Size and pericentric inversion heteromorphisms of secondary constriction regions (h) of chromosomes 1, 9, and 16 as detected by CBG technique in Caucasians: Classification,frequencies, and incidence

Eighty normal Caucasians were studied by CBG technique for estimation of size and inversion heteromorphisms of chromosomes 1, 9, and 16. Size heteromorphisms were classified into one of five sizes using 16p as a reference standard: very small, small, intermediate, large, and very large. Inversion heteromorphisms were also classified into 5 categories – eg, no inversion; partial inversion – minor; half inversion; partial inversion – major; and complete inversion. The frequencies of size heteromorphisms for chromosomes 1, 9, and 16 were 11.3%, 47.5%, and 7.5%, respectively. Thirty-four chromosomes were found to have inversions. Of these, 16 were in chromosome 1, and 18 were in chromosome 9. No inversions were found in chromosome 16. An increase in the size of the h region was more frequently associated with inversion, suggesting that there is a possible relationship between size and inversion. For example, there were 118 chromosomes that were classified as “intermediate” by size; 23 (19.5%) had inversions. In contrast, there were 225 that were “small” in size, and only 10 (4.4%) had inversions. There was no significant difference between males and females for size and position heteromorphisms.     

Size and pericentric inversion heteromorphisms of secondary constriction regions (h) of chromosomes 1, 9, and 16 as detected by CBG technique in Caucasians: classification, frequencies, and incidence.

Eighty normal Caucasians were studied by CBG technique for estimation of size and inversion heteromorphisms of chromosomes 1, 9, and 16. Size heteromorphisms were classified into one of five sizes using 16p as a reference standard: very small, small, intermediate, large, and very large. Inversion heteromorphisms were also classified into 5 categories - eg, no inversion; partial inversion - minor; half inversion; partial inversion - major; and complete inversion. The frequencies of size heteromorphisms for chromosomes 1, 9, and 16 were 11.3%, 47.5%, and 7.5%, respectively. Thirty-four chromosomes were found to have inversions. Of these, 16 were in chromosome 1, and 18 were in chromosome 9. No inversions were found in chromosome 16. An increase in the size of the h region was more frequently associated with inversion, suggesting that there is a possible relationship between size and inversion. For example, there were 118 chromosomes that were classified as "intermediate" by size; 23 (19.5%) had inversions. In contrast, there were 225 that were "small" in size, and only 10 (4.4%) had inversions. There was no significant difference between males and females for size and position heteromorphisms.     

C-band heteromorphism in breast cancer patients

The pattern of heteromorphism in the C-band-positive constitutive heterochromatin of human chromosomes #1, #9, and #16 was studied in peripheral lymphocytes of 54 breast cancer patients and 78 control individuals. The parameters of the heterochromatic regions analyzed were relative size, symmetry-asymmetry within homologous pairs, and prevalence of inversions. Significant differences between the two groups were found in C-band size of chromosomes #1, #9, and #16 and in incidence of inversions on chromosomes #1 and #9. Significant differences were noted between premenopausal and postmenopausal cancer patients in regard to inversions on chromosome #9 and between familial and sporadic patients in regard to C-band size on chromosome #16.     

Constitutive heterochromatin C-band polymorphism in prostatic cancer

The size of the heterochromatin C-bands on chromosomes has been reported to be associated with some, but by no means all, human malignancies. No studies along these lines have been performed in prostatic cancer. We therefore investigated the size, incidence of inversions, and symmetry versus asymmetry of C-band heteromorphisms on chromosomes 1, 9, and 16 in peripheral blood lymphocytes from 52 prostatic cancer patients and 183 healthy individuals. There were no differences in C-band heteromorphism on chromosomes 1, 9, and 16 between the patients and the controls. Neither were there any differences when patients with early-stage disease were compared with patients with more advanced cancer. Younger (aged less than 70 years) cancer patients had significantly higher frequencies of larger C-bands on chromosomes 1 (p less than 0.01) and 16 (p less than 0.001) than did patients aged more than 70 years at diagnosis. This could indicate a possible relationship between the amount of constitutive heterochromatin on chromosomes 1 and 16 and susceptibility to early development of prostatic cancer but could also result from the age differences between the two patient groups.     

