Nature of telomere dimers and chromosome looping in human spermatozoa.

Specific and well-organized chromosome architecture in human sperm cells is supported by the prominent interactions between centromeres and between telomeres. The telomere-telomere interactions result in telomere dimers that are positioned at the nuclear periphery. It is unknown whether composition of sperm telomere dimers is random or specific. We now report that telomere dimers result from specific interactions between the two ends of each chromosome. FISH using pairs of subtelomeric DNA probes that correspond to the small and long arms of seven human chromosomes demonstrates that subtelomeres of one chromosome are brought together. Statistical analysis confirmed that telomere associations could not result from the random proximity of DNA sequences. Therefore, chromosomes in human sperm nuclei adopt a looped conformation. This higher-order chromosome structure is most likely required for chromosome withdrawal/decondensation during the early fertilization events leading to zygote formation.

Heterochromatiun C sizes distribution of chromosomes 1, 9, 16 and y in a sample of the Mexican population: comparison of two quantitative methods of measurement

En 147 mexicanos del sexo masculino, se investigó la distribución de los tamaños de los bloques de heterocromatina C de los cromosomas 1, 9, 16 e Y. Los tamaños fueron establecidos por dos métodos cuantitativos: longitud y área. Las curvas de distribución fueron muy cercanas a la normal con un leve sesgo positivo, sugiriendo que el tamaño de los segmentos C es un rasgo multifactorial continuo. Las comparaciones de nuestros resultados del largo mostraron ser muy similares con aquellos de otros grupos étnios, sugiriendo que esta característica presenta poca variabilidad racial. Utilizándose como criterio a la media y los intervalos de confianza de la varianza los tamaños de los segmentos C se clasificaron en 5 categorías: muy pequeños, pequeños, intermedios, grandes y muy grandes, encontrándose en todas las mediciones que la frecuencia de las variantes muy grandes fue mayor que las de tamaño muy pequeño. Los coeficientes de variación (CV) de ambos métodos fue aproximadamente del 5%, sin embargo del CV intercelular del área fue la mitad que el del largo. El CV de la muestra fue mayor para el área que para el largo, sugiriendo estos datos, que la medición de la primera, discrimina mejor variaciones de menor tamaño. En conclusión, consideramos que aunque el método de medir el área es más complicado y requiere de mayor tiempo que la cuantificación del largo, el primero determina mejor el tamaño de los segmentos de heterochromatina C

High resolution chromosome analysis of constitutional and acquired t(15;17) maps c-erbA to subband 17q11.2.

High resolution chromosome analysis was performed on bone marrow cells from four patients with acute promyelocytic leukemia and t(15;17), and in lymphocytes from two unrelated, phenotypically normal persons with an apparently identical constitutional translocation. Scrutiny of prophase-prometaphase chromosomes localized the breakpoints in all six cases to subbands 15q22.3 and 17q11.2. Molecular genetic studies have localized the oncogene c-erbA to chromosome #17 between the breakpoints of the constitutional and the acquired anomaly. The present results, therefore, map c-erbA to subband 17q11.2.

[Cloned fragment of human alphoid DNA--a molecular marker of the pericentromeric region of chromosome 18]. / Klonirovannyi fragment al'foidnoi DNK cheloveka--molekuliarnyi marker pritsentromernogo raiona 18-i khromosomy.

From the library of cloned fragments of human DNA we have isolated two recombinant plasmids containing alphoid DNA sequences pBRHS13, pBRHS65. Both cloned sequences hybridized in situ predominantly to pericentromeric regions of chromosome 18 and with less intensity to pericentromeric regions of chromosomes 2, 9, 20, and were characterized by populational copy number polymorphism in homologous chromosomes. These sequences may appear very useful in the diagnostics and cytogenetic analysis of chromosomal aberrations and in studies of polymorphisms of heterochromatic regions of human chromosomes.

Familial transmission of a non-Robertsonian translocation dicentric.

A second family showing transmission of a dicentric through three generations involving chromosomes 13 and 18 is presented. Features of non-Robertsonian dicentric chromosomes are presented and discussed.

[C-polymorphism of chromosomes 1, 9, 16 and Y in newborn infants of various gestational ages]. / C-polimorfizm khromosom 1, 9, 16 i Y u novorozhdennykh detei razlichnogo gestatsionnogo vozrasta.

Comparative evaluation of absolute C-segment lengths of chromosomes 1, 9, 16 and Y in new-born children of different gestational age has revealed no significant differences in their value between individuals with unfinished intrauterine development and those born in time.

Nucleotide sequence of a t(14;18) chromosomal breakpoint in follicular lymphoma and demonstration of a breakpoint-cluster region near a transcriptionally active locus on chromosome 18.

