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Jose L Badano

Publications and source records attributed to Jose L Badano.

15 recordsLinked to original sources
PubMed2006

The Meckel-Gruber Syndrome proteins MKS1 and meckelin interact and are required for primary cilium formation.

Meckel-Gruber syndrome (MKS) is an autosomal recessive lethal malformation syndrome characterized by renal cystic dysplasia, central nervous system malformations (typically, posterior occipital encephalocele), and hepatic developmental defects. Two MKS genes, MKS1 and MKS3, have been identified recently. The present study describes the cellular, sub-cellular and functional characterization of the novel proteins, MKS1 and meckelin, encoded by these genes. In situ hybridization studies for MKS3 in early human embryos showed transcript localizations in agreement with the tissue phenotype of MKS patients. Both MKS proteins predominantly localized to epithelial cells, including proximal renal tubules and biliary epithelial cells. MKS1 localized to basal bodies, while meckelin localized both to the primary cilium and to the plasma membrane in ciliated cell-lines and primary cells. Meckelin protein with the Q376P missense mutation was unable to localize at the cell membrane. siRNA-mediated reduction of Mks1 and Mks3 expression in a ciliated epithelial cell-line blocked centriole migration to the apical membrane and consequent formation of the primary cilium. Co-immunoprecipitation experiments show that wild-type meckelin and MKS1 interact and, in three-dimensional tissue culture assays, epithelial branching morphogenesis was severely impaired. These results suggest that MKS proteins mediate a fundamental developmental stage of ciliary formation and epithelial morphogenesis.

Abnormalities, Multiple↗
PubMed2006

Life without centrioles: cilia in the spotlight.

Centrioles are critical cellular components that form the architectural core of both centrosomes and basal bodies, the nucleating structures of cilia. New work, including a study in this issue (), highlights the unexpected finding that lack of centrioles does not impede development in the fruit fly. Rather, flies reach maturity but then die because their sensory neurons lack cilia.

Animals↗
PubMed2006

The ciliopathies: an emerging class of human genetic disorders.

Cilia and flagella are ancient, evolutionarily conserved organelles that project from cell surfaces to perform diverse biological roles, including whole-cell locomotion; movement of fluid; chemo-, mechano-, and photosensation; and sexual reproduction. Consistent with their stringent evolutionary conservation, defects in cilia are associated with a range of human diseases, such as primary ciliary dyskinesia, hydrocephalus, polycystic liver and kidney disease, and some forms of retinal degeneration. Recent evidence indicates that ciliary defects can lead to a broader set of developmental and adult phenotypes, with mutations in ciliary proteins now associated with nephronophthisis, Bardet-Biedl syndrome, Alstrom syndrome, and Meckel-Gruber syndrome. The molecular data linking seemingly unrelated clinical entities are beginning to highlight a common theme, where defects in ciliary structure and function can lead to a predictable phenotypic pattern that has potentially predictive and therapeutic value.

Ciliary Motility Disorders↗
PubMed2005

Dissection of epistasis in oligogenic Bardet-Biedl syndrome.

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.

Alleles↗
PubMed2005

MKKS/BBS6, a divergent chaperonin-like protein linked to the obesity disorder Bardet-Biedl syndrome, is a novel centrosomal component required for cytokinesis.

Chaperonins are multisubunit, cylinder-shaped molecular chaperones involved in folding newly synthesized polypeptides. Here we show that MKKS/BBS6, one of several proteins associated with Bardet-Biedl syndrome (BBS), is a Group II chaperonin-like protein that has evolved recently in animals from a subunit of the eukaryotic chaperonin CCT/TRiC, and diverged rapidly to acquire distinct functions. Unlike other chaperonins, cytosolic BBS6 does not oligomerize, and the majority of BBS6 resides within the pericentriolar material (PCM), a proteinaceous tube surrounding centrioles. During interphase, BBS6 is confined to the lateral surfaces of the PCM but during mitosis it relocalizes throughout the PCM and is found at the intercellular bridge. Its predicted substrate-binding apical domain is sufficient for centrosomal association, and several patient-derived mutations in this domain cause mislocalization of BBS6. Consistent with an important centrosomal function, silencing of the BBS6 transcript by RNA interference in different cell types leads to multinucleate and multicentrosomal cells with cytokinesis defects. The restricted tissue distribution of BBS6 further suggests that it may play important roles in ciliated epithelial tissues, which is consistent with the probable functions of BBS proteins in basal bodies (modified centrioles) and cilia. Our findings provide the first insight into the nature and cellular function of BBS6, and shed light on the potential causes of several ailments, including obesity, retinal degeneration, kidney dysfunction and congenital heart disease.

Amino Acid Sequence↗
PubMed2005

The centrosome in human genetic disease.

The centrosome is an indispensable component of the cell-cycle machinery of eukaryotic cells, and the perturbation of core centrosomal or centrosome-associated proteins is linked to cell-cycle misregulation and cancer. Recent work has expanded our understanding of the functional complexity and importance of this organelle. The centrosomal localization of proteins that are involved in human genetic disease, and the identification of novel centrosome-associated proteins, has shown that numerous, seemingly unrelated, cellular processes can be perturbed by centrosomal dysfunction. Here, we review the mechanistic relationship between human disease phenotypes and the function of the centrosome, and describe some of the newly-appreciated functions of this organelle in animal cells.

