RESUMEN

Determining the mechanisms by which genes are switched on and off during development is a key aim of current biomedical research. Gene transcription has been widely observed to occur in a discontinuous fashion, with short bursts of activity interspersed with periods of inactivity. It is currently not known if or how this dynamic behaviour changes as mammalian cells differentiate. To investigate this, using an on-microscope analysis, we monitored mouse α-globin transcription in live cells throughout erythropoiesis. We find that changes in the overall levels of α-globin transcription are most closely associated with changes in the fraction of time a gene spends in the active transcriptional state. We identify differences in the patterns of transcriptional bursting throughout differentiation, with maximal transcriptional activity occurring in the mid-phase of differentiation. Early in differentiation, we observe increased fluctuation in transcriptional activity whereas at the peak of gene expression, in early erythroblasts, transcription is relatively stable. Later during differentiation as α-globin expression declines, we again observe more variability in transcription within individual cells. We propose that the observed changes in transcriptional behaviour may reflect changes in the stability of active transcriptional compartments as gene expression is regulated during differentiation.

Asunto(s)

Eritroblastos , Eritropoyesis , Ratones , Animales , Eritroblastos/metabolismo , Diferenciación Celular/genética , Eritropoyesis/genética , Cromatina/metabolismo , Globinas alfa/genética , Globinas alfa/metabolismo , Transcripción Genética , Globinas/genética , Mamíferos/genética

RESUMEN

The alpha- and beta-globin gene clusters have been extensively studied. Regulation of these genes ensures that proteins derived from both loci are produced in balanced amounts, and that expression is tissue-restricted and specific to developmental stages. Here we compare the subnuclear location of the endogenous alpha- and beta-globin loci in primary human cells in which the genes are either actively expressed or silent. In erythroblasts, the alpha- and beta-globin genes are localized in areas of the nucleus that are discrete from alpha-satellite-rich constitutive heterochromatin. However, in cycling lymphocytes, which do not express globin genes, the distribution of alpha- and beta-globin genes was markedly different. beta-globin loci, in common with several inactive genes studied here (human c-fms and SOX-1) and previously (mouse lambda5, CD4, CD8alpha, RAGs, TdT and Sox-1), were associated with pericentric heterochromatin in a high proportion of cycling lymphocytes. In contrast, alpha-globin genes were not associated with centromeric heterochromatin in the nucleus of normal human lymphocytes, in lymphocytes from patients with alpha-thalassaemia lacking the regulatory HS-40 element or entire upstream region of the alpha-globin locus, or in mouse erythroblasts and lymphocytes derived from human alpha-globin transgenic mice. These data show that the normal regulated expression of alpha- and beta-globin gene clusters occurs in different nuclear environments in primary haemopoietic cells.

Asunto(s)

Núcleo Celular/fisiología , Globinas/genética , Células Madre Hematopoyéticas/fisiología , Células Cultivadas , Expresión Génica , Humanos , Linfocitos/fisiología

RESUMEN

We have examined the phenotypic effects of 21 independent deletions from the fully sequenced and annotated 356 kb telomeric region of the short arm of chromosome 16 (16p13.3). Fifteen genes contained within this region have been highly conserved throughout evolution and encode proteins involved in important housekeeping functions, synthesis of haemoglobin, signalling pathways and critical developmental pathways. Although a priori many of these genes would be considered candidates for critical haploinsufficient genes, none of the deletions within the 356 kb interval cause any discernible phenotype other than alpha thalassaemia whether inherited via the maternal or paternal line. These findings contrast with previous observations on patients with larger (> 1 Mb) deletions from the 16p telomere and therefore address the mechanisms by which monosomy gives rise to human genetic disease.

Asunto(s)

Cromosomas Humanos Par 16 , Monosomía , Telómero , Adolescente , Adulto , Secuencia de Bases , Niño , Preescolar , Femenino , Humanos , Hibridación Fluorescente in Situ , Masculino , Persona de Mediana Edad , Datos de Secuencia Molecular , Fenotipo , Eliminación de Secuencia , Homología de Secuencia de Ácido Nucleico

