Biomedical subjects

Robert Ritter

Publications and source records attributed to Robert Ritter.

6 recordsLinked to original sources

PubMed2005

Complement factor H polymorphism and age-related macular degeneration.

Age-related macular degeneration (AMD) is a common, late-onset, and complex trait with multiple risk factors. Concentrating on a region harboring a locus for AMD on 1q25-31, the ARMD1 locus, we tested single-nucleotide polymorphisms for association with AMD in two independent case-control populations. Significant association (P = 4.95 x 10(-10)) was identified within the regulation of complement activation locus and was centered over a tyrosine-402 --> histidine-402 protein polymorphism in the gene encoding complement factor H. Possession of at least one histidine at amino acid position 402 increased the risk of AMD 2.7-fold and may account for 50% of the attributable risk of AMD.

Aged↗

PubMed2004

Genetic linkage of snowflake vitreoretinal degeneration to chromosome 2q36.

PURPOSE: To identify the chromosomal location of the gene causing snowflake vitreoretinal degeneration (SVD), an autosomal dominant retinal degeneration characterized by small yellow-white dots in the retina, fibrillar anomaly of the vitreous humor, and retinal detachment. METHODS: Clinical data were collected on 31 family members by history and examination. Thirteen family members underwent prospective examination. Genotyping was performed using microsatellite markers spaced at approximately 10 cM intervals. Two-point and multipoint linkage analysis was performed (FASTLINK version of the MLINK program and the VITESSE algorithm, both available at http://linkage.rockefeller.edu/soft/list.html). Direct DNA sequencing of amplified genomic DNA and mRNA was performed for candidate gene analysis. RESULTS: The SVD locus was linked to markers in a region of chromosome 2q36 defined by D2S2158 and D2S2202, based on meiotic breakpoint mapping of affected individuals. A maximum two-point lod score of 5.5 was obtained with marker D2S172 at theta; = 0 within this region. Direct DNA sequencing of all 52 exons of the COL4A3 gene revealed no potentially pathogenic coding sequence variation or evidence for deletion. CONCLUSIONS: The genetic locus for SVD lies in a 9 Mb region flanked by D2S2158 and D2S2202. Localization of SVD to a genomic region distinct from both Wagner disease and the Stickler syndromes indicates that SVD is a distinct genetic entity. The absence of coding sequence variation in the only collagen gene within the disease-region, suggests a novel pathogenesis for vitreoretinal degeneration. Snowflake vitreoretinal degeneration should be considered in the differential diagnosis of families with fibrillar anomaly of the vitreous.

Autoantigens↗

PubMed2003

Posterior chorioretinal atrophy and vitreous phenotype in a family with Stickler syndrome from a mutation in the COL2A1 gene.

PURPOSE: To report posterior chorioretinal atrophy (PCRA) and correlate the vitreous phenotype with inheritance of the disease mutation in a family with vitreoretinal dystrophy. DESIGN: Prospective observational case series. METHODS: Twenty-four members of a family with 14 affected individuals were examined, and genetic linkage analysis was performed at the COL2A1, COL11A1, and Wagner disease loci. The vitreous phenotype was prospectively graded as optically empty with retrolenticular membrane, fibrillar, or normal. Ocular ultrasonography and optical coherence tomography (OCT) were performed on selected individuals to study the vitreous structure and vitreoretinal interface. RESULTS: The 6-year-old proband had PCRA and optically empty vitreous without systemic features, suggestive of Wagner disease. The family history was negative for systemic disease, except for one cousin with cleft palate. However, when examined, clinical features of the 14 affected subjects included 5 with small chin, 4 with at least submucosal cleft palate, and 9 with a myopic refractive error greater than 5 diopters. Lens opacity or previous cataract extraction was found in 13 family members. All affected individuals in whom the vitreous could be examined had an optically empty vitreous with retrolental membrane. Posterior chorioretinal atrophy was found in eight of the affected subjects. The finding was not limited to highly myopic subjects, nor did all the high myopes have PCRA. Ultrasonography and OCT revealed vitreous adherent to the retina, but without apparent retinal distortion or edema of the macula. Significant linkage was established to the COL2A1 locus; the other loci were excluded. A single nucleotide insertion mutation (c.2012 2013insC) was identified in exon 34, leading to a downstream premature stop codon in the COL2A1 gene. CONCLUSIONS: Although posterior chorioretinal atrophy and vitreoretinal degeneration have been classically associated with Wagner disease, we demonstrate its presence in a family with typical Stickler syndrome. On the basis of clinical, ultrasonographic, and OCT studies, the etiology of PCRA in this family does not seem to be attributable to vitreomacular traction or myopia. The vitreous findings in this large family confirm reports that mutations in the COL2A1 gene lead to the optically empty vitreous with retrolenticular membrane phenotype.

Adolescent↗

PubMed2003

Snowflake vitreoretinal degeneration: follow-up of the original family.

