The quantitative analysis of polymorphism on human chromosomes 1, 9, 16, and Y

Summary Comparative analysis of the polymorphism of C segments on chromosomes 1, 9, 16, and Y was conducted in 50 normal boys and 50 normal girls. Quantitative methods revealed that the mean lengths of C segments, their variability, and their distribution on the chromosomes mentioned are quite identical in the two groups. Methodological problems related to the study of chromosome polymorphism are discussed.     

Analysis of centromere size in human chromosomes 1, 9, 15, and 16 by electron microscopy.

Human chromosomes were treated with 5-azacytidine and analyzed by whole-mount electron microscopy. This base analogue produces undercondensation of heterochromatin and separation of the centromere from the bulk of pericentromeric heterochromatin in chromosomes 1, 9, 15, and 16, which allows clear delimitation of the centromere regions. A quantitative analysis of centromeres showed that chromosomes 1, 9, and 16 have centromeres of different size. The centromere of chromosome 15 is similar in size to that of chromosome 9 and different from those of chromosomes 1 and 16. No interindividual variation for centromere size was found. A positive correlation between centromere and chromosome size was found for the chromosomes analyzed.     

Equivalence of the total constitutive heterochromatin content by an interchromosomal compensation in the C band sizes of chromosomes 1, 9, 16, and Y in Caucasian and Japanese individuals

A quantitative analysis of C bands by densitometric measurements in chromosomes 1, 9, 16, and Y was conducted in Caucasians and Japanese living in Brazil. Sixty normal unrelated subjects (30 males and 30 females) were studied in each racial group. Caucasians presented C bands of chromosomes 1, 9, and 16 larger than Japanese, but, on average, only the difference for C bands of chromosome 9 was statistically significant. In the Japanese, the C band sizes of chromosomes Y were, on average, significantly larger than in the Caucasians. The mean C band size of chromosome 9 and the sum of the three pairs were significantly larger in Caucasian than in Japanese males. The total values of constitutive heterochromatin, sigma (1qh,9qh,16qh,Yq12), did not show significant difference between Caucasian and Japanese males. The relative C band sizes of chromosomes 1, 9, and 16 were, on average, similar in Caucasians and Japanese. No sex difference was found in both racial groups. As regards the heteromorphism, only the values of C bands of chromosome 9 were, on average, significantly larger in Caucasians than in Japanese. Partial inversions were detected only among the Caucasians.     

Heterochromatic regions of human chromosomes 1, 9, 16 and Y and the phenotype

The relationship between variability of the heterochromatic regions of chromosomes 1, 9, 16, Y and the anthropometric characteristics (the height, the biacromial diameter and weight) was studied in two groups of children; 70 children had embryopathies of unknown etiology and 40 children had the Down syndrome. The positive statistically significant correlation of the C-segments lengths of chromosomes 1, 9, 16, their sum included, and above characteristics was found. The correlation coefficients of Y-chromosome were non-significant. The problems of functional role of the structural heterochromatin and its influence on viability and physical development of the organism are discussed.     

Relationship of the variability of the heterochromatic regions of chromosomes 1, 9, 16, and Y to some anthropometric characteristics in children with embryopathies of unknown etiology and in children with Down syndrome

Summary The relationship between variability of the heterochromatic regions of chromosomes 1, 9, 16, and Y, and anthropometric characteristics (length and mass of body, shoulder diameter) in 70 children with embryopathies of unknown etiology and in 40 children with Down syndrome was studied. The positive statistically significant correlations of the C segment lenghts of chromosomes 1, 9, 16, their sum included, and the above characteristics were found. The correlation coefficients of Y chromosome were not significant. The questions of the functional role of the structural heterochromatin and its influence on the viability and physical development of the organism are discussed.     

The quantitative analysis of polymorphism on human chromosomes 1, 9, 16, and Y

This study was made to establish a stable quantitative characteristic of C segments on chromosomes 1, 9, 16, and Y in an individual karyotype that was reproducible in successive experiments. The C segment of these chromosomes were measured in successive cultures of cells from three males and the C segments of chromosomes 1, 9, and 16 in cells from three pairs of female monozygotic twins were measured. The results show that the absolute lengths of C segments tend to vary considerably with the cell samples analyzed, while the relative length, i.e., the length of a single C segment as a percentage of the total length of all C segments of the chromosomes being studied, is more stable and can be used for individual characteristics.     

