Trisomy 8 mosaicism: a further five cases illustrating marked clinical and cytogenetic variability.

Trisomy 8 mosaicism is extremely variable in its phenotypic and cytogenic expression. We present five patients clearly demonstrating the lack of correlation between clinical and laboratory findings, and show that the aneuploid cell lines decreases with time in relation to the normal. This poses a counseling dilemma.

Presence of Y chromosome sequences and their effect on the phenotype of six patients with Y chromosome anomalies.

The extent of Y chromosome material was determined in 6 southern African subjects with sex chromosome anomalies. Four of the subjects were phenotypically female, and 2 were phenotypically male. Molecular and cytogenetic findings were correlated with phenotypic expression. An X;Y translocation was found in both male subjects, and in one female subject. The remaining female subjects were characterized by an isodicentric Y, an isochromosome Yq, and a micromarker of undetermined origin, respectively. The individuals were tested for the presence of a number of Y-specific DNA sequences. Molecular findings were generally compatible with the cytogenetic findings, and also with the phenotypic sex of the patients. All the female subjects had Y material and all but one were negative for the sex determining region of the Y (SRY). The somatic Ullrich-Turner-like findings present in 3 of the females were attributed to either the presence of a 45,X cell line and/or a single copy of Xp. The males both showed X;Y translocations without any detectable loss of Y DNA. Although molecularly very similar, the disparate clinical findings in these 2 subjects could have been accounted for by different X inactivation patterns.

Comparative study of Fanconi anemia in children of different ethnic origin in South Africa.

A comparative study of clinical, hematologic, and cytogenetic findings was made in 40 black and 35 white children with Fanconi anemia. The black children were Bantu-speaking Negroid stock of diverse tribal origin. The white children were predominantly Afrikaans stock of Dutch/German/French Huguenot origin. All of the patients had IFAR scores of 2 to 4+ and over 80% in each group had increased spontaneous and/or mutagen-induced chromosomal breakage (CB-positive). There were no significant clinical differences between black and white patients or between CB-pos and CB-neg patients, with the exception of white children in whom significantly more CB-pos patients had thumb and radial anomalies than the CB-neg patients. The age-at-onset of hematologic manifestations was the same for all groups, but more black than white CB-pos patients were severely anemic at the time of diagnosis. Response to androgen and steroid therapy occurred in only 33% of black children compared with 86-90% of white children; 81% of black patients died during the 18 year study period compared with 30% of white children, but the age at death was similar. More sophisticated studies are required to determine whether these differences are genetically determined or related to cultural, educational, and socio-economic differences between the two ethnic groups.

Prenatal diagnosis for Huntington's disease: a molecular and psychological study.

Two linked probes were used to determine the Huntington's disease status of the fetus conceived by a woman affected with the condition. The fetus was found to be unaffected with a certainty of 97 per cent. The ethical issues associated with presymptomatic testing were avoided since the mother presented with initial symptoms of Huntington's disease, but other psychological and ethical issues arose. The concerns of an affected woman planning a pregnancy, and the dilemmas involved in decision-making regarding prenatal diagnosis and possible selective abortion were exposed and explored with the patient and her husband.

Fanconi anemia in black African children.

Fanconi anemia (FA) has rarely been reported in black children either in the United States or Africa. This report describes 25 black African children with FA seen in Johannesburg over an 11-year period. The prevalence of homozygotes was estimated to be 1:476,000. Clinical manifestations, mean age at diagnosis, and hematologic and chromosome abnormalities were similar to those described in other ethnic groups. Response to androgens was poor and most patients required regular transfusions. Seventeen (68%) of the children died during the 11-year observation period. Leukemia was the terminal event in 2 patients. The mean age at death was 9.8 years and the mean time between diagnosis and death 2.3 years. The poor response to androgens, high mortality, and early mean age at death would favor consideration of early bone marrow transplantation in these children.

Establishment and characterization of two new human ovarian cancer cell lines UWOV1 and UWOV2 and a subline UWOV2 (Sf) growing in serum-free conditions: growth characteristics, biochemical, and cytogenetic studies.

The establishment, growth, and characterization of two new continuously growing human ovarian cancer cell lines (UWOV1 and UWOV2) as well as a subline (UWOV2 Sf) grown in chemically defined, serum-free medium are described. The cell lines were derived from ascitic tumors of two patients suffering from cystadenocarcinomas of the ovary. Both UWOV1 and UWOV2 lines grow in anchorage-dependent fashion as monolayers, whereas UWOV2 (Sf) forms multilayered domelike structures. Cytogenetic studies revealed nonrandom abnormalities involving chromosomes 1 and 11 in all three cell lines. Secretion of soluble collagen was detected in all three lines. In addition, UWOV2 (Sf) produces and secretes large amounts of extracellular matrix material with an ordered fibrillar structure which may function as an attachment factor for the serum-free cells. These cell lines seem to be useful for further studies of the biology of human ovarian cancer.

A decade of mid-trimester amniocentesis in Johannesburg. Prenatal diagnosis, problems and counselling.

