Mitotic cycles in human cell strains with sex chromosomes aneuploidy

Detailed analysis of X chromosome inactivation in a 49,XXXXX pentasomy

Background

Pentasomy X (49,XXXXX) has been associated with a severe clinical condition, presumably resulting from failure or disruption of X chromosome inactivation. Here we report that some human X chromosomes from a patient with 49,XXXXX pentasomy were functionally active following isolation in inter-specific (human-rodent) cell hybrids. A comparison with cytogenetic and molecular findings provided evidence that more than one active X chromosome was likely to be present in the cells of this patient, accounting for her abnormal phenotype.

Results

5-bromodeoxyuridine (BrdU)-pulsed cultures showed different patterns among late replicating X chromosomes suggesting that their replication was asynchronic and likely to result in irregular inactivation. Genotyping of the proband and her mother identified four maternal and one paternal X chromosomes in the proband. It also identified the paternal X chromosome haplotype (P), indicating that origin of this X pentasomy resulted from two maternal, meiotic non-disjunctions. Analysis of the HUMANDREC region of the androgen receptor (AR) gene in the patient's mother showed a skewed inactivation pattern, while a similar analysis in the proband showed an active paternal X chromosome and preferentially inactivated X chromosomes carrying the 173 AR allele. Analyses of 33 cell hybrid cell lines selected in medium containing hypoxanthine, aminopterin and thymidine (HAT) allowed for the identification of three maternal X haplotypes (M1, M2 and MR) and showed that X chromosomes with the M1, M2 and P haplotypes were functionally active. In 27 cell hybrids in which more than one X haplotype were detected, analysis of X inactivation patterns provided evidence of preferential inactivation.

Conclusion

Our findings indicated that 12% of X chromosomes with the M1 haplotype, 43.5% of X chromosomes with the M2 haplotype, and 100% of the paternal X chromosome (with the P haplotype) were likely to be functionally active in the proband's cells, a finding indicating that disruption of X inactivation was associated to her severe phenotype.

Parental GM and HLA genotypes and reduced birth weight in patients with Turner's syndrome

We investigated a possible influence on birth weight in Turner's syndrome of many clinical, hormonal, genetic and immunogenetic variables. We considered 97 patients with Turner's syndrome. Patients with parents with identical GM (Gamma heavy chains Marker) phenotype had a significantly lower birth weight than those with parents with different GM phenotype. Karyotype other than 45,X, HLA (Human Leukocyte Antigen) parental sharing, mother-patient compatibility and elevated 17-hydroxyprogesterone (17OHP) serum level after adrenocorticotropin hormone (ACTH) and absence of heart and kidney malformations and lymphedema were associated with a lower birth weight, but not significantly. Multiple interactions showed that the presence of an identical GM phenotype in parents, together with other conditions (karyotype other than 45,X, adrenal dysfunction, HLA parental sharing, mother-child compatibility, KM(3) [Kappa light chains Marker] phenotype) resulted in a further decrease of birth weight. These data might suggest a negative effect of genetic similarity on intrauterine growth in Turner's syndrome.

Head circumference and IQ of children with sex chromosome abnormalities

At all ages XXX girls had significantly smaller head circumferences than control girls. Their IQ deficit was 24 points and IQ at age seven correlated significantly with head circumference at birth. In XXY boys, head circumference was significantly reduced at birth and up to nine years of age. The XXY boys' IQ deficit was 22 points, but IQ did not correlate with head circumference, as reductions in the two parameters did not always occur in tandem. The ratio of height-to-head circumference differed most in this group and could be useful in clinical recognition of this condition. XYY boys' head size did not differ from controls, despite their greater height, lower IQ scores indicating an adverse effect of an additional Y chromosome on brain development. The major factor affecting IQ outcome in the cohort was abnormal karyotype, with smaller effects from social class and head growth.

