Interferon effect on ribosomal ribonucleic acid related to chromosome 21 ploidy.

Antiviral and cell-growth-inhibitory activities of human interferon were shown to be related to the activity of a gene or genes present on chromosome 21. The 18s rRNA is vital to cell growth; it is capable of a viral-mRNA-recognition function and it is coded for by genes a portion of which are present on chromosome-21. A previously reported ability of human interferon to affect rRNA metabolism is characterized by a decrease in the sucrose-gradient-peak ratio of radiolabelled 28S to 18S rRNA in extracts from the cytoplasm of interferon-treated human fibroblasts. In the present report, interferon dose-response curves are presented demonstrating a direct relationship between a decrease in this ratio and interferon concentrations in the media. By using this virus-independent cytoplasmic rRNA assay, eight human fibroblast lines, differing in chromosome 21 ploidy, were tested for sensitivity to human interferon. Two monosomy-21, two euploid-21 and four trisomy-21 cell lines were tested. The monosomy-21 cell populations were significantly less sensitive to interferon than the other six cell types tested. Of the cell lines tested, the most sensitive, by a wide margin, was a trisomy-21 line. Trisomy-21 cell monolayer sensitivity, however, varied widely within the range from normal to supersensitive. These observations suggest that interferon's ability to affect rRNA metabolism is related to the activity of a gene or genes present on chromosome 21.     

The Chromosome Abnormality in Mongolism

In an examination of our present knowledge regarding chromosome anomalies in mongolism the anomalies of trisomy-21 (the commonest anomaly in association with mongolism), 13-15/21 translocation and 21-22/21 translocation were illustrated and discussed. The relatively uncommon chromosome translocations and chromosome mosaicisms found in association with mongolism have especial clinical importance. Translocation of either type may occur as an isolated finding in a mongoloid patient. However, the translocation chromosome is frequently also found in one of the phenotypically normal parents. This is associated with an increased incidence of mongolism in the offspring, though the actual risk figure is uncertain in view of the small number of families described to date. The occurrence of chromosome mosaicism in mongolism may be associated with incomplete manifestation of the syndrome, and the ultimate mental development in such patients has varied from normal to severely retarded in cases described in the literature.     

Distribution of extracellular matrix components in nuchal skin from fetuses carrying trisomy 18 and trisomy 21

We have investigated histologically the elevations of the skin in dorsal and lateral neck (nuchal) regions of human fetuses carrying karyotypes of trisomy 18 (Edwards' syndrome) and trisomy 21 (Down's syndrome). Cavities filled with interstitial fluid were found in the dermis, epidermal basement membrane and occasionally in the epidermis of trisomy-18 fetuses, but were not delineated by an epithelium or basement membrane as judged by the absence of immunostaining for laminin, collagen IV and collagen VII. Dilated vessels were also found at the interface between dermis and subcutis. Neither normal fetal skin nor that of trisomy-21 fetuses contained cavities or dilated vessels. In order to detect possible alterations of the extracellular matrix in trisomy-18 and trisomy-21 skin, the distribution of glycoproteins, glycosaminoglycans and proteoglycans was studied immunohistochemically. In trisomy-21 and control skin, the dermis stained intensely for fibronectin, whereas the subcutis reacted only weakly. In trisomy-18 skin, the stronger staining for fibronectin appeared in the subcutis, and the prevailing collagen type was collagen III, collagen type I being absent. In the skin of trisomy-21 fetuses, collagen VI was more irregularly arranged and densely packed, whereas collagen I was more widely spaced than in normal fetuses. More hyaluronan was present in the dermis and subcutis of trisomy-21 fetuses than in that of trisomy-18 and control fetuses. A correlation seems to exist between undelimited cavities and collagen III in trisomy-18 skin, and between hyaluronan and the specific arrangement of collagen in trisomy-21 skin.Abbreviations bm Basement membrane - ep epidermis - d dermis - sc subcutis - hf hair follicle - c capillary This article is dedicated to Professor Dr. Konrad Märkel on the occasion of his 70^th birthday     

A Service for Human Chromosome Studies in Saskatchewan

A service has been developed in Saskatchewan to make available the results of studies of human chromosomes, the material being forwarded to the laboratory by local transport facilities. During the first year of this project chromosome studies were requested for five doubtful cases of trisomy-21 (two were found to be normal) and for 20 definite cases of trisomy-21 in young patients (two had translocations but the parents of both these children had normal karyotypes). Eleven confirmed cases of Turner''s syndrome, two of Klinefelter''s syndrome, and one each of the D and E syndromes were also studied. The largest group for which studies were requested comprised 36 patients with mental retardation; only two abnormal karyotypes were encountered in this group.     

