DNA analysis of Huntington's disease: five years of experience in Germany, Austria, and Switzerland.

OBJECTIVE: To review the direct DNA testing for Huntington's disease (HD) in Germany, Switzerland, and Austria from 1993 to 1997, and to analyze the population with regard to age structure, gender, and family history. METHODS: Twelve laboratories (nine in Germany, two in Austria, and one in Switzerland) recorded data pertaining to repeat number, gender, age at molecular diagnosis, and family history of probands. The molecular test was categorized as either diagnostic (for symptomatic individuals), presymptomatic (for individuals at risk), and prenatal (for pregnancies at risk). RESULTS: A total of 3,090 HD patients, 992 individuals at risk, and 24 fetuses were investigated using DNA analysis. The clinical diagnosis was confirmed in 65.6% of patients. A total of 38.5% of individuals at risk inherited an expanded CAG repeat. The female-to-male ratio showed a distinct predominance of women both in the diagnostic and presymptomatic groups. Of the fetuses tested, six were carriers of an expanded CAG repeat. Two pregnancies were interrupted; one pregnancy was not. No information about the parents' decision was obtained for the remaining three pregnancies. CONCLUSIONS: Approximately 20% of the estimated 10,000 HD patients living in Germany, Switzerland, and Austria have been identified by DNA analysis (total population, approximately 100 million; incidence of HD, 1:10,000). Assuming a ratio of HD patients to individuals at risk of 1:3, approximately 30,000 individuals are, in principle, eligible for a presymptomatic test. Less than 3 to 4% of individuals at risk have requested a presymptomatic test. This shows that the assumed enormous request of predictive testing has not occurred. More surprisingly, prenatal diagnoses were found to be rare.

Molecular cloning, chromosomal localization, and expression analysis of CYRN1 and CYRN2, two human genes coding for cyritestin, a sperm protein involved in gamete interaction.

Germ cell cyritestin is a membrane-anchored protein belonging to the ADAM family of proteins. Sequencing of eight human cyritestin cDNA clones revealed that they are identical at their 5' and 3' ends but differ from each other in the length of an internal deletion, suggesting that the human cyritestin mRNA is alternatively spliced. Internal deletions that are present in some cDNA isoforms do not cause a frameshift in the C-terminal coding region. Analysis of the predicted amino acid sequences demonstrated that the human cyritestin is a polymorphic protein that could include membrane-anchored and soluble forms. Southern blot analysis and characterization of human cyritestin genomic fragments revealed that the human genome contains two copies of the cyritestin gene instead of one as in the mouse. The human CYRN1 and CYRN2 genes were assigned to the region p12-21 of chromosome 8 and q12 of chromosome 16, respectively. Northern blot and RT-PCR analyses revealed that both human genes are expressed in the testis. Amino acid sequence comparisons between cyritestin and other members of the metalloprotease-disintegrin family of proteins suggested that human and mouse cyritestin and monkey tMDCI are homologous molecules.

A phenotypically normal liveborn male after prenatal diagnosis of trisomy 20 mosaicism.

We report on a case of prenatally diagnosed true trisomy 20 mosaicism in amniocytes. Cytogenetic analysis was performed postnatally on lymphocytes and extra-embryonic tissues. For analysing uroepithelial cells we established a new cell nuclei preparation protocol for FISH (Fluorescence In Situ Hybridization). Trisomy 20 cells could not be confirmed after birth. The origin or trisomy 20 cells in amniotic fluid remains unclear. The phenotypically normal male baby is developing normal.

Molecular cytogenetic characterization of a de novo supernumerary ring chromosome 7 resulting in partial trisomy, tetrasomy, and hexasomy in a child with dysmorphic signs, congenital heart defect, and developmental delay.

We report on a girl with mosaicism (65%) of a de novo supernumerary ring chromosome 7. The main clinical features were delayed psychomotor development, congenital heart defect, facial dysmorphisms, and long hands, fingers, feet and toes. Molecular cytogenetic analysis revealed that the ring chromosome was duplicated in 20% of the analyzed metaphases with marker chromosome and quadruplicated in 5% thereof. Uniparental disomy (UPD) of the two normal sister chromosomes 7 was excluded. This is, to our knowledge, the first report of a partial tetrasomy to hexasomy due to a ring chromosome 7. Additionally, the ring evolution could be reconstructed according to the FISH-results.

Extra euchromatic band in the qh region of chromosome 9.

Chromosomal analysis of amniotic cell culture revealed an extra euchromatic band in the variable heterochromatin region 9q12. Cytogenetic analysis of the fetus was compared with the chromosomes of the parents. Using different cytogenetic banding techniques and fluorescence in situ hybridization with specific DNA probes, the structural rearrangements involved were considered. The very rare variant proved to be familial. Demonstrating the inheritance of a normal individual supports the interpretation of the prenatal analysis of chromosome 9 as a variant without clinical relevance for the fetus.

Molecular cloning, expression and chromosome location of the human pelota gene PELO.

