Localization of MRX82: A new nonsyndromic X-linked mental retardation locus to Xq24-q25 in a Basque family

Clinical and molecular studies are reported on a Basque family (MRX82) with nonsyndromic X-linked mental retardation (XLMR) in five affected males. A total of 38 microsatellite markers were typed. The XLMR locus has been linked to DXS8067, DXS1001, DXS425, DXS7877, and DXS1183 with a maximum LOD score of 2.4. The haplotype studies and multipoint linkage analysis suggest a localization of the MRX82 locus to an interval of 7.6 Mb defined by markers DXS6805 and DXS7346, in Xq24 and Xq25, respectively. No gene contained in this interval has been so far associated with nonsyndromic mental retardation, except for GRIA3, disrupted by a balanced translocation in a female patient with bipolar affect…

Chromosome 5 abnormalities in acute lymphoblastic leukemia

Abstract We report two cases of acute lymphoblastic leukemia with involvement of chromosome 5. One of them showed a del(5)(q13q33) in a 5-year-old boy who had previously received antineoplastic chemotherapy for an L1-ALL that had been diagnosed nine months before. The other one showed a t(5;7)(q12–13;q36) together with a t(8;14)(q24;q32) and a der(1) in a 66-year-old man with an L3-ALL. Both chromosome 5 aberrations are interpreted as evolutionary events. In the first case, it was secondary to chemotherapy treatment; in the second, an evolutionary chromosome rearrangement, considering the translocation between chromosomes 8 and 14 as the primary cytogenetic event.

Dejerine-Sottas neuropathy associated with De Novo S79P mutation of the peripheral myelin protein 22 (PMP22) gene

A two base pair deletion in the PQBP1 gene is associated with microphthalmia, microcephaly, and mental retardation.

X-linked mental retardation has been traditionally divided into syndromic (S-XLMR) and non-syndromic forms (NS-XLMR), although the borderlines between these phenotypes begin to vanish and mutations in a single gene, for example PQBP1, can cause S-XLMR as well as NS-XLMR. Here, we report two maternal cousins with an apparently X-linked phenotype of mental retardation (MR), microphthalmia, choroid coloboma, microcephaly, renal hypoplasia, and spastic paraplegia. By multipoint linkage analysis with markers spanning the entire X-chromosome we mapped the disease locus to a 28-Mb interval between Xp11.4 and Xq12, including the BCOR gene. A missense mutation in BCOR was described in a family with …

Diagnóstico temprano del retinoblastoma: importancia de la búsqueda de mutaciones en el gen RB1

Fundamento El retinoblastoma, cancer intraocular infantil mas frecuente, se presenta como esporadico (unilateral o bilateral) o afectando a varios miembros de una familia. En los casos hereditarios aparece por una mutacion germinal transmitida o surgida de novo, mientras que en los no hereditarios se debe a dos mutaciones somaticas en una celula de la retina. El presente trabajo se planteo con objeto de analizar desde el punto de vista genetico el gran numero de familias con algun miembro afectado de retinoblastoma, recopiladas en los ultimos anos, para ahondar en los mecanismos moleculares que inciden en este proceso patologico y ofrecerles consejo genetico. Pacientes y metodo Se han anali…

Genetics of retinoblastoma: A study

Abstract We have analyzed 43 families with either familial retinoblastoma (RB) (four kindreds), bilateral sporadic RB (10 individuals), or unilateral sporadic RB (29 individuals). Genetic studies focused on karyotype analysis, loss of heterozygosity of intragenic polymorphisms, and search for point mutations. We have been able to identify the genetic defect underlying the disease in eight cases. Deletions have been found in three patients with sporadic RB, two bilateral in one of which karyotyping had previously detected an interstitial deletion of chromosome 13 affecting (q13–q31) and one unilateral. Five different point mutations were responsible for three cases of bilateral sporadic RB, …

An autosomal dominant retinitis pigmentosa family with close linkage to D7S480 on 7q.

