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M'hamdi O, Ouertani I, Chaabouni-Bouhamed H. Update on the genetics of bardet-biedl syndrome. Mol Syndromol 2013; 5:51-6. [PMID: 24715851 DOI: 10.1159/000357054] [Citation(s) in RCA: 67] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 10/10/2013] [Indexed: 12/18/2022] Open
Abstract
Bardet-Biedl syndrome (BBS) is an autosomal recessive disease characterized by retinal dystrophy, obesity, postaxial polydactyly, learning disabilities, renal involvement, and male hypogenitalism. BBS is genetically heterogeneous, and to date 18 genes (BBS1-18) have been described. Mutations in known BBS genes account for approximately 70-80% of cases, and triallelic inheritance has been suggested in about 5%. Many minor features can be helpful in making the clinical diagnosis. Recently, the use of next-generation sequencing technologies has accelerated the identification of novel genes and causative disease mutations in known genes. This report presents a concise overview of the current knowledge on clinical data in BBS and the progress in molecular genetics research. A future objective will be the development of BBS diagnosis kits in order to offer genetic counseling for families at risk.
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Affiliation(s)
- O M'hamdi
- Department of Human Genetics, Faculty of Medicine, Tunis El-Manar University, Tunis, Tunisia
| | - I Ouertani
- Department of Human Genetics, Faculty of Medicine, Tunis El-Manar University, Tunis, Tunisia ; Department of Hereditary and Congenital Disorders, Charles Nicolle Hospital, Tunis, Tunisia
| | - H Chaabouni-Bouhamed
- Department of Human Genetics, Faculty of Medicine, Tunis El-Manar University, Tunis, Tunisia ; Department of Hereditary and Congenital Disorders, Charles Nicolle Hospital, Tunis, Tunisia
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Pretorius PR, Aldahmesh MA, Alkuraya FS, Sheffield VC, Slusarski DC. Functional analysis of BBS3 A89V that results in non-syndromic retinal degeneration. Hum Mol Genet 2011; 20:1625-32. [PMID: 21282186 PMCID: PMC3063988 DOI: 10.1093/hmg/ddr039] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023] Open
Abstract
Bardet–Biedl syndrome (BBS) is a syndromic form of retinal degeneration. Recently, homozygosity mapping with a consanguineous family with isolated retinitis pigmentosa identified a missense mutation in BBS3, a known BBS gene. The mutation in BBS3 encodes a single amino acid change at position 89 from alanine to valine. Since this amino acid is conserved in a wide range of vertebrates, we utilized the zebrafish model system to functionally characterize the BBS3 A89V mutation. Knockdown of bbs3 in zebrafish alters intracellular transport, a phenotype observed with knockdown of all BBS genes in the zebrafish, as well as visual impairment. Here, we find that BBS3 A89V is sufficient to rescue the transport delays induced by the loss of bbs3, indicating that this mutation does not affect the function of BBS3 as it relates to syndromic disease. BBS3L A89V, however, was unable to rescue vision impairment, highlighting a role for a specific amino acid within BBS3 that is necessary for visual function, but dispensable in other cell types. These data aid in our understanding of why patients with the BBS3 A89V missense mutation only present with isolated retinitis pigmentosa.
