RESUMEN
Mutations in FOXL2, a forkhead transcription factor gene, have recently been shown to cause blepharophimosis-ptosis-epicanthus inversus syndrome (BPES) types I and II, a rare genetic disorder. In BPES type I a complex eyelid malformation is associated with premature ovarian failure (POF), whereas in BPES type II the eyelid defect occurs as an isolated entity. In this study, we describe the identification of novel mutations in the FOXL2 gene in BPES types I and II families, in sporadic BPES patients, and in BPES families where the type could not be established. In 67% of the patients studied, we identified a mutation in the FOXL2 gene. In total, 21 mutations (17 of which are novel) and one microdeletion were identified. Thirteen of these FOXL2 mutations are unique. In this study, we demonstrate that there is a genotype--phenotype correlation for either types of BPES by the finding that mutations predicted to result in a truncated protein either lacking or containing the forkhead domain lead to BPES type I. In contrast, duplications within or downstream of the forkhead domain, and a frameshift downstream of them, all predicted to result in an extended protein, cause BPES type II. In addition, in 30 unrelated patients with isolated POF no causal mutations were identified in FOXL2. Our study provides further evidence that FOXL2 haploinsufficiency may cause BPES types I and II by the effect of a null allele and a hypomorphic allele, respectively. Furthermore, we propose that in a fraction of the BPES patients the genetic defect does not reside within the coding region of the FOXL2 gene and may be caused by a position effect.
Asunto(s)
Blefarofimosis/diagnóstico , Blefarofimosis/genética , Blefaroptosis/diagnóstico , Blefaroptosis/genética , Proteínas de Unión al ADN/genética , Párpados/anomalías , Mutación , Factores de Transcripción/genética , Alelos , Secuencia de Aminoácidos , Secuencia de Bases , Salud de la Familia , Femenino , Proteína Forkhead Box L2 , Factores de Transcripción Forkhead , Mutación del Sistema de Lectura , Eliminación de Gen , Genotipo , Humanos , Hibridación Fluorescente in Situ , Masculino , Modelos Genéticos , Datos de Secuencia Molecular , Mutación Missense , Linaje , Fenotipo , SíndromeRESUMEN
PURPOSE: We previously reported linkage of North Carolina macular dystrophy in a single isolated family to a broad region on chromosome 6q16. In order to refine the localization of the MCDR1 gene (North Carolina macular dystrophy), additional families with this disease and new markers were studied. METHODS: We ascertained 10 families with the North Carolina macular dystrophy phenotype (MCDR1). These families were of various ethnic and geographic origins such as Caucasian, Mayan Indian, African-American, French, British, German, and American of European decent. Two hundred thirty-two individuals in these families underwent comprehensive ophthalmic examinations and blood was collected for genotyping. One hundred seventeen were found to be affected. Linkage simulation studies were performed. Two-point linkage, haplotype analysis, and multipoint linkage was performed using VITESSE and FASTLINK. HOMOG was used to test for genetic heterogeneity. RESULTS: The clinical features were consistent with the diagnosis of North Carolina macular dystrophy in all families. Multipoint linkage analysis indicates that the MCDR1 gene is in the interval between D6D249 and D6S1671 with a maximum LOD score of 41.52. There was no evidence of genetic heterogeneity among the families studied. Families 765, 768, 772, 1193, and 1292 shared the same chromosomal haplotype in this region. CONCLUSIONS: This is the largest single data set of families with the MCDR1 phenotype. The single large family from North Carolina continues to be informative for the closest flanking markers and alone supports the minimal candidate region as suggested by previous studies. There remains no evidence of genetic heterogeneity in this disease. Most of the American families appear to have descended from the same ancestral mutation. The remaining families could each represent independent origins of the mutation in the MCDR1 gene.
