Non-random association of trypsin-banded human acrocentric chromosomes

Summary This paper deals with a computer-aided study of the associations between acrocentric chromosomes as well as between those other chromosomes which in our investigations were revealed to be significantly closer to each other than random. The chromosome pairs were identified by a trypsinbanding technique. The method used has been elaborated previously with the specific aim of determining associations in a manner that avoids all subjective criteria.The tendency for association between homologous chromosomes is in decreasing order: 21 and 13>1>14, 18 and 19>17. Among the nonhomologous acrocentric chromosomes the significant tendencies for associations are between D-D: 13–14>13–15>14–15; between D-G: 13–21>14–21>13–22>15–22.The implication of the different tendencies to associate are dicussed in terms of aetiology of numerical and structural chromosome abnormalities.     

In vitro alteration of association patterns of human acrocentric chromosomes

Summary Association patterns of the human acrocentric chromosomes are supposed to reflect the metabolic and structural behavior of interphase nucleoli. Attempts were made to alter the association patterns by the action of chemical and physical agents (glucose, actinomycin D, temperature), which presumably influence nucleolar ultrastructur and function.A decrease in association frequency was noted after doubling the concentration of glucose in the culture medium. This effect might be due to elevated synthetic activity and growth rate of PHA-stimulated lymphocytes in the presence of excess glucose. More pronounced changes were obtained by increasing the temperature to 41.5°C 6 hrs prior to harvesting. This finding probably reflects the well known ultrastructural and biochemical lesions caused by supranormal temperatures in the nucleoli of mammalian cells. Addition of actinomycin D did not yield any significant response. Due to the mechanism of action of this inhibitor, its application is restricted to a time interval starting late in G₂.

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Zusammenfassung Die Assoziationsmuster der menschlichen akrozentrischen Chromosomen werden als Ausdruck des metabolischen und strukturellen Verhaltens der Interphasennucleoli angesehen. Es wurde versucht, diese Muster durch Einwirkung chemischer und physikalischer Agentien (Glucose, Actinomycin D, Temperatur) zu verändern, von denen angenommen werden kann, daß sie die Funktion und die Ultrastruktur des Nucleolus beeinflussen.Verdoppelung des Glucosegehaltes im Kulturmedium bewirkte eine Verringerung der Assoziationshäufigkeit. Dieser Effekt beruht vermutlich auf einer vermehrten synthetischen Aktivität und erhöhter Wachstumsgeschwindigkeit bei hohen Glucosekonzentrationen. Deutlichere Veränderungen wurden durch Erhöhung der Temperatur, 6 Std vor dem Abbrechen der Kulturen, auf 41,5°C erzielt. Dieses Ergebnis steht wahrscheinlich mit den bekannten ultrastrukturellen und biochemischen Störungen in Zusammenhang, die man durch erhöhte Temperaturen im Nucleolus von Säugerzellen erzeugen kann. Mit Actinomycin D ergaben sich keine signifikanten Veränderungen der Assoziationsmuster. Auf Grund seines Wirkungsmechanismus ist die Anwendung dieses Inhibitors auf das Zeitintervall zwischen der späten G₂-Phase und der Mitose beschränkt.

     

Non-random participation of chromosomes 13, 14 and 15 in acrocentric associations

Summary The patterns of association of chromosomes 13, 14 and 15 have been examined in a sample of 23 normal individuals. Significant deviations from the expectation of equality of participation have been detected in many of the individuals studied. The implications of the findings in terms of the aetiology of chromosome abnormality in the D group have been discussed.     

N-Band polymorphism of human acrocentric chromosomes and its relevance to satellite association

Summary With the aid of Q- and N-banding techniques we investigated the relationship between the length of satellite stalks, the appearance of N-bands and the frequency of satellite association of individual acrocentric chromosomes in the cells of seven individuals, including one male with a satellited and small Y-chromosome. The appearance of N-bands seemed to be a constant and characteristic property of individual acrocentric chromosomes, independent of the status of concentration of the chromosomes at metaphase. The homolog with longer satellite stalks had larger N-bands and participated in satellite association at a higher frequency than the one with shorter stalks. It appeared that N-bands were present along the whole length of the satellite stalk, the size of which could possibly reflect the amount of rDNA present in the nucleolar organizers in human chromosomes.     

