-Biedl Syndrome/genetics , Cell Cycle Proteins/genetics , Cell Cycle Proteins/metabolism , Epistasis, Genetic , Multifactorial Inheritance/genetics , Alleles , Alternative Splicing/genetics , Animals , Base Sequence , Cell Line , Cytoskeletal Proteins , Exons/genetics , Female , Heterozygote , Humans , Linkage Disequilibrium , Male , Microtubule-Associated Proteins , Mutation/genetics , Pedigree , Phenotype , Protein Binding , Proteins/genetics , Proteins/metabolism , RNA Splice Sites/genetics , RNA, Messenger/genetics , RNA, Messenger/metabolism , Zebrafish/embryology , Zebrafish/geneticsABSTRACT
Hirschsprung disease (HSCR) is a common, multigenic neurocristopathy characterized by incomplete innervation along a variable length of the gut. The pivotal gene in isolated HSCR cases, either sporadic or familial, is RET. HSCR also presents in various syndromes, including Shah-Waardenburg syndrome (WS), Down (DS), and Bardet-Biedl (BBS). Here, we report 3 families with BBS and HSCR with concomitant mutations in BBS genes and regulatory RET elements, whose functionality is tested in physiologically relevant assays. Our data suggest that BBS mutations can potentiate HSCR predisposing RET alleles, which by themselves are insufficient to cause disease. We also demonstrate that these genes interact genetically in vivo to modulate gut innervation, and that this interaction likely occurs through complementary, yet independent, pathways that converge on the same biological process.
Subject(s)
Epistasis, Genetic , Hirschsprung Disease/genetics , Mutation , Proteins/genetics , Proto-Oncogene Proteins c-ret/genetics , Stomach/innervation , Alleles , Cytoplasm/metabolism , Enhancer Elements, Genetic , Family Health , Female , Genotype , Humans , Male , Microtubule-Associated Proteins , PedigreeABSTRACT
Ciliary dysfunction has emerged as a common factor underlying the pathogenesis of both syndromic and isolated kidney cystic disease, an observation that has contributed to the unification of human genetic disorders of the cilium, the ciliopathies. Such grouping is underscored by two major observations: the fact that genes encoding ciliary proteins can contribute causal and modifying mutations across several clinically discrete ciliopathies, and the emerging realization that an understanding of the clinical pathology of one ciliopathy can provide valuable insight into the pathomechanism of renal cyst formation elsewhere in the ciliopathy spectrum. In this review, we discuss and attempt to stratify the different lines of proposed cilia-driven mechanisms for cystogenesis, ranging from mechano- and chemo-sensation, to cell shape and polarization, to the transduction of a variety of signaling cascades. We evaluate both common trends and differences across the models and discuss how each proposed mechanism can contribute to the development of novel therapeutic paradigms.
Subject(s)
Ciliary Motility Disorders/pathology , Ciliary Motility Disorders/physiopathology , Kidney Diseases, Cystic/pathology , Kidney Diseases, Cystic/physiopathology , Animals , Ciliary Motility Disorders/genetics , Humans , Kidney Diseases, Cystic/geneticsABSTRACT
Photoreceptor cells of the vertebrate neural retina originate in the neuroepithelium, and like other neurons, must undergo cell body translocation and polarity transitions to acquire their final functional morphology, which includes features of neuronal and epithelial cells. We analyzed this process in detail in zebrafish embryos using in vivo confocal microscopy and electron microscopy. Photoreceptor progenitors were labeled by the transgenic expression of enhanced green fluorescent protein under the regulation of the photoreceptor-specific promoter crx, and structures of interest were disrupted using morpholino oligomers to knock-down specific genes. Photoreceptor progenitors detached from the basal retina at pre-mitotic stages, rapidly retracting a short basal process as the cell body translocated apically. They remained at an apical position indefinitely to form the outer nuclear layer (ONL), initially extending and retracting highly dynamic neurite-like processes, tangential to the apical surface. Many photoreceptor progenitors presented a short apical primary cilium. The number and length of these cilia was gradually reduced until nearly disappearing around 60 hpf. Their disruption by knocking-down ift88 and elipsa caused a notorious defect on basal process retraction. To assess the role of cell adhesion in the organization of photoreceptor progenitors, we knocked-down cdh2/N-cadherin and observed the cell behavior by time-lapse microscopy. The ectopic photoreceptor progenitors initially migrated in an apparent random manner, profusely extending cell processes, until they encountered other cells to establish cell rosettes in which they stayed, acquiring photoreceptor-like polarity. Altogether, our observations indicate a complex regulation of photoreceptor progenitor dynamics to form the retinal ONL, previous to the post-mitotic maturation stages.
