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A Schinzel

Publications and source records attributed to A Schinzel.

At least 55 records · Page 3Linked to original sources
PubMed2000

Parental origin and mechanisms of formation of triploidy: a study of 25 cases.

Triploidy is one of the most frequently observed chromosome abnormalities in spontaneous abortions in humans. The parental origin of the additional chromosome set is known to have a major impact on the phenotype of the foetuses and to result in differences in size and structure of the placenta. Early studies based on cytogenetic polymorphisms indicated a preponderant diandric origin of the triploidies; such detection method, however, is known to be prone to error. Other studies revealed a predominant digynic origin in cases with longer intrauterine survival. It is now thought that, to some extent, a detection bias in favour of cases with associated partial hydatidiform moles may account for the high incidences of diandric cases reported in some studies. Furthermore, depending on the gestational age of the cases analysed there may indeed be differences in the proportion of diandric and digynic triploidies. We investigated the parental origin and mechanisms of formation of triploidy in a group of 25 probands with gestational ages ranging from 8 to 37 weeks. DNA samples were extracted from foetal material and from blood samples of the parents, and were analysed using microsatellite markers. The parental origin of the triploidies was found to be maternal in 20 cases and paternal in 5. Regarding the digynic cases, an error at meiosis I was inferred in 10 cases, whereas in the other half an error occurred at meiosis II. All five diandric cases included in this study were found to be due to dispermy. No significant differences in the average maternal ages were found amongst the different subgroups of patients.

Adult↗
PubMed2000

A supernumerary marker chromosome originating from two different regions of chromosome 18.

By random amplification of a microdissected chromosome using the degenerate oligonucleotide primed polymerase chain reaction (DOP-PCR) and forward painting (microFISH), we characterised an extra structurally abnormal chromosome (ESAC) or supernumerary marker chromosome in a mentally retarded girl with a pattern of dysmorphic features. It could be clearly shown that the small marker chromosome originates from two different regions of chromosome 18, 18p11.1-->18q11.1 and 18q12.3-->18q21.1 respectively. Maternal origin of the de novo ESAC and biparental origin of the normal homologues of chromosome 18 were shown by PCR of several highly polymorphic microsatellites. In this case, application of microFISH was a prerequisite for rapid and precise characterisation of an ESAC. A definite identification of this discontinuous supernumerary marker chromosome would not have been possible using FISH with centromere specific probes or multicolour FISH approaches.

Adolescent↗
PubMed2000

Parental origin and mechanisms of formation of cytogenetically recognisable de novo direct and inverted duplications.

Cytogenetic, FISH, and molecular results of 20 cases with de novo tandem duplications of 18 different autosomal chromosome segments are reported. There were 12 cases with direct duplications, three cases with inverted duplications, and five in whom determination of direction was not possible. In seven cases a rearrangement between non-sister chromatids (N-SCR) was found, whereas in the remaining 13 cases sister chromatids (SCR) were involved. Paternal and maternal origin (7:7) was found almost equally in cases with SCR (3:4) and N-SCR (4:3). In the cases with proven inversion, there was maternal and paternal origin in one case each. Twenty three out of 43 cytogenetically determined breakpoints correlated with common or rare fragile sites. In five cases, including all those with proven inverse orientation, all breakpoints corresponded to common or rare fragile sites. In at least two cases, one with an interstitial duplication (dup(19)(q11q13)) and one with a terminal duplication (dup(8) (p10p23)), concomitant deletions (del(8) (p23p23.3) and del(19)(q13q13)) were found.

Abnormalities, Multiple↗
PubMed2000

Discrepancies in cytogenetic results between different tissues in two fetuses with Wolf- Hirschhorn syndrome.