The t(14;18)(q32;21) chromosomal translocation characteristic of follicular lymphomas is the most common cytogenetic abnormality known to be associated with any specific type of hematolymphoid malignancy. A fragment of DNA containing the crossover point between chromosomes 14 and 18 was cloned from the tumor cells of a patient with a follicular lymphoma carrying this translocation. Nucleotide sequence analysis of the breakpoint DNA revealed that the break in chromosome 14 occurred in joining region 4(J4) of the nonfunctional immunoglobulin heavy chain allele. This finding and other structural similarities of the breakpoint with the functional diversity region-joining region (D-J) joint in this lymphoma suggest that D-J recombination enzymes played a role in the mechanism of the t(14;18) translocation. Hybridization analysis of DNA from 40 follicular lymphomas showed that the majority of t(14;18) translocations occur on chromosome 18 DNA within 4.2 kilobases of the cloned breakpoint. A DNA probe from this breakpoint-cluster region detects transcription products in the tumor cells from which it was cloned and in a B-lymphoma cell line containing a t(14;18) translocation.

[Tetrasomy of the short arm of human chromosome 18: cytogenetics and phenotypic disorders]. / Tetrasomiia po korotkomu plechu khromosomy 18 cheloveka: tsitogenetika, narusheniia fenotipa.

Two mentally retarded girls with a small metacentric nonsatellite extrachromosome were examined. Probands were found to share many clinical features: asthenic constitution, microcephalia, low-set malformed ears, high arched palate, long fingers and toes, a wide gap between first and second toes, clinodactyly of the 1st and 5th fingers, scoliosis. The extrachromosome was unequivocally interpreted as an isochromosome for the short arm of chromosome 18. Review of 12 i (18p) cases permits characterizing a syndrome of tetrasomy 18p.

Fragile sites on human chromosomes: description and clinical significance.

The fragile sites of human chromosomes are specific sites that are characterized by a tendency to show gaps, multiradial figures, acentric fragments, and deleted chromosomes on microscopy. These characteristics seem to reflect an inherent fragility at the site, although the underlying biochemical cause of fragile sites is unknown. Investigators have proposed several categories of fragile sites: "rare" or "heritable," "common," and "constitutive." Although the clinical significance of most fragile sites is unknown, fragile site Xq27.3 is associated with one form of X-linked mental retardation. In this article, the three types of chromosome fragile sites are described, and their possible relevance to chromosomal breakage that results in birth defects or cancer is discussed.

The t(14;18) chromosome translocations involved in B-cell neoplasms result from mistakes in VDJ joining.

In this study, the joining sequences between chromosomes 14 and 18 on the 14q+ chromosomes of a patient with pre-B-cell leukemia and four patients with follicular lymphoma carrying a t(14;18) chromosome translocation were analyzed. In each case, the involved segment of chromosome 18 has recombined with the immunoglobulin heavy-chain joining segment (JH) on chromosome 14. The sites of the recombination on chromosome 14 are located close to the 5' end of the involved JH segment, where the diversity (D) regions are rearranged with the JH segments in the production of active heavy-chain genes. As extraneous nucleotides (N regions) were observed at joining sites and specific signal-like sequences were detected on chromosome 18 in close proximity to the breakpoints, it is concluded that the t(14;18) chromosome translocation is the result of a mistake during the process of VDJ joining at the pre-B-cell stage of differentiation. The putative recombinase joins separated DNA segments on two different chromosomes instead of joining separated segments on the same chromosome, causing a t(14;18) chromosome translocation in the involved B cells.

Centromeric instability of chromosomes 1 and 16 with variable immune deficiency: a new syndrome.

We describe an extended study of a boy with combined immunodeficiency and centromeric fragility of chromosomes 1 and 16. This case, together with three previously reported cases with similar clinical, immunological and chromosomal features, appears to confirm a specific syndrome of immune deficiency associated with centromeric fragility of chromosomes 1, 9 and 16.

Gene mapping of Malaysian alpha thalassemias with alpha and zeta globin gene probes.

Restriction enzyme analysis of the alpha and zeta globin genes was carried out in four cases of Hb Bart's hydrops fetalis, in three patients with Hb H disease without Hb CoSp, in three patients with Hb H disease with Hb CoSp, in 47 individuals with alpha thalassemia trait, and in 47 normal individuals. All four cases of Hb Bart's hydrops fetalis resulted from deletions of alpha 1 and alpha 2 globin genes which did not extend to the psi zeta 1 and zeta 2 globin genes. The same type of deletion was observed in alpha thal1 carriers, but two newborns (one Malay and one of Chinese extraction) had a nondeletion type of alpha thal1 which was confirmed by quantitative alpha globin gene analysis. In addition, two other newborns diagnosed as alpha thal1 trait carriers (one Malay, one Chinese) were shown to have a deletion of both alpha globin genes by quantitative alpha globin gene analysis, but further testing with zeta globin gene probe failed to reveal an abnormal fragment length characteristic of an alpha globin gene deletion. We believe that this last condition is due to a large deletion which includes all alpha globin genes and all zeta globin genes on the same chromosome. On another front, Bgl II restriction analysis of all four Hb Bart's hydrops fetalis cases and the alpha thal1 trait carriers showed a 10.5-kb Bgl II restriction fragment, in the hydrops fetalis as a single band, while in the carriers this 10.5-kb fragment was accompanied by the usual normal 12.5-kb and 11.3-kb fragments. We report that this 10.5-kb fragment, previously thought to be specific for the Southeast Asian alpha thal1 gene deletion, is also common in normal individuals. Nevertheless, digestion with other enzymes can clearly differentiate the alpha thal1 and normal genotypes. We distinguish the findings in the alpha thalassemias from the extensive DNA polymorphism in the region of the alpha and zeta globin genes.

