RESUMEN

Pathogenic variants in the CEP290 gene may result in a broad spectrum of diseases, ranging from lethal neonatal syndromes to isolated retinopathy. A detailed review of the clinical spectrum with the incidence of affected extraocular systems has not yet been published. A review of published papers was carried out to provide a comprehensive report on systemic signs and symptoms associated with CEP290 ciliopathies and to explore the genotype-phenotype correlation. Genetic and clinical data were collected on patients with biallelic variants in the CEP290 gene and the extraocular tissues affected. Genotype-phenotype analysis was performed. Two hundred thirty-five patients were included in the analysis. The most frequently reported organs affected, after the eye, were the central nervous system (82.6%, 194/235), followed by the kidney (53.2%, 125/235), skeletal system (15.3% 36/235), and a large spectrum of other, less frequently reported clinical manifestations. Patients with two variants that together predictably resulted in a low amount of CEP290 protein showed a significant association with having two or more extraocular organ systems affected. This is the most extensive report to date on patients with CEP290-ciliopathy and affected extraocular tissues. Based on these findings and previous publications, systemic screening is proposed, together with a clinical pathway for patients with CEP290-related ciliopathy.

RESUMEN

Ciliopathies represent a major category of rare multisystem disease. Arriving at a specific diagnosis for a given patient is challenged by the significant genetic and clinical heterogeneity of these conditions. We report the outcome of the diagnostic odyssey of a child with obesity, renal, and retinal disease. Genome sequencing identified biallelic splice site variants in sodium channel and clathrin linker 1 (SCLT1), an emerging ciliopathy gene. We review the literature on all patients reported with biallelic SCLT1 variants highlighting a frequent clinical presentation that overlaps Bardet-Biedl and Senior-Loken syndromes. We also discuss current concepts in syndrome designation in light of these data.

RESUMEN

A precise diagnosis in medicine allows appropriate disease-specific management. Kidney failure of unknown aetiology remains a frequent diagnostic label within the haemodialysis unit and kidney transplant clinic, accounting for 15-20% of these patients. Approximately 10% of such cases may have an underlying monogenic cause of kidney failure. Modern genetic approaches can provide a precise diagnosis for patients and their families. A search for extra-renal disease manifestations is also important as this may point to a specific genetic diagnosis. Here, we present two patients where molecular genetic testing was performed because of kidney failure of unknown aetiology and associated retinal phenotypes. The first patient reached kidney failure at 16 years of age but only presented with a retinal phenotype at 59 years of age and was found to have evidence of rod-cone dystrophy. The second patient presented with childhood kidney failure at the age of 15 years and developed visual difficulties and photophobia at the age of 32 years and was diagnosed with cone dystrophy. In both cases, genetic tests were performed which revealed a homozygous whole-gene deletion of NPHP1-encoding nephrocystin-1, providing the unifying diagnosis of Senior-Løken syndrome type 1. We conclude that reviewing kidney and extra-renal phenotypes together with targeted genetic testing was informative in these cases of kidney failure of unknown aetiology and associated retinal phenotypes. The involvement of an interdisciplinary team is advisable when managing such patients and allows referral to other relevant specialities. The long time lag and lack of diagnostic clarity and clinical evaluation in our cases should encourage genetic investigations for every young patient with unexplained kidney failure. For these and similar patients, a more timely genetic diagnosis would allow for improved management, a risk assessment of kidney disease in relatives, and the earlier identification of extra-renal disease manifestations. Supplementary Information: The online version contains supplementary material available at 10.1007/s44162-024-00031-4.

