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Owen N, Toms M, Tian Y, Toualbi L, Richardson R, Young R, Tracey‐White D, Dhami P, Beck S, Moosajee M. Loss of the crumbs cell polarity complex disrupts epigenetic transcriptional control and cell cycle progression in the developing retina. J Pathol 2023; 259:441-454. [PMID: 36656098 PMCID: PMC10601974 DOI: 10.1002/path.6056] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2022] [Revised: 12/22/2022] [Accepted: 01/17/2023] [Indexed: 01/20/2023]
Abstract
The crumbs cell polarity complex plays a crucial role in apical-basal epithelial polarity, cellular adhesion, and morphogenesis. Homozygous variants in human CRB1 result in autosomal recessive Leber congenital amaurosis (LCA) and retinitis pigmentosa (RP), with no established genotype-phenotype correlation. The associated protein complexes have key functions in developmental pathways; however, the underlying disease mechanism remains unclear. Using the oko meduzym289/m289 (crb2a-/- ) zebrafish, we performed integrative transcriptomic (RNA-seq data) and methylomic [reduced representation bisulphite sequencing (RRBS)] analysis of whole retina to identify dysregulated genes and pathways. Delayed retinal cell specification was identified in both the crb2a-/- zebrafish and CRB1 patient-derived retinal organoids, highlighting the dysfunction of cell cycle modulation and epigenetic transcriptional control. Differential DNA methylation analysis revealed novel hypermethylated pathways involving biological adhesion, Hippo, and transforming growth factor β (TGFβ) signalling. By integrating gene expression with DNA methylation using functional epigenetic modules (FEM), we identified six key modules involving cell cycle control and disturbance of TGFβ, bone morphogenetic protein (BMP), Hippo, and SMAD protein signal transduction pathways, revealing significant interactome hotspots relevant to crb2a function and confirming the epigenetic control of gene regulation in early retinal development, which points to a novel mechanism underlying CRB1-retinopathies. © 2023 The Authors. The Journal of Pathology published by John Wiley & Sons Ltd on behalf of The Pathological Society of Great Britain and Ireland.
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Affiliation(s)
- Nicholas Owen
- UCL Institute of OphthalmologyUniversity College LondonLondonUK
- The Francis Crick InstituteLondonUK
| | - Maria Toms
- UCL Institute of OphthalmologyUniversity College LondonLondonUK
- The Francis Crick InstituteLondonUK
| | - Yuan Tian
- Medical Genomics, UCL Cancer InstituteUniversity College LondonLondonUK
| | - Lyes Toualbi
- UCL Institute of OphthalmologyUniversity College LondonLondonUK
- The Francis Crick InstituteLondonUK
| | - Rose Richardson
- UCL Institute of OphthalmologyUniversity College LondonLondonUK
| | - Rodrigo Young
- UCL Institute of OphthalmologyUniversity College LondonLondonUK
| | | | - Pawan Dhami
- Medical Genomics, UCL Cancer InstituteUniversity College LondonLondonUK
| | - Stephan Beck
- Medical Genomics, UCL Cancer InstituteUniversity College LondonLondonUK
| | - Mariya Moosajee
- UCL Institute of OphthalmologyUniversity College LondonLondonUK
- The Francis Crick InstituteLondonUK
- Department of OphthalmologyGreat Ormond Street Hospital for Children NHS Foundation TrustLondonUK
- Department of GeneticsMoorfields Eye Hospital NHS Foundation TrustLondonUK
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2
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Duan W, Zhou T, Jiang H, Zhang M, Hu M, Zhang L. A novel nonsense variant (c.1499C>G) in CRB1 caused Leber congenital amaurosis-8 in a Chinese family and a literature review. BMC Med Genomics 2022; 15:197. [PMID: 36115989 PMCID: PMC9482190 DOI: 10.1186/s12920-022-01356-z] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/21/2022] [Accepted: 09/09/2022] [Indexed: 12/04/2022] Open
Abstract
Background Leber’s congenital amaurosis (LCA) is a severe hereditary retinopathy disease that is characterized by early and severe reduction of vision, nystagmus, and sluggish or absent pupillary responses. To date, the pathogenesis of LCA remains unclear, and the majority of cases are caused by autosomal recessive inheritance. In this study, we explored the variant in the Crumbs homologue 1 (CRB1) gene in a Chinese family with LCA.
Methods We conducted comprehensive ocular examinations and collected 5 ml of blood samples from members of a Chinese family with LCA. A pathogenic variant was identified by capturing (the panel in NGS) and Sanger sequencing validation. Results A nonsense variant (c.1499C>G) in the 6th exon of CRB1 gene in a Chinese family with LCA was identified, which predicted a change in the protein p. S500*, may lead to loss of gene function. We summarized the 76 variants reported thus far in CRB1 that caused LCA8. Conclusions This study reported a novel variant c.1499C>G (p. S500*) of the CRB1 gene occurred in a Chinese family with LCA, thus expanding the spectrum of CRB1 variants causing LCA.
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3
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Sun JX, Yan HX, Hu D, Zhou J, Wang YS, Wu J, Song XJ, Hou X. Biallelic Heterozygous Mutations in Crumbs Homolog-1 Gene Associated With Macular Retinoschisis and Angle-Closure Glaucoma: A Case Report and Literature Review. FRONTIERS IN OPHTHALMOLOGY 2022; 2:902898. [PMID: 38983543 PMCID: PMC11182100 DOI: 10.3389/fopht.2022.902898] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 03/23/2022] [Accepted: 05/03/2022] [Indexed: 07/11/2024]
Abstract
Background Mutations in the Crumbs homolog-1 (CRB1) gene are associated with a variety of retinal degenerations including Leber congenital amaurosis (LCA) and retinitis pigmentosa (RP). It is also important to highlight atypical features to make proper diagnosis and treatment. Case Presentation We present the case of a 7-year-old girl with biallelic heterozygous CRB1 mutations. The clinical features include macular retinoschisis, Coats-like vasculopathy, short axial length, and angle-closure glaucoma (ACG). We also briefly review the current opinion on CRB1 mutation-related diseases. Conclusion CRB1 mutations could result in a combined manifestation in anterior and posterior segments. This case emphasizes the importance of genetic diagnosis for those young patients with complicated rare clinical features to call for a specific treatment and follow-up plan. It also highlights the crucial role of CRB1 in eyeball development.