Quantitative analysis of C bands in chromosomes 1, 9, and 16 of Brazilian Indians and Caucasoids

Summary Densitometric C-band measurements in chromosomes 1, 9, and 16 of 394 Indians and 40 Caucasoids living in Brazil are reported. No significant intratribal variability in the average length of these regions was observed, and the intertribal variation showed no consistent patterns. But the Caucasoids always presented lower means. The relative C-band sizes of these three chromosomes, however, were very similar in Indians and Caucasoids. The indices of heteromorphism displayed analogous results; only in chromosome 16 are they dissimilar in these two ethnic groups. An unexpected sex difference was observed in the C-band sizes of this chromosome, females uniformly presenting higher averages than males. Centromeric heterochromatin appeared in 6% and 9% respectively of the short arms of chromosomes 1 and 9 among the Caucasoids, while among the Indians its prevalence was 2% in both chromosomes.     

Patterns of exchange induced by mitomycin C in C-bands of human chromosomes. I. Relationship to C-band size in chromosomes 1, 9, and 16

Summary Frequencies of exchange were determined in C-bands of chromosomes 1, 9 and 16 in six normal males, and related to relative C-band area. Comparing these different chromosomes, more exchanges occurred on average in 9 than in 1 although their mean C-band sizes were similar. Chromosome 16 exchanges were fewer, both overall and relative to C-band area. Comparing the same chromosome between individuals, there was a positive correlation between relative frequency and band size in both 1-1 and 9-9 exchanges. No clear trend was observed for other exchange events.If homology is required for interchange, if cannot be dependent solely on overall C-band size. Perhaps certain DNA sequences, sensitive to mitomycin C damage, are located in part of each C-band, with less per unit area in chromosome 1 than in 9 and still less in chromosome 16.X- and U-type exchanges between chromosome 9s occurred in near equal frequencies in all individuals. If synapsis of specific, affected sequences is a pre-requisite for interchange, this observation suggests that the affected sequence in chromosome 9 is arranged in both orientations relative to the centromere.     

Quantitative analysis of C-segments of chromosomes 1, 9, 16 and Y in couples with reproductive disorders

A comparative analysis of structural variability of C-bands on chromosomes 1, 9, 16 and Y was conducted in 50 phenotypically normal adults and 25 couples with repeated spontaneous abortions. Reduction of both the total amount of heterochromatin in the cell and the lengths of these regions on chromosomes 1, 9, and 16 is revealed in the group of pathology. No differences were found in the lengths of C-bands on Y chromosome.     

Heterochromatin is not an adequate explanation for close proximity of interphase chromosomes 1--Y, 9--Y, and 16--Y in human spermatozoa

Analysis of human spermatozoa and lymphocytes using C-banding techniques and in situ hybridization has shown a higher order packaging of the human genome. Chromosomes are not distributed entirely at random within the nucleus. In particular, chromosomes 1, 9, and 16, carrying large blocks of pericentromeric heterochromatin, and the Y chromosome, carrying heterochromatin in Yq12, are in close proximity to each other within the nucleus and are involved in somatic pairing with nonhomologous chromosomes. In order to determine whether the close proximity of these chromosomes in any way is attributable to the distribution of heterochromatin, double in situ hybridization was performed on chromosomes 1--Y, 9--Y, and 16--Y as well as on 1--X, 9--X, and 16--X-with chromosome X as the other gonosome carrying less heterochromatin-in human spermatozoa. Each pair was found to have a nonrandom spatial distribution. However, comparison of the arrangement of chromosomes 1--Y versus 1--X and 9--Y versus 9--X revealed that heterochromatin cannot be the only cause for the tendency of chromosome fusion, because only the results of the chromosome pair 1--Y/1--X could support this proposition. In conclusion, the heterochromatin effect cannot be, in itself, an adequate explanation for chromosome association, implicating as well other mechanisms.     