Selected data from 4,554 cases of amniocentesis performed in Johannesburg over a decade are presented. The demand for the service increased fivefold over the 10 years. The indications were: chromosome defects (83%), neural tube defects (11%), other disorders (4%) and parental anxiety (2%). A correct prenatal diagnosis was made in 99.9% of cases and sexing was correct in 99.6% of cases. Abnormalities were detected in 3.2% of pregnancies. The rate of 'spontaneous' abortion within 1 week after amniocentesis was 0.7%, and the total 16-28-week fetal loss rate is not much increased over the risk for such an event in any second-trimester pregnancy. The procedure has become a safe and a successful one in expert hands.

First trimester prenatal diagnosis by chorionic villus sampling. The Johannesburg experience with 48 cases.

Chorionic villus sampling (CVS) is a first trimester alternative to amniocentesis for the prenatal detection of genetic disorders. Initial experience in 48 patients, in whom transcervical CVS was utilised for the diagnosis of chromosomal, biochemical or molecular disorders, is reported. An adequate villus sample was obtained in all cases and a diagnostic result was achieved in 90% of cases. In this series, the miscarriage rate was 4.2%. It is concluded that CVS appears to be a relatively safe and reliable procedure, but the risk of miscarriage can only be accurately assessed after further investigation.

Fanconi's anemia--chromosome breakage studies in homozygotes and heterozygotes.

The in vitro enhancement of chromosome breakage by diepoxybutane (DEB) and mitomycin C (MMC) was studied in 24 Fanconi's anemia (FA) homozygotes and 28 heterozygotes. Both drugs were shown to enhance chromosome breakage significantly in the homozygotes. In the great majority of cases, DEB and MMC stressing are reliable techniques for the definitive cytogenetic diagnosis of FA homozygosity. However, the present study provides no evidence that individual FA heterozygotes can be differentiated from normal individuals on the basis of spontaneous, DEB- or MMC-induced chromosome breakage.

Fanconi anemia: another disease of unusually high prevalence in the Afrikaans population of South Africa.

We have investigated the prevalence of homozygous and heterozygous Fanconi anemia (FA) in the Afrikaans community of the southern Transvaal Province. The minimum birth incidence of FA in white, Afrikaans-speaking South Africans was estimated to be 1 in 22,000, with the calculated heterozygote prevalence being approximately 1 in 77. Alternatively, based on a point prevalence of 1 in 26,000, the carrier rate may be estimated as 1 in 83. It is postulated that this unusually high frequency of the gene for FA is attributable to founder effect.

A unique dicentric X;Y translocation with Xq and Yp breakpoints: cytogenetic and molecular studies.

A 32-year-old woman presented with secondary amenorrhea and infertility. She was of normal height and her breasts were well developed, but she had streak gonads; there were no signs of virilization, and she showed no somatic stigmata of Turner syndrome. Chromosome analysis revealed a dicentric X;Y translocation with Xq and Yp breakpoints. Centromeric banding demonstrated a Y centromere and a "suppressed" X centromere. The karyotype of the patient was interpreted as 46,X,t(X;Y)(q22;p11). The Yp breakpoint was confirmed by DNA-hybridization studies with six probes detecting Y-specific sequences. These DNA-hybridization studies were consistent with the presence of the long arm, centromere, and much of the proximal short arm of the Y. The Y-DNA studies of this female also revealed the absence of the distal short arm of the Y chromosome, to which the testis-determining factor has previously been localized.

Cytogenetic and molecular studies on a recombinant human X chromosome: implications for the spreading of X chromosome inactivation.

A pericentric inversion of a human X chromosome and a recombinant X chromosome [rec(X)] derived from crossing-over within the inversion was identified in a family. The rec(X) had a duplication of the segment Xq26.3----Xqter and a deletion of Xp22.3----Xpter and was interpreted to be Xqter----Xq26.3::Xp22.3----Xqter. To characterize the rec(X) chromosome, dosage blots were done on genomic DNA from carriers of this rearranged X chromosome using a number of X chromosome probes. Results showed that anonymous sequences from the distal end of the long arm to which probes 4D8, Hx120A, DX13, and St14 bind as well as the locus for glucose-6-phosphate dehydrogenase (G6PD) were duplicated on the rec(X). Mouse-human cell hybrids were constructed that retained the rec(X) in the active or inactive state. Analyses of these hybrid clones for markers from the distal short arm of the X chromosome showed that the rec(X) retained the loci for steroid sulfatase (STS) and the cell surface antigen 12E7 (MIC2); but not the pseudoautosomal sequence 113D. These molecular studies confirm that the rec(X) is a duplication-deficiency chromosome as expected. In the inactive state in cell hybrids, STS and MIC2 (which usually escape X chromosome inactivation) were expressed from the rec(X), whereas G6PD was not. Therefore, in the rec(X) X chromosome inactivation has spread through STS and MIC2 leaving these loci unaffected and has inactivated G6PD in the absence of an inactivation center in the q26.3----qter region of the human X chromosome. The mechanism of spreading of inactivation appears to operate in a sequence-specific fashion. Alternatively, STS and MIC2 may have undergone inactivation initially but could not be maintained in an inactive state.

