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Query: UMLS:C0028754 (obesity)
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Bardet-Biedl syndrome (BBS) is a genetically heterogeneous disorder, the primary features of which include obesity, retinal dystrophy, polydactyly, hypogenitalism, learning difficulties, and renal malformations. Conventional linkage and positional cloning have led to the mapping of six BBS loci in the human genome, four of which (BBS1, BBS2, BBS4, and BBS6) have been cloned. Despite these advances, the protein sequences of the known BBS genes have provided little or no insight into their function. To delineate functionally important regions in BBS2, we performed phylogenetic and genomic studies in which we used the human and zebrafish BBS2 peptide sequences to search dbEST and the translation of the draft human genome. We identified two novel genes that we initially named "BBS2L1" and "BBS2L2" and that exhibit modest similarity with two discrete, overlapping regions of BBS2. In the present study, we demonstrate that BBS2L1 mutations cause BBS, thereby defining a novel locus for this syndrome, BBS7, whereas BBS2L2 has been shown independently to be BBS1. The motif-based identification of a novel BBS locus has enabled us to define a potential functional domain that is present in three of the five known BBS proteins and, therefore, is likely to be important in the pathogenesis of this complex syndrome.
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PMID:Identification of a novel Bardet-Biedl syndrome protein, BBS7, that shares structural features with BBS1 and BBS2. 1256 24

Bardet-Biedl syndrome (BBS) is a pleiotropic genetic disorder with the cardinal features of obesity, photoreceptor degeneration, polydactyly, hypogenitalism, renal abnormalities, and developmental delay. Other associated clinical findings in BBS patients include diabetes, hypertension, and congenital heart defects. The clinical diagnosis is based on the presence of at least four of the cardinal symptoms. BBS is recognized to be a genetically heterogeneous autosomal recessive disorder mapping to eight known loci. Positional cloning and candidate gene evaluation have resulted in the identification of six BBS genes. Mutation of one of these genes, BBS6, also causes McKusick-Kaufman syndrome. The BBS6 gene is predicted to code for a protein with sequence similarity to the chaperonin family of proteins. The predicted BBS1, BBS2, BBS4, BBS7, and BBS8 gene products do not seem to be molecular chaperones, on the basis of a lack of sequence similarity to the chaperonin family of proteins. The identification of BBS8 suggests a possible role in cilia function for BBS gene products. It remains to be determined whether the multiple BBS proteins are part of a multisubunit complex or do not directly interact with each other but are part of a common pathway. The study of BBS illustrates the value of using isolated inbred populations for the study of human genetic diseases and suggests strategies for facilitating the study of complex diseases and traits.
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PMID:Use of isolated populations in the study of a human obesity syndrome, the Bardet-Biedl syndrome. 1515 61

Bardet-Biedl syndrome (BBS) is a multisystemic disorder characterized by postaxial polydactyly, progressive retinal dystrophy, obesity, hypogonadism, renal dysfunction, and learning difficulty. Other manifestations include diabetes mellitus, heart disease, hepatic fibrosis, and neurological features. The condition is genetically heterogeneous, and eight genes (BBS1-BBS8) have been identified to date. A mutation of the BBS1 gene on chromosome 11q13 is observed in 30%-40% of BBS cases. In addition, a complex triallelic inheritance has been established in this disorder--that is, in some families, three mutations at two BBS loci are necessary for the disease to be expressed. The clinical features of BBS that can be observed at birth are polydactyly, kidney anomaly, hepatic fibrosis, and genital and heart malformations. Interestingly, polydactyly, cystic kidneys, and liver anomalies (hepatic fibrosis with bile-duct proliferation) are also observed in Meckel syndrome, along with occipital encephalocele. Therefore, we decided to sequence the eight BBS genes in a series of 13 antenatal cases presenting with cystic kidneys and polydactyly and/or hepatic fibrosis but no encephalocele. These fetuses were mostly diagnosed as having Meckel or "Meckel-like" syndrome. In six cases, we identified a recessive mutation in a BBS gene (three in BBS2, two in BBS4, and one in BBS6). We found a heterozygous BBS6 mutation in three additional cases. No BBS1, BBS3, BBS5, BBS7, or BBS8 mutations were identified in our series. These results suggest that the antenatal presentation of BBS may mimic Meckel syndrome.
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PMID:Antenatal presentation of Bardet-Biedl syndrome may mimic Meckel syndrome. 1566 42