RESUMEN

We have sequenced 1949 kb from the terminal Giemsa light band of human chromosome 16p, enabling us to fully annotate the region extending from the telomeric repeats to the previously published tuberous sclerosis disease 2 (TSC2) and polycystic kidney disease 1 (PKD1) genes. This region can be subdivided into two GC-rich, Alu-rich domains and one GC-rich, Alu-poor domain. The entire region is extremely gene rich, containing 100 confirmed genes and 20 predicted genes. Many of the genes encode widely expressed proteins orchestrating basic cellular processes (e.g. DNA recombination, repair, transcription, RNA processing, signal transduction, intracellular signalling and mRNA translation). Others, such as the alpha globin genes (HBA1 and HBA2), PDIP and BAIAP3, are specialized tissue-restricted genes. Some of the genes have been previously implicated in the pathophysiology of important human genetic diseases (e.g. asthma, cataracts and the ATR-16 syndrome). Others are known disease genes for alpha thalassaemia, adult polycystic kidney disease and tuberous sclerosis. There is also linkage evidence for bipolar affective disorder, epilepsy and autism in this region. Sixty-three chromosomal deletions reported here and elsewhere allow us to interpret the results of removing progressively larger numbers of genes from this well defined human telomeric region.

Asunto(s)

Cromosomas Humanos Par 16/química , Cromosomas Humanos Par 16/genética , Mapeo Físico de Cromosoma , Adolescente , Animales , Asma/genética , Composición de Base , Trastorno Bipolar/genética , Niño , Preescolar , Islas de CpG/genética , Epilepsia/genética , Femenino , Ligamiento Genético/genética , Humanos , Discapacidad Intelectual/genética , Masculino , Ratones , Monosomía , Fenotipo , Riñón Poliquístico Autosómico Dominante/genética , Recombinación Genética , Análisis de Secuencia de ADN , Síndrome , Telómero/química , Telómero/genética , Esclerosis Tuberosa/genética , Talasemia alfa/genética

RESUMEN

Functional analyses have indicated that the human CD164 sialomucin may play a key role in hematopoiesis by facilitating the adhesion of human CD34(+) cells to the stroma and by negatively regulating CD34(+)CD38(lo/-) cell proliferation. We have identified three novel human CD164 variants derived by alternative splicing of bona fide exons from a single genomic transcription unit. The predominant CD164(E1-6) isoform, encoded by six exons, is a type I transmembrane protein containing two extracellular mucin domains (I and II) interrupted by a cysteine-rich non-mucin domain. The 103B2/9E10 and 105A5 epitopes, which specify ligand binding characteristics, are located on the exon 1-encoded mucin domain I. Three human CD164(E1-6) mRNA species, exhibiting differential polyadenylation site usage, are differentially expressed in hematopoietic and non-hematopoietic tissues. This study provides additional evidence that human CD164(E1-6) represents the ortholog of murine MGC-24v and rat endolyn. Comparative analysis of murine MGC-24v/CD164(E1-6) with human CD164(E1-6) revealed two potential splice variants and a similar genomic structure. Whereas the human CD164 gene is located on chromosome 6q21, the mouse gene occurs in a syntenic region on chromosome 10B1-B2. By confocal microscopy, human CD164 in CD34(+)CD38(+) hematopoietic progenitor (KG1B) and epithelial cell lines appears to be localized primarily in endosomes and lysosomes, with low concentrations at the cell surface. However, in a minority of KG1B cells, CD164 is more prominently expressed at the plasma membrane and in the recycling endosomes, suggesting that its distribution is regulated in cells of hematopoietic origin.

Asunto(s)

Antígenos CD , Glicoproteínas de Membrana , Moléculas de Adhesión de Célula Nerviosa , Isoformas de Proteínas/metabolismo , Receptores de Superficie Celular/metabolismo , Fracciones Subcelulares/metabolismo , Secuencia de Aminoácidos , Animales , Secuencia de Bases , Northern Blotting , Antígeno CD146 , Línea Celular , Mapeo Cromosómico , ADN Complementario , Endolina , Humanos , Datos de Secuencia Molecular , Reacción en Cadena de la Polimerasa , Empalme del ARN , ARN Mensajero/genética , Receptores de Superficie Celular/química , Receptores de Superficie Celular/genética , Relación Estructura-Actividad

RESUMEN

Arylamine N-acetyltransferases (NATs) catalyse acetylation reactions which can result in either detoxification or activation of arylamine carcinogens. The human NAT loci (NAT1, NAT2, and a pseudogene, NATP) have been mapped to human chromosome 8p22, a region frequently deleted in tumours. There are three functional genes in mice (Nat1, Nat2, and Nat3) encoding for three NAT isoenzymes. Different alleles at the Nat2 locus are responsible for the acetylation polymorphism identified in different mouse strains. We show that Nat3 is close to Nat1 and Nat2, by screening of a P1 artificial chromosome (PAC) library and provide cytogenetic evidence for co-localisation of the three genes in chromosome region 8 B3.1-B3.3. The Nat region of mouse and human is homologous. We also provide sequence information and a restriction map in the vicinity of Nat1 and Nat2 and describe a noncoding exon located 6 kb upstream of the Nat2 coding region.

