Trisomy no. 15 in murine thymomas induced by chemical carcinogens, X-irradiation, and an endogenous murine leukemia virus.

Chromosome banding techniques were used to examine the karyotype of tumor cells from thymic lymphomas induced by three different carcinogens (X-irradiation, polycyclic aromatic hydrocarbons, and an endogenous leukemogenic virus) after injection into neonatal mice of 2 different inbred mouse strains (CFW/D and C57BL/Ka). A total of 89 tumors were studied, and of these 85.4% were characterized by a modal chromosome number of 41. The additional chromosome was the result of a specific abnormality identified as trisomy of chromosome no. 15. The results obtained were independent of the carcinogenic agents and the strain of mouse used. Of the 13 tumors found to have a normal chromosome complement, 4 were induced by X-irradiation and the remaining 9 by the chemical carcinogens. All 15 virus-induced tumors analyzed had a modal chromosome number of 41.

Trisomy 22 mosaicism syndrome and Ullrich-Turner stigmata.

Mosaic trisomy 22, ascertained in three unrelated patients, was found to be associated with body asymmetry and signs of the Ullrich-Turner syndrome including short stature, ptosis, webbed neck, nevi, cubitus valgus, dysplastic nails, malformed great vessels, and abnormal ovaries. These anomalies in trisomy 22 mosaicism have not been emphasized heretofore. In each of our patients, trisomy 22 mosaicism was found only in fibroblasts. In one patient, the trisomy resulted from a paternal first meiotic nondisjunction, and in the 46,XX cells, both chromosomes 22 were of paternal origin.

The clinical syndrome of triploidy.

The clinical syndrome associated with triploidy is quite typical but is rarely reported in near-term stillborns and newborns. The occurrence of a large placenta with areas of hydatidiform changes in combination with an edematous fetus with macroglossia, facial clefts, eye defects, dysplastic cranial bones, omphalocele, meningomyelocele, syndactyly, and, in males, genital maldevelopment is suggestive of a triploid chromosomal constitution.

Anterior segment mesenchymal dysgenesis associated with partial duplication of the short arm of chromosome 2.

We present a case of partial duplication of the short arm of chromosome 2 (karyotype 46,XX, dup [2p21-2p25]) in a newborn girl. The infant was born at 41 weeks of gestation and died approximately 3 hours after birth. At autopsy the characteristic dysmorphic features (hypertelorism, high, prominent forehead, micrognathia and low-set, malformed ears) and numerous other congenital malformations were observed. Bilateral microcornea with opacities was noted. Histopathological examination of the eyes showed dysgenesis of Bowman's membrane, with glycosaminoglycan deposition and a series of structural anomalies that form part of the anterior segment mesenchymal dysgenesis (ASMD) complex. To our knowledge this is the first case of partial duplication of the short arm of chromosome 2 in which the ocular histopathological features have been studied. Our case provides a further example of the association of ASMD with a chromosomal abnormality.

Cytogenetic practice in a mental retardation clinic.

Chromosome abnormalities are known to be associated with a wide variety of psychiatric disorders varying from severe mental retardation to aberrant social behaviour. Principles and methods used in contemporary cytogenetic laboratories are discussed and an attempt is made to illustrate how the integration of these techniques can be of considerable value for diagnostic and genetic counselling purposes.

Supernumary marker chromosomes in a mentally retarded population identified as inv dup(15).

Bisattelited supernumary chromosomes, identified as inv dup(15)s, were detected at a prevalence of 8/1000 among institutionalized, mentally retarded (non-Down syndrome) males. This finding suggests that the inv dup(15) contributes significantly to the etiology of mental retardation among institutionalized individuals.

The use of testicular volume as a clinical marker for cytogenetic disorders in mentally retarded males.

The testicular volumes (V) of 817 adult (non-Down's syndrome) institutionalized males were calculated. The mean testicular volume was 19.5 +/- 15.8 ml, comparable to the normal adult male mean of 17-19 ml. However, the number of institutionalized males with V greater than or equal to 25 ml and V less than or equal to 10 ml was increased approximately fourfold over the normal male population. Resident adult males were grouped into three categories based on their testicular volumes: (1) V greater than or equal to 25 ml (macro-orchid); (2) V less than or equal to 15 ml (micro-orchid); and (3) 15 less than V less than 25 ml ('normal'). An equal number of randomly selected males from each category were cytogenetically screened for the fra(X) syndrome as well as for non-fra(X) chromosome abnormalities. The overall frequencies of these disorders were 3.1% and 3.9%, respectively. The fra(X) syndrome was found in a significantly higher percentage of macro-orchid males (10.3%) as compared to males with either micro-orchidism (1.2%) or normal testicular volume (1.2%). There was no significant difference in the distribution of either fra(X) negative non-specific XLMR or non-fra(X) chromosome abnormalities among resident males from these three categories. Testicular volumes greater than or equal to 25 ml, especially those exceeding 40 ml, were thus shown to be useful clinical markers in the diagnosis of the fra(X) syndrome. Reduced testicular volume was not a useful clinical marker in the evaluation of other non-Down's syndrome chromosome abnormalities.

Human ETS2 gene on chromosome 21 is not rearranged in Alzheimer disease.