Bardet-Biedl syndrome is a genetically heterogeneous multisystem disorder that causes severe visual impairment. Retinitis pigmentosa (RP), hypogonadism, digit and renal anomalies, obesity, and a variable degree of mental retardation characterize the disorder. Eight different loci have been identified on 2q31(BBS5), 3p13 (BBS3), 4q27 (BBS7), 11q13 (BBS1), 14q32 (BBS8), 15q22.3 (BBS4), 16q21 (BBS2), and 20p12 (BBS6). The ocular manifestations of Bardet-Biedl syndrome include an early and severe rod-cone dystrophy causing legal blindness in the second decade. Features of systemic phenotypic variability were proposed to distinguish patients mapped to either the BBS2, BBS3, or BBS4 loci but no phenotype-genotype correlation has been established for the ocular phenotype. We studied the three original families used for the identification of BBS2, BBS3, and BBS4 loci to define the ocular phenotypes of patients (n = 34) and obligate carriers (n = 32) using clinical examination and electroretinography (ERG). RP was severe and early in all cases. Myopia was associated with BBS3 and BBS4, but not BBS2. One patient with Bardet-Biedl syndrome also had iris and chorioretinal colobomata, features suggestive of Biemond syndrome.
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PMID:Ocular phenotypes of three genetic variants of Bardet-Biedl syndrome. 1569 Mar 72

Until recently, Bardet-Biedl syndrome was considered as a classic autosomal recessive condition. The disorder is defined by the association of the following clinical features: retinitis pigmentosa, polydactyly, obesity, hypogonadism, and possible mental retardation. This syndrome leads to multiple handicaps (visual impairment, complications of obesity, kidney failure, endocrine dysfunction). This condition, apparently clearly defined from a clinical point of view, appears to be genetically heterogenous. To date, six different genes have been identified: BBS1, BBS2, BBS4, BBS6, BBS7 and BBS8. Interestingly, this condition has recently been linked to a failure of cellular ciliogenesis. Moreover, this disorder is characterized by an additional degree of complexity, as it is the first example of triallelic inheritance described in human beings. However, this new finding appears to be less frequent than expected in this syndrome.
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PMID:[Update on Bardet-Biedl syndrome]. 1576 6

The phenotype of Bardet-Biedl syndrome (BBS) is defined by the association of retinitis pigmentosa, obesity, polydactyly, hypogenitalism, renal disease and cognitive impairement. The significant genetic heterogeneity of this condition is supported by the identification, to date, of eight genes (BBS1-8) implied with cilia assembly or function. Triallelic inheritance has recently been suggested on the basis of the identification of three mutated alleles in two different genes for the same patient. In a cohort of 27 families, six BBS genes (namely BBS1, BBS2, BBS4, BBS6, BBS7 and BBS8) have been studied. Mutations were identified in 14 families. Two mutations within the same gene have been identified in seven families. BBS1 is most frequently implied with the common M390R substitution at the homozygous state (n=2), or associated with another mutation at BBS1 (n=3). Compound heterozygous mutations have been found in BBS2 (one family) and BBS6 (one family). In seven other families, only one heterozygous mutation has been identified (once in BBS1, twice for BBS2 and three times in BBS6). Although our study did not reveal any families with bona fide mutations in two BBS genes, consistent with a triallelic hypothesis, we have found an excess of heterozygous single mutations. This study underlines the genetic heterogeneity of the BBS and the involvement of possibly unidentified genes.
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PMID:Testing for triallelism: analysis of six BBS genes in a Bardet-Biedl syndrome family cohort. 1577 Feb 29

Bardet-Biedl syndrome (BBS) is a rare, developmental disorder characterized by six major symptoms: rod-cone dystrophy, obesity, polydactyly, renal abnormalities, learning difficulties, and hypogonadism. Secondary features include cardiac and hepatic anomalies, metabolic disturbancies, and hearing loss. BBS is genetically heterogeneous with 12 disease genes (BBS1-BBS12) described thus far. Current data suggest a functional disturbance in ciliary function and intraflagellar transport being associated with the phenotype. However, the precise functions of the BBS proteins have yet to be elucidated. This study focuses on the detection of protein factors interacting with BBS proteins. Applying yeast two-hybrid (Y2H) technology we found a series of novel, functionally potentially plausible binding partners of BBS1, BBS2, BBS4, and BBS7. Protein interactions were supported by coimmunoprecipitation analyses (ALDOB, EPAS1) and substantiated by colocalization studies at the subcellular level (ALDOB, EXOC7, FLOT1, KRT18, PAX2). Our work provides new insights into the understanding of BBS interactions and thus their biological function.
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PMID:Novel interaction partners of Bardet-Biedl syndrome proteins. 1800 Aug 79