RESUMEN

A patient who had been diagnosed with infantile retinal dystrophy developed renal failure in his twenties, at which time the diagnosis was revised to Senior-Loken syndrome. He was poorly compliant. At 36 years old, he experienced a sudden drop in visual acuity in the setting of cramping and fatigue and was found to be in uremic crisis. Six months after the event and its treatment, his vision failed to improved. Optic nerve pallor was out of proportion to the retinal dystrophy, and the presumed reason for his new visual loss was uremic optic neuropathy. The patient's younger sister also had been diagnosed with infantile retinal dystrophy, and metabolic screening confirmed subclinical renal dysfunction that was to be carefully followed going forward. Infantile retinal dystrophy can be associated with later systemic disease. Early detection of such disease can potentially decrease morbidity. Patients with retinal dystrophy can develop new visual loss from causes other than the retinopathy itself.

RESUMEN

Nephronophthisis (NPHP) is an autosomal recessive cystic kidney disease and is one of the most frequent genetic causes for kidney failure (KF) in children and adolescents. Over 20 genes cause NPHP and over 90 genes contribute to renal ciliopathies often involving multiple organs. About 15-20% of NPHP patients have additional extrarenal symptoms affecting other organs than the kidneys. The involvement of additional organ systems in syndromic forms of NPHP is explained by shared expression of most NPHP gene products in centrosomes and primary cilia, a sensory organelle present in most mammalian cells. This finding resulted in the classification of NPHP as a ciliopathy. If extrarenal symptoms are present in addition to NPHP, these disorders are defined as NPHP-related ciliopathies (NPHP-RC) and can involve the retina (e.g., with Senior-Løken syndrome), CNS (central nervous system) (e.g., with Joubert syndrome), liver (e.g., Boichis and Arima syndromes), or bone (e.g., Mainzer-Saldino and Sensenbrenner syndromes). This review focuses on the pathological findings and the recent genetic advances in NPHP and NPHP-RC. Different mechanisms and signaling pathways are involved in NPHP ranging from planar cell polarity, sonic hedgehog signaling (Shh), DNA damage response pathway, Hippo, mTOR, and cAMP signaling. A number of therapeutic interventions appear to be promising, ranging from vasopressin receptor 2 antagonists such as tolvaptan, cyclin-dependent kinase inhibitors such as roscovitine, Hh agonists such as purmorphamine, and mTOR inhibitors such as rapamycin.

RESUMEN

Senior-Loken syndrome (SLS) is a rare autosomal recessive disorder affecting the eyes and the kidneys. It is an extremely rare disorder with an incidence of 1/1,000,000. Like most hereditary disorders, it is more commonly seen in families with consanguineous marriages. Here, we present a case of a 35-year-old male with a complicated past medical history, who presented to us in the outpatient department for kidney transplant consideration. The patient was diagnosed case of Senior-Loken syndrome with a family history of autoimmune diseases, renal disease, and multiple unexplained miscarriages. He also had multiple dialysis access-related complications requiring frequent access changes. He previously had an unrelated pre-emptive renal transplant which resulted in graft failure within 48 hours. In view of his history, a prothrombotic condition was suspected and the patient was started on warfarin. Workup was positive for lupus anticoagulant and hematology recommended lifelong anticoagulation. The patient had a related renal transplant that was successful. He is now on apixaban and has not had any thrombotic complications to date. This patient had antiphospholipid syndrome leading to multiple thrombotic events and a failed graft, but was never worked up for autoimmune disorders despite having a strong family history. His renal disease was presumed to be secondary to a rare condition - Senior-Loken syndrome and he was not investigated for a co-existing condition (e.g., antiphospholipid syndrome {APLS} in this case) which led to early graft failure. Hence when considering a patient for transplant, care should be taken to rule out autoimmune diseases and not ignore possible co-existing conditions in the presence of a renal pathology.

RESUMEN

Our case report and review contribute to the understanding of ocular manifestations in NPHP1 ciliopathies by reinforcing the relationship between pathogenic genetic variants and a wide array of ophthalmic abnormalities.