Asunto(s)

Regiones no Traducidas 5'/genética , Arilamina N-Acetiltransferasa/genética , Arilamina N-Acetiltransferasa/metabolismo , Carcinógenos/metabolismo , Exones/genética , Mapeo Físico de Cromosoma , Animales , Clonación Molecular , Sondas de ADN , Humanos , Hibridación Fluorescente in Situ , Ratones , Ratones Endogámicos , Reacción en Cadena de la Polimerasa , Mapeo Restrictivo

RESUMEN

Three founder transgenic mice were generated with a 108 kb human genomic fragment containing the entire autosomal dominant polycystic kidney disease (ADPKD) gene, PKD1, plus the tuberous sclerosis gene, TSC2. Two lines were established (TPK1 and TPK3) each with approximately 30 copies of the transgene. Both lines produced full-length PKD1 mRNA and polycystin-1 protein that was developmentally regulated, similar to the endogenous pattern, with expression during renal embryogenesis and neonatal life, markedly reduced at the conclusion of renal development. Tuberin expression was limited to the brain. Transgenic animals from both lines (and the TPK2 founder animal) often displayed a renal cystic phenotype, typically consisting of multiple microcysts, mainly of glomerular origin. Hepatic cysts and bile duct proliferation, characteristic of ADPKD, were also seen. All animals with two copies of the transgenic chromosome developed cysts and, in total, 48 of the 100 transgenic animals displayed a cystic phenotype. To test the functionality of the transgene, animals were bred with the Pkd1(del34) knockout mouse. Both transgenic lines rescued the embryonically lethal Pkd1(del34/del34) phenotype, demonstrating that human polycystin-1 can complement for loss of the endogenous protein. The rescued animals were viable into adulthood, although more than half developed hepatic cystic disease in later life, similar to the phenotype of older Pkd1(del34/+) animals. The TPK mice have defined a minimal area that appropriately expresses human PKD1. Furthermore, this model indicates that over-expression of normal PKD1 can elicit a disease phenotype, suggesting that the level of polycystin-1 expression may be relevant in the human disease.

Asunto(s)

Riñón Poliquístico Autosómico Dominante/genética , Riñón Poliquístico Autosómico Dominante/patología , Proteínas/metabolismo , Transgenes/genética , Animales , Southern Blotting , Western Blotting , Eliminación de Gen , Dosificación de Gen , Prueba de Complementación Genética , Genotipo , Humanos , Inmunohistoquímica , Riñón/metabolismo , Riñón/patología , Hígado/metabolismo , Hígado/patología , Ratones , Ratones Noqueados , Ratones Transgénicos , Datos de Secuencia Molecular , Ensayos de Protección de Nucleasas , Fenotipo , Riñón Poliquístico Autosómico Dominante/metabolismo , Proteínas/genética , ARN Mensajero/análisis , ARN Mensajero/genética , Proteínas Represoras/análisis , Canales Catiónicos TRPP , Proteína 2 del Complejo de la Esclerosis Tuberosa , Proteínas Supresoras de Tumor