C-band pattern in lymphocytes of patients with soft tissue sarcomas

The pattern of heteromorphisms in the C-band-positive constitutive heterochromatin of human chromosomes No. 1, 9, and 16 was studied in peripheral lymphocytes of 45 patients with soft tissue sarcomas and 78 control individuals. The parameters of the heterochromatic regions analyzed were relative size, symmetry-asymmetry within homologous pairs, and incidence of inversions. No consistent differences were found in these parameters between controls and sarcoma patients.     

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.     

Human chromosomal heteromorphisms in American blacks. VI. Higher incidence of longer Y owing to non-fluorescent (nf) segment.

Sixty normal male American blacks were selected to study the length of fluorescent (f), non-fluorescent (nf), and total length of the Y chromosome by the QFQ technique. The length of the Y chromosome was classified into five groups: very small, small, average, large, and very large. The frequencies of Y/F indices for these groups were 0.0, 3.33, 56.67, 30.00, and 10.00%, respectively. The variation in the total length of the Y chromosome was accounted for by variations in the length of the nf as well as the f segment. A longer Y was noted in blacks owing to an increase in size of the nf segment in comparison with a normal Caucasian population. Forty percent of American blacks had large or very large Y chromosomes, while this class comprised only 18.3% of Caucasians, which is significantly different (p less than 0.05). Furthermore, the length of the Y chromosome was normally distributed among Caucasians, while among blacks the distribution was skewed to the left. The mean Y/F, f/F, and nf/F indices were 1.09 +/- 0.10, 0.42 +/- 0.09, and 0.67 +/- 0.04, respectively.     

Breakpoints in alpha, beta, and satellite III DNA sequences of chromosome 9 result in a variety of pericentric inversions.

Human chromosome 9 with a pericentric inversion involving the qh region is considered normal. It has probably evolved through breakage and reunion and is retained through mendelian inheritance without any apparent phenotypic consequences. Fluorescent in situ hybridisation (FISH) technique using alpha, beta, and satellite III DNA probes showed that the breakpoints are variable and can be localised in the alpha or in the satellite III and beta DNA regions or both. Three types of inversions are proposed which appear similar by CBG banding: pericentric inversions with two alphoid, one beta, and one satellite III hybridisation signals were classified as type A. Type B were those with two beta, one alpha, and one satellite III hybridisation signals, while type C was complex, and most likely involved two inversions, since two separate hybridisation signals were detected in each of the alphoid, beta satellite, and satellite III DNA regions. Based on eight cases, type A is likely to be the most frequent, but the frequencies, which at present appear non-random for these different types of inversions in the population, can only be estimated by studying a larger sample size. Inversion heteromorphisms may promote reshuffling of tandem arrays of DNA repeat sequences, thereby giving rise to new heteromorphic domains. Alternatively, the repetitive nature of the sequences lends to the structural variations observed within the inv(9) chromosomes (or any other abnormal chromosome that is the result of recombination between, or breakage within, repetitive DNA).     

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 less than 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.     

Chromosomal polymorphisms of 1, 9, 16, and Y in 4 major ethnic groups: a large prenatal study

Using trypsin Giemsa banding (GTG), major polymorphisms of the constitutive heterochromatin regions of chromosome 1, 9, 16, and Y were recorded in a New York City population. Polymorphisms were recorded from amniotic fluid specimens received from 6,250 patients from 4 major population groups, ie, White (European)-2,334 cases, American Black-1,795 cases, Hispanic descent-1,737 cases, and Asian (Oriental and Indian)-384 cases. The major chromosomal polymorphisms were classified as follows: obvious pericentric inversion of the constitutive heterochromatin of the long arm of the chromosome (inv qh); significantly enlarged heterochromatic region of the long arm (qh + is greater than, or equal to, twice the size of the short arm of chromosome 16 [16p]); very small or deficient heterochromatic region in the long arm (qh-); large Y (Yq + greater than size of chromosome 18), small Y (Yq- less than size of a G-group chromosome), and pericentric inversion of Y. Our prenatal study confirmed that the incidence of specific chromosomal variants is different in each population group. The most striking examples of this are the pericentric inversion of chromosome 9 and the different polymorphisms of the Y chromosome. The incidence of inv (9) is highest in the Black population (3.57%); slightly above average in Hispanics (2.42%); and relatively low in Whites (0.73%) and Asians (0.26%). The Y appears to be more variable in Asian (3.37%) and Hispanic (1.82%) than in White or Black groups. The 9qh+ is seen more frequently than 1qh+, or 16qh+. Inv (1), 9qh-, and 16qh- are rare. There were no cases of either 1qh- or inv (16).(ABSTRACT TRUNCATED AT 250 WORDS)     