RESUMEN

Pulmonary sequestration is a rare congenital malformation. It represents 0.15-6.4% of all congenital pulmonary malformations. It is characterized by non-functional, dysplastic mass of lung tissue that is not in communication with the normal tracheobronchial tree and is associated with a systemic arterial supply. We report a young gentleman in his mid-thirties who presented with community-acquired pneumonia from an infected intralobar pulmonary sequestration which subsequently developed a hemothorax from an anomalous bronchial artery bleed.

RESUMEN

Mutations in the IQ calmodulin-binding motif containing B1 (IQCB1)/NPHP5 gene encoding the ciliary protein nephrocystin 5 cause early-onset blinding disease Leber congenital amaurosis (LCA), together with kidney dysfunction in Senior-Løken syndrome. For in vitro disease modeling, we obtained dermal fibroblasts from patients with NPHP5-LCA that were reprogrammed into induced pluripotent stem cells (iPSCs) and differentiated into retinal pigment epithelium (RPE) and retinal organoids. Patient fibroblasts and RPE demonstrated aberrantly elongated ciliary axonemes. Organoids revealed impaired development of outer segment structures, which are modified primary cilia, and mislocalization of visual pigments to photoreceptor cell soma. All patient-derived cells showed reduced levels of CEP290 protein, a critical cilia transition zone component interacting with NPHP5, providing a plausible mechanism for aberrant ciliary gating and cargo transport. Disease phenotype in NPHP5-LCA retinal organoids could be rescued by adeno-associated virus (AAV)-mediated IQCB1/NPHP5 gene augmentation therapy. Our studies thus establish a human disease model and a path for treatment of NPHP5-LCA.

Asunto(s)

Calmodulina , Ciliopatías , Antígenos de Neoplasias/genética , Calmodulina/genética , Calmodulina/metabolismo , Proteínas de Unión a Calmodulina/genética , Proteínas de Unión a Calmodulina/metabolismo , Proteínas de Ciclo Celular/metabolismo , Ciliopatías/genética , Proteínas del Citoesqueleto/genética , Proteínas del Citoesqueleto/metabolismo , Humanos , Mutación , Pigmentos Retinianos/metabolismo

RESUMEN

This case series describes the ocular and retinal manifestations of rare eye diseases in systemic syndromes. This observational case series consists of five patients with varied ophthalmic manifestations and documentation of imaging in rare pediatric and adult retinopathies. Two patients had Kearns Sayre syndrome (KSS) based on the classical triad of external ophthalmoplegia, pigmentary retinopathy, and onset before 20 years of age. In one patient of KSS, the mitochondrial retinopathy was seen in an asymmetric pattern, and the second patient presented with KSS after being mis-diagnosed as myasthenia gravis elsewhere. A case of Senior Loken syndrome in pediatric age is described in this series with varied ophthalmic manifestations ranging from retinitis pigmentosa to orbital abscess. This series also enlightens features of Hallervorden Spatz syndrome presenting with bull's eye maculopathy and a case of spino-cerebellar ataxia type 7 presenting with pigmentary retinopathy.

Asunto(s)

Síndrome de Kearns-Sayre , Oftalmoplejía , Enfermedades de la Retina , Retinitis Pigmentosa , Adulto , Niño , Cara , Humanos , Síndrome de Kearns-Sayre/complicaciones , Síndrome de Kearns-Sayre/diagnóstico , Enfermedades Raras , Enfermedades de la Retina/diagnóstico , Enfermedades de la Retina/etiología , Retinitis Pigmentosa/diagnóstico