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Affiliation(s)
| | | | | | | | | | | | | | - Xu Hou
- Department of Ophthalmology, Eye Institute of Chinese PLA, Xijing Hospital, Fourth Military Medical University, Xi’an, China
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4
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Cheng Z, Hagan R, Yeo DCM. Identification of a novel CRB1 variant in a compound heterozygous state in a patient with CRB1-associated maculopathy and foveal retinoschisis. Ophthalmic Genet 2021; 43:253-257. [PMID: 34783605 DOI: 10.1080/13816810.2021.1998551] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/19/2022]
Abstract
PURPOSE To report a novel CRB1 variant responsible for autosomal recessive foveal retinoschisis and its associated clinical and electrophysiological data. METHODS A case report. RESULTS A 15-year-old boy has foveal retinoschisis similar to those seen in X-linked retinoschisis (XLRS). During follow-up, we observed the co-existence of foveoschitic changes and parafoveal macular atrophy. Molecular genetic testing identified compound heterozygous variants in the CRB1 gene, including a novel variant, c.3878 G > A, predicted to disrupt the normal translation of CRB1 and a previously reported likely pathogenic mutation, c.498_506del. Full-field electroretinograms (ERG) were normal but multifocal ERG showed focal reduced waveform amplitude corresponding to the area of atrophy. CONCLUSIONS A novel missense variant existing in a compound heterozygous state was identified. Biallelic CRB1 mutations can cause anatomical fovea disruption similar to XLRS but have very different electroretinogram findings. This case report enhances our understanding of the spectrum of biallelic CRB1 mutations.
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Affiliation(s)
- Zhihang Cheng
- Alder Hey Children's Nhs Foundation Trust, Department of Ophthalmology, Alder Hey Children's Hospital, Liverpool, United Kingdom of Great Britain and Northern Ireland
| | - Richard Hagan
- Alder Hey Children's Nhs Foundation Trust, Department of Ophthalmology, Alder Hey Children's Hospital, Liverpool, United Kingdom of Great Britain and Northern Ireland.,Clinical Engineering Department, Royal Liverpool University Hospital, Liverpool, United Kingdom of Great Britain and Northern Ireland
| | - Damien C M Yeo
- Alder Hey Children's Nhs Foundation Trust, Department of Ophthalmology, Alder Hey Children's Hospital, Liverpool, United Kingdom of Great Britain and Northern Ireland
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5
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PHENOTYPE-GUIDED GENETIC TESTING OF PEDIATRIC INHERITED RETINAL DISEASE IN THE UNITED ARAB EMIRATES. Retina 2021; 40:1829-1837. [PMID: 31725702 DOI: 10.1097/iae.0000000000002675] [Citation(s) in RCA: 16] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
PURPOSE Inherited retinal disease is relatively common in the Arabian Gulf, but details regarding pediatric inherited retinal disease in the region are lacking. The purpose of this study is to report the experience of a regional Ocular Genetics Service with childhood-onset inherited retinal disease in the United Arab Emirates. METHODS Retrospective series of consecutive Emirati patients referred to the Ocular Genetics Service of Cleveland Clinic Abu Dhabi over a 3-year period (2016-2018) who were diagnosed with childhood-onset inherited retinal disease (onset before 16 years old) and underwent diagnostic genetic testing guided by clinical phenotype (single gene, next-generation panel, or exome sequencing). RESULTS Seventy-one probands were identified (38 male and 33 females), the majority of whom were symptomatic with visual problems within the first 5 years of life. All patients had disease causing mutations in 1 of 26 retinal disease genes. Recessive disease was frequently due to homozygous mutations. The most frequently mutated genes (and number of probands) were ABCA4 (14), KCNV2 (8), CRB1 (6), and CNGA3 (5). Recurrent specific gene mutations included ABCA4 p.Gly1961Glu/p.Leu857Pro, KCNV2 p.Glu143*, MERTK p.Cys738Trpfs*32, and RS1 c.52+3A>G. Some probands had mutations in syndromic genes and were confirmed to have extraocular findings. CONCLUSION Phenotype-guided genetic testing had a remarkable yield for this patient population. Recessive disease is often from homozygous mutations. Cone-dominated phenotypes are common. There are apparent founder mutations for several genes that could be used in a targeted genetic testing strategy. Molecular diagnosis is particularly important in affected children when inherited retinal dystrophy could be a sign of syndromic disease as proper earlier diagnosis minimizes potential extraocular morbidity.
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Leung KCP, Ko TCS. Childhood cone-rod dystrophy with macular cyst formation in ABCA4 mutation identified by serial spectral-domain optical coherence tomography. Taiwan J Ophthalmol 2021; 11:312-316. [PMID: 34703750 PMCID: PMC8493982 DOI: 10.4103/tjo.tjo_54_20] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/22/2020] [Accepted: 07/26/2020] [Indexed: 11/04/2022] Open
Abstract
Cone-rod dystrophy (CORD) is a type of progressive hereditary retinal dystrophies that causes cone predominant photoreceptor degeneration characterized by wide genotypic and phenotypic heterogeneity. Macular cyst (MC) occurs very infrequently in the pediatric age group and has rarely been described in CORD. We report a case of young-onset CORD that was affected by an isolated ABCA4 mutation complicated by the development of MC. Through serial spectral-domain ocular coherence tomography MC has been observed to persist for 24 months before its resolution, followed by retinal thinning and macular atrophy with corresponding visual acuity decline. The formation of MC and visual acuity appeared to be directly correlated in ABCA4-related CORD and its manifestation is invaluable in predicting eventual visual loss. We further speculate that dysfunctional outer blood-retinal barrier may play a role in the pathophysiology of MC development in CORD.
