Asunto(s)
Cromosomas Humanos Par 6/genética , Clonación Molecular , Biología Computacional , Bases de Datos Factuales , Genes , Enfermedades Genéticas Congénitas/genética , Humanos , Complejo Mayor de Histocompatibilidad/genética , Mapeo Físico de Cromosoma , Análisis de Secuencia de ADN , Transcripción Genética/genéticaRESUMEN
Human genome diversity studies analyse genetic variation among individuals and between populations in order to understand the origins and evolution of anatomically modern humans (Homo sapiens sapiens). The availability of thousands of DNA polymorphisms (genetic markers) brings analytic power to these studies. Human genome diversity studies have clearly shown that the large part of genetic variability is due to differences among individuals within populations rather than to differences between populations, effectively discrediting a genetic basis of the concept of 'race'. Evidence from paleontology, archaeology and genetic diversity studies is quite consistent with an African origin of modern humans more than 100,000 years ago. The evidence favors migrations out of African as the source of the original peopling of Asia, Australia, Europe and Oceania. An international program for the scientific analysis of human genome diversity and of human evolution has been developed. The Human Genome Diversity Project (HGDP) aims to collect and preserve biologic samples from hundreds of populations throughout the world, make DNA from these samples available to scientists and distribute to the scientific community the results of DNA typing with hundreds of genetic markers.
Asunto(s)
Evolución Molecular , Variación Genética , Genoma Humano , Marcadores Genéticos , Humanos , Polimorfismo GenéticoRESUMEN
CAG and CGG expansion is associated with 10 inherited neurological diseases and is thought to be involved in other human genetic diseases. To identify new candidate genes, we have undertaken a large-scale screening project for CAG/CTG ([CAG]n) and CGG/GCC ([CGG]n) repeats in human brain reference cDNAs. Here, we present the final classification for 597 cDNAs selected by CAG and CGG hybridization from two libraries (100,128 clones) and the updated characterization of [CAG]n- and [CGG]n-positive cDNAs (repeat polymorphism and cDNA localization). We have selected 124 CAG and 83 CGG hybridization-positive clones representing new genes, from which 49 CAG and 7 CGG repeats could be identified. New [CAG]n and [CGG]n with more than seven to nine units were rare (1/2000), and perfect [CAG]n 9 were more likely polymorphic. Overall, highly polymorphic to monomorphic new [CAG]n > 9 and [CGG]n > 7 were characterized. The comparison of our data with other [CAG]n and [CGG]n resources suggests that the screening of reference cDNAs leads to unique sources of new [CAG]n and [CGG]n and will enhance the study of enlarged triplet repeats in human genetic diseases.
Asunto(s)
Encéfalo/metabolismo , ADN Complementario/aislamiento & purificación , Mutación , Repeticiones de Trinucleótidos/genética , Paseo de Cromosoma , Feto , Frecuencia de los Genes , Biblioteca de Genes , Pruebas Genéticas , Genoma Humano , Humanos , Lactante , Hibridación de Ácido NucleicoRESUMEN
Expansion of polymorphic CAG and CTG repeats in transcripts is the cause of six inherited neurodegenerative or neuromuscular diseases and may be involved in several other genetic disorders of the central nervous system. To identify new candidate genes, we have undertaken a large-scale screening project for CAG and CTG repeats in human reference cDNAs. We screened 100 128 brain cDNAs by hybridization. We also scanned GenBank expressed sequence tags for the presence of long CAG/CTG repeats in the extremities of cDNAs from several human tissues. Of the selected clones, 286 were found to represent new genes, and 72 have thus far been shown to contain CAG/CTG repeats. Our data indicate that CAG/CTG repeated 10 or more times are more likely to be polymorphic, and that new 3'-directed cDNAs with such repeats are very rare (1/2862). Nine new cDNAs containing polymorphic (observed heterozygote frequency: 0.05-0.90) CAG/CTG repeats have been currently identified in cDNAs. All of the cDNAs have been assigned to chromosomes, and six of them could be mapped with YACs to 1q32-q41, 3p14, 4q28, 3p21 and 12q13.3, 13q13.1-q13.2, and 19q13.43. Three of these clones are highly polymorphic and represent the most likely candidate genes for inherited neurodegenerative diseases and, perhaps, neuropsychiatric disorders of multifactorial origin.