Localization of subtelomeric sequences of human chromosomes 1q, 11p, 13q, and 16q in the higher primates

Relative phylogenetic divergence of the members of the Pongidae family has been based on genetic evidence. The recent isolation of subtelomeric probes specific for human (HSA) chromosomes 1q, 11p, 13q, and 16q has prompted us to cross hybridize these to the chromosomes of the chimpanzee (Pan troglodytes, PTR), gorilla (Gorilla gorilla, GGO), and orangutan (Pongo pygmaeus, PPY) to search for their equivalent locations in the great apes. Hybridization signals to the 1q subtelomeric DNA sequence probe were observed at the termini of human (HSA) 1q, PTR 1q, GGO 1q, PPY 1q, while the fluorescent signals to the 11p subtelomeric DNA sequence probe were observed at the termini of HSA 11p, PTR 9p, GGO 9p, and PPY 8p. Fluorescent signals to the 13q subtelomeric DNA sequence probe were observed at the termini of HSA 13q, PTR 14q, GGO 14q, and PPY 14q, and positive signals to the 16p subtelomeric DNA sequence probe were observed at the termini of HSA 16q, PTR 18q, GGO 17q, and PPY 19q. These findings apparently suggest sequence homology of these DNA families in the ape chromosomes. Obviously, analogous subtelomeric sequences exist in apes' chromosomes that apparently have been conserved through the course of differentiation of the hominoid species. This revised version was published online in July 2006 with corrections to the Cover Date.     

Variability of the C-segment sizes of chromosomes 1, 9, 16 and Y in the human chromosome set]

The investigation of chromosome polymorphism by quantitative methods is a rather hard task. The manual method for measuring C-segments of chromosomes 1, 9, 16 and Y in man is suggested, which is not difficult, being reasonably precise for the population research. Metaphases of the average level of chromosome condensation were taken for analysis. Only the C-segments were measured without measuring chromosomes. The negative chromosome image was 4000-fold magnified, compared to the chromosome natural size, and the boundaries of C-segments of each chromosome were five-fold dotted on a sheet of paper specially printed for this purpose. C-segments were measured by magnifying glass with 0.025 mcm scale unit. For every individuum, C-segments were measured in 5-7 cells only. The data are presented on the estimation of measurement errors and on individual (intercellular) and population (interindividual) variations of C-segments of chromosomes.     

DNA methylation and chromosome instability in lymphoblastoid cell lines

In order to gain more insight into the relationships between DNA methylation and genome stability, chromosomal and molecular evolutions of four Epstein-Barr virus-transformed human lymphoblastoid cell lines were followed in culture for more than 2 yr. The four cell lines underwent early, strong overall demethylation of the genome. The classical satellite-rich, heterochromatic,juxtacentromeric regions of chromosomes 1, 9, and 16 and the distal part of the long arm of the Y chromosome displayed specific behavior with time in culture. In two cell lines, they underwent a strong demethylation, involving successively chromosomes Y, 9, 16, and 1, whereas in the two other cell lines, they remained heavily methylated. For classical satellite 2-rich heterochromatic regions of chromosomes 1 and 16, a direct relationship could be established between their demethylation, their undercondensation at metaphase, and their involvement in non-clonal rearrangements. Unstable sites distributed along the whole chromosomes were found only when the heterochromatic regions of chromosomes 1 and 16 were unstable. The classical satellite 3-rich heterochromatic region of chromosomes 9 and Y, despite their strong demethylation, remained condensed and stable. Genome demethylation and chromosome instability could not be related to variations in mRNA amounts of the DNA methyltransferases DNMT1, DNMT3A, and DNMT3B and DNA demethylase. These data suggest that the influence of DNA demethylation on chromosome stability is modulated by a sequence-specific chromatin structure.     

Relation between the size of C-segments and corresponding euchromatic regions of human chromosomes 1, 9 and 16 during their mitotic condensation

The nature of associations between the length of C-segments and the corresponding euchromatic regions of chromosomes 1, 9, and 16 in the process of their mitotic condensation has been studied. Their statistically significant linear nature in the range of chromosome 2 condensation from 11 to 4 micron has been established. Within the interval of 6.5-8.5 micron the above association is less significant, at the same time minimal variability of C-segment length is observed as compared to other stages of mitotic condensation. It is recommended to define the absolute size of C-segments in chromosomes 1, 9 and 16 by measuring their dimensions in metaphase plates with chromosome 2 length from 6.5 to 8.5 micron. The regressional correction of the results of C-segment measurements or approximation of values depending on the statistical significance of linear regression equation coefficient has been demonstrated.     