Investigation of human chromosome polymorphisms by scanning electron microscopy.

Human chromosome polymorphisms were investigated by scanning electron microscopy (SEM). Centromeric heterochromatin was of a constricted morphology. The extent of the C banded region was demarcated by a prominent circumferential groove in G banded chromosomes. Circumferential grooves were observed within the heterochromatin of chromosome 9, and the number of grooves present reflected the size of the region. Three dimensional viewing of satellites and short arms of acrocentric chromosomes, from different angles in the SEM, provided the opportunity for accurate assessment of the size of satellites to be made. Also, small morphological variations were defined in the SEM when definition was uncertain in the light microscope (LM).

Cotransfer of syntenic human genes into mouse cells using isolated metaphase chromosomes or cellular DNA.

Chromosome-mediated gene transfer (CMGT) of the human genes for hypoxanthine phosphoribosyl transferase (HPRT) and cytosol thymidine kinase (TK1) into HPRT deficient mouse A9 cells or TK deficient Swiss mouse 3T3TK- cells was found to occur at frequencies at least one order of magnitude higher than DNA-mediated gene transfer (DMGT). The frequency of CMGT into 3T3TK- cells was reduced by more than an order of magnitude by a posttreatment of the recipient cells with dimethyl sulphoxide (DMSO). After CMGT, expression of the non-selected genes coding for galactokinase (GALK) and acid alpha-glucosidase (GAA), both syntenic with TK1, was observed in a number of transformants. From the pattern of cotransfer, a tentative gene ordering of CENTROMERE-GALK-TK1-GAA on human chromosome 17 was deduced. Chromosome-mediated cotransfer of X-linked human phosphoglycerate kinase (PGK) with HPRT was observed in two out of 33 A9 transformants analysed. DNA-mediated cotransfer of a syntenic gene was only observed for GALK, cotransferred with TK1 in two out of 18 TK+ transformants of mouse LTK- cells. Therefore, with murine cells as recipients of human donor genetic material, CMGT results in a higher frequency of transfer and a higher incidence of cotransfer of syntenic genes than DMGT using cellular DNA in the same cell system.

[Rearrangement of the chromosome 17 in colonic adenocarcinoma]. / Remaniement du chromosome 17 dans l'adénocarcinome colique.

Chromosome studies on five cases of large bowel adenocarcinoma show a systematic rearrangement of chromosome No. 17 after breakage in its juxtacentromeric region (band 17 q 11). A frequent involvement of chromosome No. 8 (juxtacentromeric break) and the loss of chromosome No. 18 are also noticed. A review of the literature strengthens the hypothesis of a preferential involvement of these chromosomes in large bowel cancer.

The structural basis for C-banding. A scanning electron microscopy study.

The same C-banded human polymorphic chromosomes were observed in the light microscope (LM) and then in the scanning electron microscope (SEM) to investigate the structural changes produced by the C-banding technique. C-banded regions, which stained positively in LM, were highly condensed with tightly packed chromatin fibres, resembling non-banded chromosomes. In striking contrast, adjacent non-C-banded regions were represented by loosely arranged fibres, resembling G-banded chromosomes. The significance of these observations in relation to current theories on the effects of C-banding on chromosome structure is discussed.

Cloning the complete human adenine phosphoribosyl transferase gene.

We have isolated a clone from a human genomic lambda library which cross-hybridises with the cloned hamster adenine phosphoribosyl transferase gene (aprt). After restriction mapping and further hybridisation to the hamster gene, a series of putative human aprt-containing fragments has been isolated and tested for ability to transform adenine phosphoribosyl transferase-deficient (aprt-) strains of Chinese hamster ovary (CHO) cells to APRT proficiency. Transforming activity was detected in a 48-kb lambda clone, the 17.4-kb EcoRI insert, and an 8.6-kb HincII fragment. Smaller fragments have thus far shown no transforming activity. Transformants appear to be stable for the APRT+ phenotype, and human aprt DNA sequences are present in the hamster transformants. The 8.6-kb HincII fragment has been subcloned and the insert mapped. Nonrepetitive regions of this subclone have been identified, and should prove valuable for chromosome walking studies on human chromosome 16, familial studies of a human aprt- trait, the analysis of restriction fragment length polymorphisms (RFLPs) in the area surrounding the aprt gene, and the fine structure mapping of the mutations induced by chemical carcinogens and alkylating agents.