Asunto(s)
ADN Complementario/genética , Enfermedades del Sistema Nervioso/genética , Polimorfismo Genético , Repeticiones de Trinucleótidos/genética , Encéfalo/embriología , Química Encefálica , Mapeo Cromosómico , Cromosomas Humanos , Clonación Molecular , Expresión Génica , Biblioteca de Genes , Genes/genética , Humanos , Recién Nacido , Datos de Secuencia Molecular , Análisis de Secuencia de ADNRESUMEN
In this paper, we describe labeling and hybridization conditions for oligonucleotide probes that detect human triplet repeat sequences in yeast artificial chromosomes (YACs). Restriction digests of YACs containing the CAG repeat sequence of the SCA1 gene were used as positive controls. Several hybridization mixtures and temperatures and two different labeling techniques were tested in order to determine optimal conditions. CAG, CGG, AGG, and ATT repeat sequences were mapped on YACs from a contig in 6p23, where SCA1 is located.
Asunto(s)
Cromosomas Artificiales de Levadura/química , Repeticiones de Trinucleótidos , Ataxina-1 , Ataxinas , Southern Blotting , Cromosomas Humanos Par 6 , Genes , Humanos , Proteínas del Tejido Nervioso/genética , Proteínas Nucleares/genética , Hibridación de Ácido NucleicoRESUMEN
The spinocerebellar ataxia 3 locus (SCA3) for type I autosomal dominant cerebellar ataxia (ADCA type I), a clinically and genetically heterogeneous group of neurodegenerative disorders, has been mapped to chromosome 14q32.1. ADCA type I patients from families segregating SCA3 share clinical features in common with those with Machado-Joseph disease (MJD), the gene of which maps to the same region. We show here that the disease gene segregating in each of three French ADCA type I kindreds and in a French family with neuropathological findings suggesting the ataxochoreic form of dentatorubropallidoluysian atrophy carries an expanded CAG repeat sequence located at the same locus as that for MJD. Analysis of the mutation in these families shows a strong negative correlation between size of the expanded CAG repeat and age at onset of clinical disease. Instability of the expanded triplet repeat was not found to be affected by sex of the parent transmitting the mutation. Evidence was found for somatic and gonadal mosaicism for alleles carrying expanded trinucleotide repeats.
Asunto(s)
Heterogeneidad Genética , Enfermedad de Machado-Joseph/genética , Secuencias Repetitivas de Ácidos Nucleicos , Degeneraciones Espinocerebelosas/genética , Adolescente , Adulto , Edad de Inicio , Secuencia de Bases , Niño , Humanos , Persona de Mediana Edad , Mosaicismo , FenotipoAsunto(s)
Cromosomas Artificiales de Levadura/química , Hibridación de Ácido Nucleico , Secuencias Repetitivas de Ácidos Nucleicos , Enzimas de Restricción del ADN , ADN de Hongos/análisis , ADN de Hongos/química , Desoxirribonucleasa EcoRI , Desoxirribonucleasas de Localización Especificada Tipo II , Sondas de OligonucleótidosRESUMEN
SCA3, the gene for spinal cerebellar ataxia 3, was recently mapped to a 15-cM interval between D14S67 and D14S81 on chromosome 14q, by linkage analysis in two families of French ancestry. The SCA3 candidate region has now been refined by linkage analysis with four new microsatellite markers (D14S256, D14S291, D14S280, and AFM343vf1) in the same two families, in which 19 additional individuals were genotyped, and in a third French family. Combined two-point linkage analyses show that the new markers, D14S280 and AFM343vf1, are tightly linked to the SCA3 locus, with maximal lod scores, at recombination fraction, (theta) = .00, of 7.05 and 13.70, respectively. Combined multipoint and recombinant haplotype analyses localize the SCA3 locus to a 3-cM interval flanked by D14S291 and D14S81. The same allele for D14S280 segregates with the disease locus in the three kindreds. This allele is frequent in the French population, however, and linkage disequilibrium is not clearly established. The SCA3 locus remains within the 29-cM region on 14q24.3-q32.2 containing the gene for the Machado-Joseph disease, which is clinically related to the phenotype determined by SCA3, but it cannot yet be concluded that both diseases result from alterations of the same gene.