Non-random distribution of Alu-family repeats in human chromosomes

A phage lambda recombinant clone containing at least 8 Alu-family repeats (AFRs) has been isolated from a human genomic library, and DNA from the phage was used as a probe for in situ hybridization on G-banded human metaphase chromosomes of healthy donors and leukemic patients. Some chromosome bands show prominent clusters of silver grains in all individuals examined: 1p34, 1q23, 2q21–22, 10p14, 11p14, 10q21 and 11q14. The data suggest non-random distribution of AFRs in the human genome.     

Localization of ribosomal RNA genes on human acrocentric chromosomes

Summary Clonal derivatives of a human heteroploid cell line, with different numbers of acrocentric chromosomes, show different rDNA contents. A linear relationship has been found between the rDNA content and the relative mass of the acrocentric chromosomes (D+G) expressed as the ratio between the mass of their DNA and the mass of the DNA of the whole chromosomal complement. The results suggest that human rRNA genes are located exclusively on the chromosomes of the groups D and G and that all these chromosomes contain rRNA genes.     

Nature of the silver staining and association of acrocentric chromosomes in normal and leukemic human cells

Silver staining and acrocentric chromosome association (ACA) patterns were investigated in bone marrow cells as well as in peripheral blood cells (cultures with or without PHA) from 39 patients with chronic myelocytic leukemia (CML), including 20 cases being in blastic phase (BP CML), and 51 patients with acute leukemia (AL). Bone marrow cells and PHA-stimulated peripheral blood lymphocytes (from 10 and 17 healthy donors, respectively) were used as a control. The frequency of ACA in metaphases from bone marrow cells of all the above groups of patients was shown to be decreased compared to that in PHA-stimulated lymphocytes. Patients with BP CML and AL constituted the most heterogeneous groups although some of them demonstrated the highest ACA-frequency per cell. There is a pronounced correlation between Ag+-nucleolus organizer regions (NOR's) and the frequency of ACA. With the exception of CML, the correlation coefficients (0.83, 0.74, and 0.72) were highly significant for all the above groups (donors, BP CML, and AL patients, respectively). The distribution pattern of single chromosome pairs, according to their ACA frequency, differed with every individual studied, but it was similar in normal and leukemic cells of the same individual. From the above data a conclusion is made that the frequency of ACA may depend on the functional activity of the NOR's as well as on the cells type.     

Polymorphism of 5-methylcytosine-rich DNA in human acrocentric chromosomes

Summary The acrocentric chromosomes of 18 unrelated individuals were analyzed by sequential staining by the chromomycin A₃/methyl green R-banding technique to identify the chromosomes, followed by an indirect immunoperoxidase technique to detect 5-methylcytosine (5MeC)-rich DNA. The short arms of both chromosomes 15 usually (92% of the chromosomes) had a large collection of 5MeC-rich DNA, which was always rich in AT base pairs. Much less commonly (11% of the possible occasions), a collection of 5MeC-rich DNA was seen on the short arm of a chromosome 13, 14, 21 or 22, and this DNA was always rich in GC base pairs. Sequential distamycin A/DAPI (DA/DAPI) and R-banding studies were carried out in 13 of these 18 individuals. There was bright DA/DAPI fluorescence of the 5MeC-rich region on the short arm of chromosome 15 but not on that of any other acrocentric chromosome. One implication of these findings is that bisatellited or other abnormal chromosomes that are DA/DAPI negative and 5MeC positive cannot be derived from number 15. In the case of a de novo chromosome of this type, the specific origin from any other acrocentric chromosome could be demonstrated by examining 5MeC-binding of the parental chromosomes.     

Chromatid association in acrocentric chromosomes of abnormal sexual development (ASD) cases

Concordant/discordant associations at chromatid level were compared and found significant (P less than 0.05) in females with primary amenorrhea. This probably suggested that the acrocentric association pattern in this group of ASD and infertility did not follow a random segregation in subsequent cell divisions and that the concordant acrocentric chromosomes have regularly established physical connections with one another, held together for several cell cycles. It could only be speculated that the association of acrocentric chromosome anomalies in some females with abnormal sex chromosomes are due to this reason. In the event that chromosome association has a bearing on chromosome aberrations, the non-random pattern of acrocentric association probably would increase the choice for translocation and non disjunction in the somatic cells in females with primary amenorrhea during ontogenesis.