RESUMEN

Mutations in serologically defined colon cancer autoantigen protein 8 ( SDCCAG8) were first identified in retinal ciliopathy families a decade ago with unknown function. To investigate the pathogenesis of SDCCAG8-associated retinal ciliopathies in vivo, we employed CRISPR/Cas9-mediated homology-directed recombination (HDR) to generate two knock-in mouse models, Sdccag8Y236X/Y236X and Sdccag8E451GfsX467/E451GfsX467 , which carry truncating mutations of the mouse Sdccag8, corresponding to mutations that cause Bardet-Biedl syndrome (BBS) and Senior-Løken syndrome (SLS) (c.696T>G p.Y232X and c.1339-1340insG p.E447GfsX463) in humans, respectively. The two mutant Sdccag8 knock-in mice faithfully recapitulated human SDCCAG8-associated BBS phenotypes such as rod-cone dystrophy, cystic renal disorder, polydactyly, infertility, and growth retardation, with varied age of onset and severity depending on the hypomorphic strength of the Sdccag8 mutations. To the best of our knowledge, these knock-in mouse lines are the first BBS mouse models to present with the polydactyly phenotype. Major phototransduction protein mislocalization was also observed outside the outer segment after initiation of photoreceptor degeneration. Impaired cilia were observed in the mutant photoreceptors, renal epithelial cells, and mouse embryonic fibroblasts derived from the knock-in mouse embryos, suggesting that SDCCAG8 plays an essential role in ciliogenesis, and cilium defects are a primary driving force of SDCCAG8-associated retinal ciliopathies.

Asunto(s)

Síndrome de Bardet-Biedl , Ciliopatías , Polidactilia , Enfermedades de los Roedores , Animales , Autoantígenos/genética , Autoantígenos/metabolismo , Síndrome de Bardet-Biedl/genética , Síndrome de Bardet-Biedl/metabolismo , Síndrome de Bardet-Biedl/veterinaria , Ciliopatías/genética , Ciliopatías/metabolismo , Ciliopatías/veterinaria , Fibroblastos , Ratones , Mutación , Proteínas de Neoplasias/genética , Proteínas de Neoplasias/metabolismo , Polidactilia/veterinaria

RESUMEN

Primary cilia are specialized sensory organelles that protrude from the apical surface of most cell types. During the past 2 decades, they have been found to play important roles in tissue development and signal transduction, with mutations in ciliary-associated proteins resulting in a group of diseases collectively known as ciliopathies. Many of these mutations manifest as renal ciliopathies, characterized by kidney dysfunction resulting from aberrant cilia or ciliary functions. This group of overlapping and genetically heterogeneous diseases includes polycystic kidney disease, nephronophthisis, and Bardet-Biedl syndrome as the main focus of this review. Renal ciliopathies are characterized by the presence of kidney cysts that develop due to uncontrolled epithelial cell proliferation, growth, and polarity, downstream of dysregulated ciliary-dependent signaling. Due to cystic-associated kidney injury and systemic inflammation, cases result in kidney failure requiring dialysis and transplantation. Of the handful of pharmacologic treatments available, none are curative. It is important to determine the molecular mechanisms that underlie the involvement of the primary cilium in cyst initiation, expansion, and progression for the development of novel and efficacious treatments. This review updates research progress in defining key genes and molecules central to ciliogenesis and renal ciliopathies.

Asunto(s)

Síndrome de Bardet-Biedl/genética , Cilios/metabolismo , Ciliopatías/genética , Enfermedades Renales Poliquísticas/genética , Anomalías Múltiples/genética , Anomalías Múltiples/metabolismo , Anomalías Múltiples/fisiopatología , Proteínas Adaptadoras Transductoras de Señales/genética , Proteínas Adaptadoras del Transporte Vesicular/genética , Síndrome de Bardet-Biedl/metabolismo , Síndrome de Bardet-Biedl/fisiopatología , Cerebelo/anomalías , Cerebelo/metabolismo , Cerebelo/fisiopatología , Chaperoninas/genética , Cilios/fisiología , Trastornos de la Motilidad Ciliar/genética , Trastornos de la Motilidad Ciliar/metabolismo , Trastornos de la Motilidad Ciliar/fisiopatología , Ciliopatías/metabolismo , Ciliopatías/fisiopatología , Proteínas del Citoesqueleto/genética , Encefalocele/genética , Encefalocele/metabolismo , Encefalocele/fisiopatología , Anomalías del Ojo/genética , Anomalías del Ojo/metabolismo , Anomalías del Ojo/fisiopatología , Humanos , Enfermedades Renales Quísticas/genética , Enfermedades Renales Quísticas/metabolismo , Enfermedades Renales Quísticas/fisiopatología , Amaurosis Congénita de Leber/genética , Amaurosis Congénita de Leber/metabolismo , Amaurosis Congénita de Leber/fisiopatología , Proteínas de la Membrana/genética , Proteínas Asociadas a Microtúbulos/genética , Atrofias Ópticas Hereditarias/genética , Atrofias Ópticas Hereditarias/metabolismo , Atrofias Ópticas Hereditarias/fisiopatología , Enfermedades Renales Poliquísticas/metabolismo , Enfermedades Renales Poliquísticas/fisiopatología , Proteínas/genética , Retina/anomalías , Retina/metabolismo , Retina/fisiopatología , Retinitis Pigmentosa/genética , Retinitis Pigmentosa/metabolismo , Retinitis Pigmentosa/fisiopatología , Canales Catiónicos TRPP/genética