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Affiliation(s)
- Kai Ching Peter Leung
- Department of Ophthalmology, Tung Wah Eastern Hospital, Causeway Bay, Hong Kong, China
| | - Tak Chuen Simon Ko
- Department of Ophthalmology, Tung Wah Eastern Hospital, Causeway Bay, Hong Kong, China
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7
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Talib M, Schooneveld MJ, Wijnholds J, Genderen MM, Schalij‐Delfos NE, Talsma HE, Florijn RJ, Brink JB, Cremers FP, Thiadens AA, Born LI, Hoyng CB, Meester‐Smoor MA, Bergen AA, Boon CJ. Defining inclusion criteria and endpoints for clinical trials: a prospective cross-sectional study in CRB1-associated retinal dystrophies. Acta Ophthalmol 2021; 99:e402-e414. [PMID: 33528094 PMCID: PMC8248330 DOI: 10.1111/aos.14597] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/05/2019] [Revised: 07/20/2020] [Accepted: 07/21/2020] [Indexed: 11/29/2022]
Abstract
Purpose To investigate the retinal structure and function in patients with CRB1‐associated retinal dystrophies (RD) and to explore potential clinical endpoints. Methods In this prospective cross‐sectional study, 22 patients with genetically confirmed CRB1‐RD (aged 6–74 years), and who had a decimal best‐corrected visual acuity (BCVA) ≥ 0.05 at the last visit, were studied clinically with ETDRS BCVA, corneal topography, spectral‐domain optical coherence tomography (SD‐OCT), fundus autofluorescence, Goldmann visual field (VF), microperimetry, full‐field electroretinography (ERG) and full‐field stimulus testing (FST). Ten patients were from a genetic isolate (GI). Results Patients had retinitis pigmentosa (n = 19; GI and non‐GI), cone‐rod dystrophy (n = 2; GI) or macular dystrophy (n = 1; non‐GI). Median age at first symptom onset was 3 years (range 0.8–49). Median decimal BCVA in the better and worse‐seeing eye was 0.18 (range 0.05–0.83) and 0.08 (range light perception‐0.72), respectively. Spectral‐domain optical coherence tomography (SD‐OCT) showed cystoid maculopathy in 8 subjects; inner retinal thickening (n = 20), a well‐preserved (para)foveal outer retina (n = 7) or severe (para)foveal outer retinal atrophy (n = 14). All retinal layers were discernible in 13/21 patients (62%), with mild to moderate laminar disorganization in the others. Nanophthalmos was observed in 8 patients (36%). Full‐field stimulus testing (FST) provided a subjective outcome measure for retinal sensitivity in eyes with (nearly) extinguished ERG amplitudes. Conclusions Despite the generally severe course of CRB1‐RDs, symptom onset and central visual function are variable, even at advanced ages. Phenotypes may vary within the same family. Imaging and functional studies in a prospective longitudinal setting should clarify which endpoints may be most appropriate in a clinical trial.
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Affiliation(s)
- Mays Talib
- Department of Ophthalmology Leiden University Medical Center Leiden The Netherlands
| | - Mary J. Schooneveld
- Department of Ophthalmology Amsterdam UMC University of Amsterdam Amsterdam The Netherlands
- Bartiméus Diagnostic Centre for complex visual disorders Zeist The Netherlands
| | - Jan Wijnholds
- Department of Ophthalmology Leiden University Medical Center Leiden The Netherlands
| | - Maria M. Genderen
- Bartiméus Diagnostic Centre for complex visual disorders Zeist The Netherlands
| | | | - Herman E. Talsma
- Department of Ophthalmology Leiden University Medical Center Leiden The Netherlands
- Bartiméus Diagnostic Centre for complex visual disorders Zeist The Netherlands
| | - Ralph J. Florijn
- Department of Clinical Genetics Amsterdam UMC University of Amsterdam Amsterdam The Netherlands
| | - Jacoline B. Brink
- Department of Clinical Genetics Amsterdam UMC University of Amsterdam Amsterdam The Netherlands
| | - Frans P.M. Cremers
- Department of Human Genetics and Donders Institute for Brain Cognition and Behaviour Radboud University Medical Center Nijmegen The Netherlands
| | | | | | - Carel B. Hoyng
- Department of Ophthalmology Radboud University Medical Center Nijmegen The Netherlands
| | | | - Arthur A. Bergen
- Department of Clinical Genetics Amsterdam UMC University of Amsterdam Amsterdam The Netherlands
- The Netherlands Institute for Neuroscience (NIN‐KNAW) Amsterdam The Netherlands
| | - Camiel J.F. Boon
- Department of Ophthalmology Leiden University Medical Center Leiden The Netherlands
- Department of Ophthalmology Amsterdam UMC University of Amsterdam Amsterdam The Netherlands
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8
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Wang Y, Sun W, Xiao X, Li S, Jia X, Wang P, Zhang Q. Clinical and Genetic Analysis of 63 Families Demonstrating Early and Advanced Characteristic Fundus as the Signature of CRB1 Mutations. Am J Ophthalmol 2021; 223:160-168. [PMID: 33342761 DOI: 10.1016/j.ajo.2020.10.006] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/21/2020] [Revised: 09/17/2020] [Accepted: 10/12/2020] [Indexed: 11/28/2022]
Abstract
PURPOSE To reveal the characteristics of ocular changes in patients with biallelic CRB1 mutations. DESIGN Comparative exome sequencing and retrospective case series on clinical data. METHODS Seventy-four patients from 63 families with biallelic potential pathogenic variants in CRB1 were selected from our in-house exome sequencing. The clinical data were reviewed and evaluated in detail, including best-corrected visual acuity, fundus photography, optical coherence tomography (OCT), and electroretinogram (ERG). RESULTS Biallelic CRB1 variants, involving 45 variants including 23 novel, were identified in 40 novel families based on exome sequencing. Analyzing clinical data of the 74 individuals from 63 families revealed the following CRB1-associated phenotypes: (1) early-onset reduced visual acuity with congenital nystagmus; (2) 2 types of characteristic retinal changes including yellowish geographic macular degeneration (YMD) or nummular pigment deposits (NPD) at posterior retina with bone-spicule pigmentation at midperipheral retina; (3) undetectable rod and cone responses on ERG; (4) cystoid macular edema or macular atrophy on OCT. YMD and NPD are unique and CRB1-associated. Long-term follow-up examination as well as age- and variant-dependent phenotypic analysis suggested YMD is the early fundus change that would gradually progress to NPD. CONCLUSIONS YMD and NPD are 2 major characteristic CRB1-associated fundus changes and the former one will advance to the latter with age. Recognizing such characteristic signs associated with biallelic CRB1 variants may be of value in areas without widespread access to genetic testing where a more targeted approach is needed and might be biomarkers for evaluation of effects for future intervention.