Heterochromatic regions on chromosomes 1, 9, 16, and Y in children with some disturbances occurring during embryo development

Some reduction of C-segment lengths and their variability on chromosomes 1, 9, 16, and Y was exhibited by children who had had some disturbances at early stages of morphogenesis. The data obtained might suggest a certain activity of the heterochromatic regions during embryo development. Based on this data one may also suppose that reduction of the amount of heterochromatin might affect the normal morphogenetic processes.     

Centromeric instability of chromosomes 1, 9, and 16 associated with combined immunodeficiency

Summary Instability of the centromeric regions of chromosomes 1, 9, and 16 in cultured lymphocytes of an 8-month-old girl with malabsorption and combined immunodeficiency is reported. Together with the two previous reports on this condition, the present report seems to confirm the specific association of combined immunodeficiency and centromeric instability of chromosomes 1, 9 and 16 with multibranching.     

The quantitative analysis of polymorphism on human chromosomes 1, 9, 16 and Y

Summary The generalized characteristic of the C-segment lengths on chromosomes 1, 9, 16, and Y is suggested for a study of population heterogeneity. For this purpose, the concept of the distance D is introduced, taking into account the individual C-segment lengths, the mean lengths and standard deviations of C-segment lengths in a group of subjects, as well as the coefficients of correlation of the C-segment lengths on the said chromosomes.It is demonstrated that distance D may be employed to study the relevance of the given subject to the group studied, the relation to the mean characteristics within the group, and selection of subjects' pairs with almost identical C-segment lengths on respective chromosomes.In the study of such problems as zygosity of twins, family analysis, etc., along with the absolute C-segment lengths, it is recommended to employ the relative C-segment lengths on chromosomes 1, 9, 16, and Y, calculated as a part of the sum total of their absolute lengths.     

Differential digestion of the centromeric heterochromatic regions of the 5-azacytidine-decondensed human chromosomes 1, 9, 15, and 16 by NdeII and Sau3AI restriction endonucleases

A study on the factors involved in chromosome digestion by restriction endonuclease was carried out on 5-azacytidine treated and untreated human chromosomes 1, 9, 15 and 16 by using NdeII and Sau3AI isoschizomers. After treatment with 5-azacytidine, chromosomes 1, 9, 15, and 16 showed two differentiated areas at the centromeric regions: the centromere, fully condensed, and the pericentromeric heterochromatin, decondensed. Chromosomes not treated with 5-azacytidine after digestion with Sau3AI and NdeII showed all the centromeric regions undigested, except pair number 1, digested at the pericentromeric area. Digestion of the 5-azacytidine decondensed chromosomes with Sau3AI and NdeII showed the centromeres undigested in the four chromosome pairs while the pericentromeric heterochromatin appeared largely digested. Other factors, different to target distribution, are necessary to explain the pattern of restriction endonuclease digestion observed in this communication.     

C-polymorphism of chromosomes 1, 9, 16 and Y in newborn infants of various gestational ages

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.     

Multibranched chromosomes 1, 9, and 16 in a patient with combined IgA and IgE deficiency

Summary Instability of the centromeric region of chromosome 1 and multibranched configurations formed by different numbers and combinations of arms of chromosomes 1, 9, and 16 were found in cultured lymphocytes of 12-year-old male with combined IgA and IgE deficiency. No chromosome abnormalities were found in fibroblast cultures from the patient or in blood cultures from his parents.A possible effect on the frequency of the abnormalities of the almost continuous antibiotic treatment received by the patient was found both in vivo and in vitro, but no abnormalities were found in blood cultures from control subjects who received similar treatment. Interphase association of chromosomes 1, 9, and 16 and a high frequency of interchanges among the centromeric regions of these chromosomes due to the presence of a fragile site is assumed to be the cause of the abnormalities.