RESUMEN
BACKGROUND: Mutations in the OA1 gene on the short arm of the X chromosome are known to cause X-linked ocular albinism (x1OA) in males. A four-generation family with this disorder, including asymptomatic carrier females, was investigated by molecular analysis of the OA1 gene. METHODS: DNA samples were available from 22 individuals of this family, including 6 affected males and 6 obligate carriers. The nine exons of the OA1 gene were amplified and further analyzed by SSCP and sequencing. RESULTS: A detailed clinical examination of the index patient and two female carriers showed the typical signs of ocular albinism. Visual evoked potential responses showed markedly asymmetrical responses from the two hemispheres in the affected person as well as in the carriers, as a result of misrouting and decussation of optic nerve fibers. Molecular genetic analysis demonstrated a previously undescribed 29-bp deletion at position 225-253 in exon 1 of the OA1 gene, which segregated in the family. CONCLUSION: Clinical examination combined with molecular genetic analysis enhances the potential for a precise diagnosis for persons at risk of x1OA and provide an accurate basis for genetic counseling.
Asunto(s)
Albinismo Ocular/genética , Exones/genética , Ligamiento Genético/genética , Eliminación de Secuencia , Cromosoma X/genética , Adulto , Albinismo Ocular/diagnóstico , Secuencia de Aminoácidos , Secuencia de Bases , Preescolar , Análisis Mutacional de ADN , Electrorretinografía , Potenciales Evocados Visuales , Femenino , Fondo de Ojo , Tamización de Portadores Genéticos , Humanos , Lactante , Masculino , Datos de Secuencia Molecular , Oftalmoscopía , Linaje , Polimorfismo Conformacional Retorcido-Simple , Agudeza VisualRESUMEN
A number of distinct, partly non-overlapping genetic loci have been reported for the complete type of X-linked congenital stationary night blindness (CSNB1), suggesting genetic heterogeneity. In order to refine the localization of the CSNB1 gene and to demonstrate genetic homogeneity, linkage analysis was performed in two large CSNB1 families. Clinical features consistent with the diagnosis of CSNB1 were documented in five patients from a German seven-generation kindred by full ophthalmological examination including psychophysical and electroretinographical testing. Haplotype analysis in 30 members of the large German family was performed with 38 polymorphic markers predominantly covering the critical region. Linkage analyses defined a locus for CSNB1 with flanking markers DXS8042 and DXS228, refining the interval to 2.5 cM in Xp11.4. In addition, two-point linkage analysis was carried out using the MLINK computer program. In agreement with meiotic breakpoints, lod scores of 3.0 and greater were obtained for markers located to the proximal site of the former 5 cM CSNB consensus interval. A large Dutch CSNB1 family was re-evaluated with markers from the Xp11.4 region, and supports the CSNB1 minimal interval found in the German family. Together with previous results from three unrelated families from Sweden, Sardinia and Great Britain, our results provide evidence of genetic homogeneity in the disorder. Subsequent mutation analyses in CSNB1 patients revealed no pathogenic sequence alterations in DFFRX and CASK genes, but retain candidates for other diseases mapping to that region.
Asunto(s)
Ligamiento Genético , Ceguera Nocturna/genética , Cromosoma X/genética , Proteínas Quinasas Dependientes de Calcio-Calmodulina/genética , Mapeo Cromosómico , Endopeptidasas/genética , Europa (Continente) , Femenino , Haplotipos , Humanos , Escala de Lod , Masculino , Ceguera Nocturna/congénito , LinajeRESUMEN
X-linked congenital stationary night blindness (XLCSNB) is characterized by impaired scotopic vision with associated ocular symptoms such as myopia, hyperopia, nystagmus and reduced visual acuity. Genetic mapping in families with XLCSNB revealed two different loci on the proximal short arm of the X chromosome. These two genetic subtypes can be distinguished on the basis of electroretinogram (ERG) responses and psychophysical testing as a complete (CSNB1) and an incomplete (CSNB2) form. The CSNB1 locus has been mapped to a 5-cM linkage interval in Xp11.4 (refs 2,5-7). Here we construct and analyse a contig between the markers DXS993 and DXS228, leading to the identification of a new gene mutated in CSNB1 patients. It is partially deleted in 3 families and mutation analysis in a further 21 families detected another 13 different mutations. This gene, designated NYX, encodes a protein of 481 amino acids (nyctalopin) and is expressed at low levels in tissues including retina, brain, testis and muscle. The predicted polypeptide is a glycosylphosphatidylinositol (GPI)-anchored extracellular protein with 11 typical and 2 cysteine-rich, leucine-rich repeats (LRRs). This motif is important for protein-protein interactions and members of the LRR superfamily are involved in cell adhesion and axon guidance. Future functional analysis of nyctalopin might therefore give insight into the fine-regulation of cell-cell contacts in the retina.