The growth of XXX females: population-based studies

Longitudinal measurements of height, sitting height and leg length are compared between 11 XXX girls identified by cytogenetic screening, and 16 chromosomally normal controls from the same population using a nonparametric method. While height velocity did not differ between the two groups either during the pubertal or the mid-childhood spurts, leg length velocity was significantly increased during the mid-childhood spurt, between 4 and 9 years of age. A further contribution to the increased leg length came from the slower decline in leg length velocity at the end of the pubertal spurt. The possible mechanisms involved in these changes are discussed.

Mosaicism in 45,X Turner syndrome: does survival in early pregnancy depend on the presence of two sex chromosomes?

Cytogenetic and molecular genetic findings in 91 patients with Turner syndrome are reported. In 87 patients, chromosome studies were carried out both in lymphocyte and fibroblast cultures. Mosaicism was demonstrated in 58 of these patients (66.7%), whereas only 18 (20.7%) were apparent non-mosaic 45,X, and 11 patients (12.6%) showed non-mosaic structural aberrations of the X chromosome. Among the mosaic cases 16 (18.4% of all patients) displayed a second cell line containing small marker chromosomes. The association of Y-specific chromosomal material with the presence of marker chromosomes was demonstrated in 6 out of 7 mixoploid fibroblast cell lines by polymerase chain reaction amplification and by Southern-blot analysis. The observation of ring formation and morphological variability in vivo and in vitro, and the continuous reduction in the percentage of cells containing marker chromosomes in longterm cultivation experiments indicated an increased instability of marker chromosomes. The findings suggest that in vivo selection of structurally altered sex chromosomes exists. Thus, the observation of apparent non-mosaic 45,X chromosomal complements in liveborn individuals with Turner syndrome does not contradict the hypothesis that some degree of mosaicism is necessary for survival in early pregnancy.

Effect of sex chromosome aneuploidy on growth of human skin fibroblasts in cell culture

Growth of human skin fibroblast lines with sex chromosome aneuploidy was studied in cell culture. Two lines were derived from individuals with 45,X and two from individuals with 47,XYY chromosome constitution. The aneuploid cell lines were compared with normal skin fibroblasts derived from age-matched same-sex siblings. To ensure similar conditions in culture, each study-control pair was treated simultaneously and equally in all steps. Growth in both 45,X cell cultures slowed down earlier than in control cultures. One of the 47,XYY cultures grew faster and the other at a similar speed to the control culture. Thus, the 45,X cell lines seemed to have lesser, and one of the 47,XYY cell lines greater, growth potential than the 46,XX and 46,XY cells, respectively. These differences in the final cell numbers may relate to changes in the rate of cell division of the aneuploid cell lines. However, the results do not support the hypothesis that an increasing number of sex chromosomes decreases the rate of cell division.

Growth disadvantage of 45,X and 46,X,del(X)(p11) fibroblasts

We have previously shown that cell generation time (CGT) is prolonged in 45,X and certain X-deletion fibroblast lines (Simpson & Le Beau 1981). A consequence of that finding should be that cells with 45,X or an X-structural abnormality are at a competitive disadvantage when cocultivated with 46,XX cells. To test this hypothesis we prepared 15 minutes of cells from combinations of 9 different cell lines: four 45,X; one 46,Xdel(X)(p11); and four 46,XX. Each culture was monitored cytogenetically at frequent passage intervals for the percentage of the two cell lines. Significant differences were found between normal and abnormal lines in culture predominance, in the order predicted by our hypothesis (p less than 0.01). The specific mechanism by which absence of an X chromosome confers growth disadvantage is unknown, but is consistent with prolongation of CGT. Prolongation of CGT could also be responsible for the embryonic lethality, intrauterine growth retardation, short stature, and somatic anomalies commonly observed in individuals with absent or aberrant X chromosomes.