Retinitis pigmentosa is the most prevalent inherited disorder of the retina. It can be autosomal dominant (adRP), autosomal recessive (arRP) or X-linked (XLRP). A form of adRP mapping to chromosome 7q was reported in a large Spanish pedigree. We have typed DNA from the members of another Spanish family for polymorphic markers from the known candidate genes. Positive lod scores were obtained only for the markers located on 7q31-35, giving a maximum lod score of 2.98 (3.01 by multipoint analysis) at theta = 0.00 for D7S480. A brief clinical evaluation is given.

Localization of non-specific X-linked mental retardation gene (MRX73) to Xp22.2.

Clinical and molecular studies are reported on a family (MRX73) of five males with non-specific X-linked mental retardation (XLMR). A total of 33 microsatellite and RFLP markers was typed. The gene for this XLMR condition was been linked to DXS1195, with a lod score of 2.36 at theta = 0. The haplotype and multipoint linkage analyses suggest localization of the MRX73 locus to an interval of 2 cM defined by markers DXS8019 and DXS365, in Xp22.2. This interval contains the gene of Coffin-Lowry syndrome (RSK2), where a missense mutation has been associated with a form of non-specific mental retardation. Therefore, a search for RSK2 mutations was performed in the MRX73 family, but no causal muta…

Screening for microdeletions of the X-chromosome in non-specific mental retardation

Evidence for a common origin of most Friedreich ataxia chromosomes in the Spanish population

Haplotype analysis is a powerful approach to understand the spectrum of mutations accounting for a disease in a homogeneous population. We show that haplotype variation for 10 markers linked to the Friedreich ataxia locus (FRDA) argues in favor of an important mutation homogeneity in the Spanish population, and positions the FRDA locus in the region where it has been recently isolated. We also report the finding of a new single nucleotide polymorphism called FAD1. The new marker shows a very strong linkage disequilibrium with Friedreich ataxia (FA) in both the Spanish and French populations. suggesting the existence of an ancient and widespread FRDA mutations. Inclusion of FAD1 in the exten…

Intronic L1 insertion and F268S, novel mutations in RPS6KA3 (RSK2) causing Coffin-Lowry syndrome

Two novel mutations of the ribosomal S6 kinase 2 gene (also known as RSK2) have been identified in two unrelated patients with Coffin–Lowry syndrome. The first mutation consists of a de novo insertion of a 5′-truncated LINE-1 element at position −8 of intron 3, which leads to a skipping of exon 4, leading to a shift of the reading frame and a premature stop codon. The L1 fragment (2800 bp) showed a rearrangement with a small deletion, a partial inversion of the ORF 2, flanked by short direct repeats which duplicate the acceptor splice site. However, cDNA analysis of the patient shows that both sites are apparently not functional. The second family showed the nucleotide change 803T>C in exon…

Gly114Asp mutation of rhodopsin in autosomal dominant retinitis pigmentosa

Two autosomal dominant retinitis pigmentosa families of different origin were screened for rhodopsin mutations using the method of single strand conformation polymorphism and direct sequencing. We found a CGG-CAG substitution in codon 114 of rhodopsin in both families. This change predicted the replacement of a glycine by an aspartic acid and suggested that this change is the cause of the disease in these families.

Attenuation of disease phenotype through alternative translation initiation in low-penetrance retinoblastoma

Hereditary predisposition to retinoblastoma (RB) is caused by germline mutations in the retinoblastoma 1 (RB1) gene and transmits as an autosomal dominant trait. In the majority of cases disease develops in greater than 90% of carriers. However, reduced penetrance with a large portion of disease-free carrier is seen in some families. Unambiguous identification of the predisposing mutation in these families is important for accurate risk prediction in relatives and their genetic counseling but also provides conceptual information regarding the relationship between the RB1 genotype and the disease phenotype. In this study we report a novel mutation detected in 10 individuals of an extended fa…