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Affiliation(s)
- Yingwei Wang
- State Key Laboratory of Ophthalmology, Zhongshan Ophthalmic Center, Sun Yat-sen University, Guangzhou, China
| | - Wenmin Sun
- State Key Laboratory of Ophthalmology, Zhongshan Ophthalmic Center, Sun Yat-sen University, Guangzhou, China
| | - Xueshan Xiao
- State Key Laboratory of Ophthalmology, Zhongshan Ophthalmic Center, Sun Yat-sen University, Guangzhou, China
| | - Shiqiang Li
- State Key Laboratory of Ophthalmology, Zhongshan Ophthalmic Center, Sun Yat-sen University, Guangzhou, China
| | - Xiaoyun Jia
- State Key Laboratory of Ophthalmology, Zhongshan Ophthalmic Center, Sun Yat-sen University, Guangzhou, China
| | - Panfeng Wang
- State Key Laboratory of Ophthalmology, Zhongshan Ophthalmic Center, Sun Yat-sen University, Guangzhou, China
| | - Qingjiong Zhang
- State Key Laboratory of Ophthalmology, Zhongshan Ophthalmic Center, Sun Yat-sen University, Guangzhou, China.
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9
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Talib M, Van Cauwenbergh C, De Zaeytijd J, Van Wynsberghe D, De Baere E, Boon CJF, Leroy BP. CRB1-associated retinal dystrophies in a Belgian cohort: genetic characteristics and long-term clinical follow-up. Br J Ophthalmol 2021; 106:696-704. [PMID: 33579689 DOI: 10.1136/bjophthalmol-2020-316781] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/24/2020] [Revised: 11/19/2020] [Accepted: 12/05/2020] [Indexed: 11/04/2022]
Abstract
AIM To investigate the natural history in a Belgian cohort of CRB1-associated retinal dystrophies. METHODS An in-depth retrospective study focusing on visual function and retinal structure. RESULTS Forty patients from 35 families were included (ages: 2.5-80.1 years). In patients with a follow-up of >1 year (63%), the mean follow-up time was 12.0 years (range: 2.3-29.2 years). Based on the patient history, symptoms and/or electroretinography, 22 patients (55%) were diagnosed with retinitis pigmentosa (RP), 15 (38%) with Leber congenital amaurosis (LCA) and 3 (8%) with macular dystrophy (MD), the latter being associated with the p.(Ile167_Gly169del) mutation (in compound heterozygosity). MD later developed into a rod-cone dystrophy in one patient. Blindness at initial presentation was seen in the first decade of life in LCA, and in the fifth decade of life in RP. Eventually, 28 patients (70%) reached visual acuity-based blindness (<0.05). Visual field-based blindness (<10°) was documented in 17/25 patients (68%). Five patients (13%) developed Coats-like exudative vasculopathy. Intermediate/posterior uveitis was found in three patients (8%). Cystoid maculopathy was common in RP (9/21; 43%) and MD (3/3; 100%). Macular involvement, varying from retinal pigment epithelium alterations to complete outer retinal atrophy, was observed in all patients. CONCLUSION Bi-allelic CRB1 mutations result in a range of progressive retinal disorders, most of which are generalised, with characteristically early macular involvement. Visual function and retinal structure analysis indicates a window for potential intervention with gene therapy before the fourth decade of life in RP and the first decade in LCA.
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Affiliation(s)
- Mays Talib
- Department of Ophthalmology, Leiden University Medical Center, Leiden, The Netherlands
| | - Caroline Van Cauwenbergh
- Department of Ophthalmology, Ghent University and Ghent University Hospital, Ghent, Belgium.,Center for Medical Genetics, Ghent University and Ghent University Hospital, Ghent, Belgium
| | - Julie De Zaeytijd
- Department of Ophthalmology, Ghent University and Ghent University Hospital, Ghent, Belgium
| | | | - Elfride De Baere
- Center for Medical Genetics, Ghent University and Ghent University Hospital, Ghent, Belgium
| | - Camiel J F Boon
- Department of Ophthalmology, Leiden University Medical Center, Leiden, The Netherlands.,Department of Ophthalmology, Amsterdam UMC, Academic Medical Center, University of Amsterdam, Amsterdam, Netherlands
| | - Bart Peter Leroy
- Department of Ophthalmology, Ghent University and Ghent University Hospital, Ghent, Belgium.,Center for Medical Genetics, Ghent University and Ghent University Hospital, Ghent, Belgium.,Division of Ophthalmology, The Children's Hospital of Philadelphia, Philadelphia, PA, USA.,Centre for Cellular & Molecular Therapeutics, The Children's Hospital of Philadelphia, Philadelphia, PA, USA
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10
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Sallum JMF, Motta FL, Arno G, Porto FBO, Resende RG, Belfort R. Clinical and molecular findings in a cohort of 152 Brazilian severe early onset inherited retinal dystrophy patients. AMERICAN JOURNAL OF MEDICAL GENETICS PART C-SEMINARS IN MEDICAL GENETICS 2020; 184:728-752. [PMID: 32865313 DOI: 10.1002/ajmg.c.31828] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/25/2020] [Revised: 07/25/2020] [Accepted: 07/28/2020] [Indexed: 12/17/2022]
Abstract
Leber congenital amaurosis (LCA) and early-onset retinal dystrophy (EORD) are severe inherited retinal dystrophy that can cause deep blindness childhood. They represent 5% of all retinal dystrophies in the world population and about 10% in Brazil. Clinical findings and molecular basis of syndromic and nonsyndromic LCA/EORD in a Brazilian sample (152 patients/137 families) were studied. In this population, 15 genes were found to be related to the phenotype, 38 new variants were detected and four new complex alleles were discovered. Among 123 variants found, the most common were CEP290: c.2991+1655A>G, CRB1: p.Cys948Tyr, and RPGRIP1: exon10-18 deletion.