RESUMEN

The chromosomal abnormality represented by an isodicentric X chromosome [idic(X)(q13)] is associated with a subset of acute myeloid leukemia (AML) and preleukemia observed in elderly females. A previous study localized the breakpoints of two acquired isodicentric X chromosomes associated with myelodysplasia to a 450-kb region proximal to the XIST gene. Here we report the construction and extensive characterization of a reliable 1-Mb P1 artificial chromosome and bacterial artificial chromosome contig covering a highly problematic region in Xq13 that includes the previously described isodicentric breakpoint region. In addition to mapping of the brain-specific gene (NAP1L2) and the phosphoglyceryl kinase alpha subunit 1 gene (PHKA1) and generation and mapping of a large number of STSs throughout the contig, we have mapped a putative transcriptional regulatory protein (HDACL1), and 35 ESTs. Sequencing data, Southern blot analysis, and fiber-FISH analysis have permitted characterization of extensive region-specific duplications and triplications in addition to an unusually high concentration of long interspersed repeat elements, both of which could be implicated in isodicentric chromosome formation and other Xq13 chromosome aberrations. FISH analysis of metaphase chromosomes from two previously unpublished AML patients and one preleukemic patient using cosmid clones and selected subclones allowed mapping of the idic(X)(q13) breakpoints to a 100-kb interval, consistent with the involvement of an X-linked gene in the genesis of this form of preleukemia, disruption of which may represent a preliminary step in progression to AML. Assembly and physical mapping of this complex 1-Mb contig establish a foundation for ongoing sequencing and gene identification projects in the region.

Asunto(s)

Rotura Cromosómica , Leucemia Mieloide/genética , Preleucemia/genética , Aberraciones Cromosómicas Sexuales/genética , Cromosoma X , Enfermedad Aguda , Anciano , Southern Blotting , Centrómero , Cromosomas Artificiales de Levadura , Cromosomas Bacterianos , Clonación Molecular , Mapeo Contig , Cósmidos , Etiquetas de Secuencia Expresada , Femenino , Duplicación de Gen , Humanos , Hibridación Fluorescente in Situ , Elementos de Nucleótido Esparcido Largo , Datos de Secuencia Molecular , Síndromes Mielodisplásicos/genética , Análisis de Secuencia de ADN

RESUMEN

ATRX is a member of the SNF2 family of helicase/ATPases that is thought to regulate gene expression via an effect on chromatin structure and/or function. Mutations in the hATRX gene cause severe syndromal mental retardation associated with alpha-thalassemia. Using indirect immunofluorescence and confocal microscopy we have shown that ATRX protein is associated with pericentromeric heterochromatin during interphase and mitosis. By coimmunofluorescence, ATRX localizes with a mouse homologue of the Drosophila heterochromatic protein HP1 in vivo, consistent with a previous two-hybrid screen identifying this interaction. From the analysis of a trap assay for nuclear proteins, we have shown that the localization of ATRX to heterochromatin is encoded by its N-terminal region, which contains a conserved plant homeodomain-like finger and a coiled-coil domain. In addition to its association with heterochromatin, at metaphase ATRX clearly binds to the short arms of human acrocentric chromosomes, where the arrays of ribosomal DNA are located. The unexpected association of a putative transcriptional regulator with highly repetitive DNA provides a potential explanation for the variability in phenotype of patients with identical mutations in the ATRX gene.

Asunto(s)

Centrómero/química , ADN Helicasas , Proteínas de Unión al ADN/análisis , Heterocromatina/química , Proteínas Nucleares/análisis , Factores de Transcripción/análisis , Animales , Anticuerpos Monoclonales/inmunología , Células COS , Fraccionamiento Celular , Línea Celular Transformada , Homólogo de la Proteína Chromobox 5 , Proteínas Cromosómicas no Histona/metabolismo , Cromosomas/química , Proteínas de Unión al ADN/genética , Proteínas de Unión al ADN/inmunología , Células HeLa , Humanos , Ratones , Ratones Endogámicos BALB C , Proteínas Nucleares/genética , Proteínas Nucleares/inmunología , Ovinos , Factores de Transcripción/genética , Factores de Transcripción/inmunología , Proteína Nuclear Ligada al Cromosoma X

RESUMEN

The probe StB12.3 has been used to screen the FMR-1 gene in 42 pedigrees with a distal Xq fragile site for expansion of the CCG repeat and aberrant methylation of the FRAXA locus. Four families did not have a FRAXA mutation and were investigated further. Fluorescent in situ hybridisation (FISH) and molecular analyses showed that three of these families had an expansion at FRAXE and one at FRAXE. Detailed psychiatric, psychological, and behavioural features of three families with FRAXE identified in the study are presented. All the males who expressed FRAXE had a large methylated CCG repeat at FRAXF. All males with the mutation had some degree of mental handicap. This study illustrates the need for the FRAXE phenotype to be defined further.