Discrepant unbalanced structural chromosome aberrations between placental and fetal tissue, both involving the short arm of chromosome 4, were found in two human fetuses affected with Wolf-Hirschhorn syndrome. In the first instance, placental chromosome examination revealed a del(4) (p14), whereas fetal fibroblast chromosomes showed an unbalanced der(4)t(4;13)(p14;q11) translocation. In the second instance, placental karyotyping revealed a 4p+ chromosome, while amniocytes showed a submicroscopic deletion at 4p16.3. Since confirmation of structural aberrations from placental tissue is mostly not sought if the phenotype of the fetus is abnor- mal, discrepancies between karyotypes obtained from placental tissue and amniocytes or fetal tissues might be more frequent than the rare reports published so far would suggest. It is unclear whether the simple deletion or the more complex rearrangement is the primary aberration from which the other derived. Structural chromosome aberrations often have a much more complex mechanism of formation than the end product would suggest, and secondary rearrangements of a given aberration in the zygote are more frequent than expected.

Abnormalities, Multiple↗
PubMed1999

Short stature, myopia, severe developmental delay, and peculiar facial appearance in two brothers: a new syndrome?

We report on 2 brothers with short stature, microcephaly, myopia, retarded osseous maturation, severe developmental delay, and minor anomalies including temporal narrowing, periorbital fullness, full cheeks in infancy, and protruding lower lip. Both brothers and their parents had normal chromosomes. Fluorescence in situ hybridization with probes from all (sub-)telomeric chromosomal regions excluded a structural rearrangement involving telomeric segments. Because the pattern of congenital abnormalities is not like that of any well-known multiple congenital anomaly/mental retardation syndrome, we suggest a previously undescribed syndrome of autosomal recessive or X-linked inheritance.

Adult↗
PubMed1999

Molecular and clinical correlation study of Williams-Beuren syndrome: No evidence of molecular factors in the deletion region or imprinting affecting clinical outcome.

Williams-Beuren syndrome (WBS) results from a deletion of 7q11.23 in 90-95% of all clinically typical cases. Clinical manifestation can be variable and therefore, deletion size, inherited elastin (ELN) and LIM kinase 1 (LIMK1) alleles, gender, and parental origin of deletion have been investigated for associations with clinical outcome. In an analysis of 85 confirmed deletion cases, no statistically significant associations were found after Bonferroni's correction for multiple pairwise comparisons. Furthermore, the present data do not support presence of imprinted genes in the WBS common deletion despite a nonsignificant excess of maternal over paternal deletions. Maternal deletion cases were more likely to have a large head circumference in the present data. Also, pairwise comparisons between individual WBS clinical features have been conducted and revealed significant associations between (1) low birth weight and poor postnatal weight gain (<10th percentile at the time of examination) and (2) transient infantile hypercalcemia and a stellate iris pattern. The latter association could indicate a common underlying etiology.

Alleles↗
PubMed1999

"Essentially pure" partial trisomy (6)(p23-->pter) in two brothers due to maternal t(6;17)(p23;p13.3).

We report on two brothers with low birth weight, growth retardation, microcephaly, minor facial anomalies, mental retardation, and trisomy (6)(p23-->pter) due to a maternal t(6;17)(p23;p13.3). As demonstrated by fluorescent in situ hybridisation (FISH) with the Miller-Dieker cosmid probe (D17S379) and with a subtelomeric probe (D17S34) the additional deletion on 17p13 is very small, and therefore, the phenotype of these two boys is most likely the result of essentially pure partial trisomy 6p. Comparison of the clinical findings with those of ten cases from the literature of dup(6p) with a breakpoint in or more distal to 6p23 allows delineation of a specific phenotype of dup(6)(p23-->pter) characterized by low birth weight, growth retardation, microcephaly, and blepharophimosis, blepharoptosis, microstomia, and abnormal ears.

Abnormalities, Multiple↗
PubMed1999

Terminal deletion, del(1)(p36.3), detected through screening for terminal deletions in patients with unclassified malformation syndromes.