The human ETS2 gene, a member of the ETS gene family, with sequence homology with the retroviral ets sequence of the avian erythroblastosis retrovirus E26 is located on chromosome 21. Molecular genetic analysis of Down syndrome (DS) patients with partial trisomy 21 allowed us to reinforce the supposition that ETS2 may be a gene of the minimal DS genetic region. It was originally proposed that a duplication of a portion of the DS region represents the genetic basis of Alzheimer disease, a condition associated also with DS. No evidence of either rearrangements or duplications of ETS2 could be detected in DNA from fibroblasts and brain tissue of Alzheimer disease patients with either the sporadic or the familiar form of the disease. Thus, an altered ETS2 gene dosage does not seem to be a genetic cause or component of Alzheimer disease.

Prenatal diagnosis of 45,X/46,XY mosaicism in a fetus with asymmetric gonadal dysgenesis.

An 18 week abortus had been prenatally diagnosed as a 45,X/46,XY mosaic. The fetus was a phenotypic male with glandular hypospadias, a horseshoe kidney and asymmetric gonadal dysgenesis. This case represents a rare instance of prenatally diagnosed 45,X/46,XY mosaicism with an abnormal phenotype.

Gene expression and metastasis of somatic cell hybrids between murine fibroblast cell lines of different malignant potential.

We have used somatic cell hybrids to study the relationship between ras sensitivity, metastasis, and the expression of ras-responsive or "metastasis-associated" genes. We have previously shown that NIH 3T3 cells are nontumorigenic, but are made metastatic by transfection and expression of activated ras (i.e., they are ras-sensitive). LTA cells, however, are initially tumorigenic, but nonmetastatic, and are not altered in malignancy by ras (i.e., they are ras-resistant). We also have shown that patterns of expression of ras-responsive and "metastasis-associated" genes differ markedly between these two cell types. In the present work, we have constructed three sets of somatic cell hybrids: NIH 3T3 X LTA cells (designated NL), NIH 3T3 X ras-transfected LTA cells (designated NLR), and LTA X ras-transfected NIH 3T3 cells (designated LNR). In all three sets of cell hybrids, pooled clones were found to be highly metastatic in the chick embryo assay, suggesting complementation had occurred. Those cell hybrids that contained ras (NLR and LNR hybrids) were significantly more metastatic than those that did not (NL hybrids). Selected clones of low and high metastatic ability from both NL and LNR fusions were examined for tumorigenicity and "experimental" metastatic ability in nude mice, as well as for expression of several genes thought to be involved in ras-induced progression and malignancy. Patterns of expression of these genes showed a relationship to level of malignancy of the hybrids and demonstrated a responsiveness to the expression of activated ras. These results suggest that the complementation of phenotype observed in the hybrids may arise through a gene regulatory factor(s) supplied by the NIH 3T3- to the LTA-derived parent.

Choroideremia associated with an X-autosomal translocation.

A patient with mild choroideremia has been shown to carry a balanced translocation between chromosome X and 13-46,X,t(X;13)(q21.2;p12). Loci (DXY21, DX232, DX233) shown to map to this region on the X chromosome and in some cases to be deleted in other patients with choroideremia are intact in the DNA from this patient. To our knowledge this is the first report of a translocation associated with choroideremia. One of the translocation chromosomes, derivative 13, free of the derivative X and normal X, has been isolated in a somatic cell hybrid. Because of the clinical association of the eye findings with chromosome interchange, we suggest that the breakpoint on the X is at or near the choroideremia locus. Further analysis of this translocation may be useful in cloning the choroideremia gene.

Canadian multicenter randomized clinical trial of chorion villus sampling and amniocentesis. chromosome mosaicism in CVS and amniocentesis samples.

Data on 1040 chorionic villus and 969 amniotic fluid samples were collected from women studied in the Canadian Multicentre Randomized Clinical Trial of Chorion Villus Sampling and Amniocentesis. Cytogenetic results were obtained from 98.0 per cent of chorionic villus samples and from 99.9 per cent of amniotic fluid samples. Level I mosaicism (a single cell with an abnormal karyotype) occurred frequently in both chorionic villus and amniotic fluid samples and appeared to have no clinical significance. Level II mosaicism occurred in 0.9 per cent of CVS mesenchyme and 1.5 per cent of amniotic fluid cultures and in general was not perceived to be of sufficient concern to warrant cytogenetic follow-up studies. Level III mosaicism was reported in 18 CVS cases (15 cytotrophoblast, 1 mesenchyme, and 2 with both cell methods) and in one amniotic fluid case. In all cases but one (fetus with trisomy 18), level III mosaicism was confined to the placenta. Maternal cell contamination occurring with a frequency of 6.4 per cent in the mesenchyme analyses was a concern. This study supports the final report of the Canadian Multicentre Randomized Clinical Trial of Chorion Villus Sampling and Amniocentesis. Cytogenetic analysis of chorionic villus samples appears to be an acceptable alternative to the analysis of amniotic fluid samples. However, because of mosaicism and maternal cell contamination concerns, the examination of both cytotrophoblast preparations and mesenchyme cultures from chorionic villus samples is recommended.