RESUMEN

BACKGROUND: Senior-Loken syndrome is a rare genetic disorder that presents with nephronophthisis and retinal degeneration, leading to end-stage renal disease and progressive blindness. The most frequent cause of juvenile nephronophthisis is a mutation in the nephronophthisis type 1 (NPHP1) gene. NPHP1 encodes the protein nephrocystin-1, which functions at the transition zone (TZ) of primary cilia. METHODS: We report a 9-year-old Senior-Loken syndrome boy with NPHP1 deletion, who presents with bilateral vision decrease and cystic renal disease. Renal function deteriorated to require bilateral nephrectomy and renal transplant. We performed immunohistochemistry, H&E staining, and electron microscopy on the renal sample to determine the subcellular distribution of ciliary proteins in the absence of NPHP1. RESULTS: Immunohistochemistry and electron microscopy of the resected kidney showed disorganized cystic structures with loss of cilia in renal tubules. Phosphoinositides have been recently recognized as critical components of the ciliary membrane and immunostaining of kidney sections for phosphoinositide 5-phosphatase, INPP5E, showed loss of staining compared to healthy control. Ophthalmic examination showed decreased electroretinogram consistent with early retinal degeneration. CONCLUSION: The decreased expression of INPP5E specifically in the primary cilium, coupled with disorganized cilia morphology, suggests a novel role of NPHP1 that it is involved in regulating ciliary phosphoinositide composition in the ciliary membrane of renal tubular cells.

Asunto(s)

Proteínas Adaptadoras Transductoras de Señales/genética , Ciliopatías/genética , Proteínas del Citoesqueleto/genética , Enfermedades Renales Quísticas/genética , Amaurosis Congénita de Leber/genética , Atrofias Ópticas Hereditarias/genética , Monoéster Fosfórico Hidrolasas/metabolismo , Niño , Cilios/metabolismo , Ciliopatías/metabolismo , Ciliopatías/patología , Eliminación de Gen , Humanos , Riñón/metabolismo , Riñón/patología , Enfermedades Renales Quísticas/metabolismo , Enfermedades Renales Quísticas/patología , Amaurosis Congénita de Leber/metabolismo , Amaurosis Congénita de Leber/patología , Masculino , Atrofias Ópticas Hereditarias/metabolismo , Atrofias Ópticas Hereditarias/patología , Monoéster Fosfórico Hidrolasas/genética