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Affiliation(s)
- Juliana Maria Ferraz Sallum
- Department of Ophthalmology, Universidade Federal de São Paulo, Sao Paulo, Brazil.,Instituto de Genética Ocular, Sao Paulo, Brazil
| | - Fabiana Louise Motta
- Department of Ophthalmology, Universidade Federal de São Paulo, Sao Paulo, Brazil.,Instituto de Genética Ocular, Sao Paulo, Brazil
| | - Gavin Arno
- UCL Institute of Ophthalmology, London, UK.,Moorfields Eye Hospital, London, UK
| | - Fernanda Belga Ottoni Porto
- INRET Clínica e Centro de Pesquisa, Belo Horizonte, Minas Gerais, Brazil.,Centro Oftalmológico de Minas Gerais, Belo Horizonte, Minas Gerais, Brazil
| | | | - Rubens Belfort
- Department of Ophthalmology, Universidade Federal de São Paulo, Sao Paulo, Brazil
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11
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Grudzinska Pechhacker MK, Di Scipio M, Vig A, Tumber A, Roslin N, Tavares E, Vincent A, Hèon E. CRB1-related retinopathy overlapping the ocular phenotype of S-adenosylhomocysteine hydrolase deficiency. Ophthalmic Genet 2020; 41:457-464. [PMID: 32689861 DOI: 10.1080/13816810.2020.1790013] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
BACKGROUND S-adenosylhomocysteine hydrolase deficiency due to pathologic variants in AHCY gene is a rare neurometabolic disease for which no eye phenotype has been documented. Pathologic variants in CRB1 gene are known to cause a wide spectrum of autosomal recessive retinal diseases with Leber's congenital amaurosis as a most common. The aim of this study is to report co-inheritance of neurometabolic disease and eye disease in a pedigree. MATERIALS AND METHODS Comprehensive eye examination was performed in available family members together with color vision test, visual fields, fundus images, OCT, electroretinogram and visual evoked potentials. Genetic testing included whole-exome sequencing (WES), retinal dystrophy gene panel and segregation analysis. RESULTS Two children from a family not known to be consanguineous were affected with neurometabolic disease and one of them presented with reduced vision due to maculopathy. The mother had symptoms of retinal degeneration of unspecified cause. Clinical WES revealed homozygous missense pathologic variants in AHCY gene c.148G>A, p.(Ala50Thr) as a cause of S-adenosylhomocysteine hydrolase deficiency. Retinal dystrophy gene panel sequencing revealed two heterozygous missense pathologic variants in CRB1 gene c.1831T>C, p.(Ser611Pro) and c.3955T>C, p.(Phe1319Leu) in the proband and her mother. These variants segregated with disease phenotype in family members. CONCLUSIONS Establishing an ocular genetic diagnosis may be challenging with the co-existence of a rare systemic genetic disease with previously unknown eye involvement. Extensive phenotyping and genotyping of available family members showed that the proband and her mother shared a CRB1-related retinopathy at different stages while the brother did not.
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Affiliation(s)
- Monika K Grudzinska Pechhacker
- Department of Ophthalmology and Vision Sciences, The Hospital for Sick Children , Toronto, Canada.,Department of Ophthalmology and Vision Sciences, University of Toronto , Toronto, Canada
| | - Matteo Di Scipio
- Genetics and Genome Biology, The Hospital for Sick Children , Toronto, Canada
| | - Anjali Vig
- Genetics and Genome Biology, The Hospital for Sick Children , Toronto, Canada
| | - Anupreet Tumber
- Department of Ophthalmology and Vision Sciences, The Hospital for Sick Children , Toronto, Canada
| | - Nicole Roslin
- Genetics and Genome Biology, The Hospital for Sick Children , Toronto, Canada
| | - Erika Tavares
- Genetics and Genome Biology, The Hospital for Sick Children , Toronto, Canada
| | - Ajoy Vincent
- Department of Ophthalmology and Vision Sciences, The Hospital for Sick Children , Toronto, Canada.,Department of Ophthalmology and Vision Sciences, University of Toronto , Toronto, Canada.,Genetics and Genome Biology, The Hospital for Sick Children , Toronto, Canada
| | - Elise Hèon
- Department of Ophthalmology and Vision Sciences, The Hospital for Sick Children , Toronto, Canada.,Department of Ophthalmology and Vision Sciences, University of Toronto , Toronto, Canada.,Genetics and Genome Biology, The Hospital for Sick Children , Toronto, Canada
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12
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Talib M, Boon CJF. Retinal Dystrophies and the Road to Treatment: Clinical Requirements and Considerations. Asia Pac J Ophthalmol (Phila) 2020; 9:159-179. [PMID: 32511120 PMCID: PMC7299224 DOI: 10.1097/apo.0000000000000290] [Citation(s) in RCA: 21] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2020] [Accepted: 04/01/2020] [Indexed: 12/15/2022] Open
Abstract
: Retinal dystrophies (RDs) comprise relatively rare but devastating causes of progressive vision loss. They represent a spectrum of diseases with marked genetic and clinical heterogeneity. Mutations in the same gene may lead to different diagnoses, for example, retinitis pigmentosa or cone dystrophy. Conversely, mutations in different genes may lead to the same phenotype. The age at symptom onset, and the rate and characteristics of peripheral and central vision decline, may vary widely per disease group and even within families. For most RD cases, no effective treatment is currently available. However, preclinical studies and phase I/II/III gene therapy trials are ongoing for several RD subtypes, and recently the first retinal gene therapy has been approved by the US Food and Drug Administration for RPE65-associated RDs: voretigene neparvovec-rzyl (Luxturna). With the rapid advances in gene therapy studies, insight into the phenotypic spectrum and long-term disease course is crucial information for several RD types. The vast clinical heterogeneity presents another important challenge in the evaluation of potential efficacy in future treatment trials, and in establishing treatment candidacy criteria. This perspective describes these challenges, providing detailed clinical descriptions of several forms of RD that are caused by genes of interest for ongoing and future gene or cell-based therapy trials. Several ongoing and future treatment options will be described.