Asunto(s)

Fragilidad Cromosómica , ADN/análisis , Síndrome del Cromosoma X Frágil/genética , Cromosoma X , Adulto , Células Cultivadas , Preescolar , Sitios Frágiles del Cromosoma , Femenino , Síndrome del Cromosoma X Frágil/patología , Síndrome del Cromosoma X Frágil/psicología , Pruebas Genéticas , Humanos , Hibridación in Situ , Discapacidad Intelectual/etiología , Discapacidad Intelectual/genética , Masculino , Repeticiones de Microsatélite , Mutación , Linaje

RESUMEN

We have characterised a subtelomeric rearrangement involving the short arm of chromosome 16 that gives rise to alpha-thalassaemia by deleting the major, remote regulatory element controlling alpha-globin expression. The chromosomal breakpoint lies in an Alu family repeat located only approximately 105 kb from the 16p subtelomeric region. The broken chromosome has been stabilised with a newly positioned telomere acquired by recombination between this 16p Alu element and a closely related subtelomeric Alu element of the Sx subfamily. It seems most likely that this abnormal chromosome has been rescued by the mechanism of telomere capture which may reflect a more general process by which subtelomeric sequences are normally dispersed between chromosomal ends.

Asunto(s)

Cromosomas Humanos Par 16/genética , Secuencias Repetitivas de Ácidos Nucleicos , Talasemia alfa/genética , Adolescente , Adulto , Alelos , Secuencia de Bases , Mapeo Cromosómico , Cromosomas Humanos Par 16/ultraestructura , ADN/genética , Cartilla de ADN/genética , Femenino , Reordenamiento Génico , Genotipo , Globinas/genética , Haplotipos , Humanos , Hibridación Fluorescente in Situ , Masculino , Persona de Mediana Edad , Datos de Secuencia Molecular , Familia de Multigenes , Reacción en Cadena de la Polimerasa , Recombinación Genética , Homología de Secuencia de Ácido Nucleico , Telómero/genética , Telómero/ultraestructura

RESUMEN

The hematological and clinical features of 26 patients with myelodysplasia and a chromosome 5q deletion in the bone marrow are presented. We have examined the relationship of French-American-British Co-operative Group (FAB) 1982 classification and bone marrow karyotype at diagnosis with patient outcome and the presence or absence of the classical features of the 5q-syndrome. Those patients classified as refractory anemia (RA) with no additional karyotypic abnormalities have the typical features of the 5q-syndrome and a good prognosis. None of the patients in this group transformed to acute leukemia during the period of follow-up. Patients with either refractory anemia and excess blasts (RAEB) or additional karyotypic abnormalities show many of the hematologic features of the 5q-syndrome but do not share the good prognosis. We conclude that the 5q-syndrome may be best defined as primary MDS of the FAB type RA with a 5q deletion as the sole karyotypic abnormality. This simple definition will distinguish patients with a good prognosis and all the classical features of the 5q-syndrome.

Asunto(s)

Cromosomas Humanos Par 5 , Eliminación de Gen , Síndromes Mielodisplásicos/genética , Enfermedad Aguda , Adulto , Anciano , Anciano de 80 o más Años , Anemia Refractaria/genética , Anemia Refractaria con Exceso de Blastos/genética , Médula Ósea/patología , Femenino , Humanos , Cariotipificación , Leucemia/etiología , Masculino , Persona de Mediana Edad , Síndromes Mielodisplásicos/clasificación , Síndromes Mielodisplásicos/patología , Pronóstico

RESUMEN

Transmissible chromosomal instability, characterized by non-clonal cytogenetic aberrations with a high frequency of chromatid-type aberrations together with a lower frequency of chromosome-type aberrations, has been demonstrated in the clonal descendants of human haemopoietic stem cells after alpha- but not X-irradiation. Comparable cytogenetic abnormalities have also been demonstrated in non-clonal cultures of alpha-irradiated primary human bone marrow, but a different pattern of delayed aberrations, mainly of chromosome-type, was found after X-irradiation in non-clonal cultures. In clonal analyses, delayed apoptotic cell death was evident after both X- and alpha-irradiation. It is suggested that the type of radiation exposure, the type of cell and its genetically determined susceptibility are factors that may influence the expression of delayed effects of radiation.