Chromosome Abnormalities in Patients with Syndactyly

Chromosome studies on 105 patients with syndactyly included two trisomy-21 mongols, a chromatin-positive boy with 47, XXY, a chromatin-negative short girl with 45,X0 and a boy with a familial D/D translocation. Chromosome patterns were normal in the other cases which included three patients with acrocephalosyndactyly and one patient with oro-facial-digital syndrome.The incidence of chromosome abnormalies was greater than expected since syndactyly of the fingers is uncommon in the chromosome disorders.This incidence may be related to the increased maternal age (mean: 29.4 years) of the syndactyly group compared to maternal age (mean: 26.64 years) of the control group although, paradoxically, four mothers of the five patients with chromosome abnormalities were young.     

Inherited pericentric inversion of Y-chromosome with trisomy 21. A case report

A 13-year-old boy with clinical features of Down syndrome was investigated. His karyotype was 47,X,inv(Y),+21. The proband's father and two elder brothers were also found to have the inv(Y). A spontaneous chromatid break was observed in the long arm of the X chromosome[? fra (X)] in 2% of the cells. The mother had two spontaneous abortions. This is the first case of trisomy-21 with inv(Y) in our population. This finding might be fortuitous. The frequency of inv(Y) in Down syndrome is not known.     

Variation in pattern and frequency of acrocentric association in normal and trisomy-21 individuals

Summary Chromosomally normal and trisomy-21 individuals were studied for the ability of their nucleolus-organising chromosomes to form satellite associations in G-banded lymphocyte metaphases. Two types of parameter, absolute association frequency and relative association frequency, were used. There was no significant difference between females and males or between Caucasoids and Mongoloids for either type of association parameter in the controls, nor was there significant correlation between age (17–40 years) and either type of parameter in the controls.The pattern of two chromosome associations is accounted for by two related models in both normal and trisomic individuals. These models imply that there is an extensive polymorphism for associating ability and that this ability may be zero in individual chromosomes. Homologous do not associate preferentially with each other. The absolute frequency of acrocentric association is lower in trisomy 21 individuals than disomic controls, but the relative involvement of chromosome 21 (after correction for the trisomic state) is higher than in the controls.     

Chromosome abnormalities in early chicken (Gallus domesticus) embryos

Chromosome studies were undertaken to determine if early embryonic mortality in chicken (Gallus domesticus) embryos is associated with chromosome aberrations. A rapid cytological technique was developed for screening large numbers of embryos for euploidy and aneuploidy. — Of 115 embryos examined, 6 or 5.2% had aberrant chromosome complements. All of these chromosome aberrations occurred in embryos that were phenotypically abnormal. Of 45 macroscopically abnormal embryos, 13.3 % were chromosomally aberrant. These included two cases of haploidy (A-Z), one case of trisomy-1, a case of trisomy-2 and two cases of triploidy (3A-ZZW and 3A-ZWW). — Possible modes of origin for euploid and aneuploid embryos are discussed and consideration given to the significance of these aberrations in relation to embryo viability, constancy of chromosome numbers and nucleolar organization.     

Partial trisomy 18q in a newborn with typical 18 trisomy phenotype

Summary This paper describes a case of partial trisomy of almost the entire long arm of chromosome 18 in a newborn with classic trisomy-18 phenotype, resulting from a de novo unbalanced 18q/21p translocation: karyotype: 46,XX,-21,t(18;21)(18qter18q11::21p1221qter). A review of the other reported cases of partial trisomy 18 suggests that a critical segment in chromosome 18, corresponding to bands q11-q12, might be responsible for most of the signs of trisomy 18, including failure to thrive and early death.     