Meiotic segregation analysis in spermatozoa of pericentric inversion carriers using fluorescence in-situ hybridization

BACKGROUND: Pericentric inversions are structural chromosomal abnormalities resulting from two breaks, one on either side of the centromere, within the same chromosome, followed by 180 degrees rotation and reunion of the inverted segment. They can perturb spermatogenesis and lead to the production of unbalanced gametes through the formation of an inversion loop. METHODS: We report here the analysis of the meiotic segregation in spermatozoa from six pericentric inversion carriers by multicolour fluorescence in-situ hybridization (FISH) and review the literature. RESULTS: The frequencies of the non-recombinant products (inversion or normal chromosomes) were 80% for the inv(20), 91.41% for the inv(12), 99.43% for the inv(2), 68.12% for the inv(1), 97% for the inv(8)(p12q21) and 60.94% for the inv(8)(p12q24.1). The meiotic segregation of 20 pericentric inversions (including ours) is now available. The frequency of unbalanced spermatozoa varies from 0 to 37.85%. The probability of a crossover within the inverted segment is affected by the chromosome and region involved, the length of the inverted segment and the location of the breakpoints. CONCLUSIONS: No recombinant chromosomes were produced when the inverted segment involved <30% of the chromosome length (independent of the size of the inverted segment). Between 30 and 50%, few recombinant chromosomes were produced, inducing a slightly increased risk of aneusomy of recombination in the offspring. The risk of aneusomy became very important when the inverted segment was >50% of the chromosome length. Studies on spermatozoa from inversion carriers help in the comprehension of the mechanisms of meiotic segregation. They should be integrated in the genetic exploration of the infertile men to give them a personalized risk assessment of unbalanced spermatozoa.     

Human chromosomes with shorter telomeres and large heterochromatin regions have a higher frequency of acquired somatic cell aneuploidy

Both telomere shortening and increases in aneuploidy frequencies have been associated with aging. To test if these chromosomal attributes are correlated, chromosome-specific telomere lengths and aneuploidy frequencies were estimated and compared. Aneuploidy frequencies were determined for 10 autosomes (1, 3, 5, 8, 9, 10, 13, 16, 17, 21) and the X chromosome in lymphocytes, and for chromosomes 17 and X in buccal mucosa cells. Overall, chromosomal loss was seen more often than gain in lymphocytes, with the highest loss rates being observed for chromosomes X (3.03%), 17 (2.00%), and the autosomes having large blocks of heterochromatin (1 [1.93%]; 16 [1.53%]; and 9 [1.05%]). The frequencies of loss were significantly lower in the buccal mucosa cells compared to lymphocytes for chromosomes 17 (P = 0.006) and X (P = 0.003). However, the chromosome 17 trisomy frequencies did not vary between tissues. Using a semi-quantitative FISH assay to estimate chromosome-specific telomere length, a significant negative correlation (r = -0.379; P = 0.007) was seen for chromosomal aneuploidy and telomere length, with chromosomes having higher loss rates being noted to have shorter telomeres. Collectively, these studies show that acquired, spontaneous chromosomal loss is associated with multiple factors including the amount of heterochromatin, the chromosome's telomere length, and tissue-specific factors.     