PURPOSE: The ocular findings, systemic features, and genetic loci distinguishing known genetic causes of vitreoretinal degenerations were studied in the original Snowflake family. DESIGN: Prospective, comparative study and molecular genetic investigation. PARTICIPANTS: Members of the original snowflake vitreoretinal degeneration family. METHODS: Clinical data were collected on 26 family members by history and examination. Thirteen of the 26 total family members underwent prospective examination. Linkage to known vitreoretinal degeneration loci (COL2A1, COL11A1, and the Wagner disease locus) was evaluated with short tandem repeat markers. MAIN OUTCOME MEASURES: Ocular and systemic features of known vitreoretinal degenerations. RESULTS: Six of the 13 prospectively examined subjects had snowflake vitreoretinal degeneration. Corneal guttae (4/5; 80%), early onset cataract (5/6; 83%), fibrillar vitreous degeneration (6/6; 100%), and peripheral retinal abnormalities (5/6; 83%), including minute crystallinelike deposits called snowflakes (4/6; 67%), were common. Retinal detachment was seen in 1 of 6 of these prospectively examined subjects (17%). A total of 14 affected subjects were identified within the family, and in 3 (21%), retinal detachment developed. Orofacial features, early-onset hearing loss, and arthritis typical of Stickler syndrome were absent. Linkage to known vitreoretinal degeneration loci was excluded. CONCLUSIONS: The absence of vitreous gel in the retrolental space and presence of fibrillar vitreous degeneration were consistent with the vitreous structure reported for collagen 11A1 (COL11A1) but not collagen 2A1 (COL2A1) mutations. The absence of systemic features was characteristic of the vitreoretinopathies linked to chromosome 5q13 (Wagner disease and erosive vitreoretinopathy) and mutations in exon 2 of the COL2A1 gene. Snowflakes in the peripheral retina and the absence of nyctalopia, posterior chorioretinal atrophy, and tractional retinal detachment were inconsistent with the chromosome 5q13 vitreoretinopathies. The association of Fuchs' corneal endothelial dystrophy found in this family has not been reported previously in other vitreoretinal degenerations. These findings and the exclusion of known genetic loci suggest snowflake is a distinct vitreoretinal degeneration.

Adult↗

PubMed2002

Identification of a stop codon mutation in exon 2 of the collagen 2A1 gene in a large stickler syndrome family.

PURPOSE: To describe the clinical features and identify the mutation responsible for an autosomal dominant vitreoretinal degeneration occurring in a previously unreported large family. DESIGN: Cohort study. METHODS: Family members were evaluated clinically over a 30-year period. Genealogical investigation, genetic linkage to known vitreoretinal degenerations, and mutation screening of the COL2A1 gene were performed. RESULTS: We identified a single large family (2,384 total family members) with vitreoretinal degeneration spanning 12 generations. We reviewed the clinical records of 165 family members (95 affected and 70 unaffected). The common clinical findings in affected individuals included early-onset posterior perivascular retinal degeneration, vitreous degeneration, and retinal detachment. The incidence of retinal detachment was 57% (95/165) and the mean age of onset was 15.2 years. Orofacial, skeletal, and auditory abnormalities were seen in 0%, 5%, and 7.5%, respectively, in a subset of 28 affected subjects. Linkage to the collagen COL2A1 locus was demonstrated and a cytosine to adenosine transition identified within exon 2, leading to the creation of a stop codon at position 86 (Cys86Stop). CONCLUSIONS: Identification of the mutation in this family enables diagnosis of individuals at risk for potentially blinding complications in this condition at an early age. Given the variability of the Stickler phenotype, mutation detection allows for more comprehensive genetic counseling and directs clinical monitoring to family members inheriting the disease gene.

Adolescent↗

PubMedDate not supplied

Clinical variability of Stickler syndrome: role of exon 2 of the collagen COL2A1 gene.

Stickler syndrome (progressive arthro-ophthalmopathy) is a genetically heterogeneous disorder resulting from mutations in at least three collagen genes. The most common disease-causing gene is COL2A1, a 54-exon-containing gene coding for type II collagen. At least 17 different mutations causing Stickler syndrome have been reported in this gene. Phenotypically, it is also a variably expressed disorder in which most patients present with a wide range of eye and extraocular manifestations including auditory, skeletal, and orofacial manifestations. Some patients, however, present without clinically apparent systemic findings. This observation has led to difficulty distinguishing this Stickler phenotype from other hereditary vitreoretinal degenerations, such as Wagner syndrome and Snowflake vitreoretinal degeneration. In this regard, review of the literature indicates type II collagen exists in two forms resulting from alternative splicing of exon 2 of the COL2A1 gene. One form, designated as type IIB (short form), is preferentially expressed in adult cartilage tissue. The other form, designated as type IIA (long form), is preferentially expressed in the vitreous body of the eye. Because of this selective tissue expression, mutations in exon 2 of the COL2A1 gene have been hypothesized to produce this Stickler syndrome phenotype with minimal or absent extraocular findings. We review the evidence for families with exon 2 mutations of the collagen COL2A1 gene presenting in a distinct manner from families with mutations in the remaining 53 exons, as well as other hereditary vitreoretinal degenerations without significant systemic manifestations.

Collagen Type II↗