Constitutive Heterochromatin Of Chromosomes Research Articles

Why only a man turned out to be the owner of mind?

It is considered that the main distinguishing feature of Homo sapiens from other living beings is the presence of his mind. There are many hypotheses regarding the origin of the human mind. The complexity of the problem lies in the fact that it is impossible to experimentally test any of the existing hypotheses. Perhaps we will never fully know how the human mind arose, but it is necessary to strive for this. Here we discuss the possible causes of the origin of a large brain in modern man, implying that the mind is ultimately a product of the human brain. We believe that in order for such a large brain to arise, profound and possibly unique changes in the genome and in the human body had to occur, which did not take place in other higher primates. The role of the evolution of the karyotype and heterochromatin part of the genome in the immediate ancestors of Homo s. sapiens, which led to an increase in the level of heat conductivity of their bodies changed the existing mechanisms of thermoregulation and led to the appearance of hairless skin, which, together, led to a sharp increase in the size of the brain, with the ensuing consequences, is discussed. We believe that the increase of the human brain size was not the result of drastically changes of the structural genes. Most likely it was the consequence of more ordinary events, such as evolution of karyotype, constitutive heterochromatin in chromosomes, human body heat conductivity, skin and thermoregulation. An experimental test is proposed to test the hypothesis put forward.

Sex determination and Y chromosome constitutive heterochromatin

In many animals, including us, the genetic sex is determined at fertilization by sex chromosomes. Seemingly, the sex determination (SD) in human and animals is determined by the amount of constitutive heterochromatin on Y chromosome via cell thermoregulation. It is assumed the medulla and cortex tissue cells in the undifferentiated embryonic gonads (UEG) differ in vulnerability to the increase of the intracellular temperature. If the amount of the Y chromosome constitutive heterochromatin is enough for efficient elimination of heat difference between the nucleus and cytoplasm in rapidly growing UEG cells the medulla tissue survives. Otherwise it doomed to degeneration and a cortex tissue will remain in the UEG. Regardless of whether our assumption is true or not, it remains an open question why on Y chromosome there is a large constitutive heterochromatin block? What is its biological meaning? Does it relate to sex determination, sex differentiation and development of secondary sexual characteristics? If so, what is its mechanism: chemical or physical? There is no scientifically sound answer to these questions.

Constitutive heterochromatin in chromosomes of duck hybrids and goose hybrids

Constitutive heterochromatin is a highly condensed fraction of chromatin in chromosomes. It is characterized by a high degree of polymorphism. Heterochromatin is located in the centromeric, telomeric, and interstitial parts of chromosomes. We used the CBG (C banding using B arium hydroxide by G iemsa) staining technique to identify heterochromatin in chromosomes. Analysis of karyotypes of F1 hybrids resulting from intergeneric hybridization of ducks (A. platyrhynchos × C. moschata) and interspecific crosses of geese (A. anser × A. cygnoides) were used to compare the karyotypes of 2 species of duck and 2 species of geese, as well as to compare the hybrids with the parent species. The localization of C-bands and their size were determined. In the duck hybrid, greater amounts of heterochromatin were noted in the homologous chromosomes from the duck A. platyrhynchos than in the chromosomes from the duck C. moschata. In the goose hybrid more heterochromatin was observed in the homologous chromosomes from the goose A. cygnoides than in the chromosomes from the goose A. anser. Comparison of chromosomes from the duck hybrid with chromosomes of the ducks A. platyrhynchos and C. moschata revealed nearly twice as much constitutive heterochromatin in the chromosomes of the hybrid. When chromosomes from the goose hybrid were compared with those of the geese A. anser and A. cygnoides, differences in the average content of heterochromatin were observed on only a few chromosomes.

Repetitive sequences associated with differentiation of W chromosome in Semaprochilodus taeniurus

The possible origins and differentiation of a ZZ/ZW sex chromosome system in Semaprochilodus taeniurus, the only species of the family Prochilodontidae known to possess heteromorphic sex chromosomes, were examined by conventional (C-banding) and molecular (cross-species hybridization of W-specific WCP, Fluorescence in situ hybridization (FISH) with telomere (TTAGGG)n, and Rex1 probes) cytogenetic protocols. Several segments obtained by W-specific probe were cloned, and the sequences localized on the W chromosome were identified by DNA sequencing and search of nucleotide collections of the NCBI and GIRI using BLAST and CENSOR, respectively. Blocks of constitutive heterochromatin in chromosomes of S. taeniurus were observed in the centromere of all autosomal chromosomes and in the terminal, interstitial, and pericentromeric regions of the W chromosome, which did not demonstrate interstitial telomeric sites with FISH of the telomere probe. The Rex1 probe displayed a compartmentalized distribution pattern in some chromosomes and showed signs of invasion of the pericentromeric region in the W chromosome. Chromosomal painting with the W-specific WCP of S. taeniurus onto its own chromosomes showed complete staining of the W chromosome, centromeric sites, and the ends of the Z chromosome, as well as other autosomes. However, cross-species painting using this WCP on chromosomes of S. insignis, Prochilodus lineatus, and P. nigricans did not reveal a proto-W element, but instead demonstrated scattered positive signals of repetitive DNAs. Identification of the W-specific repetitive sequences showed high similarity to microsatellites and transposable elements. Classes of repetitive DNA identified in the W chromosome suggested that the genetic degeneration of this chromosome in S. taeniurus occurred through accumulation of these repetitive DNAs.