Asunto(s)
Proteínas del Ojo/genética , Genes , Ceguera Nocturna/genética , Proteoglicanos/genética , Cromosoma X/genética , Secuencias de Aminoácidos , Secuencia de Aminoácidos , Encéfalo/metabolismo , Mapeo Cromosómico , Análisis Mutacional de ADN , ADN Complementario/genética , Electrorretinografía , Proteínas del Ojo/química , Proteínas del Ojo/fisiología , Femenino , Perfilación de la Expresión Génica , Heterogeneidad Genética , Marcadores Genéticos , Glicosilfosfatidilinositoles/metabolismo , Humanos , Riñón/metabolismo , Leucina/análisis , Masculino , Modelos Moleculares , Datos de Secuencia Molecular , Familia de Multigenes , Proteínas Musculares/biosíntesis , Proteínas Musculares/genética , Músculos/metabolismo , Proteínas del Tejido Nervioso/biosíntesis , Proteínas del Tejido Nervioso/genética , Ceguera Nocturna/clasificación , Especificidad de Órganos , Linaje , Conformación Proteica , Proteoglicanos/química , Proteoglicanos/deficiencia , Proteoglicanos/fisiología , Secuencias Repetitivas de Aminoácido , Retina/metabolismo , Retina/patología , Reacción en Cadena de la Polimerasa de Transcriptasa Inversa , Eliminación de Secuencia , Homología de Secuencia de Aminoácido , Testículo/metabolismoRESUMEN
The gene for ubiquitin hydrolase on the X chromosome (UHX1), cloned and mapped to Xp21.2-p11.2, is a candidate gene for retinal diseases. We used fine mapping techniques to localise UHX1 between markers DXS1266 and DXS337, where congenital stationary night blindness (XICSNB) and retinitis pigmentosa type 2 (RP2) are also located. Reevaluation of the UHX1 gene structure demonstrated five new exons, for a total of 21 exons and a predicted protein product of 963 amino acids. Evaluation of patients revealed no UHX1 mutations using SSCP (10 CSNB1 and 20 XLRP) or deletion screening with cDNA hybridisation (13 CSNB1 and 43 XLRP). Likewise, no aberrations were found in the nearby PCTAIRE1 (PCTK1) gene in 13 CSNB1 and 43 XLRP patients by deletion screening. Thus mutations of UHX1, and probably PCTK1, do not appear to cause common X-linked eye diseases. UHX1's role in patients with mental retardation may be appropriate for further investigations into UHX1 function.
Asunto(s)
Mapeo Cromosómico , Quinasas Ciclina-Dependientes , Proteínas Serina-Treonina Quinasas/genética , Enfermedades de la Retina/genética , Tioléster Hidrolasas/genética , Cromosoma X , Secuencia de Bases , Análisis Mutacional de ADN , Cartilla de ADN , Estudios de Evaluación como Asunto , Marcadores Genéticos , HumanosRESUMEN
X-linked lymphoproliferative syndrome (XLP or Duncan disease) is characterized by extreme sensitivity to Epstein-Barr virus (EBV), resulting in a complex phenotype manifested by severe or fatal infectious mononucleosis, acquired hypogammaglobulinemia and malignant lymphoma. We have identified a gene, SH2D1A, that is mutated in XLP patients and encodes a novel protein composed of a single SH2 domain. SH2D1A is expressed in many tissues involved in the immune system. The identification of SH2D1A will allow the determination of its mechanism of action as a possible regulator of the EBV-induced immune response.