RESUMEN

BACKGROUND: Senior-Løken syndrome (SLS) is a rare autosomal recessive disease characterised by nephronophthisis and retinal degeneration, and belongs to a group of genetically heterogeneous disorders known as the ciliopathies. MATERIALS AND METHODS: Case report of a  patient with genetically proven SLS presenting with headaches and swollen optic nerve heads, review of medical notes and ophthalmic imaging, with retinal photography, fundus autofluorescence, and OCT retinal nerve fibre layer analysis. RESULTS: We present findings in a 15 year old girl with Senior-Løken syndrome associated with compound heterozygous mutations in the SDCCAG8 gene,  who initially presented with a retinal dystrophy, and subsequent renal failure requiring renal transplantation and immunosuppression. Four and a half years later, she presented with headaches, reduced vision and clinical findings of papilloedema.  Cerebrospinal fluid analysis revealed a high opening pressure of 37cmH20 and neuroimaging was otherwise unremarkable.  Treatment with a reduced dose of oral acetazolamide resulted in symptomatic relief of headaches, and resolution of optic nerve swelling. CONCLUSION: The association of intracranial hypertension in a ciliopathy is a rare occurrence.  The aetiology of intracranial hypertension in this case is likely multi-factorial, due to renal transplantation, post-renal transplant medications and/ or weight gain.  With evidence of cilia involvement in the central nervous system, ciliary dysfunction may contribute to intracranial hypertension, and should be considered in these patients presenting with headaches. Diagnosis may be difficult with advanced retinal degeneration and baseline retinal nerve fibre layer thinning. Treatment requires careful monitoring of renal function.

Asunto(s)

Ciliopatías/patología , Hipertensión Intracraneal/patología , Enfermedades Renales Quísticas/patología , Amaurosis Congénita de Leber/patología , Atrofias Ópticas Hereditarias/patología , Adolescente , Ciliopatías/complicaciones , Femenino , Humanos , Hipertensión Intracraneal/complicaciones , Enfermedades Renales Quísticas/complicaciones , Amaurosis Congénita de Leber/complicaciones , Atrofias Ópticas Hereditarias/complicaciones , Pronóstico

RESUMEN

Senior-Loken syndrome is a rare disorder that presents in the first two decades of life. It commonly manifests with nephronophthisis and retinal dystrophy. We describe a teenager who had end-stage renal failure presenting with bilateral visual impairment due to retinal dystrophy with concomitant unilateral Coats disease and exudative retinal detachment. The patient was treated with a combination of endolaser photocoagulation and external drainage of the subretinal fluid. The final visual acuity remained poor in both eyes. Options of treatment in this challenging situation is discussed in this case report.

RESUMEN

Senior-Løken syndrome is a rare autosomal recessive disease with a prevalence of 1:1,000,000. Retinopathy may progress as Leber congenital amaurosis (LCA), retinitis pigmentosa (RP), or sector RP (Figs. 34.1 and 34.2). Onset of photophobia, nystagmus, and hyperopia can occur in the first few years of life or later in childhood. Patients experience nephronophthisis, characterized by cystic kidney disease (medullary cystic kidney disease), reduced concentrating ability, and chronic tubulointerstitial nephritis, which progresses to end-stage renal disease. Hypertension is common.

Asunto(s)

Ciliopatías/fisiopatología , Enfermedades Renales Quísticas/fisiopatología , Amaurosis Congénita de Leber/fisiopatología , Atrofias Ópticas Hereditarias/fisiopatología , Humanos , Mutación