C-Band Heteromorphism in Breast Cancer Patients

C-band heteromorphism, including size and localization variants, has been shown to correlate well with the occurrence of malignant diseases. The study was conducted with the aim of investigating aberrations of the C-band region of chromosomes 1, 9 and 16 including size variation, intra pair size asymmetry and inversion by comparing the frequency of heteromorphism in patients with breast cancer and healthy subjects. This is useful to establish the significance of variability of chromosome constitutive heterochromatin areas in a risk of malignancy. The study included 27 female patients with breast cancer and 30 normal healthy female subjects as controls. Peripheral lymphocytes culture and C-banding were done for all of them. The size of the heterochromatic region was evaluated using 16 p as a reference. Size heteromorphism between homologous chromosomes was considered when there was an intra-pair difference of one or more levels. Inversions whether partial or total were recorded. There was a significant increase in size of C-band for chromosome 1 between patients and controls [X2 = 9.17]. Intra pair size asymmetry of heterochromatin was more frequent in breast cancer patients than in the controls and the differences were statistically significant for chromosomes 1, 9 and 16 [X² = 4.4, 5 and 4 respectively]. For localization variants, a significant increase in frequency of partial inversion in chromosome No. 1 was found between the two groups [X2 = 4.44]. In conclusion, the present study showed that C-band heteromorphism occurs with higher frequency among breast cancer patients and supports the reported bassociation between presence of C-band heteromorphism and occurrence of malignant disease.

A ZZ/ZW Sex Chromosome System in Imparfinis mirini (Pisces, Siluriformes).

Imparfinis mirini belongs to the family Pimelodidae, which constitutes a large, diversified, and well distributed fish group in the neotropical region. Thus far 14 or 15 species of the genus Imparfinis have been described (Burges 1989) and three were investigated from the cytogenetic point of view (Fenocchio 1993, Vicente et al. 1994). The present paper describes the karyotype, the number and position of the nucleolus organizer region (NORs) and the pattern of distribution of constitutive heterochromatin in chromosomes of males and females of Imparfinis mirini.

Difference in constitutive heterochromatin behaviour between human amniocytes and lymphocytes detected by a sequential in situ exonuclease III digestion-random primer extension procedure.

Fixed chromosomes from human amniotic fluid cells and peripheral blood lymphocytes were digested in situ with exonuclease III and the single stranded DNA obtained was used as template for an in situ random primer extension. Under these conditions an R banding pattern, more evident in lymphocytes than in amniocytes, was obtained. Nevertheless, constitutive heterochromatin of chromosomes 1, 16, Yq, and mainly the pericentromeric region of chromosome 9 was far more intensely labelled in amniocytes than in lymphocytes. Fluorescence in situ hybridisation with a specific classical satellite DNA probe, showed that this differential labelling was dependent on a greater sensitivity of chromosome 9 constitutive heterochromatin to exonuclease III digestion in amniocytes than in lymphocytes, thus indicating qualitative differences in this region between both human cellular materials.

Human α-satellite DNAs are not susceptible to undercondensation after 5-azacytidine treatment

Localization of alphoid human satellite DNAs using fluorescence in situ hybridization (FISH) of metaphase chromosomes following treatment with 5-azacytidine to produce undercondensation showed that human alpha-satellite DNA is not sensitive to the condensation-inhibition effect of 5-azacytidine. The difference in heterochromatic DNA subsets was particularly evident in the constitutive heterochromatin of chromosomes 1 and 9. Comparison of the results obtained after FISH with those obtained from electron microscopy and G-banding enabled accurate localization of this DNA domain.

C-band polymorphisms in lymphocytes of patients with ovarian or breast adenocarcinoma

To establish the significance of the variability of human chromosome constitutive heterochromatin areas (C-band variants) in a risk of malignancy, C-banding pattern study has been performed in 33 female patients with ovarian or breast adenocarcinoma. The control group included 180 healthy women. The following characteristics of C-bands on chromosomes #1, #9, and #16 were studied: (a) size, (b) size heteromorphisms and (c) inversions, using quantitative and semiquantitative methods of analysis. Our data show no significant difference in the presence of C-band size and location variants in chromosomes #1, #9, and #16 between the patients with adenocarcinoma of the ovary or breast and healthy women. From that we conclude that there is no causal association between the presence of C-band variants on chromosomes #1, #9, and #16 and an elevated risk of ovarian and breast adenocarcinoma.