Mosaicism for an additional partial chromosome 8: 46,XX/47,XX+der(8)(p21→qter)

Summary Report on mosaicism of an additional deleted chromosome 8 in a 12-year-old girl. She exhibits several typical but minor features of the trisomy-8 syndrome. Her IQ is 77 (Hawik).     

Multiple birth and Down's disease]

The frequency of twinning among newborns with Down's syndrome (2,11+/-0,6%)was significantly higher than in the general populaltion (0,73+/-0,3%). The increase in the rate of multiple births of children with trisomy-21 occurred due to almost three-fold excess in the frequency of dizygotic (discordant) twin pairs over the expected level. The increase in the frequency of dizygotic twins with Down's syndrome was explained by the combined effect of two independent factors: the increase in probability of dizgotic twins natality and the enhanced rate of children birth with trisomy-21, which depended on the increase in mother's age.     

Linkage analysis of autosomal dominant atrio ventricular canal defects: exclusion of chromosome 21

The association between trisomy 21 and a high incidence of atrioventricular canal defects (AVCDs) indicates that a locus on chromosome 21 is involved in this congenital heart defect. We have investigated whether a genetic locus on chromosome 21 is also involved in familial nonsyndromic AVCDs. Short tandem repeat polymorphisms (STRPs) from chromosome 21 were used for linkage analysis of a family having multiple members affected with AVCDs. In this family, the gene for AVCDs is transmitted as an autosomal dominant with incomplete penetrance. The affected family members are nonsyndromic and have normal karyotypes. Two-point and multipoint linkage analyses produced significantly negative LOD scores for all informative markers. A comparison of the overlapping exclusion distances obtained for each marker at LOD equal -2.0 with the 1000:1 consensus genetic map of the markers, excludes chromosome 21 as the genetic location for AVCDs in this family. The exclusion of chromosome 21 indicates that another gene, not located on chromosome 21, is involved in atrioventricular canal defect formation.     

Chromosome anomalies of infants dying during the perinatal period and premature newborn

Summary 363 samples of different tissues were taken for cultivation from 118 antepartum deaths, 85 intrapartum deaths and 112 newborn dying during the first days after delivery. Successful growth of culture was noticed in 48.2% (15.4%) of antepartum deaths; 71.8% of intrapartum deaths and 68.1% of newborn dying during the first days of life. Among the 22 antepartum deaths 3 (13.6%) infants were found to have anomalies of karyotype; among 61 intrapartum deaths 3 (4.9%) infants were found to have karyotype anomalies; and among 92 early neonatal deaths 6 ones (6.5%) had karyotype anomalies. The total frequency of chromosome anomalies among the infants dying during the perinatal period was 6.9%.The final result of cytogenetic investigation of 607 premature infants was that chromosome anomalies were found among 2.5%, that is 3.5 times as much, as in the general newborn population. Among the types of chromosome anomalies the main defects were anomalies in the system of sex chromosomes and trisomy-21, and that is the proof of the fact, that other types of anomalies, found in newborn populations lead to earlier lethality.     

Cytogenetic,FISH and DNA studies in 11 individuals from a family with two siblings with dup(21q) Down syndrome

A Spanish family has previously been described with two siblings with dup(21q) Down syndrome. The father has a normal karyotype. The mother has a microchromosome. Cytogenetic, fluorescence in situ hybridization and DNA studies have now been carried out on the family. Findings include that the mother has three different chromosome anomalies, viz. (1) a chromosome 22 with an unusual pericentromeric region that contains alphoid DNA from chromosomes 21/13 and chromosome 22, (2) an isochromosome 21p in the frequent cell line and (3) an isochromosome 21q in a rare second cell line. A possible explanation is that the mother developed from a zygote with trisomy 21 and that mitotic error in early development resulted in the formation of two cell lines with karyotypes of 47,XX,+i(21p) and 47,XX,+i(21q), respectively. The unusual chromosome 22 represents a hitherto undescribed chromosome anomaly and one possible explanation is a translocation of the short arms between chromosomes 21/13 and 22 in the ancestry of the family. The relationship between the unusual chromosome 22 and the isochromosome formation in the mother is not known. However, all three chromosome anomalies involve the alphoid DNA of chromosome 21/13, indicating that this is not a chance finding.     

