title: Novel GUCY2D mutation causes phenotypic variability of Leber congenital amaurosis in a large kindred.
abstract: Leber congenital amaurosis (LCA) is a severe retinal degenerative disease that manifests as blindness or poor vision in infancy. The purpose of this study was to clinically characterize and identify the cause of disease in a large inbred Bedouin Israeli tribe with LCA.
  
  
  
  Thirty individuals of a single kindred, including eight affected with LCA, were recruited for this study. Patients' clinical data and electroretinography (ERG) findings were collected. Molecular analysis included homozygosity mapping with polymorphic markers and Sanger sequencing of candidate genes.
  
  
  
  Of the eight affected individuals of the kindred, nystagmus was documented in five subjects and keratoconus in three. Cataract was found in 5 of 16 eyes. Photopic and scotopic ERG performed in 5 patients were extinguished. All affected subjects were nearly blind, their visual acuity ranged between finger counting and uncertain light perception. Assuming autosomal recessive heredity of a founder mutation, studies using polymorphic markers excluded homozygosity of affected individuals at the genomic loci of all previously known genes associated with LCA, except GUCY2D. Sequencing of GUCY2D identified a novel missense mutation (c.2129C>T; p.Ala710Val) resulting in substitution of alanine by valine at position 710 within the protein kinase domain of the retina-specific enzyme guanylate cyclase 1 (GC1) encoded by GUCY2D. Molecular modeling implied that the mutation changes the conformation of the regulatory segment within the kinase styk-domain of GC1 and causes loss of its helical structure, likely inhibiting phosphorylation of threonine residue within this segment, which is needed to activate the catalytic domain of the protein.
  
  
  
  This is the first documentation of the p.Ala710Val mutation in GC1 and the second ever described mutation in its protein kinase domain. Our findings enlarge the scope of genetic variability of LCA, highlight the phenotypic heterogeneity found amongst individuals harboring an identical LCA mutation, and possibly provide hope for gene therapy in patients with this congenital blinding disease. As the Bedouin kindred studied originates from Saudi Arabia, the mutation found might be an ancient founder mutation in that large community.
authors.affiliation: Department of Ophthalmology, Soroka Medical Center and Clalit Health Services, Faculty of Health Sciences, Ben Gurion University, Beer Sheva, 84101, Israel.
authors.forename: Libe
authors.initials: L
authors.lastname: Gradstein
authors.affiliation: The Morris Kahn Laboratory of Human Genetics, National Institute for Biotechnology in the Negev and Faculty of Health Sciences, Ben Gurion University of the Negev, Beer-Sheva, 84105, Israel.
authors.forename: Jenny
authors.initials: J
authors.lastname: Zolotushko
authors.affiliation: National Eye Institute, National Institutes of Health, Bethesda, MD, USA.
authors.forename: Yuri V
authors.initials: YV
authors.lastname: Sergeev
authors.affiliation: Department of Ophthalmology, Soroka Medical Center and Clalit Health Services, Faculty of Health Sciences, Ben Gurion University, Beer Sheva, 84101, Israel.
authors.forename: Itay
authors.initials: I
authors.lastname: Lavy
authors.affiliation: The Morris Kahn Laboratory of Human Genetics, National Institute for Biotechnology in the Negev and Faculty of Health Sciences, Ben Gurion University of the Negev, Beer-Sheva, 84105, Israel.
authors.forename: Ginat
authors.initials: G
authors.lastname: Narkis
authors.affiliation: The Morris Kahn Laboratory of Human Genetics, National Institute for Biotechnology in the Negev and Faculty of Health Sciences, Ben Gurion University of the Negev, Beer-Sheva, 84105, Israel.
authors.forename: Yonatan
authors.initials: Y
authors.lastname: Perez
authors.affiliation: Department of Ophthalmology, Soroka Medical Center and Clalit Health Services, Faculty of Health Sciences, Ben Gurion University, Beer Sheva, 84101, Israel.
authors.forename: Sarah
authors.initials: S
authors.lastname: Guigui
authors.affiliation: Department of Ophthalmology, Hadassah-Hebrew University Medical Center, Jerusalem, Israel.
authors.forename: Dror
authors.initials: D
authors.lastname: Sharon
authors.affiliation: Department of Ophthalmology, Hadassah-Hebrew University Medical Center, Jerusalem, Israel.
authors.forename: Eyal
authors.initials: E
authors.lastname: Banin
authors.affiliation: Department of Ophthalmology, Soroka Medical Center and Clalit Health Services, Faculty of Health Sciences, Ben Gurion University, Beer Sheva, 84101, Israel.
authors.forename: Eyal
authors.initials: E
authors.lastname: Walter
authors.affiliation: Department of Ophthalmology, Soroka Medical Center and Clalit Health Services, Faculty of Health Sciences, Ben Gurion University, Beer Sheva, 84101, Israel.
authors.forename: Tova
authors.initials: T
authors.lastname: Lifshitz
authors.affiliation: The Morris Kahn Laboratory of Human Genetics, National Institute for Biotechnology in the Negev and Faculty of Health Sciences, Ben Gurion University of the Negev, Beer-Sheva, 84105, Israel. obirk@bgu.ac.il.|Genetics Institute, Soroka Medical Center, Faculty of Health Sciences, Ben-Gurion University of the Negev, Beer-Sheva, 84101, Israel. obirk@bgu.ac.il.
authors.forename: Ohad S
authors.initials: OS
authors.lastname: Birk
mesh_terms: D000328:Adult; D000595:Amino Acid Sequence; D000818:Animals; D020134:Catalytic Domain; D002648:Child; D002675:Child, Preschool; D004247:DNA / Q000737:chemistry / Q000302:isolation & purification / Q000378:metabolism; D004252:DNA Mutational Analysis; D004596:Electroretinography; D005123:Eye / Q000000981:diagnostic imaging; D005260:Female; D005838:Genotype; D006162:Guanylate Cyclase / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D006720:Homozygote; D006801:Humans; D057130:Leber Congenital Amaurosis / Q000235:genetics* / Q000473:pathology; D008297:Male; D056004:Molecular Dynamics Simulation; D008969:Molecular Sequence Data; D020125:Mutation, Missense; D010375:Pedigree; D010641:Phenotype; D020641:Polymorphism, Single Nucleotide; D011956:Receptors, Cell Surface / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D016415:Sequence Alignment; D014792:Visual Acuity
chemical_list: D011956:Receptors, Cell Surface; C110715:guanylate cyclase 1; D004247:DNA; D006162:Guanylate Cyclase
keywords: Blindness; GUCY2D; Guanylate cyclase; Leber Congenital Amaurosis