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.

Double in situ hybridization in combination with digital image analysis: a new approach to study interphase chromosome topography.

Double in situ hybridization with mercurated and biotinylated chromosome specific DNA probes in combination with digital image analysis provides a new approach to compare the distribution of homologous and nonhomologous chromosome targets within individual interphase nuclei. Here we have used two DNA probes representing tandemly repeated sequences specific for the constitutive heterochromatin of the human chromosomes 1 and 15, respectively, and studied the relative arrangements of these chromosome targets in interphase nuclei of human lymphocytes, amniotic fluid cells, and fibroblasts, cultivated in vitro. We have developed a 2D-image analysis approach which allows the rapid evaluation of large numbers of interphase nuclei. Models to test for a random versus nonrandom distribution of chromosome segments are discussed taking into account the three-dimensional origin of the evaluated 2D-distribution. In all three human diploid cell types the measurements of target-target and target-center distances in the 2D-nuclear image revealed that the labeled segments of the two chromosomes 15 were distributed both significantly closer to each other and closer to the center of the nuclear image than the labeled chromosome 1 segments. This result can be explained by the association of nucleolus organizer regions on the short arm of chromosome 15 with nucleoli located more centrally in these nuclei and does not provide evidence for a homologous association per se. In contrast, evaluation of the interphase positioning of the two chromosome 1 segments fits the random expectation in amniotic fluid and fibroblast cells, while in experiments using lymphocytes a slight excess of larger distances between these homologous targets was occasionally observed. 2D-distances between the labeled chromosome 1 and 15 segments showed a large variability in their relative positioning. In conclusion our data do not support the idea of a strict and permanent association of these homologous and nonhomologous targets in the cell types studied so far.

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

Interstitial deletion of the short arm of chromosome 3 (3p14).

Deletions of 3p usually involve the terminal portion (3p25). An interstitial deletion of a proximal 3p segment (3p14) was detected at amniocentesis. The clinical and cytogenetic characteristics of this case and of three previously published cases are reviewed. Cardiovascular and gastrointestinal malformations have not been reported before in association with this particular chromosome abnormality.

Trisomy and tetrasomy for long arm of chromosome 1 in near-diploid human endometrial adenocarcinomas.

Karyotypic analysis by R-banding after short-term culture, carried out on 7 cases of human endometrial adenocarcinoma, showed in 4 of these a trisomy or a tetrasomy for the long arm of chromosome I. In the 4 cases, these imbalances were due to rearrangements involving centromeric or para-centromeric break-points: 46,XX,-16, +der(1q16p) t(1;16)(1p16q;1q16p); 46,XX,-21, +der (1q21q)t(1;21) (1p21p;1q21q); 46,XX, -21, +der(21) t(1;21)(q11;p13); 48, XX, +2, +i(1q). Two other cases showed only a numerical aberration: 47, XX, +10 and 47, XX, +12. In the last case, only cells with apparently normal karyotype were seen. In the 4 cases with an anomaly of chromosome I, two normal I chromosomes coexisted with abnormal elements. This shows that the rearrangement very likely occurred in G2 phase of the cell cycle.

Sideroblastic anemia associated with thrombocytosis and a chromosome 3 abnormality.

A unique patient with sideroblastic anemia and thrombocytosis with a recurrent and ultimately fatal thromboembolic phenomenon is described. Cytogenetic analysis of bone marrow metaphases revealed a pseudodiploid chromosome complement, 46,XY,ins(3;3)(q26;q21q26). The association of thrombocytosis and ins(3;3) in patients with preleukemia or myelogenous leukemia has been reported previously. The association of ins(3;3) and thrombocytosis in our patient with sideroblastic anemia suggests that the disorder may involve a hematopoietic progenitor cell capable of giving rise to all three cell lineages. Our findings also support the suggestion that a gene on the long arm of chromosome #3 may encode a protein that, at least in part, regulates megakaryopoiesis.

A case of rhabdomyosarcoma of the bladder with a (2;5) chromosomal translocation in peripheral lymphocytes.

Chromosome analysis was performed on peripheral blood lymphocytes of a patient with rhabdomyosarcoma of the urinary bladder. It showed a reciprocal t(2;5) translocation with the breakpoints at 2q37.3 and 5q31.3. This is the first report of such an anomaly in the peripheral lymphocytes of a patient with rhabdomyosarcoma of the urinary bladder.

[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.

Nonrandom chromosomal changes in retinoblastomas.

The analysis of the karyotype in 76 retinoblastomas (24 our cases and 52 described in the literature) has revealed nonrandom changes of Iq, 6p, 13, 16 and the sex chromosomes. Complete or partial trisomy Iq was observed in 44 out of 76 tumours. Tetra-or trisomy 6p was found in 35 and 6 cases respectively. Chromosome 13 monosomy or its long arm deletion was described in 11 tumours. Monosomy 16 and loss of the X or Y--in 18 and 12 cases. The specific feature of retinoblastoma karyotype is presence (along with two normal homologues of the pair 6) of the marker chromosome i (6p). Possible causes of unexpectedly rare abnormalities of chromosome 13 in retinoblastoma cells were discussed in the light of well known data on predisposing role of constitutional deletion 13q14, and recent molecular genetic studies showing the significance of recessive tumour genes in carcinogenesis. The cytological signs of gene amplification (HSRs, DMs) were revealed in few retinoblastomas. However, the recent data on N-myc gene amplification and its elevated expression in several retinoblastomas indicate that amplification of the oncogene(s) might be involved in the genesis of this tumour. Further studies are needed to understand the correlative role of specific chromosome rearrangements, gene(s) amplification and action of recessive rb gene, located at 13q14 in initiation and progression of retinoblastoma.