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Affiliation(s)
- Pamela R Pretorius
- Department of Biology, Howard Hughes Medical Institute, University of Iowa, Iowa City, Iowa 52242, USA
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Pretorius PR, Baye LM, Nishimura DY, Searby CC, Bugge K, Yang B, Mullins RF, Stone EM, Sheffield VC, Slusarski DC. Identification and functional analysis of the vision-specific BBS3 (ARL6) long isoform. PLoS Genet 2010; 6:e1000884. [PMID: 20333246 PMCID: PMC2841623 DOI: 10.1371/journal.pgen.1000884] [Citation(s) in RCA: 64] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2009] [Accepted: 02/15/2010] [Indexed: 02/02/2023] Open
Abstract
Bardet-Biedl Syndrome (BBS) is a heterogeneous syndromic form of retinal degeneration. We have identified a novel transcript of a known BBS gene, BBS3 (ARL6), which includes an additional exon. This transcript, BBS3L, is evolutionally conserved and is expressed predominantly in the eye, suggesting a specialized role in vision. Using antisense oligonucleotide knockdown in zebrafish, we previously demonstrated that bbs3 knockdown results in the cardinal features of BBS in zebrafish, including defects to the ciliated Kupffer's Vesicle and delayed retrograde melanosome transport. Unlike bbs3, knockdown of bbs3L does not result in Kupffer's Vesicle or melanosome transport defects, rather its knockdown leads to impaired visual function and mislocalization of the photopigment green cone opsin. Moreover, BBS3L RNA, but not BBS3 RNA, is sufficient to rescue both the vision defect as well as green opsin localization in the zebrafish retina. In order to demonstrate a role for Bbs3L function in the mammalian eye, we generated a Bbs3L-null mouse that presents with disruption of the normal photoreceptor architecture. Bbs3L-null mice lack key features of previously published Bbs-null mice, including obesity. These data demonstrate that the BBS3L transcript is required for proper retinal function and organization. Retinitis pigmentosa (RP), a disorder of retinal degeneration resulting in blindness, occurs due to mutations in dozens of different genes encoding proteins with highly diverse functions. To date, there are no effective therapies to delay or arrest retinal degeneration. RP places a large burden on affected families and on society as a whole. We have studied a syndromic form of RP known as Bardet-Biedl Syndrome (BBS), which leads to degeneration of the photoreceptor cells and is associated with non-vision abnormalities including obesity, hypertension, diabetes, and congenital abnormalities of the kidney, heart, and limbs. In this study we utilized two model systems, the zebrafish and mouse, to evaluate the function of a specific form of BBS (BBS3). We have identified a novel protein product of the BBS3 gene and demonstrated that functional and structural abnormalities of the eye occur when this form of BBS3 is absent. This finding is of significance because it indicates that BBS3 mutations can lead to non-syndromic blindness, as well as blindness associated with other clinical features. This work also indicates that treatment of BBS3 blindness will require replacement of a specific form of the BBS3 gene.
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Affiliation(s)
- Pamela R. Pretorius
- Department of Biology, University of Iowa, Iowa City, Iowa, United States of America
- Howard Hughes Medical Institute, Chevy Chase, Maryland, United States of America
- Department of Pediatrics, University of Iowa, Iowa City, Iowa, United States of America
| | - Lisa M. Baye
- Department of Biology, University of Iowa, Iowa City, Iowa, United States of America
| | - Darryl Y. Nishimura
- Howard Hughes Medical Institute, Chevy Chase, Maryland, United States of America
- Department of Pediatrics, University of Iowa, Iowa City, Iowa, United States of America
| | - Charles C. Searby
- Howard Hughes Medical Institute, Chevy Chase, Maryland, United States of America
- Department of Pediatrics, University of Iowa, Iowa City, Iowa, United States of America
| | - Kevin Bugge
- Howard Hughes Medical Institute, Chevy Chase, Maryland, United States of America
- Department of Pediatrics, University of Iowa, Iowa City, Iowa, United States of America
| | - Baoli Yang
- Department of Obstetrics and Gynecology, University of Iowa, Iowa City, Iowa, United States of America
| | - Robert F. Mullins
- Department of Ophthalmology and Visual Sciences, University of Iowa, Iowa City, Iowa, United States of America
| | - Edwin M. Stone
- Howard Hughes Medical Institute, Chevy Chase, Maryland, United States of America
- Department of Ophthalmology and Visual Sciences, University of Iowa, Iowa City, Iowa, United States of America
| | - Val C. Sheffield
- Howard Hughes Medical Institute, Chevy Chase, Maryland, United States of America
- Department of Pediatrics, University of Iowa, Iowa City, Iowa, United States of America
- * E-mail:
| | - Diane C. Slusarski
- Department of Biology, University of Iowa, Iowa City, Iowa, United States of America
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Spaggiari E, Salati R, Nicolini P, Borgatti R, Pozzoli U, Polenghi F. Evolution of ocular clinical and electrophysiological findings in pediatric Bardet-Biedl syndrome. Int Ophthalmol 2001; 23:61-7. [PMID: 11196121 DOI: 10.1023/a:1026560721525] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
Bardet-Biedl syndrome (BBS) is a hereditary autosomal-recessive disorder, characterized by mental retardation, obesity, pigmentary retinopathy, polydactyly and, only in males, hypogenitalism. Even though genetic studies have revealed five different forms of BBS correlated to distinct loci on different chromosomes, a diagnosis of BBS is still primarily based on clinical data. The present study discusses the evolution of clinical ophthalmological and electrophysiological characteristics of BBS patients in developmental age. The main results obtained on a sample of 13 pediatric patients are the following: * progressive loss of visual acuity arised early in the first decade of life * ophthalmoscopic signs of pigmentary retinopathy were present only in 46% of the children studied * striking anomalies in the electroretinogram were also detected in the cases without pigmentary retinopathy * the electroretinographic results, when detectable, suggested a greater involvement of the photopic system as against the scotopic system.