Asunto(s)
Proteínas Portadoras/genética , Infecciones por Herpesviridae/complicaciones , Herpesvirus Humano 4 , Péptidos y Proteínas de Señalización Intracelular , Trastornos Linfoproliferativos/genética , Mutación , Dominios Homologos src/genética , Antígenos CD , Linfocitos B/inmunología , Linfocitos B/virología , Proteínas Portadoras/metabolismo , Clonación Molecular , Femenino , Ligamiento Genético , Glicoproteínas/metabolismo , Infecciones por Herpesviridae/inmunología , Infecciones por Herpesviridae/virología , Humanos , Inmunoglobulinas/metabolismo , Trastornos Linfoproliferativos/complicaciones , Trastornos Linfoproliferativos/inmunología , Trastornos Linfoproliferativos/virología , Masculino , Datos de Secuencia Molecular , Linaje , Receptores de Superficie Celular , Alineación de Secuencia , Eliminación de Secuencia , Proteína Asociada a la Molécula de Señalización de la Activación Linfocitaria , Miembro 1 de la Familia de Moléculas Señalizadoras de la Activación Linfocitaria , Linfocitos T/inmunología , Linfocitos T/virología , Cromosoma XRESUMEN
X-linked retinitis pigmentosa (xlRP) is a severe progressive retinal degeneration which affects about 1 in 25,000 of the population. The most common form of xlRP, RP3, has been localised to the interval between CYBB and OTC in Xp21.1 by linkage analysis and deletion mapping. Identification of microdeletions within this region has now led to the positional cloning of a gene, RPGR, that spans 60 kg of genomic DNA and is ubiquitously expressed. The predicted 90 kD protein contains in its N-terminal half a tandem repeat structure highly similar to RCC1 (regulator of chromosome condensation), suggesting an interaction with a small GTPase. The C-terminal half contains a domain, rich in acidic residues, and ends in a potential isoprenylation anchorage site. The two intragenic deletions, two nonsense and three missense mutations within conserved domains provide evidence that RPGR (retinitis pigmentosa GTPase regulator) is the RP3 gene.
Asunto(s)
Proteínas Portadoras/biosíntesis , Proteínas Portadoras/genética , Proteínas de Ciclo Celular , Proteínas de Unión al ADN/genética , Proteínas del Ojo , Proteínas de Unión al GTP/genética , Factores de Intercambio de Guanina Nucleótido , Retinitis Pigmentosa/genética , Cromosoma X , Secuencia de Aminoácidos , Animales , Secuencia de Bases , Mapeo Cromosómico , Clonación Molecular , Secuencia Conservada , Cartilla de ADN , Femenino , GTP Fosfohidrolasas/metabolismo , Expresión Génica , Humanos , Masculino , Datos de Secuencia Molecular , Proteínas Nucleares/genética , Linaje , Reacción en Cadena de la Polimerasa , Prenilación de Proteína , Secuencias Repetitivas de Ácidos Nucleicos , Saccharomyces cerevisiae/genética , Homología de Secuencia de Aminoácido , Xenopus , Proteínas de XenopusRESUMEN
X-linked retinitis pigmentosa (XLRP) is characterized by retinal degeneration with night blindness and progressive reduction of the visual fields. By linkage and deletion analysis a gene locus (RP3) has been mapped to the short arm of the X chromosome between the genes CYBB and OTC. Analysis of transcript in this region has revealed a gene which is abundantly expressed in human retina and encodes a putative membrane protein with significant homologies to short consensus repeat (SCR/sushi) domains known from selections and complement proteins. The gene termed SRPX (sushi-repeat-containing protein, x chromosome) is deleted in an RP patient who also suffers from chronic granulomatous disease and McLeod syndrome. A 75 kb deletion removing exon 1 of the gene was also found in two brothers of a second XLRP family. However, no further functionally significant mutations were detected by SSCP screening of all 10 exons in 34 unrelated XLRP patients nor by full length RT-PCR sequencing in two RP3 families. The role of this highly conserved retinal gene in the pathogenesis of RP therefore remains to be determined.