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Affiliation(s)
- Mays Talib
- Department of Ophthalmology, Leiden, The Netherlands
| | - Camiel J F Boon
- Department of Ophthalmology, Leiden, The Netherlands
- Department of Ophthalmology, Amsterdam UMC, Academic Medical Center, University of Amsterdam. Amsterdam, The Netherlands
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Al-Sharif EM, Khan AO. Cycloplegic refractions in a cohort with ABCA4-related retinopathy. Ophthalmic Genet 2020; 41:96-98. [PMID: 32013674 DOI: 10.1080/13816810.2020.1720744] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
Affiliation(s)
- Eman M Al-Sharif
- Eye Institute, Cleveland Clinic Abu Dhabi, Abu Dhabi, UAE.,Department of Ophthalmology, College of Medicine, Princess Nourah Bint Abdulrahman University, Riyadh, Saudi Arabia
| | - Arif O Khan
- Eye Institute, Cleveland Clinic Abu Dhabi, Abu Dhabi, UAE.,Department of Ophthalmology, Cleveland Clinic Lerner College of Medicine, Case Western University, Cleveland, Ohio, USA
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Stingl KT, Kuehlewein L, Weisschuh N, Biskup S, Cremers FPM, Khan MI, Kelbsch C, Peters T, Ueffing M, Wilhelm B, Zrenner E, Stingl K. Chromatic Full-Field Stimulus Threshold and Pupillography as Functional Markers for Late-Stage, Early-Onset Retinitis Pigmentosa Caused by CRB1 Mutations. Transl Vis Sci Technol 2019; 8:45. [PMID: 31879567 PMCID: PMC6927735 DOI: 10.1167/tvst.8.6.45] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2019] [Accepted: 09/30/2019] [Indexed: 01/08/2023] Open
Abstract
Purpose Mutations in the CRB1 gene cause early-onset retinal degeneration (EORD). Clinical disease progression markers, such as visual fields or electrophysiology, are not reliably measurable in most patients to follow the retinal function in patients with CRB1-mutations. Methods Ten patients (five females, five males; age 22–56 years) with EORD caused by CRB1 mutations were examined in a cross-sectional manner using best corrected visual acuity (BCVA), perimetry, full-field and multifocal electroretinography, full-field stimulus threshold (FST), and pupillography to red and blue light. Disease duration was defined as the difference between the age at the first symptoms to the age at examination in years. Results BCVA was quantifiable in six patients and ranged from light perception to 20/50. The visual field was measurable only in three patients who had the shortest disease duration. Full-field and multifocal electroretinography were not measurable in any patient. FST to blue and red light were measurable in all patients except the one with the longest disease duration; the thresholds ranged from −16.7 to 1.5 dB for red light and from −40.2 to 2.5 dB for blue light (0 dB = 0.01 cd.s/m2) and showed correlations with disease duration (r = 0.87 for blue, r = 0.65 for red, r = 0.8 for blue–red difference). The maximal relative pupil constriction amplitude (MRA) showed low or no correlations with disease duration (r = −0.55 for blue, r = −0.3 for red light); the blue–red difference in the post-illumination pupil responses (PIPR) showed no correlation with disease duration (r = −0.05). Compared to healthy eyes, the MRA to red and blue light was significantly decreased (P < 0.001) and the blue–red PIPR difference was significantly increased (P = 0.003). Conclusions FST features a valid clinical marker in late-stage early-onset retinitis pigmentosa caused by CRB1 mutations correlating with disease duration. This indicates the potential as a progression marker of disease. The pupil responses to full-field chromatic stimuli show significant differences from the normal population: the remaining responses, although reduced, indicate a partially preserved inner retinal function despite severe photoreceptor dysfunction. Translational Relevance The functional measurements presented in this study present a valid clinical progression marker in late-stage early onset retinitis pigmentosa caused by biallelic CRB1 mutations. Additionally, they can be used as outcome measures for safety and efficacy in clinical therapy trials.