Heterochromatic variants and their association with neoplasias. II. Preleukemic states

A study of the heteromorphism of chromosomes #1, #9, and #16 was performed in the cells of 55 normal subjects and in those of 40 preleukemic patients including those with refractory anemia (RA) and sideroblastic anemia (SA), classified on the basis of the FAB nomenclature. Heteromorphism was present in 85% of the preleukemic patients, compared with 44% in normal controls (p less than 0.01). The patient population presented an increased incidence of C-band size variants in chromosome #1 (1qh+ and 1qh-), while chromosomes #9 and #16 showed no difference, compared with the findings in the control group.     

Ethnic distribution of primary central nervous system tumors in Washington, DC, 1971 to 1985.

An ethnic analysis was made of 8947 cases of primary central nervous system (CNS) tumors seen at the Armed Forces Institute of Pathology (AFIP), Washington, DC, from 1971 to 1985. Results showed a slightly higher frequency of primary CNS tumors in whites than in blacks with a white:black case ratio of 9:1 against the white:black population ratio in the United States of 7.4:1. Gliomas appeared to be twofold more frequent in whites than in blacks with a white:black case ratio of 12.1:1. However, meningiomas and pituitary adenomas were more common in blacks with a white:black case ratio of 6.7:1 and 4.2:1, respectively. When these results were compared with the results of a previous identical study using similar materials collected at AFIP from 1958 to 1970, the relative paucity of gliomas and higher frequency of meningiomas and pituitary adenomas in American blacks is again confirmed, thus re-emphasizing the importance of genetic factors in the genesis of primary CNS tumors. The remarkable decreasing white:black case ratio of primary CNS tumors as a whole (9:1 compared with 13.7:1) since 1970 probably reflects the socioeconomic improvement of American blacks during the same period.     

C-band polymorphism: Comparison between trisomy 21 cases and mentally retarded controls

C-banding was done prospectively on 50 Down syndrome (trisomy 21) cases and 50 mentally retarded controls. Heterochromatin was quantitated by measuring the lengths of heterochromatin blocks and comparing these segments to the length of the short arm of chromosome 16 for 1, 9 and 16 heterochromatin, and to the total length of the Y chromosome for the Y heterochromatin in the distal long arm. For the first 30 individuals in each group, there was no difference in the mean lengths of C-band blocks of the 1, 9, 16 and Y chromosomes. For the total sample, there also was no difference between the trisomy 21 cases and controls in the number or size of pericentric inversions involving the heterochromatin blocks of chromosomes 1 and 9. Assuming random segregation of the parental C-band polymorphisms, this study gives no evidence for an association between such polymorphisms of the 1, 9, 16 and Y chromosomes and nondisjunction of chromosome 21.     

Racial differences in the relaxation response of hypertensives.

Racial differences in the relaxation response of hypertensives maintained on diuretic were investigated by comparing blood pressure, muscle tension, and hand temperature changes occurring with biofeedback assisted relaxation. Resting blood pressures were not different in blacks compared with whites. Both black and white subjects decreased diastolic blood pressure significantly from baseline values, but only whites significantly decreased systolic blood pressure. Though both blacks and whites significantly decreased forehead muscle tension, black subjects showed no changes in finger temperature while whites increased temperature significantly. The lack of change in finger temperature in blacks may be a reflection of the increased peripheral resistance previously associated with the greater incidence of hypertension in the American black population.     

Evidence for large inversion polymorphisms in the human genome from HapMap data

Knowledge about structural variation in the human genome has grown tremendously in the past few years. However, inversions represent a class of structural variation that remains difficult to detect. We present a statistical method to identify large inversion polymorphisms using unusual Linkage Disequilibrium (LD) patterns from high-density SNP data. The method is designed to detect chromosomal segments that are inverted (in a majority of the chromosomes) in a population with respect to the reference human genome sequence. We demonstrate the power of this method to detect such inversion polymorphisms through simulations done using the HapMap data. Application of this method to the data from the first phase of the International HapMap project resulted in 176 candidate inversions ranging from 200 kb to several megabases in length. Our predicted inversions include an 800-kb polymorphic inversion at 7p22, a 1.1-Mb inversion at 16p12, and a novel 1.2-Mb inversion on chromosome 10 that is supported by the presence of two discordant fosmids. Analysis of the genomic sequence around inversion breakpoints showed that 11 predicted inversions are flanked by pairs of highly homologous repeats in the inverted orientation. In addition, for three candidate inversions, the inverted orientation is represented in the Celera genome assembly. Although the power of our method to detect inversions is restricted because of inherently noisy LD patterns in population data, inversions predicted by our method represent strong candidates for experimental validation and analysis.     