Introduction to the study of pre- and postnatal growth in humans: a review

This review is divided in several items. A brief introduction on the characterization of the growth processes is made; the ways of assessing fetal development and well-being, the factors acting on fetal growth and birth weight, the causes and post-natal consequences of prematurity and intrauterine growth retardation are discussed in the first part. The following items deal mainly with: the normal pattern of growth from birth to puberty according to sex, race, and nutritional status, with special mention to pubertal changes; methods for predicting adult height from skeletal age; the effect of hormones during pre- and post-natal life; and the genetics of adult stature. The remainder of this review deals with genetic causes of growth abnormalities. Constitutional delay of growth, familial short stature, hypothalamic-pituitary dwarfism, skeletal dysplasias and many genetic syndromes presenting intrauterine growth retardation are listed. Aneuploidy effects on human growth are extensively reviewed, and usual growth patterns in Down and Ullrich-Turner syndrome patients as well as other sex aneuploid individuals and mosaics are fully described. The influences of X and Y chromosomes on growth and maturation are also discussed. Finally, some remarks are made about overgrowth syndromes.

Disturbances in collagen synthesis in trisomic cells from spontaneously aborted embryos

Collagen synthesis in cells with trisomy 7 and 9 derived from human spontaneous abortuses was found to be lower (5.06% and 5.53% respectively) than in the control diploid cells (8.80%). The ratio of collagen types (I/III) in trisomic strains did not differ from the control data while the amount of the degraded procollagen in trisomic cells was increased.

Replication variants of the human inactive X chromosome. I. Variability within lymphocytes of single individuals

The sequence of DNA replication was studied within the inactive X chromosome in human lymphocytes, by means of the FPG method. Several variants of the replication sequence were found. The number of variants in the cells of a single donor exceeded 2 in each of the 4 normal individuals studied. The phenomenon is discussed with respect to the regulation of DNA synthesis and to the cell differentiation process.

Gonadal and statural determinants on the X chromosome and their relationship to in vitro studies showing prolonged cell cycles in 45,X; 46,X,del(X)(p11); 46,X,del(X)(q13); and 46,X,del(X)(q22) fibroblasts

Correlation of clinical features with cytogenetic abnormalities for individuals showing deletions of the X short arm (Xp) or the X long arm (Xq) indicate the following: (1) both Xp and Xq are necessary to assure normal ovarian development, although (2) persisting ovarian function is not infrequently associated with either (del(X)(p11) or del(Xq)(13,21,22, or 24). (3) Ovarian determinants on Xp are localized to region Xp11, but determinants on Xq cannot be precisely localized. (4) Both Xp and Xq contain statural determinants, the former localized to region Xp21 leads to Xpter. Both cell generation time and phases of the cell cycle were studied to test the hypothesis that the short stature, intrauterine growth retardation, and high embryonic lethality of 45,X can be explained on the basis of intrinsic retardation of cell division (i.e., prolonged cell cycle). Cell generation times of four 45,X fibroblast lines were significantly longer than those of for normal diploid lines, a difference accounted for by a prolonged S phase. 46,X,del(X)(p11), 46,X,del(X)(q13), and 46,X,del(X)(q22) lines also showed increased cell generation times when compared to 46,XX lines.

Effects of chromosome constitution on growth and longevity of human skin fibroblast cultures

Employing standardized cell-culture methods, 10 euploid and 22 constitutionally aneuploid human skin fibroblast strains were assessed in triplicate for total growth potential, growth rates, population-doubling times, and cloning. In addition, longitudinal growth rate studies were carried out with otherwise isogenic 45,X and 47,XXX clonal cultures derived from a mosaic parental strain. Growth rates and longevities were cell-strain specific and highly reproducible among sister cultures of a given strain. There was no systematic correlation between chromosome constitution and any of the measured growth parameters. Trisomic as well as monosomic strains showed the same degree of variability with respect to these parameters as did euploid cultures. In particular, 4 trisomy 21 strains were not unusually short-lived, nor were clones with the 47,XXX constitution compared to those with 45,X karyotypes. We therefore conclude that the cumulative number of in vitro doublings preceding senescence of fibroblast-like cells cultured from skin does not differ significantly among cultures derived from humans who have a normal karyotype, trisomy 13, 18, or 21, the 45,X constitution, or various combinations of extra X and Y chromosomes.