Heteromorphism of C-band positive chromosomal regions in CML patients

The heteromorphism of constitutive heterochromatin in chromosomes #1, #9, and #16 was investigated in 44 chronic myelocytic leukemia patients and 44 controls using bone marrow and peripheral blood lymphocyte cultures. A significant increase in the length of C-band region in all the three chromosome pairs as well as a statistically significant difference in the homologs of chromosome #1 was observed in chronic myelocytic leukemia patients when compared with the controls. The frequency of inversions was also greater in the patients than in the controls. A random translocation of 22q was found on either homolog of chromosome #9.

Constitutional C-band pattern in patients with adenomatosis of the colon and rectum

The pattern of polymorphism in the C-band-positive constitutive heterochromatin of chromosomes #1, #9, and #16 was studied in fibroblasts from 23 unrelated patients with adenomatosis of the colon and rectum and in peripheral lymphocytes from 78 control persons. The parameters of the heterochromatic regions analyzed were relative size, symmetry-asymmetry within homologous chromosome pairs, and frequency of inversions. The polyposis coli patients had a significantly higher frequency ( p < 0.05) of partial and total heterochromatin inversion on chromosome #9 than the control group (37.0% compared with 21.8%). In the other parameters studied, no significant differences were found between patients and controls.

On biological functions mapping to the heterochromatin of Drosophila melanogaster.

We examined the behavior of an autosomal recessive maternal-effect mutation, abnormal-oocyte (abo), that is located in the euchromatin of the left arm of chromosome 2. When homozygous in females, abo results in a marked reduction in the probability that an egg produced by a mutant mother will develop into an adult. However, this probability is increased if the fertilizing sperm delivers to the egg either a normal allele of the maternal-effect gene or a specific type of heterochromatin (called ABO) that is located in small regions of the X and Y chromosome constitutive heterochromatin as well as in some autosomal heterochromatin. These regions, moreover, all react to Hoechst 33258 fluorescent dye identically and specifically. The amelioration of the maternal effect produced by this heterochromatin differs temporally from that caused by the normal allele of the euchromatic gene: the heterochromatin reduces only precellular blastoderm mortality, whereas the normal allele of the euchromatic gene reduces only postblastoderm mortality. Thus, although the genome of the preblastoderm Drosophila embryo is apparently mostly silent, the ABO-containing heterochromatin functions at this early time. Finally, preliminary data indicate that abo is but one member of a cluster of linked genes, each of which interacts with its own normal allele and with a different, locus-specific, heterochromatic factor. From these observations, it appears that Drosophila heterochromatin contains developmentally important genetic elements, and that a functional concomitant of heterochromatic location is gene action at a developmental stage during which the activity of the euchromatic genome is as yet undetectable. Some general implications of these inferences are considered.

Constitutive heterochromatin of chromosomes No. 1, 9, and 16 in 90 patients with malignant disease and 91 controls

The variability of constitutive heterochromatin in chromosomes #1, #9, and #16 was investigated in 90 patients with malignant tumors (neoplasms of the head, neck, breast, and genital organs) and in 91 controls. The investigation was carried out on chromosome preparations from peripheral blood cultures. An analysis showed no significant difference in the frequency of localization variants, that is, inversions, in the patients and in the normal controls. Analysis of the variability of the C-segment size was made by measuring the length of heterochromatin blocks and showed that a correlation with the process of malignant transformation can be sought in the consequences of an uneven distribution (chromosome #1) and in quantitative changes in the constitutive heterochromatin (chromosomes #1 and #9).

Heteromorphism of Constitutive Heterochromatin in Carcinoma and Dysplasia of the Uterine Cervix

Abstract Chromosomal heteromorphism in constitutive heterochromatin of chromosomes 1, 9 and 16 was studied in 8 patients with cervix cancer and 15 patients with cervix dysplasia. Tissue cultures (diploid fibroblasts) established from tumor biopsies as well as lymphocyte cultures were used for making C-banded chromosome preparations. The heteromorphism in the appearance of the C-bands was expressed as differences in band size or position (inversions). 5 of the cervix cancer patients and 8 of those with dysplasia showed heteromorphism in chromosome 1. In two cancer patients, tissue culture as well as blood cells were available for analysis and both showed the same pattern of heteromorphism, thus suggesting an inherited origin of the variability. Heterochromatin heteromorphism was more common in chromosome 1 than in chromosomes 9 and 16. The heteromorphism in constitutive heterochromatin of chromosome 1 might be among the factors that dispose to cancer.