Asunto(s)

Apoptosis/efectos de la radiación , Médula Ósea/efectos de la radiación , Aberraciones Cromosómicas , Partículas alfa , Células de la Médula Ósea , Células Cultivadas , Cromátides/efectos de la radiación , Células Clonales , Ensayo de Unidades Formadoras de Colonias , Células Madre Hematopoyéticas/efectos de la radiación , Células Madre Hematopoyéticas/ultraestructura , Humanos , Rayos X

RESUMEN

A major challenge for human genetics is to identify new causes of mental retardation, which, although present in about 3% of individuals, is unexplained in more than half of all cases. We have developed a strategy to screen for the abnormal inheritance of subtelomeric DNA polymorphisms in individuals with mental retardation and have detected three abnormalities in 99 patients with normal routine karyotypes. Pulsed-field gel electrophoresis and reverse chromosome painting showed that one case arose from an interstitial or terminal deletion and two from the de novo inheritance of derivative translocation chromosomes. At least 6% of unexplained mental retardation is accounted for by these relatively small chromosomal abnormalities, which will be an important resource in the characterization of the genetic basis of neurodevelopment.

Asunto(s)

Discapacidad Intelectual/etiología , Discapacidad Intelectual/genética , Telómero/genética , Adulto , Niño , Preescolar , Aberraciones Cromosómicas/diagnóstico , Aberraciones Cromosómicas/epidemiología , Trastornos de los Cromosomas , Cromosomas Humanos Par 13 , Cromosomas Humanos Par 22 , Femenino , Eliminación de Gen , Reordenamiento Génico , Humanos , Discapacidad Intelectual/diagnóstico , Cariotipificación , Masculino , Prevalencia , Telómero/fisiología

RESUMEN

A young adult female with multiple exostoses, short stature, autism, mental retardation and 46,X,t(X;8)(p22.13;q22.1) is described. Although the clinical features and translocation breakpoints raise the possibility of a number of specific conditions, the constellation of problems is not consistent with any previously reported genetic syndrome. It is argued that her clinical disorder is likely due to the chromosomal abnormality and that further detailed molecular genetic investigation may shed light on the genetic basis to various components of her phenotype including the autism.

Asunto(s)

Anomalías Múltiples/etiología , Trastorno Autístico/etiología , Aberraciones Cromosómicas/genética , Cromosomas Humanos Par 8/ultraestructura , Enanismo/genética , Exostosis Múltiple Hereditaria/genética , Discapacidad Intelectual/etiología , Translocación Genética , Cromosoma X/ultraestructura , Anomalías Múltiples/genética , Adulto , Asfixia Neonatal/complicaciones , Trastorno Autístico/inducido químicamente , Trastorno Autístico/genética , Trastornos de los Cromosomas , Femenino , Hematoma Subdural/complicaciones , Hematoma Subdural/congénito , Humanos , Recién Nacido , Discapacidad Intelectual/inducido químicamente , Complicaciones del Trabajo de Parto/tratamiento farmacológico , Fenotipo , Embarazo

RESUMEN

The hallmarks of the X-linked alpha-thalassemia/mental retardation (ATR-X) syndrome are severe psychomotor retardation, minor facial anomalies, genital abnormalities, and an unusual form of alpha-thalassemia. The demonstration of HbH inclusions in red blood cells after incubation with brilliant cresyl blue confirms the diagnosis. We describe 15 previously unreported cases and analyse the phenotypic and hematologic findings in these subjects and compare them with previously published cases. This study demonstrates the consistency of the main characteristics of this syndrome and extends the phenotype. Developmental changes in phenotype, in particular the coarsening of the facial appearance, are illustrated. The hematologic findings are shown to vary widely; in some cases the manifestation of alpha-thalassemia may be subtle and missed without repeated examination.

Asunto(s)

Discapacidad Intelectual/genética , Cromosoma X , Talasemia alfa/sangre , Anomalías Múltiples/genética , Adolescente , Niño , Preescolar , Volumen de Eritrocitos , Femenino , Ligamiento Genético , Hemoglobina H/análisis , Heterocigoto , Humanos , Lactante , Masculino , Linaje , Fenotipo , Síndrome , Talasemia alfa/genética , Talasemia alfa/patología

RESUMEN

alpha-particles, which are ionising radiation of high linear-energy-transfer emitted, for example, from radon or plutonium, pass through tissue as highly structured tracks. Single target cells in the path of the tracks might be damaged by even low-dose alpha-irradiation. We found non-clonal cytogenetic aberrations, characterised by a high frequency of chromatid aberrations with chromosome aberrations, in clonal descendants of haemopoietic stem cells after exposure to alpha-particles of bone marrow cells from two of four haematologically normal individuals (up to 25% abnormal metaphases). The data are consistent with a transmissible genetic instability induced in a stem cell resulting in a diversity of aberrations in its clonal progeny many cell divisions later.