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Affiliation(s)
| | - Laura Kuehlewein
- Center for Ophthalmology, University of Tübingen, Tübingen, Germany
| | - Nicole Weisschuh
- Center for Ophthalmology, University of Tübingen, Tübingen, Germany
| | | | - Frans P M Cremers
- Department of Human Genetics, Radboud University Medical Center and Donders Institute for Brain, Cognition and Behaviour, Nijmegen, the Netherlands
| | - M Imran Khan
- Department of Human Genetics, Radboud University Medical Center and Donders Institute for Brain, Cognition and Behaviour, Nijmegen, the Netherlands
| | - Carina Kelbsch
- Center for Ophthalmology, University of Tübingen, Tübingen, Germany
| | - Tobias Peters
- Center for Ophthalmology, University of Tübingen, Tübingen, Germany
| | - Marius Ueffing
- Center for Ophthalmology, University of Tübingen, Tübingen, Germany
| | - Barbara Wilhelm
- Center for Ophthalmology, University of Tübingen, Tübingen, Germany
| | - Eberhart Zrenner
- Center for Ophthalmology, University of Tübingen, Tübingen, Germany.,Werner Reichardt Center for Integrative Neuroscience, University of Tübingen, Tübingen, Germany
| | - Katarina Stingl
- Center for Ophthalmology, University of Tübingen, Tübingen, Germany
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Khan AO, El-Ghrably IA. Overlapping retinal phenotypes in a consanguineous family harboring mutations in CRB1 and RS1. Ophthalmic Genet 2019; 40:17-21. [DOI: 10.1080/13816810.2018.1561906] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Affiliation(s)
- Arif O. Khan
- Eye Institute, Cleveland Clinic Abu Dhabi, Abu Dhabi, United Arab Emirates
- Department of Ophthalmology, Cleveland Clinic Lerner College of Medicine of Case Western University, Cleveland, OH, USA
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Motta FL, Salles MV, Costa KA, Filippelli-Silva R, Martin RP, Sallum JMF. The correlation between CRB1 variants and the clinical severity of Brazilian patients with different inherited retinal dystrophy phenotypes. Sci Rep 2017; 7:8654. [PMID: 28819299 PMCID: PMC5561187 DOI: 10.1038/s41598-017-09035-1] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/06/2017] [Accepted: 07/20/2017] [Indexed: 12/18/2022] Open
Abstract
Inherited retinal dystrophies are characterized by progressive retina degeneration and mutations in at least 250 genes have been associated as disease-causing. CRB1 is one of many genes analyzed in molecular diagnosis for inherited retinal dystrophy. Crumbs homolog-1 protein encoded by CRB1 is important for cell-to-cell contact, polarization of epithelial cells and the morphogenesis of photoreceptors. Pathogenic variants in CRB1 lead to a huge variety of phenotypes ranging from milder forms of inherited retinal dystrophy, such as retinitis pigmentosa to more severe phenotypes such as Leber congenital amaurosis. In this study, seven novel likely-pathogenic variants were identified: four missense variants (p.Leu479Pro, p.Ala921Pro, p.Cys948Arg and p.Asp1031Asn), two frameshift deletions (c.2536_2542del7 and c.3460_3461delTG) and one frameshift indel variant (c.276_294delinsTGAACACTGTAC). Furthermore, two patients with cone-rod dystrophy due to mutations in CRB1 were reported, supporting previous data, in which mutations in CRB1 can also cause cone-rod dystrophy. Finally, our data suggested there was a direct relation between phenotype severity and the mutation effect on protein functionality in 15 Brazilian CRB1 patients.
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Affiliation(s)
| | | | | | | | - Renan Paulo Martin
- Department of Biophysics, Federal University of Sao Paulo, Sao Paulo, Brazil
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Talib M, van Schooneveld MJ, van Genderen MM, Wijnholds J, Florijn RJ, Ten Brink JB, Schalij-Delfos NE, Dagnelie G, Cremers FPM, Wolterbeek R, Fiocco M, Thiadens AA, Hoyng CB, Klaver CC, Bergen AA, Boon CJF. Genotypic and Phenotypic Characteristics of CRB1-Associated Retinal Dystrophies: A Long-Term Follow-up Study. Ophthalmology 2017; 124:884-895. [PMID: 28341475 DOI: 10.1016/j.ophtha.2017.01.047] [Citation(s) in RCA: 62] [Impact Index Per Article: 8.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2016] [Revised: 01/27/2017] [Accepted: 01/27/2017] [Indexed: 12/30/2022] Open
Abstract
PURPOSE To describe the phenotype, long-term clinical course, clinical variability, and genotype of patients with CRB1-associated retinal dystrophies. DESIGN Retrospective cohort study. PARTICIPANTS Fifty-five patients with CRB1-associated retinal dystrophies from 16 families. METHODS A medical record review of 55 patients for age at onset, medical history, initial symptoms, best-corrected visual acuity, ophthalmoscopy, fundus photography, full-field electroretinography (ffERG), Goldmann visual fields (VFs), and spectral-domain optical coherence tomography. MAIN OUTCOME MEASURES Age at onset, visual acuity survival time, visual acuity decline rate, and electroretinography and imaging findings. RESULTS A retinitis pigmentosa (RP) phenotype was present in 50 patients, 34 of whom were from a Dutch genetic isolate (GI), and 5 patients had a Leber congenital amaurosis phenotype. The mean follow-up time was 15.4 years (range, 0-55.5 years). For the RP patients, the median age at symptom onset was 4.0 years. In the RP group, median ages for reaching low vision, severe visual impairment, and blindness were 18, 32, and 44 years, respectively, with a visual acuity decline rate of 0.03 logarithm of the minimum angle of resolution per year. The presence of a truncating mutation did not alter the annual decline rate significantly (P = 0.75). Asymmetry in visual acuity was found in 31% of patients. The annual VF decline rate was 5% in patients from the genetic isolate, which was significantly faster than in non-GI patients (P < 0.05). Full-field electroretinography responses were extinguished in 50% of patients, were pathologically attenuated without a documented rod or cone predominance in 30% of patients, and showed a rod-cone dysfunction pattern in 20% of RP patients. Cystoid fluid collections in the macula were found in 50% of RP patients. CONCLUSIONS Mutations in the CRB1 gene are associated with a spectrum of progressive retinal degeneration. Visual acuity survival analyses indicate that the optimal intervention window for subretinal gene therapy is within the first 2 to 3 decades of life.