Animals↗
PubMed2004

Loss of BBS proteins causes anosmia in humans and defects in olfactory cilia structure and function in the mouse.

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.

Animals↗
PubMed2004

Mutations in a member of the Ras superfamily of small GTP-binding proteins causes Bardet-Biedl syndrome.

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.

ADP-Ribosylation Factors↗
PubMed2004

Loss of C. elegans BBS-7 and BBS-8 protein function results in cilia defects and compromised intraflagellar transport.

Bardet-Biedl syndrome (BBS) is a genetically heterogeneous developmental disorder whose molecular basis is largely unknown. Here, we show that mutations in the Caenorhabditis elegans bbs-7 and bbs-8 genes cause structural and functional defects in cilia. C. elegans BBS proteins localize predominantly at the base of cilia, and like proteins involved in intraflagellar transport (IFT), a process necessary for cilia biogenesis and maintenance, move bidirectionally along the ciliary axoneme. Importantly, we demonstrate that BBS-7 and BBS-8 are required for the normal localization/motility of the IFT proteins OSM-5/Polaris and CHE-11, and to a notably lesser extent, CHE-2. We propose that BBS proteins play important, selective roles in the assembly and/or function of IFT particle components. Our findings also suggest that some of the cardinal and secondary symptoms of BBS, such as obesity, diabetes, cardiomyopathy, and learning defects may result from cilia dysfunction.

Adaptor Proteins, Signal Transducing↗
PubMed2004

The Bardet-Biedl protein BBS4 targets cargo to the pericentriolar region and is required for microtubule anchoring and cell cycle progression.

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.

Animals↗
PubMed2003

Basal body dysfunction is a likely cause of pleiotropic Bardet-Biedl syndrome.

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.

Alleles↗
PubMed2003

Heterozygous mutations in BBS1, BBS2 and BBS6 have a potential epistatic effect on Bardet-Biedl patients with two mutations at a second BBS locus.

Bardet-Biedl syndrome (BBS) is a pleiotropic genetic disorder with substantial inter- and intrafamilial variability, that also exhibits remarkable genetic heterogeneity, with seven mapped BBS loci in the human genome. Recent data have demonstrated that BBS may be inherited either as a simple Mendelian recessive or as an oligogenic trait, since mutations at two loci are sometimes required for pathogenesis. This observation suggests that genetic interactions between the different BBS loci may modulate the phenotype, thus contributing to the clinical variability of BBS. We present three families with two mutations in either BBS1 or BBS2, in which some but not all patients carry a third mutation in BBS1, BBS2 or the putative chaperonin BBS6. In each example, the presence of three mutant alleles correlates with a more severe phenotype. For one of the missense alleles, we also demonstrate that the introduction of the mutation in mammalian cells causes a dramatic mislocalization of the protein compared with the wild-type. These data suggest that triallelic mutations are not always necessary for disease manifestation, but might potentiate a phenotype that is caused by two recessive mutations at an independent locus, thus introducing an additional layer of complexity on the genetic modeling of oligogenicity.

Bardet-Biedl Syndrome↗
PubMed2003

Genetic interaction of BBS1 mutations with alleles at other BBS loci can result in non-Mendelian Bardet-Biedl syndrome.

Bardet-Biedl syndrome is a genetically and clinically heterogeneous disorder caused by mutations in at least seven loci (BBS1-7), five of which are cloned (BBS1, BBS2, BBS4, BBS6, and BBS7). Genetic and mutational analyses have indicated that, in some families, a combination of three mutant alleles at two loci (triallelic inheritance) is necessary for pathogenesis. To date, four of the five known BBS loci have been implicated in this mode of oligogenic disease transmission. We present a comprehensive analysis of the spectrum, distribution, and involvement in non-Mendelian trait transmission of mutant alleles in BBS1, the most common BBS locus. Analyses of 259 independent families segregating a BBS phenotype indicate that BBS1 participates in complex inheritance and that, in different families, mutations in BBS1 can interact genetically with mutations at each of the other known BBS genes, as well as at unknown loci, to cause the phenotype. Consistent with this model, we identified homozygous M390R alleles, the most frequent BBS1 mutation, in asymptomatic individuals in two families. Moreover, our statistical analyses indicate that the prevalence of the M390R allele in the general population is consistent with an oligogenic rather than a recessive model of disease transmission. The distribution of BBS oligogenic alleles also indicates that all BBS loci might interact genetically with each other, but some genes, especially BBS2 and BBS6, are more likely to participate in triallelic inheritance, suggesting a variable ability of the BBS proteins to interact genetically with each other.

Alleles↗
PubMed2002

Beyond Mendel: an evolving view of human genetic disease transmission.

Methodological and conceptual advances in human genetics have led to the identification of an impressive number of human disease genes. This wealth of information has also revealed that the traditional distinction between Mendelian and complex disorders might sometimes be blurred. Genetic and mutational data on an increasing number of disorders have illustrated how phenotypic effects can result from the combined action of alleles in many genes. In this review, we discuss how an improved understanding of the genetic basis of multilocus inheritance is catalysing the transition from a segmented view of human genetic disease to a conceptual continuum between Mendelian and complex traits.

Alleles↗