Asunto(s)
Cromosomas Humanos Par 14 , Genes Dominantes , Degeneraciones Espinocerebelosas/genética , Adulto , Secuencia de Bases , Mapeo Cromosómico , Femenino , Francia , Marcadores Genéticos , Haplotipos/genética , Humanos , Escala de Lod , Masculino , Datos de Secuencia Molecular , LinajeRESUMEN
A yeast artificial chromosome (YAC) contig located in 6p23 and spanning roughly 2.5 Mb has been constructed from the content of 10 sequence tagged sites (STSs) for YAC clones in 66 yeast colonies. Nine of the STSs have been genetically mapped in CEPH families. The order of STSs mapped with the contig is consistent with that of the genetic map. The order of loci that did not recombine with each other on the genetic map was inferred from the contig. Various regions of the contig are covered by multiple YAC clones that complement observed STS deletions. The STS for the CAG repeat sequence contained in the gene for spinal cerebellar ataxia 1 (gene symbol SCA1) is localized in the contig. It is likely that this gene is located in 6p23. The frequency of chimeric YAC clones in this contig is 35%. Eleven yeast colonies were found to carry two or more YACs. YAC subclones from some of these colonies showed size variation, and for several subclones, evidence consistent with deletion of a sequence tagged site.
Asunto(s)
Cromosomas Artificiales de Levadura , Cromosomas Humanos Par 6 , Lugares Marcados de Secuencia , Secuencia de Bases , Genoma Humano , Humanos , Hibridación Fluorescente in Situ , Mitosis , Datos de Secuencia Molecular , Recombinación Genética , Secuencias Repetitivas de Ácidos Nucleicos , Degeneraciones Espinocerebelosas/genéticaAsunto(s)
Cromosomas Humanos Par 6 , Antígenos HLA , Centrómero , Mapeo Cromosómico , Genes MHC Clase I , Humanos , TelómeroAsunto(s)
Cromosomas Humanos Par 6 , ADN Satélite/genética , Endotelinas/genética , Polimorfismo Genético , Secuencias Repetitivas de Ácidos Nucleicos , Secuencia de Bases , Mapeo Cromosómico , Humanos , Datos de Secuencia Molecular , Oligodesoxirribonucleótidos , Reacción en Cadena de la PolimerasaRESUMEN
There are CEPH genetic maps on each homologous human chromosome pair. Genotypes for these maps have been generated in 88 laboratories that receive DNA from a reference panel of large nuclear pedigrees/families supplied by the Centre d'Etude du Polymorphisme Humain. These maps serve as useful tools for the localization of both disease genes and other genes of interest.
Asunto(s)
Mapeo Cromosómico , Genoma Humano , Polimorfismo Genético/genética , Academias e Institutos , Francia , Proyecto Genoma Humano , HumanosRESUMEN
Human homologues of mouse t-complex genes have been cloned and localized physically to chromosome 6p or 6q. TCP1, TCP10, and PLG are human homologues of genes located in the proximal portion of the t-complex on mouse chromosome 17. We present here results of genetic mapping of these human t-complex homologues previously localized to 6q25-q27, 6q21-q27, and 6q26-q27, respectively, by physical techniques. TCP1 and PLG do not recombine with each other and are separated from TCP10 by about 15 cM, while the corresponding mouse genes are no more than 4 cM apart. Genetic mapping with markers well localized cytogenetically places TCP1 and PLG proximal to TCP10 and localizes the latter to the cytogenetic band 6q27. It is likely that the organization of human t-complex homologues on 6q is similar to that of t haplotypes rather than that of wildtype murine chromosome 17.