A case of trisomy 22 with a probable Robertsonian translocation 21/22

Summary A 2-year-old girl with a probable trisomy-22 translocation is described. The principal clinical symptoms described by the authors who have reported cases with proved trisomy 22 are presented. A probable 46, XX,-21,+t(21q;22q) karyotype was established in the patient. The proband's clinical picture is compared with other trisomy 22 cases described in the literature. The incidence of this trisomy among the human population is discussed.     

Molecular and cytogenetic characterization of a de novo t(5p;21q) in a patient previously diagnosed as monosomy 21.

Genomic single-copy DNA fragments were used to characterize an undetected chromosome translocation in an individual whose metaphase chromosome analysis revealed apparent monosomy 21. Eight RFLPs detected by six probes were used to identify homologous sequences from chromosome 21 in DNA digests from the proband and her parents. These family studies showed that the proband was disomic for the distal region of 21q. Reverse banding and in situ hybridization of chromosome 21-specific probes to metaphase chromosomes from the proband revealed a de novo translocation with breakpoints at 5p13 or 14 and 21q11 or 21. In situ hybridization permitted orientation of the translocated portion of chromosome 21 on the derivative chromosome 5 and, in conjunction with molecular analysis and previous mapping studies, refined the physical map for the long arm of chromosome 21.     

Familial translocation t(10;21)(q22;q22)

Summary A family is described with a translocation t(10;21)(q22;q22) transmitted through three generations. This family was studied for the apparition of several miscarriages and two sisters with multiple malformations. Both children had a probably partial trisomy of chromosome 10 and a monosomy of chromosome 21 due to a maternal adjacent-2 meiotic segregation.     

Characterization of a familial small supernumerary marker chromosome in a patient with adult-onset tongue cancer

Cytogenetic analysis in peripheral blood lymphocytes of a 50-year-old female with tongue cancer showed the presence of one to three copies of a small supernumerary marker chromosome (sSMC) in a mosaic state. Family studies also revealed the marker in mosaic form in four (age <29 years) of eleven clinically normal individuals studied from her family of 16 individuals spanning three generations. Due to the extremely small size of the marker chromosome, identification by classical cytogenetics was not informative. Multicolor FISH followed by whole chromosome painting identified the marker as a derivative of chromosome 21. This is the first report of sSMC21 in an adult-onset tongue cancer patient and some of her family members with no clinical symptoms.     

Familial Down syndrome due to t(10;21) translocation: evidence that the Down phenotype is related to trisomy of a specific segment of chromosome 21.

This report deals with a reciprocal t(10;21) translocation which is observed in three generations of a family. Included are examples of the balanced translocation, adjacent-2 segregation producing three patients with trisomy of the distal long arm of chromosome 21 and the Down syndrome, and 3-1 disjunction producing trisomy of the proximal segment of chromosome 21 in a mildly mentally retarded boy without phenotypic features of the Down syndrome. These data provide evidence that the Down phenotype is attributable to trisomy of the distal long arm of chromosome 21.     

Placental mosaicism and intrauterine survival of trisomies 13 and 18.

Cytogenetic analysis of 14 placentas from live newborn infants or from terminated pregnancies with trisomies 13 and 18 revealed that all were mosaic. The mosaicism was confined to the cytotrophoblast and not detected in villous stroma, chorionic plate, or amnion. The percentage of cells with a normal karyotype varied from 12% to 100%, the average being 70%. No such confined mosaicism could be detected in 12 placentas of trisomy 21 fetuses. These findings suggest that a postzygotic loss of a trisomic chromosome in a progenitor cell of trophectoderm facilitates the intrauterine survival of trisomy-13 and -18 conceptuses. They also imply that it is placental function which determines the intrauterine survival and that the mother plays no active role in rejection of trisomic conceptions. The combination of both a pre- and post-zygotic cell division defect in viable trisomy-13 and -18 conceptions points to the possibility of a genetic predisposition to such events. The detection of only a diploid cell line in the cytotrophoblast of some pregnancies with trisomies 13 and 18 also suggests that direct preparation is unreliable for prenatal diagnosis of these trisomies on chorionic villi sampling and that long-term villous culture should be used.