Asunto(s)
Cromosomas Humanos Par 6 , Proteínas del Ojo/genética , Degeneración Macular/genética , Adolescente , Adulto , Niño , Preescolar , Femenino , Ligamiento Genético , Marcadores Genéticos , Haplotipos , Humanos , Lactante , Escala de Lod , Masculino , Persona de Mediana Edad , Reacción en Cadena de la PolimerasaRESUMEN
PURPOSE: To map the gene responsible for causing a macular degeneration in a Texan family that appears clinically similar to the North Carolina macular dystrophy (MCDR1) phenotype. METHODS: A single family in Texas had all the typical clinical features of the North Carolina macular dystrophy phenotype. Of 23 family members examined, 10 were affected. Blood was collected from all 23 members and fundus photographs were obtained on those affected. A detailed family history consisting of nine generations was obtained. Genotyping and likelihood analysis was performed using the closest linked MCDR1 markers. RESULTS: The genealogic data showed no relation with the original North Carolina macular dystrophy pedigree. The dinucleotide repeat marker D6S283 yielded the highest 2-point LOD score with a Zmax = 4.1 at theta = 0. The peak LOD score generated from multipoint analysis was 6.0. CONCLUSIONS: The linkage results indicate that the macular degeneration in this Texan family is due to a mutation in the same genomic region as that causing North Carolina macular dystrophy. Furthermore, haplotype analysis suggests that the original North Carolina family and the Texan family have the same mutation and a common founder.
Asunto(s)
Degeneración Macular/genética , Adulto , Anciano , Mapeo Cromosómico , Cromosomas Humanos Par 6/genética , ADN/análisis , Femenino , Frecuencia de los Genes , Marcadores Genéticos , Genotipo , Humanos , Desequilibrio de Ligamiento , Degeneración Macular/epidemiología , Degeneración Macular/patología , Masculino , Persona de Mediana Edad , North Carolina , Linaje , Prevalencia , Texas/epidemiologíaRESUMEN
PURPOSE: To describe the clinical findings of an autosomal dominant macular dystrophy in a family of Mayan Indian ancestry in Belize, Central America, and to determine its molecular genetic relationship with the original North Carolinian family. METHODS: We performed comprehensive ophthalmic examinations on 56 members of a single family living in Chicago, Illinois, and Belize, Central America. Fundus photography and fluorescein angiography were performed on 17 affected subjects and six affected family members were serially examined over a 12-year period. Blood was collected from 26 individuals, and DNA was extracted for genotyping. Two-point linkage, multipoint linkage, and haplotype analysis was performed. RESULTS: In 17 affected individuals, the clinical features were consistent with the diagnosis of North Carolina macular dystrophy. Multipoint linkage analysis generated a peak lod score of 5.6 in the MCDR1 region. The haplotype associated with the disease was, however, different from that of the original North Carolinian family. CONCLUSIONS: This family has an autosomal dominant macular dystrophy that is clinically indistinguishable from North Carolina macular dystrophy (MCDR1). Our findings indicate that the mutated gene in this Belizean family maps precisely to the same region as that of the North Carolina macular dystrophy (MCDR1) locus. This study provides evidence that MCDR1 occurs in various ethnic groups and that there is no evidence of genetic heterogeneity.
Asunto(s)
Mapeo Cromosómico , Cromosomas Humanos Par 6/genética , Indígenas Centroamericanos , Degeneración Macular/genética , Adolescente , Adulto , Belice , Niño , Preescolar , ADN/análisis , Femenino , Angiografía con Fluoresceína , Fondo de Ojo , Genotipo , Haplotipos , Humanos , Indígenas Centroamericanos/genética , Lactante , Degeneración Macular/patología , Masculino , Persona de Mediana Edad , North Carolina , Linaje , FenotipoRESUMEN
PURPOSE: To determine if a family in France, which manifests an autosomal dominant macular dystrophy, has North Carolina macular dystrophy (MCDR1) and to determine its possible molecular genetic relationship with the original North Carolina family. METHODS: A family from Northern France with a macular dystrophy underwent comprehensive ophthalmic examinations and were ascertained for genetic studies. Blood collection and examinations were performed on 38 individuals. Fundus photographs with a hand held KOWA camera were obtained on affected subjects. DNA was extracted and genotyping performed using new microsatellite genetic markers, which have recently been found in the MCDR1 (North Carolina macular dystrophy) region. Standard two - point linkage and haplotype analysis was performed. RESULTS: Eleven individuals were found with the clinical manifestations of North Carolina macular dystrophy. Two - point linkage analysis generated a maximum peak LOD score of 4.5 with a recombination of 0% between D6S1717 and the macular dystrophy locus in the French family. The haplotype associated with the disease is, however, different from that of the original North Carolina family. CONCLUSIONS: These findings indicate that the macular dystrophy gene in this French family maps to the same region as that of North Carolina macular dystrophy (MCDR1) locus but that independent mutations are involved. The disease in the French family is clinically and genetically similar to North Carolina macular dystrophy. Therefore MCDR1 occurs in various ethnic groups, is present world-wide, and there remains no evidence of genetic heterogeneity for this clinically distinct form of macular degeneration.