We report on a 4 year-old girl with a 1p36.3-pter deletion. Clinical findings included minor anomalies of face and distal limbs, patent ductus arteriosus, the Ebstein heart anomaly, and brain atrophy with seizures. Conventional GTG-banded chromosome analysis revealed a normal (46,XX) result. Subsequent analysis by fluorescent in situ hybridization (FISH) using distal probes demonstrated a deletion of 1p36.6-pter. Molecular investigations with microsatellite markers showed hemizygosity at three loci at 1p36.3 with loss of the paternal allele. The deletion of 1p36.3 is difficult to identify by banding alone; indeed, our patient represents the third reported case with a del(1)(p36.3) that was detected only after more detailed analysis. In all three cases the deletion was detected through screening of patients with multiple congenital anomalies/mental retardation syndromes suggestive of autosomal chromosome aberrations for subtelomeric submicroscopic deletions by means of FISH or microsatellite marker analysis. On the basis of these observations we highly recommend that FISH with a subtelomeric 1p probe be routinely performed in patients with similar facial phenotype, severe mental retardation and seizures, and a heart malformation, particularly the Ebstein anomaly.

Age Determination by Skeleton↗
PubMed1999

Severe intra-uterine growth retardation in a patient with maternal uniparental disomy 22 and a 22-trisomic placenta.

We report on a maternal uniparental disomy of chromosome 22 in a patient with severe intra-uterine growth retardation. Karyotyping of a placental tissue revealed non-mosaic trisomy 22, whereas lymphocyte chromosomes from the newborn were normal 46,XY. Microsatellite analysis using DNA extracted from white blood cells showed maternal uniparental heterodisomy for chromosome 22. Thus, the conceptus started as maternal trisomy due to meiotic non-disjunction, and trisomy rescue occurred subsequently through loss of the paternal homologue resulting in maternal uniparental disomy. Normal phenotypes in previous reports have suggested that maternal UPD 22 has no impact on the phenotype. Thus, growth retardation in this patient was probably caused by dysfunction of the trisomic placenta.

Adult↗
PubMed1999

Screening for UBE3A gene mutations in a group of Angelman syndrome patients selected according to non-stringent clinical criteria.

The Angelman syndrome (AS) is caused by genetic abnormalities affecting the maternal copy of chromosome region 15q12. Until recently, the molecular diagnosis of AS relied on the detection of either a deletion at 15q11-13, a paternal uniparental disomy (UPD) for chromosome 15 or imprinting mutations. A fourth class of genetic defects underlying AS was recently described and consists of mutations of the UBE3A gene. The vast majority of mutations reported so far are predicted to cause major disruptions at the protein level. It is unclear whether mutations with less drastic consequences for the gene product could lead to milder forms of AS. We report on our results obtained by screening 101 clinically diagnosed AS patients for mutations in the UBE3A gene. Non-stringent clinical criteria were purposely applied for inclusion of AS patients in this study. The mutation search was carried out by single-strand conformation polymorphism (SSCP), and SSCP/restriction fragment length polymorphism (RFLP) analyses and revealed five novel UBE3A gene mutations as well as three different polymorphisms. All five mutations were detected in patients with typical features of AS and are predicted to cause frameshifts in four cases and the substitution of a highly conserved residue in the fifth. The results we obtained add to the as yet limited number of reports concerning UBE3A gene mutations. Important aspects that emerge from the data available to date is that the four classes of genetic defects known to underlie AS do not appear to cover all cases. The genetic defect underlying approximately 10% of AS cases, including some familial cases, remains unknown.

Amino Acid Sequence↗
PubMed1999

Maternal uniparental disomy 14 as a cause of intrauterine growth retardation and early onset of puberty.

Uniparental disomy for particular chromosomes is increasingly recognized as a cause of abnormal phenotypes in humans either as a result of imprinted genes or, in the case of isodisomy, homozygosity of mutated recessive alleles. We report on the occurrence of maternal uniparental disomy for chromosome 14 (matUPD 14) in a 25-year-old woman with a normal karyotype, normal intelligence but low birth weight, short stature, small hands, and early onset of puberty. Comparison of her phenotype with those of 15 previously described liveborn patients with matUPD14 gives further evidence for an imprinted gene region on chromosome 14 and highlights the necessity to consider this cause in children with intrauterine growth retardation and early onset of puberty caused by acceleration of skeletal maturation.