Asunto(s)

Partículas alfa , Médula Ósea/efectos de la radiación , Aberraciones Cromosómicas , Transferencia Lineal de Energía , Animales , Médula Ósea/ultraestructura , Células Madre Hematopoyéticas/efectos de la radiación , Células Madre Hematopoyéticas/ultraestructura , Humanos , Técnicas In Vitro , Leucemia Inducida por Radiación/etiología , Leucemia Inducida por Radiación/genética , Ratones

RESUMEN

An area of 500 kb at the proximal end of the polycystic kidney disease 1 (PKD1) region has been mapped in detail, with 260 kb cloned in cosmids. The area cloned from normal individuals contains two homologous but divergent regions each of 75 kb, including the previously described marker 26-6. Pulsed-field gel electrophoresis identified a duplication of 75 kb of this region, referred to as the OX duplication (OXdup), in three patients with PKD1. The OXdup probably arose by an unequal exchange promoted by misalignment of partially homologous areas. Study of the OXdup in a large PKD1 family showed that it segregated with PKD1 in just one-half of the family, indicating that a recent crossover had occurred between the OXdup and PKD1 and showing that it was not a PKD1 mutation. Further analysis identified an OXdup breakpoint fragment: the OXdup was subsequently identified in 2 normal individuals of 110 assayed. The finding of the OXdup and in other individuals an 11-kb deletion (OXdel) at a similar point within this duplicated area indicates that this is an unusually unstable genomic region.

Asunto(s)

Cromosomas Humanos Par 16 , Reordenamiento Génico , Familia de Multigenes , Riñón Poliquístico Autosómico Dominante/genética , Mapeo Cromosómico , Clonación Molecular , Cósmidos , ADN/genética , Electroforesis en Gel de Campo Pulsado , Femenino , Marcadores Genéticos , Humanos , Hibridación Fluorescente in Situ , Masculino , Linaje , Polimorfismo Genético , Recombinación Genética

RESUMEN

We have used telomeric DNA to break the human Y chromosome within the centromeric array of alphoid satellite DNA and have created two derivative chromosomes; one consists of the short arm and 140 kb of alphoid DNA, the other consists of the long arm and 480 kb of alphoid DNA. Both segregate accurately at mitosis. It is known that there is no large scale sequence duplication around the alphoid DNA and so the simplest interpretation of our results is that the sequence responsible for accurate segregation is the alphoid DNA itself. Although the long arm acrocentric derivative segregates accurately it lags with respect to the other chromosomes in about 10% of anaphase cells and thus additional sequences may be required for orderly segregation. The short arm acrocentric chromosome is probably no larger than 12 Mb in size and thus our results also demonstrate that chromosomes of this size are capable of accurate segregation.

Asunto(s)

Centrómero/genética , Clonación Molecular , ADN/genética , Cromosoma Y , Células Cultivadas , Humanos , Mapeo Restrictivo , Telómero/genética

RESUMEN

Developments in the technique of fluorescence in situ hybridization (FISH) now permit hybridization of sequences ranging from 1 kb to whole genomes. The technique can be used in applications from coarse mapping of whole chromosomes to high-resolution analysis of extended strands of DNA. The complexity, and hence the coverage, of 'paints' prepared by amplification is being improved to the extent that such methods are used in cloning strategies for the generation of region-specific probes. Interphase analysis and comparative genomic hybridization are becoming important tools in cancer cytogenetics, and the potential for routine analysis of fetal cells obtained from maternal blood may provide a fresh approach to prenatal cytogenetic screening. Functional studies of gene activity and nuclear organization are now also possible.

Asunto(s)

Citogenética/métodos , Animales , Aberraciones Cromosómicas , Cartilla de ADN , Replicación del ADN , Femenino , Genoma , Humanos , Hibridación Fluorescente in Situ , Interfase/genética , Meiosis/genética , Sondas Moleculares , Hibridación de Ácido Nucleico , Embarazo , Diagnóstico Prenatal