Heteromorphism of constitutive heterochromatin in carcinoma and dysplasia of the uterine cervix.

Chromosomal heteromorphism in constitutive heterochromatin of chromosomes 1, 9 and 16 was studied in 8 patients with cervix cancer and 15 patients with cervix dysplasia. Tissue cultures (diploid fibroblasts) established from tumor biopsies as well as lymphocyte cultures were used for making C-banded chromosome preparations. The heteromorphism in the appearance of C-bands was expressed as differences in band size or position (inversions). 5 of the cervix cancer patients and 8 of those with dysplasia showed heteromorphism in chromosome 1. In two cancer patients, tissue culture as well as blood cells were available for analysis and both showed the same pattern of heteromorphism, thus suggesting an inherited origin of the variability. Heterochromatin heteromorphism was more common in chromosome 1 than in chromosomes 9 and 16. The heteromorphism in constitutive heterochromatin of chromosome 1 might be among the factors that dispose to cancer.

Lateral asymmetry of constitutive heterochromatin in human chromosomes

Variations in lateral asymmetry of constitutive heterochromatin were studied in 30 normal individuals with reference to the chromosomal regions 1q12, 9q12, 15p11, 16q12 and Yq12. The technique consisted of growing human lymphocytes for one cell cycle in BrdU, staining with 33258 Hoechst, exposing them to UV light, treating them with 2 x SSC, and staining with Giemsa. This procedure revealed asymmetric staining in the region of constitutive heterochromatin in these chromosomal regions. Chromosomes 15, 16, and Y showed simple lateral asymmetry, whereas chromosome 1 showed both simple and compound asymmetry. In 15 cases, compound lateral asymmetry was evident in both homologues of chromosome 1, 12 cases showed compound lateral asymmetry in one homologue and simple lateral asymmetry in both the homologues. The centromere region of chromosome 9 stained symmetrically with this technique. The lateral asymmetry is presumed to reflect the strand bias in the distribution of thymine in satellite DNA fractions.

The constitutive heterochromatin in chromosomes of Fritillaria Sp., as revealed by Giemsa banding.

The incidence of C-bands (constitutive heterochromatin), as determined by differential Giemsa staining, was studied in the chromosomes of 56 species, varietal forms and subgenera of Fritillaria and 30 of them are illustrated. With the exception of the subgenera Korolkowi, a supposed link between lilies and fritillaries, and chromsome complements of all plants contained bands. There were wide differences in the size and number of these bands among species both within and between groups. In those with the largest and most abundant bands, there was a pronounced tendency for centromeric localization, both in Old and New World species. The Giemsa positive centromeres were masked when this occurred. Heteromorphy in respect of banding occurred in most species. The relation of repetitive DNA sequences with heterochromatin is discussed, as is also the problem of evolution in Fritillaria.

Variability and familial transmission of constitutive heterochromatin of human chromosomes evaluated by the method of linear measurement

Using the method of linear measurement, the lengths of constitutive heterochromatin of chromosomes 1, 9, 16, and Y were determined in 125 unrelated individuals, and in 30 members of ten families. The method used eliminates the variations in the C-band length due to different degrees of contraction of chromosomes in different mitoses, and enables the size of heterochromatin blocks to be expressed. It was found that the distribution of C-band lengths in the group of 125 individuals was normal, i.e., Gaussian, for all four classes of chromosomes measured. On the basis of length distribution and by computing the P1, P10, P90 and P99 percentiles, the actual numerical limits could be proposed for the five-step evaluation of heterochromatin length according to the Paris Conference (1971), Supplement (1975), for chromosomes 1, 9, 16, and in a preliminary way also for Y. When applying the proposed limits to data obtained in the present study, 165 C-band variants could be identified among the 125 individuals.

Karyotype analysis utilizing differentially stained constitutive heterochromatin of human and murine chromosomes.

Constitutive heterochromatin of chromosomes can be visualized utilizing a new differential staining technique which was originally developed by Gall and Pardue (1971). The method facilitates the more certain identification of specific chromosomes within and between cell populations of different origins. Marker chromosomes can be identified in established cell lines over many months of serial passage. Chromosomes of similar morphology within karyotypes of man and mouse can be distinguished in a number of instances. For example, the Y chromosomes of both mouse and man can now be easily detected. The hetero-chromatic staining method also permits discrimination between mouse and human chromosomes in somatic cell hybrids, thus facilitating the assignment of gene markers to chromosomes in somatic cell genetics systems. Instances of translocation of centric heterochromatin to other parts of chromosomes in established tissue culture cell lines are described. An instance of the inheritance of a polymorphic variation in autosomal heterochromatin in man is reported. It is postulated that polymorphisms in the centric heterochromatin may account largely for small heritable chromosome length variations previously described in human populations and termed minor chromosome variants.