The influence of inactive chromosomes on human development. Anomalous sex chromosome complements and the phenotype

Triple X syndrome: a review of the literature

The developmental and clinical aspects in the literature on triple X syndrome are reviewed. Prenatal diagnosis depends on karyotyping. The incidence is 1 of 1000 females. At birth, 47,XXX girls have a lower mean birth weight and a smaller head circumference. Triple X diagnosis was not suspected at birth. The maternal age seems to be increased. Toddlers with triple X syndrome show delayed language development. The youngest girls show accelerated growth until puberty. EEG abnormalities seem to be rather common. Many girls show motor-coordination problems and auditory-processing disorders are not rare. Scoliosis is probably more common in adolescent cases. The IQ levels are 20 points below that of controls, and verbal IQ is lowest. The girls struggle with low self-esteem and they need psychological, behavioural and educational support. They perform best in stable families. After leaving school they seem to feel better. In adults, premature ovarian failure seems to be more prevalent than in controls. MRIs of the brain seem to show decreased brain volumes. The 47,XXX women most often find jobs that reflect their performance abilities. Psychotic illness seems to be more prevalent in triple X adult women than in controls. Psychotic disorders respond well to psychotropic drugs. Triple X adults suffer more frequently from cyclothymic and labile personality traits. Research on triple X syndrome may yield more insight into brain and behaviour relations, developmental psychopathology, auditory-processing disorders, EEG disorders, personality and psychotic disorders, etc.

Early asymmetric IUGR and aneuploidy

OBJECTIVE

To determine the incidence of chromosomal abnormalities in fetuses with asymmetric growth retardation in the second and early third trimesters of pregnancy.

METHODS

From November 1989 to December 1993, 71 singleton pregnancies with asymmetrical growth retardation diagnosed at 15 to 35 weeks gestation had detailed ultrasonographic examination for structural malformations and fetal karyotyping done.

RESULTS

The fetal karyotype was abnormal in 7 (9.9%) of the cases. There were 19 growth retarded fetuses with concomitant structural defects. The incidence of chromosomal abnormalities in asymmetrical growth retarded fetuses with structural defects was 21% (4/19). The incidence of fetal aneuploidy in structurally normal fetuses with asymmetrical growth retardation detected before 23 weeks gestation was 20% (3/15); while for those presenting between 23-29 weeks gestation, no abnormal karyotypes were found.

CONCLUSION

Although more prospective data is needed, our data seems to suggest that fetal karyotyping may be unnecessary in structurally normal fetuses with early onset intrauterine growth retardation occurring between 23-29 weeks of gestation.

Root length, crown height, and root morphology in Turner syndrome

Root length, crown height, and root morphology were studied on intraoral and panoramic radiographs in 33 Turner syndrome patients aged 7.0-16.7 years, subdivided on the basis of karyotype. Thirty-three normal girls aged 10.2-16.4 years served as controls. In the 45X patients and, with the exception of a few teeth, also in the isochromosome and mosaic karyotypes, root length and crown height of incisors, canines, and premolars were significantly reduced. Some teeth showed altered crown-root proportions. Maxillary first premolars showed a significantly increased number of two-rooted and three-rooted variants. Mandibular premolars and molars had a complex root morphology, and a classification system was established including four premolar and six molar root types. Premolars had a significantly increased number of root components. Some of the variants, such as a molar-like second premolar, are apparently specific for these patients. On several first molars a radix entomolaris was identified. Two separate mesial and one or two separate distal roots were also frequently seen. Our investigation demonstrates that X-chromosome deficiency influences root formation.

Skeletal maturity, dental maturity, and eruption in young patients with Turner syndrome

A major problem for patients with Turner syndrome is their small body height. The rapid biotechnologic development has now made treatment with growth hormone possible at a larger scale. The aim of this investigation was to evaluate skeletal maturity, dental maturity, and eruption in a group of young patients before hormone therapy. The material comprised 33 patients aged 7-16.7 years. The skeletal maturity, as judged from hand radiographs, was on an average 2.3 years retarded (p < 0.001) and showed increasing retardation with increasing age. The dental maturity, assessed from the formation stages of the permanent teeth on panoramic radiographs, was accelerated, with a mean value of 1 year (p < 0.001). The timing of clinical eruption did not differ significantly from that of our reference material; the Turner girls were on an average 3.7 months ahead. Several patients had local eruption problems, especially in the maxillary lateral segments. It is suggested that disharmony between tooth size and arch size may contribute to this problem.

What causes the abnormal phenotype in a 49,XXXXY male?

The chromosome replication pattern of a man with 49,XXXXY was analyzed using 3H-thymidine and autoradiography as well as BrdU and acridine orange. The former technique showed a highly irregular replication pattern; the latter revealed one early replicating X chromosome, and the other three more or less asynchronously replicating. Two hypotheses seem to explain best the abnormal phenotype of males with an XXXXY sex chromosome constitution: The number of the always active regions (tip of Xp) and of the possibly always active regions (the Q-dark regions on both sides of the centromere) is increased from one to four. The replication pattern of the late-replicating X chromosomes is highly asynchronous, which might affect the phenotype. The possibility that more than one X chromosome might remain active in some cells, an even more abnormal and obviously deleterious situation, is still open.