Subject(s)
Cadherins , Cilia , Photoreceptor Cells/cytology , Retina/cytology , Zebrafish , Animals , Cadherins/genetics , Zebrafish/geneticsABSTRACT
White adipose tissue hyperplasia has been shown to be crucial for handling excess energy in healthy ways. Though adipogenesis mechanisms have been underscored in vitro, we lack information on how tissue and systemic factors influence the differentiation of new adipocytes. While this could be studied in zebrafish, adipocyte identification currently relies on neutral lipid labeling, thus precluding access to cells in early stages of differentiation. Here we report the generation and analysis of a zebrafish line with the transgene fabp4a(-2.7):EGFPcaax. In vivo confocal microscopy of the pancreatic and abdominal visceral depots of transgenic larvae, revealed the presence of labeled mature adipocytes as well as immature cells in earlier stages of differentiation. Through co-labeling for blood vessels, we observed a close interaction of differentiating adipocytes with endothelial cells through cell protrusions. Finally, we implemented hyperspectral imaging and spectral phasor analysis in Nile Red-labeled transgenic larvae and revealed the lipid metabolic transition towards neutral lipid accumulation of differentiating adipocytes. Altogether our work presents the characterization of a novel adipocyte-specific label in zebrafish and uncovers previously unknown aspects of in vivo adipogenesis. This article has an associated First Person interview with the first author of the paper.
Subject(s)
Adipocytes/physiology , Adipogenesis/genetics , Adipose Tissue, White/cytology , Cell Differentiation/genetics , Zebrafish/embryology , Adiponectin/metabolism , Animals , Animals, Genetically Modified , CCAAT-Enhancer-Binding Proteins/metabolism , Cell Line , Complement Factor D/metabolism , Endothelial Cells/physiology , Fatty Acid-Binding Proteins/metabolismABSTRACT
Bardet-Biedl syndrome (BBS) is a genetically heterogeneous disorder characterized primarily by retinal dystrophy, obesity, polydactyly, renal malformations and learning disabilities. Although five BBS genes have been cloned, the molecular basis of this syndrome remains elusive. Here we show that BBS is probably caused by a defect at the basal body of ciliated cells. We have cloned a new BBS gene, BBS8, which encodes a protein with a prokaryotic domain, pilF, involved in pilus formation and twitching mobility. In one family, a homozygous null BBS8 mutation leads to BBS with randomization of left-right body axis symmetry, a known defect of the nodal cilium. We have also found that BBS8 localizes specifically to ciliated structures, such as the connecting cilium of the retina and columnar epithelial cells in the lung. In cells, BBS8 localizes to centrosomes and basal bodies and interacts with PCM1, a protein probably involved in ciliogenesis. Finally, we demonstrate that all available Caenorhabditis elegans BBS homologues are expressed exclusively in ciliated neurons, and contain regulatory elements for RFX, a transcription factor that modulates the expression of genes associated with ciliogenesis and intraflagellar transport.
Subject(s)
Bardet-Biedl Syndrome/genetics , Bardet-Biedl Syndrome/pathology , Cilia/pathology , Proteins/genetics , Proteins/metabolism , Alleles , Amino Acid Sequence , Animals , Bardet-Biedl Syndrome/metabolism , Base Sequence , Caenorhabditis elegans/cytology , Caenorhabditis elegans/genetics , Caenorhabditis elegans/metabolism , Cell Line , Centrosome/metabolism , Centrosome/pathology , Cilia/metabolism , Cytoskeletal Proteins , Female , Gene Deletion , Gene Expression Profiling , Homozygote , Humans , Lod Score , Male , Molecular Sequence Data , Mutation/genetics , Neurons/cytology , Neurons/metabolism , Neurons/pathology , Pedigree , Proteins/chemistry , RNA, Messenger/genetics , RNA, Messenger/metabolismABSTRACT
An amendment to this paper has been published and can be accessed via a link at the top of the paper.
ABSTRACT
Motile cilia have long been known to play a role in processes such as cell locomotion and fluid movement whereas the functions of primary cilia have remained obscure until recent years. To date, ciliary dysfunction has been shown to be causally linked to a number of clinical manifestations that characterize the group of human disorders known as ciliopathies. This classification reflects a common or shared cellular basis and implies that it is possible to associate a series of different human conditions with ciliary dysfunction, which allows gaining insight into the cellular defect in disorders of unknown etiology solely based on phenotypic observations. Furthermore, to date we know that the cilium participates in a number of biological processes ranging from chemo- and mechanosensation to the transduction of a growing list of paracrine signaling cascades that are critical for the development and maintenance of different tissues and organs. Consequently, the primary cilium has been identified as a key structure necessary to regulate and maintain cellular and tissue homeostasis and thus its study is providing significant information to understand the pathogenesis of the different phenotypes that characterize these human conditions. Finally, the similarities between different ciliopathies at the phenotypic level are proving to be due to their shared cellular defect and also their common genetic basis. To this end, recent studies are showing that mutations in a given ciliary gene often appear involved in the pathogenesis of more than one clinical entity, complicating their genetic dissection, and hindering our ability to generate accurate genotype-phenotype correlations.