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Affiliation(s)
- E Spaggiari
- Department of Pediatric Ophthalmology, Scientific Institute E. Medea Bosisio Parini (Lc), Italy
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Iannaccone A, De Propris G, Roncati S, Rispoli E, Del Porto G, Pannarale MR. The ocular phenotype of the Bardet-Biedl syndrome. Comparison to non-syndromic retinitis pigmentosa. Ophthalmic Genet 1997; 18:13-26. [PMID: 9134546 DOI: 10.3109/13816819709057879] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
PURPOSE To investigate 20 patients affected with Bardet-Biedl (BB) syndrome and compare them to an age-matched group of 70 non-syndromic patients with retinitis pigmentosa (RP) to identify hallmarks peculiar to the BB phenotype. METHODS Patients were examined clinically and with functional tests (color vision, kinetic perimetry, electroretinography, ocular motility tests). Fundus findings were numerically graded for statistical purposes. RESULTS Recurrent ocular features in BB patients were early and severe reduction of visual acuity, constantly altered color vision, high incidence of strabismus and nystagmus, mild-to-severe atrophic changes of the optic disc, and frequently absent or minimal pigmentary retinal changes. Visual acuity was more closely correlated to optic disc than to macular conditions. These findings were remarkably different from non-syndromic RP. CONCLUSIONS This investigation further suggests that retinopathy in BB syndrome has features distinctive from those in non-syndromic RP. The early occurrence of optic disc atrophy in the BB syndrome, even in those patients with healthy maculas, suggests that optic atrophy could often be primary in nature and might play a major role in decreasing central vision in BB patients. Variability of some findings is in line with the documented heterogeneity of the BB syndrome.
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Affiliation(s)
- A Iannaccone
- Institute of Ophthalmology, University of Rome La Sapienza, Italy
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Bek T, Rosenberg T. Clinical pathology and retinal vascular structure in the Bardet-Biedl syndrome. Br J Ophthalmol 1995; 79:76-80. [PMID: 7880798 PMCID: PMC505025 DOI: 10.1136/bjo.79.1.76] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
A comparative study of clinical pathology and retinal vascular structure is described as studied by vascular casting in an eye of a patient with the Bardet-Biedl syndrome. At the time of examination the eye had been almost blind for at least 4 years. The histopathological examination showed a largely uniform loss of the outer retinal layers. The gross pathological examination of the cast ocular fundus showed three distinct zones, an inner zone inside the temporal vascular arcades where retinal vessels had been cast, a mid peripheral zone with bone spicules, and a peripheral zone with neither cast vessels nor bone spicules. The findings are discussed in relation to possible pathophysiological mechanisms involved in the development of retinal dystrophy in the Bardet-Biedl syndrome.
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Affiliation(s)
- T Bek
- Department of Ophthalmology, Arhus University Hospital, Denmark
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