The pleiotropic features of obesity, retinal degeneration, polydactyly, kidney abnormalities, cognitive impairment, hypertension, and diabetes found in Bardet-Biedl syndrome (BBS) make this disorder an important model disorder for identifying molecular mechanisms involved in common human diseases. To date, 16 BBS genes have been reported, seven of which (BBS1, 2, 4, 5, 7, 8, and 9) code for proteins that form a complex known as the BBSome. The function of the BBSome involves ciliary membrane biogenesis. Three additional BBS genes (BBS6, BBS10, and BBS12) have homology to type II chaperonins and interact with CCT/TRiC proteins and BBS7 to form a complex termed the BBS-chaperonin complex. This complex is required for BBSome assembly. Little is known about the process and the regulation of BBSome formation. We utilized point mutations and null alleles of BBS proteins to disrupt assembly of the BBSome leading to the accumulation of BBSome assembly intermediates. By characterizing BBSome assembly intermediates, we show that the BBS-chaperonin complex plays a role in BBS7 stability. BBS7 interacts with BBS2 and becomes part of a BBS7-BBS2-BBS9 assembly intermediate referred to as the BBSome core complex because it forms the core of the BBSome. BBS1, BBS5, BBS8, and finally BBS4 are added to the BBSome core to form the complete BBSome.
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PMID:Intrinsic protein-protein interaction-mediated and chaperonin-assisted sequential assembly of stable bardet-biedl syndrome protein complex, the BBSome. 2250 27

Bardet-Biedl Syndrome (BBS) is a pleiotropic and genetically heterozygous disorder caused independently by numerous genes (BBS1-BBS17). Seven highly conserved BBS proteins (BBS1, 2, 4, 5, 7, 8 and 9) form a complex known as the BBSome, which functions in ciliary membrane biogenesis. BBS7 is both a unique subunit of the BBSome and displays direct physical interaction with a second BBS complex, the BBS chaperonin complex. To examine the in vivo function of BBS7, we generated Bbs7 knockout mice. Bbs7(-/-) mice show similar phenotypes to other BBS gene mutant mice including retinal degeneration, obesity, ventriculomegaly and male infertility characterized by abnormal spermatozoa flagellar axonemes. Using tissues from Bbs7(-/-) mice, we show that BBS7 is required for BBSome formation, and that BBS7 and BBS2 depend on each other for protein stability. Although the BBSome serves as a coat complex for ciliary membrane proteins, BBS7 is not required for the localization of ciliary membrane proteins polycystin-1, polycystin-2, or bitter taste receptors, but absence of BBS7 leads to abnormal accumulation of the dopamine D1 receptor to the ciliary membrane, indicating that BBS7 is involved in specific membrane protein localization to cilia.
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PMID:BBS7 is required for BBSome formation and its absence in mice results in Bardet-Biedl syndrome phenotypes and selective abnormalities in membrane protein trafficking. 2357 16

Bardet-Biedl syndrome (BBS) is an autosomal recessive disorder characterized by central obesity, mental impairment, rod-cone dystrophy, polydactyly, hypogonadism in males, and renal abnormalities. The causative genes have been identified as BBS1-19. In Western countries, this disease is often reported, but remains undiagnosed in many patients until later in life, while only a few patients with no mutations identified have been reported in Japan. We thus conducted the first nationwide survey of BBS in Japan by sending questionnaires to 2,166 clinical departments with board-certified specialists and found 7 patients with clinically definite BBS. We performed exome analyses combined with analyses of mRNA and protein in these patients. We identified 2 novel mutations in the BBS5 gene (p.R89X and IVS7-27 T>G) in 2 sibling patients. The latter mutation that resided far from the authentic splicing site was associated with skipping of exon 8. We also found 3 previously reported mutations in the BBS2 (p.R413X and p.R480X) and BBS7 (p.C243Y) genes in 2 patients. To our knowledge, a nationwide survey of BBS has not been reported in any other country. In addition, this is the first study to identify genetic alterations in Japanese patients with BBS. Our results indicate that BBS in Japan is genetically heterogeneous and at least partly shares genetic features with BBS in other countries.
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PMID:The First Nationwide Survey and Genetic Analyses of Bardet-Biedl Syndrome in Japan. 2632 87


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