Asunto(s)
Cromosomas Humanos Par 6 , Péptidos y Proteínas de Señalización Intracelular , Proteínas Asociadas a Microtúbulos , Proteínas Nucleares/genética , Animales , Mapeo Cromosómico , Femenino , Marcadores Genéticos , Humanos , Masculino , Ratones , Proteínas , Especificidad de la Especie , Hormonas Testiculares/genética , Ubiquitina-Proteína Ligasas , Región del Complejo T del GenomaRESUMEN
We studied three large kindreds with the HLA-linked form of spinocerebellar ataxia (SCA1) in order to localize the SCA1 locus on the short arm of chromosome 6 (6p). Two loci containing highly informative dinucleotide repeat sequences were used for linkage analysis. These two loci are D6S89, which is telomeric to the HLA region, and T complex-associated testes-expressed 1 (TCTE1), centromeric to HLA. Pairwise linkage analysis of SCA1 and D6S89 revealed a maximum lod score of 5.86 in the Houston SCA1 (HSCA1) kindred and of 8.08 in the Calabrian SCA1 (SCA1) kindreds, at recombination fractions of .050 and .022, respectively. A maximum pairwise lod score of 4.54 at a recombination frequency of .100 was obtained for SCA1 and TCTE1 in the HSCA1 kindred. No evidence for linkage was detected between TCTE1 and SCA1 in the CSCA1 kindreds. Multilocus linkage analysis of SCA1, HLA, and D6S89 in all three kindreds provided strong evidence for localization of the SCA1 locus telomeric to the HLA regions. However, multilocus linkage analysis of SCA1, HLA, and TCTE1 with HSCA1 family genotypes indicated the possibility of a location of the SCA1 locus centromeric to HLA. An analysis of HSCA1 recombinants in this region of chromosome 6 revealed relatively high recombination frequencies between HLA and each of the other two markers and relatively low frequencies between the latter and SCA1, predicting that the SCA1 locus would tend to segregate away from HLA together with D6S89 or TCTE1, as found with the three-point linkage analyses for this family.(ABSTRACT TRUNCATED AT 250 WORDS)
Asunto(s)
Alelos , Mapeo Cromosómico , Cromosomas Humanos Par 6 , Genes Dominantes , Ligamiento Genético , Antígenos HLA-A/genética , Degeneraciones Espinocerebelosas/genética , Femenino , Antígenos HLA-B/genética , Humanos , Masculino , Reacción en Cadena de la PolimerasaRESUMEN
A genetic map of the short arm of chromosomes 6 (6p) has been constructed with 20 genetic markers that define 16 loci, including a locus at the centromere. The 40 CEPH families and, for 4 loci, 13 additional Utah families were genotyped. All 16 loci form a single linkage group extending from near the telomeric region to the centromere, covering 159 cM (Haldane) on the female map and 94 cM on the male map. Sex differences in recombination frequencies are noted for the 6p map, with an excess occurring in males at the distal end. The genetic order of loci is consistent with their physical localization on 6p. Proximal to the three most distal loci on the map, markers are especially dense, providing an extended region on 6p useful for localizing genes of interest.
Asunto(s)
Mapeo Cromosómico , Cromosomas Humanos Par 6 , Southern Blotting , Línea Celular , Centrómero , Clonación Molecular , Sondas de ADN , Femenino , Frecuencia de los Genes , Marcadores Genéticos , Humanos , Masculino , Polimorfismo Genético , Recombinación Genética , Caracteres SexualesRESUMEN
Prior to constructing a library of yeast artificial chromosomes (YACs) containing very large human DNA fragments, we performed a series of preliminary experiments aimed at developing a suitable protocol. We found an inverse relationship between YAC insert size and transformation efficiency. Evidence of occasional rearrangement within YAC inserts was found resulting in clonally stable internal deletions or clonally unstable size variations. A protocol was developed for preparative electrophoretic enrichment of high molecular mass human DNA fragments from partial restriction digests and ligation with the YAC vector in agarose. A YAC library has been constructed from large fragments of DNA from an Epstein-Barr virus-transformed human lymphoblastoid cell line. The library presently contains 50,000 clones, 95% of which are greater than 250 kilobase pairs in size. The mean YAC size of the library, calculated from 132 randomly isolated clones, is 430 kilobase pairs. The library thus contains the equivalent of approximately seven haploid human genomes.