The pelota gene of Drosophila melanogaster encodes a protein that was found to be included in cell cycle regulation. Mutations were found to result in spermatogenic arrest, female sterility and disturbances in the patterning of the eye. Here we describe the cloning of the human pelota cDNA (PELO) that encodes a 385-amino-acid protein. Southern blot and fluorescence in situ hybridization analyses revealed that PELO is present as a single copy gene in the human genome and is localized on chromosome 5q11.2. Northern blot analysis revealed the presence of a 1.6-kb transcript in all tissues studied and an additional 2.0-kb transcript in testis.

[Clinical aspects and genetics of Williams-Beuren syndrome. Clinical and molecular genetic study of 44 patients with suspected Williams-Beuren syndrome]. / Klinik und Genetik des Williams-Beuren-Syndroms. Klinische und molekulargenetische Untersuchung von 44 Patienten mit Verdacht auf WBS.

BACKGROUND: The suspected diagnosis of Williams-Beuren syndrome (WBS), which is a retardation syndrome with great clinical variability, was cause for comparison of molecular genetic, molecular cytogenetic analysis to clinical symptoms. The results of the genetical analysis of a microdeletion of the elastin gene region on chromosome 7 were compared to the clinical symptoms. Are there any differences between symptoms in case of deletion or non-deletion? How informative are the molecular genetic, molecular cytogenetic analysis? PATIENTS AND METHODS: 44 patients with suspected diagnosis of WBS were examined using molecular genetic and molecular cytogenetic methods. The clinical symptoms as general symptoms, heart anomaly, dysmorphic signs and unusual neurobehavioural features were reported during clinical investigation in standardized questionnaires. The genomic DNA of the patients and their parents was analyzed using microsatellite markers. In some cases (e.g. uninformative microsatellite studies) we also used fluorescence in situ hybridization (FISH) with an elastin gene probe and performed a conventional chromosome banding analysis. RESULTS: 15 patients had a microdeletion. 4 patients had a deletion of the paternal allel and 7 patients showed the deletion of the maternal allel. The polymorphisms were of limited informativeness. In 2 cases microsatellite analysis was not able to determine whether the paternal or the maternal allel had been lost. In 2 cases the microsatellite analysis was uninformative so that FISH analysis was performed. All FISH analysis performed had an informative result. 80% of the children with a microdeletion of chromosome 7q11.23 showed the typical dysmorphic signs, 70% exhibited the typical WBS behaviour pattern, 50% had a specific heart anomaly. In contrast, in the group of children without a chromosomal microdeletion only 30-40% showed typical dysmorphic signs, only 10% had a typical heart anomaly and none of them showed specific behavioural changes. We found no indication to association of specific symptoms with paternal versus maternal origin of the deletion. The FISH analysis combined with a conventional chromosome banding analysis is very informative for diagnostic values. The results are compared to data of literature. CONCLUSIONS: Children with developmental retardation and WBS dysmorphic signs and an unusual behaviour should be examined by a molecular cytogenetic FISH analysis. If a microdeletion of band 7q11.23 is found a special cardiologic examination should be offered.

Prenatal diagnosis and fetopathological findings in a fetus with ring chromosome 18.

We report on a fetus with ring chromosome 18 and monosomy 18 mosaicism [mos 45,XX,-18/46,XX,r(18)] detected in cultured amniotic fluid cells at 15 weeks' gestation. Chromosome analysis of fetal blood, cultured chorionic villi and fetal fibroblasts confirmed the aberrant karyotype. The aberrant chromosome complement could not be detected in a short-term culture of chorionic villi (46,XX in 21 metaphases). These findings suggest that the aberrant karyotype was a postzygotic event. Fetal ultrasound was normal and the parents decided to terminate the pregnancy at 21 weeks' gestation. Autopsy revealed multiple abnormalities including facial dysmorphy, partial agenesis of the corpus callosum and an interatrial septal defect.

Analysis of the origin of the extra chromosome in trisomy 8 in 4 cases of spontaneous abortions.

OBJECTIVE: To determine the origin of the extra chromosome in trisomy 8 in spontaneous abortions. METHODS: We analyzed 4 cases of nonmosaic trisomy 8 in 1st-trimester spontaneous abortions and their parents with DNA polymorphism analysis using microsatellite DNA markers. RESULTS: In 3 cases the extra chromosome was maternal in origin and in 1 case paternal in origin. In 2 of the cases the nondisjunction had occurred in maternal meiosis, while the other 2 cases were consistent with a postzygotic (mitotic) origin of the additional chromosome. CONCLUSION: Although a small number of cases studied, these results suggest differences from the common autosomal trisomies 21, 18, 16, and 13 where the vast majority of cases are due to errors in maternal meiosis.

Autistic disorder and chromosomal mosaicism 46,XY[123]/46,XY,del(20)(pter --> p12.2)[10].

We report on a 3-year-old boy with a moderate to severe mental retardation, autistic behavior patterns, and myoclonic epilepsy of early childhood. The cytogenetic analysis of blood lymphocytes revealed a deletion of chromosome 20pter --> p12.2 occurring as mosaicism in 8% of the analyzed metaphases: 46,XY[123]/46,XY,del(20)(pter --> p12.2)[10]. The deletion was confirmed by the recently developed multicolor banding approach and additionally by region specific fluorescence in situ hybridization (FISH) probes. To the best of our knowledge, this is the first report on a patient with autistic behavior with terminal 20p deletion mosaicism reported up to present.