RESUMEN

BACKGROUND AND OBJECTIVES: Genetic heterogeneity and phenotypic variability are major challenges in familial nephronophthisis and related ciliopathies. To date, mutations in 20 different genes (NPHP1 to -20) have been identified causing either isolated kidney disease or complex multiorgan disorders. In this study, we provide a comprehensive and detailed characterization of 152 children with a special focus on extrarenal organ involvement and the long-term development of ESRD. DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS: We established an online-based registry (www.nephreg.de) to assess the clinical course of patients with nephronophthisis and related ciliopathies on a yearly base. Cross-sectional and longitudinal data were collected. Mean observation time was 7.5±6.1 years. RESULTS: In total, 51% of the children presented with isolated nephronophthisis, whereas the other 49% exhibited related ciliopathies. Monogenetic defects were identified in 97 of 152 patients, 89 affecting NPHP genes. Eight patients carried mutations in other genes related to cystic kidney diseases. A homozygous NPHP1 deletion was, by far, the most frequent genetic defect (n=60). We observed a high prevalence of extrarenal manifestations (23% [14 of 60] for the NPHP1 group and 66% [61 of 92] for children without NPHP1). A homozygous NPHP1 deletion not only led to juvenile nephronophthisis but also was able to present as a predominantly neurologic phenotype. However, irrespective of the initial clinical presentation, the kidney function of all patients carrying NPHP1 mutations declined rapidly between the ages of 8 and 16 years, with ESRD at a mean age of 11.4±2.4 years. In contrast within the non-NPHP1 group, there was no uniform pattern regarding the development of ESRD comprising patients with early onset and others preserving normal kidney function until adulthood. CONCLUSIONS: Mutations in NPHP genes cause a wide range of ciliopathies with multiorgan involvement and different clinical outcomes.

Asunto(s)

Proteínas Adaptadoras Transductoras de Señales/genética , Ciliopatías/genética , Enfermedades Renales Quísticas/congénito , Fallo Renal Crónico/genética , Proteínas de la Membrana/genética , Fenotipo , Adolescente , Anemia/genética , Antígenos de Neoplasias/genética , Proteínas de Unión a Calmodulina/genética , Proteínas Portadoras/genética , Proteínas de Ciclo Celular , Niño , Ciliopatías/complicaciones , Estudios Transversales , Proteínas del Citoesqueleto , Femenino , Tasa de Filtración Glomerular/genética , Homocigoto , Humanos , Riñón/diagnóstico por imagen , Enfermedades Renales Quísticas/complicaciones , Enfermedades Renales Quísticas/diagnóstico por imagen , Enfermedades Renales Quísticas/genética , Fallo Renal Crónico/fisiopatología , Cinesinas/genética , Estudios Longitudinales , Masculino , Proteínas de Neoplasias/genética , Enfermedades del Sistema Nervioso/genética , Poliuria/genética , Proteínas/genética , Ultrasonografía , Adulto Joven

RESUMEN

Upwards of 90% of individuals with Bardet-Biedl syndrome (BBS) display rod-cone dystrophy with early macular involvement. BBS is an autosomal recessive, genetically heterogeneous, pleiotropic ciliopathy for which 21 causative genes have been discovered to date. In addition to retinal degeneration, the cardinal features of BBS include obesity, cognitive impairment, renal anomalies, polydactyly, and hypogonadism. Here, we review the genes, proteins, and protein complexes involved in BBS and the BBS model organisms available for the study of retinal degeneration. We include comprehensive lists for all known BBS genes, their known phenotypes, and the model organisms available. We also review the molecular mechanisms believed to lead to retinal degeneration. We provide an overview of the mode of inheritance and describe the relationships between BBS genes and Joubert syndrome, Leber Congenital Amaurosis, Senior-Løken syndrome, and non-syndromic retinitis pigmentosa. Finally, we propose ways that new advances in technology will allow us to better understand the role of different BBS genes in retinal formation and function.

RESUMEN

BACKGROUND: Ciliopathies are clinically diverse disorders of the primary cilium. Remarkable progress has been made in understanding the molecular basis of these genetically heterogeneous conditions; however, our knowledge of their morbid genome, pleiotropy, and variable expressivity remains incomplete. RESULTS: We applied genomic approaches on a large patient cohort of 371 affected individuals from 265 families, with phenotypes that span the entire ciliopathy spectrum. Likely causal mutations in previously described ciliopathy genes were identified in 85% (225/265) of the families, adding 32 novel alleles. Consistent with a fully penetrant model for these genes, we found no significant difference in their "mutation load" beyond the causal variants between our ciliopathy cohort and a control non-ciliopathy cohort. Genomic analysis of our cohort further identified mutations in a novel morbid gene TXNDC15, encoding a thiol isomerase, based on independent loss of function mutations in individuals with a consistent ciliopathy phenotype (Meckel-Gruber syndrome) and a functional effect of its deficiency on ciliary signaling. Our study also highlighted seven novel candidate genes (TRAPPC3, EXOC3L2, FAM98C, C17orf61, LRRCC1, NEK4, and CELSR2) some of which have established links to ciliogenesis. Finally, we show that the morbid genome of ciliopathies encompasses many founder mutations, the combined carrier frequency of which accounts for a high disease burden in the study population. CONCLUSIONS: Our study increases our understanding of the morbid genome of ciliopathies. We also provide the strongest evidence, to date, in support of the classical Mendelian inheritance of Bardet-Biedl syndrome and other ciliopathies.