Asunto(s)
Eliminación de Gen , Proteínas de la Membrana/genética , Retinitis Pigmentosa/genética , Cromosoma X , Adulto , Secuencia de Aminoácidos , Animales , Secuencia de Bases , Bovinos , Clonación Molecular , ADN Complementario , Femenino , Humanos , Masculino , Datos de Secuencia Molecular , Ratas , Mapeo Restrictivo , Retina/metabolismoAsunto(s)
Proteínas del Ojo/genética , Mutación , Proteínas del Tejido Nervioso/genética , Displasia Retiniana/genética , Vitreorretinopatía Proliferativa/genética , Adulto , Secuencia de Bases , Preescolar , Femenino , Humanos , Masculino , Persona de Mediana Edad , Datos de Secuencia Molecular , Polimorfismo de Longitud del Fragmento de Restricción , Análisis de Secuencia de ADNRESUMEN
Carrier detection in X-linked immunodeficiencies (X-SCID, WAS, XLA) relies on the demonstration of non-random X inactivation patterns in blood cell lineages. Only a limited number of cells are available after cell separation methods. PCR-based techniques are therefore necessary to analyze active and inactive X chromosomes. Amplifying a polymorphic CAG repeat in the first exon of the androgen receptor gene after selective digestion of the active X chromosome with a methylation-sensitive restriction enzyme allows to distinguish between the paternal and maternal alleles and to identify their methylation status. DNA from B-, T-lymphocytes and total peripheral leukocytes of normal males, females and obligate carriers of X-linked immunodeficiencies were analyzed. The results of this PCR-based X inactivation assay are concordant with the standard methylation studies at the DXS255 locus using Southern blotting. This PCR assay provides a rapid and informative (heterozygosity > 90%) method in carrier detection of X-linked immunodeficiencies and other X-linked disorders, which show non-random X inactivation in cell lineages from the affected tissues.
Asunto(s)
Compensación de Dosificación (Genética) , Tamización de Portadores Genéticos/métodos , Ligamiento Genético/genética , Síndromes de Inmunodeficiencia/genética , Reacción en Cadena de la Polimerasa/métodos , Receptores Androgénicos/genética , Cromosoma X/genética , ADN/análisis , Femenino , Humanos , Masculino , MetilaciónAsunto(s)
ADN/genética , Bases de Datos Factuales , Polimorfismo Genético , Secuencias Repetitivas de Ácidos Nucleicos , Cromosoma X , Secuencia de Bases , Mapeo Cromosómico , Cromosomas Artificiales de Levadura , Cromosomas Humanos , Cartilla de ADN , Humanos , Datos de Secuencia Molecular , Reacción en Cadena de la PolimerasaAsunto(s)
Fibrosis Quística/genética , Proteínas de la Membrana/genética , Mutación/genética , Población Blanca/genética , Adolescente , Secuencia de Bases , Fibrosis Quística/etnología , Regulador de Conductancia de Transmembrana de Fibrosis Quística , ADN/análisis , Análisis Mutacional de ADN , Exones/genética , Femenino , Genes/genética , Pruebas Genéticas , Alemania , Humanos , Recién Nacido , Masculino , Datos de Secuencia Molecular , Ácidos Nucleicos Heterodúplex , Reacción en Cadena de la PolimerasaRESUMEN
Employing a modified Goss-Harris irradiation fusion protocol, we have generated a panel of somatic cell hybrids containing various overlapping fragments of the Xcen-Xp11.4 interval. This region of the human X chromosome is known to carry genes for several hereditary eye diseases including retinitis pigmentosa (RP2), congenital stationary night blindness (CSNB-1) and Norrie disease. These hybrid cell lines were employed to isolate 17 new DNA probes by making use of the Alu polymerase chain reaction (PCR) method and subsequent cloning of the PCR products in a plasmid vector. With these probes, we have characterized two previously described microdeletions spanning the Norrie locus; these deletions have enabled us to subdivide the Xp11.4-p11.3 region into three defined intervals.
Asunto(s)
Sondas de ADN/aislamiento & purificación , Células Híbridas , Cromosoma X , Animales , Secuencia de Bases , Mapeo Cromosómico , Cricetinae , Cricetulus , ADN de Cadena Simple , Humanos , Hibridación Fluorescente in Situ , Datos de Secuencia Molecular , Plásmidos , Reacción en Cadena de la PolimerasaRESUMEN
A candidate gene for Norrie disease, an X-linked disorder characterized by blindness, deafness and mental disturbances, was recently isolated and found to contain microdeletions in numerous patients. No strong homologies were identified. By studying the number and spacing of cysteine residues, we now detect homologies between the Norrie gene product and a C-terminal domain which is common to a group of proteins including mucins. Three newly-characterized missense mutations, replacing evolutionarily conserved cysteines or creating new cysteine codons, emphasize the functional importance of these sites. These findings and the clinical features of this disorder suggest a possible role for the Norrie gene in neuroectodermal cell-cell interaction.