Localization of the human c-mos gene by in situ hybridization in two cases of acute nonlymphocytic leukemia type M2.

The t(8;21)(q22.1;q22.3) is specific for the FAB-M2 subtype of acute nonlymphocytic leukemia (ANLL). The human c-mos protooncogene is located near the site of rearrangement on chromosome #8, at a position corresponding to band 8q22. The present in situ hybridization studies were performed in order to establish if c-mos is transposed from chromosome #8 to chromosome #21, in two cases of M2-ANLL showing the typical t(8;21). A statistical analysis of the results revealed that the c-mos oncogene was definitely not translocated from chromosome #8 to #21 in one of these patients, and was inconclusive in the other patient. The findings in the former patient suggest that either c-mos is not involved in the etiology of M2-ANLL or, alternatively, if c-mos is important in the pathogenesis of this disease, it must be activated by some mechanism other than transposition of this oncogene to an aberrant position.

Inverted Y chromosome polymorphism in the Gujerati Muslim Indian population of South Africa.

An inverted Y chromosome has been found at a very high frequency in a Muslim Indian community living in the Johannesburg-Witwatersrand area of the Transvaal Province of South Africa: 8 of 141 (5.7%) retrospectively identified Indian males had an inv(Y)(p11.2q11.23) and all were of the Muslim faith. The inversion was found in 22 of 72 (30.5%) prospectively studied normal Muslim Indian males. All the carriers of the inversion were Gujarati-speakers whose families migrated to the Transvaal from the Gujerat Province of India during the first half of this century. The origins of the ancestors of the individuals with inv(Y) were traced to a small village, Kholvad, near the city of Surat, and some neighbouring villages. The polymorphic frequency of the inv(Y) has probably been produced through random genetic drift in a reproductively isolated community, maintained by strict endogamous marriage customs based on religious and linguistic affiliations. There was no indication that the inverted Y was associated with any reproductive disadvantages.

Chorionic villus sampling for first trimester diagnosis of beta-thalassaemia. Report of the first South African case.

The first South African report of chorionic villus sampling for molecular diagnosis of beta-thalassaemia in a 10-weeks' pregnant Indian Muslim woman is presented. The sampling procedure and molecular techniques for sexing the fetus and establishing whether it was affected by beta-thalassaemia are described. From the sample of villi obtained a male fetus was identified, using an X-Y-specific DNA probe. A preliminary family study on both parents, the affected proband and his 4 phenotypically normal siblings, revealed two informative restriction fragment length polymorphisms in the mother, but none in the father. It was therefore not possible to differentiate between the two beta-globin gene alleles of the father. The fetus thus had a 50% chance of being a heterozygote or a 50% risk of being affected. Synthetic oligonucleotide hybridization of parental and fetal DNA was attempted by the Genetics Unit of Johns Hopkins Hospital, Baltimore, but the fetal hybridization was unsuccessful. Results on the parents were obtained too late to be of assistance in the present pregnancy as the parents requested termination of the pregnancy before 16 weeks' gestation for religious reasons.

"Masked" Ph1 chromosome abnormalities in CML: a report of two unique cases.

Two patients with chronic myeloid leukemia (CML) showed previously undescribed variants of a "masked" Ph1 abnormality. The first patient had the karyotype 46,XY, + 21, -9, -22, +mar9,mar18 at presentation in the chronic phase. The dicentric marker 9 was interpreted as representing the usual translocation of 22q11 to 9q34, followed by translocation of the Ph1 chromosome (the deleted 22) to 9p and probable translocation of 9p to the distal long arm of the marker. The patient developed clones containing 2 and 3 copies of the "Ph1-containing" marker 9 concomitant with the metamorphosis of his disease to a more aggressive phase. The second case presented with the karyotype 46,XY,-9,-22,+two D-group markers. A complex rearrangement of chromosomes 9 and 22 is postulated, with interstitial insertion of either 9p or distal 9q into chromosome 22q11. This patient is still in the chronic phase of his disease 9 mo after presentation. The common denominator in these unusual "masked" cases is the 22q11 breakpoint. The paucity of published reports of duplication of 9q + without concurrent duplication of the Ph1 chromosome, supported by the findings in our first case, leads us to conclude that the amplification of genes on the Ph1 chromosome are more important for the evolution of the abnormal stem cell in CML than the chromosome 9 derivative.

Elevated alpha-fetoprotein levels in the 45,x (Turner syndrome) fetus with cystic hygroma. Case reports.

A 45,X fetus with cystic hygroma, associated with an elevated amniotic alpha-fetoprotein (AFP) level (greater than 80 microgram/ml). Is described, as are macroscopic and microscopic characteristics of this fetus and two other female fetuses with cystic hygroma. The ultrasonographic diagnosis of fetal cystic hygroma is discussed. The association of a high amniotic AFP level with cystic hygroma is considered. The relationship between cystic hygroma and pterygium colli in liveborn infants with Turner syndrome, and the evolution of neck webbing, as seen in the adult with turner syndrome, is also discussed.