Cytogenetics of laboratory colonies of simulium vittatum cytospecies IS-7 (Diptera: Simuliidae)

Laboratory colonies of the black fly Simulium vittatum Zetterstedt cytospecies IS-7 were analyzed cytogenetically and compared with the original New York population from which source material was collected 18 yr earlier. All sex chromosomes and major autosomal polymorphisms that were present in the source population were still represented in the laboratory colonies. However, the extent of sex linkage and the frequencies of four of the five major autosomal inversions changed significantly in at least one colony, perhaps because of bottlenecks experienced by the colony. A complete absence of males homozygous for the IS-7 inversion in both field and colony material is explained by postulating that the Y2 chromosome, representing the inverted condition for the IS-7 sequence, is absent from the population or acts as a rare reproductive lethal. This example possibly represents pseudo-partial sex linkage involving the X-linked sequences.     

Estimation of aneuploidy for chromosomes 3, 7, 16, X and Y in spermatozoa from 10 normospermic men using fluorescence in-situ hybridization

Fluorescence in-situ hybridization (FISH) is a fast and efficient method of estimating aneuploidy in human spermatozoa. In this study, we have estimated baseline disomy frequencies in spermatozoa from a group of 10 normospermic men, using stringent scoring criteria. A triple- probe FISH procedure was used for chromosomes 3, X and Y, while a double-probe FISH method was used for chromosomes 7 and 16. A total of 101273 spermatozoa were scored for chromosomes 3, X and Y, resulting in 97.83% haploidy (3X or 3Y), 0.39% disomy (33X, 33Y, 3XX, 3YY or 3XY) and 0.35% diploidy (33XX, 33YY or 33XY). A total of 100760 spermatozoa were scored for chromosomes 7 and 16, giving 98.9% haploidy (716), 0.11% disomy (7716 or 71616) and 0.27% diploidy (771616). Disomy frequencies for individual chromosomes differed (chromosome 3, 0.20%; chromosome 7, 0.05%, chromosome 16, 0.06%; X + Y, 0.19%). The frequency of disomy 3 was significantly higher than disomy 7 (P = 0.019) and disomy 16 (P = 0.022), while the frequency of sex chromosome disomy was significantly higher than disomy 7 (P = 0.0058) and disomy 16 (P = 0.0067), but not disomy 3 (P = 0.73). The disomy and diploidy (0.27- 0.35%) estimates obtained for this normospermic population were generally low and were similar to other recent reports.      

Apparent transmission distortion of a pericentric chromosome one inversion in a large multi-generation pedigree

Pericentric chromosome inversions are often associated with infertility, recurrent pregnancy loss, and an increased risk for offspring with congenital anomalies. We report on a chromosome 1 inversion between 1p36.21 and 1q42.13, one of the largest described familial pericentric inversions of chromosome 1. The inversion was ascertained following the birth of a female with multiple congenital anomalies due to a recombinant chromosome 1. The inversion was subsequently detected or inferred in 16 healthy individuals over five generations. Interestingly, with a ratio of 16 carriers to 6 noncarriers, there appears to be transmission distortion of the inverted chromosome 1 within the family. Although there is no reported difficulty conceiving in the family, the risk of miscarriage is higher than predicted at 34% (13/38). The recurrence risk of a recombinant chromosome also appears to be lower than expected based on the mode of ascertainment. This case contributes to the spectrum of clinical features of chromosome 1 recombinants and raises the question of whether or not there is a selective advantage of the inverted chromosome at meiosis, conception, or post-zygotically that has contributed to transmission distortion of the inverted chromosome.