Asunto(s)

Cilios/genética , Trastornos de la Motilidad Ciliar/genética , Ciliopatías/genética , Encefalocele/genética , Mutación/genética , Enfermedades Renales Poliquísticas/genética , Alelos , Cilios/patología , Trastornos de la Motilidad Ciliar/patología , Ciliopatías/patología , Análisis Mutacional de ADN , Encefalocele/patología , Estudios de Asociación Genética , Heterogeneidad Genética , Predisposición Genética a la Enfermedad , Humanos , Fenotipo , Enfermedades Renales Poliquísticas/patología , Retina/metabolismo , Retina/patología , Retinitis Pigmentosa

RESUMEN

Null mutations in the human IQCB1/NPHP5 (nephrocystin-5) gene that encodes NPHP5 are the most frequent cause of Senior-Løken syndrome, a ciliopathy that is characterized by Leber congenital amaurosis and nephronophthisis. We generated germline Nphp5-knockout mice by placing a ß-Geo gene trap in intron 4, thereby truncating NPHP5 at Leu87 and removing all known functional domains. At eye opening, Nphp5-/- mice exhibited absence of scotopic and photopic electroretinogram responses, a phenotype that resembles Leber congenital amaurosis. Outer segment transmembrane protein accumulation in Nphp5-/- endoplasmic reticulum was evident as early as postnatal day (P)6. EGFP-CETN2, a centrosome and transition zone marker, identified basal bodies in Nphp5-/- photoreceptors, but without fully developed transition zones. Ultrastructure of P6 and 10 Nphp5-/- photoreceptors revealed aberrant transition zones of reduced diameter. Nphp5-/- photoreceptor degeneration was complete at 1 mo of age but was delayed significantly in Nphp5-/-;Nrl-/- (cone only) retina. Nphp5-/- mouse embryonic fibroblast developed normal cilia, and Nphp5-/- kidney histology at 1 yr of age showed no significant pathology. Results establish that nephrocystin-5 is essential for photoreceptor outer segment formation but is dispensable for kidney and mouse embryonic fibroblast ciliary formation.-Ronquillo, C. C., Hanke-Gogokhia, C., Revelo, M. P., Frederick, J. M., Jiang, L., Baehr, W. Ciliopathy-associated IQCB1/NPHP5 protein is required for mouse photoreceptor outer segment formation.

Asunto(s)

Proteínas de Unión a Calmodulina/genética , Proteínas de Unión a Calmodulina/metabolismo , Mutación/genética , Retina/metabolismo , Células Fotorreceptoras Retinianas Conos/metabolismo , Degeneración Retiniana/genética , Animales , Cilios/metabolismo , Ciliopatías/genética , Ciliopatías/metabolismo , Guanilato Ciclasa/genética , Humanos , Enfermedades Renales Quísticas/genética , Enfermedades Renales Quísticas/metabolismo , Amaurosis Congénita de Leber/genética , Amaurosis Congénita de Leber/metabolismo , Ratones Noqueados , Atrofias Ópticas Hereditarias/genética , Atrofias Ópticas Hereditarias/metabolismo , Degeneración Retiniana/metabolismo