Preparation of metaphase spreads from chorionic villus samples.

Chorionic villi are composed of an outer layer of trophoblastic cells and an inner mesenchymal cell core, both of fetal origin. Cytogenetic analysis of chorionic villi can be accomplished using material prepared in either of two ways. In the culture method described in this unit, villi are disaggregated by mechanical and enzymatic methods, and the resulting cell suspension is used to establish primary cultures. Mesenchymal cells of the villus core are released by this procedure and the fibroblasts are actively proliferative in tissue culture. Cultures can be used for cytogenetic analysis after 1 week. In the "direct" technique, presented here in an Alternate Protocol, Langhans cells of the cytotrophoblast, actively dividing cells in first-trimester villi, are synchronized and arrested in mitosis after a short incubation period, and metaphase spreads are prepared. Chorionic villi are composed of an outer layer of trophoblastic cells and an inner mesenchymal cell core, both of fetal origin.

Ring chromosome 4 mosaicism coincidence of oligomeganephronia and signs of Seckel syndrome.

We present a patient with features suggestive of Seckel syndrome who was found to be mosaic for ring 4 chromosome. Seckel syndrome is a rare entity characterized by marked growth retardation, microcephaly, facies characterized by receding forehead and chin, large beaked nose, and severe retardation, usually thought to be inherited as an autosomal recessive condition. In addition, our patient had oligomeganephronia, a rare and usually sporadic renal malformation, previously reported in two other patients with abnormalities of chromosome 4. Besides pointing out the overlap between the Seckel phenotype and Wolf-Hirschhorn syndrome, our patient illustrates the need to consider cytogenetic studies in patients with the Seckel phenotype, so that accurate diagnoses can be given to families. Also, the case suggests that there may be a locus for oligomeganephronia distal to the Wolf-Hirschhorn critical region on 4p.

Submicroscopic deletions at 16p13.3 in Rubinstein-Taybi syndrome: frequency and clinical manifestations in a North American population.

Rubinstein-Taybi syndrome (RTS) is a well delineated multiple congenital anomaly syndrome characterised by mental retardation, broad thumbs and toes, short stature, and specific facial features. The recent localisation of the disorder to 16p13.3 and subsequent identification of a submicroscopic deletion of this region in RTS patients led us to screen a large cohort of affected subjects using the RT1 probe. Among 64 patients with clinical evidence of RTS, seven (11%) had a deletion. Another patient had a translocation of the region without evidence of a deletion. The features of coloboma, growth retardation, naevus flammeus, and hypotonia have a positive predictive value for the presence of an RT1 deletion. Because of the relatively low frequency of deletions in RTS, the RT1 probe is useful in diagnostic confirmation, but has limited use as a screening tool.

Diagnosis of a complex chromosomal rearrangement using fluorescent in situ hybridisation.

We report the use of fluorescent in situ hybridisation (FISH) to clarify a complex chromosomal rearrangement (CCR) carried by a woman presenting with recurrent miscarriages. CCRs are rare cytogenetic rearrangements involving three or more chromosomes, which can be difficult to interpret using routine cytogenetic studies with GTG banding. FISH was used to establish a correct interpretation of the maternal karyotype before amniocentesis in a present pregnancy.

Non-isotopic procedure with silver staining of polyacrylamide gels in detection of genomic abnormalities in tumors using microsatellites.

Microsatellite-based PCR (polymerase chain reaction) with silver staining of polyacrylamide gels as an alternative approach to detect genomic abnormalities in tumors has been developed. In experiments with a series of primers for microsatellite sequences located on human chromosome 5 we found that a 2- to 4-fold increase or decrease in the ratio of amount of allelic microsatellite sequences can be reliably assessed from the relative intensity of corresponding PCR products. Results of the studies of renal carcinoma cell lines carrying increased or decreased numbers of specific allelic markers on chromosome 5 assessed by cytogenetics, Southern blotting-restriction fragment length polymorphism and microsatellite analyses were consistent. Microsatellite studies performed on samples obtained from formalin-fixed paraffin-embedded archival material allowed detection of genomic abnormalities of chromosome 5 in five of ten primary renal cell carcinomas.

Translocation (X;19) with involvement of the inactive X chromosome in oligoblastic granulocytic leukemia.

