G. von Beust

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.

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.

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.

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.

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.

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.