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Affiliation(s)
- Mays Talib
- Department of Ophthalmology, Leiden University Medical Center, Leiden, The Netherlands
| | | | - Maria M van Genderen
- Bartiméus, Diagnostic Centre for Complex Visual Disorders, Zeist, The Netherlands
| | - Jan Wijnholds
- Department of Ophthalmology, Leiden University Medical Center, Leiden, The Netherlands
| | - Ralph J Florijn
- Department of Clinical Genetics, Academic Medical Center, Amsterdam, The Netherlands
| | - Jacoline B Ten Brink
- Department of Clinical Genetics, Academic Medical Center, Amsterdam, The Netherlands
| | | | - Gislin Dagnelie
- Wilmer Eye Institute, Johns Hopkins University, Baltimore, Maryland
| | - Frans P M Cremers
- Department of Human Genetics and Donders Institute for Brain, Cognition and Behaviour, Radboud University Medical Center, Nijmegen, The Netherlands
| | - Ron Wolterbeek
- Department of Medical Statistics, Leiden University Medical Center, Leiden, The Netherlands
| | - Marta Fiocco
- Department of Medical Statistics, Leiden University Medical Center, Leiden, The Netherlands; Mathematical Institute, Leiden University, Leiden, The Netherlands
| | - Alberta A Thiadens
- Department of Ophthalmology, Erasmus Medical Center, Rotterdam, The Netherlands
| | - Carel B Hoyng
- Department of Ophthalmology, Radboud University Medical Center, Nijmegen, The Netherlands
| | - Caroline C Klaver
- Department of Ophthalmology, Erasmus Medical Center, Rotterdam, The Netherlands; Department of Ophthalmology, Radboud University Medical Center, Nijmegen, The Netherlands; Department of Epidemiology, Erasmus Medical Center, Rotterdam, The Netherlands
| | - Arthur A Bergen
- Department of Clinical Genetics, Academic Medical Center, Amsterdam, The Netherlands; The Netherlands Institute for Neuroscience (NIN-KNAW), Amsterdam, The Netherlands
| | - Camiel J F Boon
- Department of Ophthalmology, Leiden University Medical Center, Leiden, The Netherlands; Department of Ophthalmology, Academic Medical Center, Amsterdam, The Netherlands.
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Expansion of phenotype and genotypic data in CRB2-related syndrome. Eur J Hum Genet 2016; 24:1436-44. [PMID: 27004616 DOI: 10.1038/ejhg.2016.24] [Citation(s) in RCA: 32] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/20/2015] [Revised: 01/26/2016] [Accepted: 02/17/2016] [Indexed: 01/01/2023] Open
Abstract
Sequence variants in CRB2 cause a syndrome with greatly elevated maternal serum alpha-fetoprotein and amniotic fluid alpha-fetoprotein levels, cerebral ventriculomegaly and renal findings similar to Finnish congenital nephrosis. All reported patients have been homozygotes or compound heterozygotes for sequence variants in the Crumbs, Drosophila, Homolog of, 2 (CRB2) genes. Variants affecting CRB2 function have also been identified in four families with steroid resistant nephrotic syndrome, but without any other known systemic findings. We ascertained five, previously unreported individuals with biallelic variants in CRB2 that were predicted to affect function. We compiled the clinical features of reported cases and reviewed available literature for cases with features suggestive of CRB2-related syndrome in order to better understand the phenotypic and genotypic manifestations. Phenotypic analyses showed that ventriculomegaly was a common clinical manifestation (9/11 confirmed cases), in contrast to the original reports, in which patients were ascertained due to renal disease. Two children had minor eye findings and one was diagnosed with a B-cell lymphoma. Further genetic analysis identified one family with two affected siblings who were both heterozygous for a variant in NPHS2 predicted to affect function and separate families with sequence variants in NPHS4 and BBS7 in addition to the CRB2 variants. Our report expands the clinical phenotype of CRB2-related syndrome and establishes ventriculomegaly and hydrocephalus as frequent manifestations. We found additional sequence variants in genes involved in kidney development and ciliopathies in patients with CRB2-related syndrome, suggesting that these variants may modify the phenotype.
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Slavotinek A, Kaylor J, Pierce H, Cahr M, DeWard S, Schneidman-Duhovny D, Alsadah A, Salem F, Schmajuk G, Mehta L. CRB2 mutations produce a phenotype resembling congenital nephrosis, Finnish type, with cerebral ventriculomegaly and raised alpha-fetoprotein. Am J Hum Genet 2015; 96:162-9. [PMID: 25557780 DOI: 10.1016/j.ajhg.2014.11.013] [Citation(s) in RCA: 59] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/08/2014] [Accepted: 11/21/2014] [Indexed: 12/17/2022] Open
Abstract
We report five fetuses and a child from three families who shared a phenotype comprising cerebral ventriculomegaly and echogenic kidneys with histopathological findings of congenital nephrosis. The presenting features were greatly elevated maternal serum alpha-fetoprotein (MSAFP) or amniotic fluid alpha-fetoprotein (AFAFP) levels or abnormalities visualized on ultrasound scan during the second trimester of pregnancy. Exome sequencing revealed deleterious sequence variants in Crumbs, Drosophila, Homolog of, 2 (CRB2) consistent with autosomal-recessive inheritance. Two fetuses with cerebral ventriculomegaly and renal microcysts were compound heterozygotes for p.Asn800Lys and p.Trp759Ter, one fetus with renal microcysts was a compound heterozygote for p.Glu643Ala and p.Asn800Lys, and one child with cerebral ventriculomegaly, periventricular heterotopias, echogenic kidneys, and renal failure was homozygous for p.Arg633Trp in CRB2. Examination of the kidneys in one fetus showed tubular cysts at the corticomedullary junction and diffuse effacement of the epithelial foot processes and microvillous transformation of the renal podocytes, findings that were similar to those reported in congenital nephrotic syndrome, Finnish type, that is caused by mutations in nephrin (NPHS1). Loss of function for crb2b and nphs1 in Danio rerio were previously shown to result in loss of the slit diaphragms of the podocytes, leading to the hypothesis that nephrosis develops from an inability to develop a functional glomerular barrier. We conclude that the phenotype associated with CRB2 mutations is pleiotropic and that the condition is an important consideration in the evaluation of high MSAFP/AFAFP where a renal cause is suspected.
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