A 72-year-old female with metastatic breast cancer developed oligoblastic granulocytic leukemia 6 months after initiation of chemotherapy. Cytogenetic examination of the bone marrow cells revealed a balanced t(X;19)(q12;q13.3) as the sole abnormality in 50% of the metaphases. The remaining cells showed a normal female karyotype. The der(19) chromosome displayed consistent folding in the Xq13-q23 region in all metaphases, indicating involvement of the inactive X chromosome in translocation.

A simple technique for obtaining high quality chromosome preparations from chorionic villus samples using FdU synchronization.

A fluorordeoxyuridine (FdU) synchronization technique was applied to 30 chorionic villus samples (CVS) from patients undergoing first trimester fetal diagnosis. The villi were incubated for 15 h in the presence of FdU. The block in DNA synthesis was subsequently released using thymidine and after an additional 5 h of incubation the mitotic cells were arrested in metaphases using a high concentration of colcemid. This method results in improved morphology of the chromosomes and a high mitotic index. A diagnostic chromosome analysis could be obtained in each clinical case using at least 15 well-spread metaphases. G-banded karyotypes were prepared of four metaphases in each case. The diagnostic procedure was completed within 48 h from the time of CVS. Use of this technique significantly improves the success rate of 'direct' chromosome analyses from CVS in a busy cytogenetic laboratory.

Gardner syndrome in a man with an interstitial deletion of 5q.

Chromosome analysis of blood cells from a 42-year-old white male with mental retardation, colon carcinoma, horseshoe kidney, absence of left lobe of the liver, agenesis of the gallbladder, and possible Gardner syndrome revealed a constitutional marker chromosome due to del(5)(q13q15) or del(5)(q15q22). A polymorphic chromosome #22 with enlarged satellites was inherited from the father, who is phenotypically normal, and was probably unrelated to the congenital malformations. This is the first report of a Gardner syndrome patient with an interstitial deletion of 5q.

Cytogenetic changes at 11q11, 11q23, and 17q11 in myelodysplastic syndrome.

Cytogenetic studies were performed on two patients with myelodysplastic syndromes. One patient was a 68 year old Japanese male in whose bone marrow cells two translocations were established, i.e., t(4;11)(q13;q23) and t(11;17)(q11?;q11), as well as other karyotypic changes (-6,-18,15p+). The other patient was a 74 year old white male whose bone marrow cells showed six marker chromosomes, i.e., der(5),t(5;17)(q12;q11), der(6),t(6;5)(q27;q22), der(8),t(8;11;?)(q11;q11----q23;?), der(11),t(11;?)(q11;?), an isochromosome of the long arm of chromosome #8, and a small G-group sized marker chromosome of unknown origin. Though the translocation patterns in the abnormal cells in these two cases were different, the breakpoints of the marker chromosomes were almost the same, i.e., 11q11, 11q23, and 17q11. Also, changes of chromosome #6 were observed; the first case showed monosomy 6 and the second a 6q+ marker chromosome. In these two cases of myelodysplastic syndromes, common sites of chromosome breakage and reunion of 11q23 and 17q11 were close to recently established sites of human cellular oncogene homologs, c-ets (11q23) and c-erbA (17q21----24). These associations draw attention to a possible relationship between chromosome changes in myelodysplastic syndromes and oncogene (or other gene) activation and/or dysfunction.

Cytogenic analysis of transplantable mouse B16 melanomas.

The cytogenetic analysis of transplantable in vivo melanotic and amelanotic lines of mouse B16 melanoma was performed. The second line arose by spontaneous alteration of the first one and these lines are the same in the rate of malignant growth during passages in vivo. The melanotic line shows stable near-diploid karyotype with modal chromosome number 41. The amelanotic line is mostly hypotetraploid karyotype with modal chromosome number 76. The balance of the diploids in the melanotic line is disturbed by the fact that chromosome 15 is partially trisomic, chromosome 6 trisomic, and chromosome 13 and X monosomic. Four marker chromosomes were common to both lines: M1-rob(12;12), M2-rob(5;15), M3-minute, M4-inv(1), M5-del-(14q-), but in the amelanotic line in most cases their number was doubled. Additionally, in the amelanotic line other specific aberrations rob(6;6) and rob(16;16) were observed. Both lines had comparable SCE frequencies. Constitutive heterochromatin in amelanotic line revealed the nonrandom deletion of the heterochromatic segments in chromosome 11 and, occasionally in chromosome 19.