Adult↗
PubMed1999

Recombinant balanced and unbalanced translocations as a consequence of a balanced complex chromosomal rearrangement involving eight breakpoints in four chromosomes.

We report on a family with a balanced complex chromosomal rearrangement (CCR) involving eight breakpoints between chromosomes 6, 7, 18, and 21 in the father. All three sons inherited one derivative chromosome from the father and in addition each inherited a different recombinant chromosome resulting in a partial trisomy 6q in the first, an apparently balanced karyotype in the second, and a partial trisomy 7q in the third son. Fluorescence in situ hybridisation (FISH) and microsatellite analysis were essential for the identification of the breakpoints. In addition, the results were confirmed by a 24-colour FISH experiment using the spectral karyotyping (SKYtrade mark) system. Paternal origin of the de novo CCR in the father was demonstrated for the first time by haplotype analysis. This is the second report of a CCR leading to simpler but unbalanced translocations in offspring as a consequence of recombination during gametogenesis, and the first report of a family case of CCR exhibiting as many as eight breakpoints in the transmitting carrier. The initial prediction that viable offspring would be quite unlikely had to be revised after the birth of three children. Genetic counselling of carriers of balanced complex rearrangements has to consider a higher probability for unbalanced recombinations than has been so far commonly assumed.

Adult↗
PubMed1999

A chromosomal duplication map of malformations: regions of suspected haplo- and triplolethality--and tolerance of segmental aneuploidy--in humans.

The distribution of simple autosomal duplications associated with congenital malformations has been analyzed by means of data contained in the Human Cytogenetics Database. For each of the 47 malformations, the frequency of duplication of a given chromosome band associated with the malformation was compared with the overall frequency of duplication of that band recorded in the database. In total, there were 143 malformation-associated chromosomal regions (MACR); 21 of these contained at least one band with a highly significant (P<.001) association. The average number of bands per MACR was 3.1. Eight bands, representing 2.1% of haploid autosomal length, were not involved in any duplication, and we suggest that these are potentially triplolethal. This compares with 31 bands, representing 11% of haploid autosomal length, that were identified in the previously reported deletion map and that were not involved in any deletion and are potentially haplolethal. In both cases, approximately half of these bands are pericentromeric. The longest duplication involves 4.3% of haploid autosomal length, and the longest deletion involves 2.7%.

Chromosome Aberrations↗
PubMed1999

The spectrum of mutations in TBX3: Genotype/Phenotype relationship in ulnar-mammary syndrome.

Ulnar-mammary syndrome (UMS) is a pleiotropic disorder affecting limb, apocrine-gland, tooth, hair, and genital development. Mutations that disrupt the DNA-binding domain of the T-box gene, TBX3, have been demonstrated to cause UMS. However, the 3' terminus of the open reading frame (ORF) of TBX3 was not identified, and mutations were detected in only two families with UMS. Furthermore, no substantial homology outside the T-box was found among TBX3 and its orthologues. The subsequent cloning of new TBX3 cDNAs allowed us to complete the characterization of TBX3 and to identify alternatively transcribed TBX3 transcripts, including one that interrupts the T-box. The complete ORF of TBX3 is predicted to encode a 723-residue protein, of which 255 amino acids are encoded by newly identified exons. Comparison of other T-box genes to TBX3 indicates regions of substantial homology outside the DNA-binding domain. Novel mutations have been found in all of eight newly reported families with UMS, including five mutations downstream of the region encoding the T-box. This suggests that a domain(s) outside the T-box is highly conserved and important for the function of TBX3. We found no obvious phenotypic differences between those who have missense mutations and those who have deletions or frameshifts.

Abnormalities, Multiple↗