Chromosome abnormalities in pupils attending ESN/M schools

One hundred and sixty six children attending educationally subnormal/mild (ESN/M) schools were karyotyped as part of a project investigating the aetiology of mild mental retardation. Nine had significant chromosome abnormalities. Five of six children identified during the survey had no dysmorphic features--47,XXY (two), 48,XXYY, 46,XX 15q-, and 46,XX,t(X;19). One dysmorphic boy had a balanced translocation--46,XY,t(3;15). Three were already known--47,XX+21 (two) and 46,XY, 14q+. We suggest that routine karyotyping of children with mild mental retardation be considered.

Chromosome studies of children with specific speech and language delay

Among 88 children with speech and language problems from whom chromosome results were obtained, four were identified with a chromosome anomaly. Three had sex chromosome aneuploidy and had developmental problems, particularly with articulation. The fourth child had low-grade trisomy 21 in blood, with minimal signs of Down's syndrome but with bilateral conductive hearing loss. It is suggested that delay in speech development is one facet of the developmental problems that may be significant in later behavioural problems in adolescent and adult males with X and Y aneuploidy.

A synopsis of the human Y chromosome

Phenotypic features and functions known to depend on the presence of the Y chromosome or the H-Y antigen are discussed in relation to structural anomalies of the Y chromosome and other abnormalities of sexual and somatic development. Recent knowledge about molecular organization of constitutive heterochromatin in relation to the human Y is presented. An attempt is made at assigning different functions, genes and DNA sequences to different regions of the Y chromosome.

X chromosome constitution and the human female phenotype

The correlations of abnormal X chromosome constitutions and the resulting phenotypes in the human female are reviewed. The following hypotheses put forward to explain these correlations are discussed in detail: (1) The damage is done before X inactivation; (2) An effect is exerted between reactivation of the X chromosome(s) and meiosis in oocytes; (3) A recessive gene(s) in hemizygous condition might be expressed in the cases in which the same X is active in all cells; (4) A change in the number of presumed active regions on the inactive X chromosomes might have an effect; (5) A position effect, in that the region Xq13-q27 has to be intact in both X chromosomes to allow normal development, may be responsible; (6) An effect during the period when cells with different inactivation patterns compete is a probability; (7) The original X inactivation may be neither regular nor random. The conclusion reached is that the phenotypic effects of a specific X chromosome aberration may be simultaneously exerted through different pathways (Tables 1 and 2). Hypotheses (2), (4), (5), and (6) are considered probable. Hypothesis (3) has been discarded, and there is very little evidence for hypotheses (1) and (7).

Follow-up 10 years later of 34 Klinefelter males with karyotype 47,XXY and 16 hypogonadal males with karyotype 46,XY

A 10-year follow-up study is reported of 50 hypogonadal males, 34 of whom had the karyotype 47,XXY and 16 karyotype 46,XY. The social class of the former group was significantly lower and the frequency of criminal behaviour higher when compared with the latter group and the Danish male population. The frequency of mental illness was higher in the Klinefelter males with karyotype 47,XXY than in the remainder. The aetiology and pathogenesis of deviant mental development in the patient population and various aspects of their treatment are discussed.

Chromosomal variants in mentally retarded and normal men

The possible phenotypic effect of chromosomal variants is as yet an unsolved problem. QM- and C-banded chromosomes of 100 male patients with idiopathic mental retardation were compared with chromosomes of 100 Royal Military College cadets, as controls. Increased size of 9qh seems to be a factor with possible negative effects. 9qh- was found to be more common in the control sample. Another variant found more often in the retarded subjects was 16qh-. Increased frequencies of Yq+ or small inversions in chromosomes 3 and 9 were not found in the retarded.

Psychiatric examination of all eight adult males with the karyotype 46,XX diagnosed in Denmark till 1976

Psychiatric examination has been made in all eight adult males with the karyotype 46,XX diagnosed in Denmark til 1976. Apart from emotional immaturity in most probands, no psychopathological traits were found, except in one who had neurotic symptoms. They were all of normal intelligence and socially well adjusted. All had male psychosexual orientation, but weak sexual libido and potency were found in the oldest probands. In several respects males with 46,XX differ from Klinefelter males with the karyotype 47,XXY, and the reasons for this are discussed.

Mitotic cycles in human cell strains with sex chromosomes aneuploidy

A persistence of the embryonic type of mitotic cycle was found in postnatal strains with aneuploidy of sex chromosomes (45,X; 47,XXX; 49,XXXXX; 47,XYY; 49,XXXXY). Life-span and proliferating activity of the strains did not differ from those of diploid postnatal cells.