Acute megakaryoblastic leukaemia with 3q inversion and elevated thrombopoietin (TSF): an autocrine role for TSF?

A patient with acute megakaryoblastic leukaemia is described in whom exactly the same paracentric inversion of 3q was detected as in three previously documented cases. The patient's serum thrombopoietin (TSF) was significantly raised. Based on these findings we postulate a role for a gene (? oncogene) on chromosome 3q in thrombopoietin production. Abnormalities of 3q may assist in delineating a subgroup of acute nonlymphocytic leukaemia, namely acute megakaryoblastic leukaemia.

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.

Light and scanning electron microscopy of the same human metaphase chromosomes.

A technique has been developed to examine the same G-banded human metaphase chromosomes, first in the light microscope and then in the scanning electron microscope (SEM). A structural involvement in chromosome banding was confirmed by a positional correlation between the G-positive bands observed in the light microscope and the circumferential grooves between the quaternary coils of the metaphase chromosomes, observed in the SEM. In further support of this the regions between the grooves showed a positional relationship with the G-negative or reverse (R) bands. The examination of slightly extended metaphase chromosomes in the light microscope demonstrated that the G-banding pattern corresponded to that described by the Paris nomenclature for metaphase chromosomes. The arrangement of the circumferential grooves of the same chromosomes, observed in the SEM, was shown to relate to that described by the Paris nomenclature for prometaphase chromosomes. Therefore, using the SEM it is possible to demonstrate the details of prometaphase banding in metaphase chromosomes.

Chromosome 1 abnormalities: a common feature of pediatric solid tumors.

Abnormalities of chromosome 1 were found in 32 of 46 pediatric solid tumors including Ewing's sarcoma, Wilms' tumor, rhabdomyosarcoma, primitive neuroectodermal tumor, and hepatoblastoma. Trisomy of 1q was the most common abnormality, and breakpoints were most frequent in the region 1cen to 1p22. Abnormalities of chromosome 1 are not specific to any type of tumor. However, their frequent occurrence indicates that they may endow a clonal advantage in the development of cancer.

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.

Persistent Epstein-Barr virus infection associated with monosomy 7 or chromosome 3 abnormality in childhood myeloproliferative disorders.

This report deals with myeloproliferative disorders associated with chronic, persistent Epstein-Barr virus (EBV) infection and with monosomy 7 and aberrations concerning chromosomes 3 and 5. Altogether five children were affected, their age ranging from 1 to 4 years at time of clinical diagnosis. Principal symptoms were: hepatomegaly, splenomegaly, recurring upper respiratory tract infection and anaemia. The serum IgG level remained persistently increased. Anti EBV antibody concentrations were measured over a period of 9 months to 6 years, demonstrating persistently increased concentrations of IgG antibodies to viral capsid antigen (VCA) and against early antigen (EA). In three patients IgA antibodies were also studied and were found to be elevated. Within 2-5 years two children developed chronic myelomonocytic leukaemia from the chronic myeloproliferative syndrome. A third patient who initially was diagnosed as chronic myelomonocytic leukaemia developed acute leukaemia within a period of 12 months. A fourth patient with myeloproliferative syndrome went into spontaneous remission after an observation period of 2 years. A fifth patient, the only one with translocation t(3;5)(q27;q33), displayed symptoms and a clinical course that can best be characterized as juvenile chronic myelocytic leukaemia. The clinical, haematological, serological and cytogenetic findings may be related.

Clinical correlations of the 3q21;q26 cytogenetic anomaly. A leukemic or myelodysplastic syndrome with preserved or increased platelet production and lack of response to cytotoxic drug therapy.

Three patients presenting with acute leukemic disorder and chromosome 3 rearrangement involving bands q21;q26 are reported, and the literature on chromosome 3q abnormalities is reviewed. All reported patients carrying a paracentric 3q inversion or a translocation 3;3 with breakpoints in q21;q26 had a myelodysplastic or acute leukemic disorder with a normal or elevated platelet count and lack of response to cytotoxic drug therapy. They showed an associated incidence of -7 or 7q- anomalies higher than de novo acute leukemia and appear to constitute a definite subgroup of the leukemic disorders with very poor prognosis. The majority of patients showing other chromosome 3 long arm rearrangements showed evidence of leukemic process, were in blastic crisis, or had been exposed to chemotherapy, exhibiting also a higher incidence of associated -5 or -7 cytogenetic abnormalities than is observed in patients not exposed to toxic agents.

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).