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Biomedical subjects

A Schinzel

Publications and source records attributed to A Schinzel.

At least 37 records · Page 2Linked to original sources
PubMed2001

Submicroscopic terminal deletions and duplications in retarded patients with unclassified malformation syndromes.

Unbalanced submicroscopic subtelomeric chromosomal rearrangements represent a significant cause of unexplained moderate to severe mental retardation with and without phenotypic abnormalities. We investigated 254 patients (102 from Zürich, 152 from Liège) for unbalanced subtelomeric rearrangements by using fluorescence in situ hybridisation with probes mapping to 41 subtelomeric regions. Mental retardation combined with a pattern of dysmorphic features, with or without major malformations, and growth retardation and a normal karyotype by conventional G-banding were the criteria of inclusion. Selection criteria were more restrictive for the Zürich series in terms of clinical and cytogenetic pre-investigation. We found 13 unbalanced rearrangements and two further aberrations, which, following the investigation of other family members, had to be considered as variants without influence on the phenotype. The significant aberrations included three de novo deletions (two of 1pter, one of 5pter), three de novo duplications (8pter, 9pter, Xpter), one de novo deletion 13qter-duplication 4qter, and five familial submicroscopic translocations [(1q;18p), (2q;4p), (2p;7q), (3p;22q), (4q;10q), (12p;22q)], most of them with several unbalanced offspring with deletion-duplication. Although the incidence of abnormal results was higher (10/152) in the Liège versus the Zürich series (3/102), similar selection criteria in Zürich as in Liège would have resulted in an incidence of 7/106 and thus similar figures. In our series, submicroscopic unbalanced rearrangements explain the phenotype in 13/254 study probands. The most important selection criterion seems to be the presence of more than one affected member in a family. An examination of subtelomeric segments should be included in the diagnostic work-up of patients with unexplained mental retardation combined with physical abnormalities, when a careful conventional examination of banded chromosomes has yielded a normal result and a thorough clinical examination does not lead to another classification. The proportion of abnormal findings depends strongly on selection criteria: more stringent selection can eliminate some examinations but necessitates a high workload for experienced clinical geneticists. Once the costs and workload of screening are reduced, less selective approaches might finally be more cost-effective.

Adult↗
PubMed2001

Epilepsy and trisomy 19q--different seizure patterns in a brother and a sister.

In symptomatic epilepsies due to chromosomal aberrations, epileptogenesis may be either the direct consequence of deletion or duplication of a gene causing seizures or may have a more complex etiology caused by the disturbance of the interaction of several genes and environmental factors. We report on a brother and a sister with trisomy 19q13.3-->qter who present different epileptologic features and discuss epileptogenesis in this syndrome with respect to genes known to be located on the distal part of chromosome 19q. Both patients share mental retardation and several dysmorphic features. The boy was hypoxic at birth and showed an extremely delayed psychomotor development. The girl, however, had no significant neonatal problems, and her psychomotor development was better. Although the male had an abnormal EEG in childhood, his first partial seizures occurred only as late as at age 31 years. He subsequently became seizure-free with carbamazepine (CBZ). In contrast, the girl already suffered from absence-like seizures during childhood and became seizure-free under ethosuccimide (ESM). A photoparoxysmal response, however, is still visible in her EEG. The difference between the epileptologic features in these siblings points to epileptogenic mechanisms placed far downstream on the way from genotype to phenotype. The photoparoxysmal response--otherwise a facultative finding in genetically determined epilepsies--in the EEG of the sister, however, points to a closer relationship between the duplicated genes and epileptogenesis. The fact that genes encoding potassium channels are located on 19q13.3-q13.4 may also support the latter assumption.

Adult↗
PubMed2000

The contribution of uniparental disomy to congenital development defects in children born to mothers at advanced childbearing age.

Most instances of maternal uniparental disomy (UPD) start as trisomies and, similar to the latter, show a significant increase of mean maternal age at delivery. To investigate the incidence of UPD in offspring of older mothers, we investigated two groups of patients: 1) 50 patients with unclassified developmental defects born to mothers 35 years or older at delivery were tested for UPD for all autosomes by means of microsatellite marker analysis; 2) The incidence of UPD versus other etiologies in correlation, with maternal age below versus 35 years and above at delivery was studied in patients investigated in our laboratory for maternal UPD 15 (Prader-Willi syndrome, PWS), paternal UPD 15 (Angelman syndrome, AS), and maternal UPD 7 (Silver-Russell syndrome, SRS). In group 1, four patients of 50 showed UPD for an autosome that clarified the etiology of their developmental problems: a 27-year-old woman with growth retardation and early puberty disclosed maternal heterodisomy 14; a 15-year-old girl revealed paternal isodisomy 15; a 6-year-old boy with suspected Smith-Lemli-Opitz syndrome was shown to have maternal heterodisomy 16 with additional mosaic partial trisomy 16(pter-p13); a 16-month-old girl with intrauterine growth retardation and a dysmorphic pattern revealed maternal heterodisomy 7. In group 2 the offspring of older mothers showed a clear increase of UPD compared with the mothers below 35 years at delivery. The binomial distribution gave P-values of 1.9 x 10(-10), 2.6 x 10(-4), and 0.01 for PWS, AS, and SRS, respectively. The correlation between increase of paternal UPD 15 with advanced maternal age might be explained by maternal non-disjunction leading to hypohaploid gamete (nullisomy) for chromosome 15 with subsequent or concomitant duplication of the paternal homologue (paternal isodisomy). The three UPD 15 AS cases with mothers older than 35 years at delivery revealed isodisomy, whereas the three cases from younger mothers showed heterodisomy. This study confirms the hypothesis that uniparental disomy is a not negligible cause of congenital developmental anomalies in children of older mothers.

Abnormalities, Multiple↗
PubMed2000

[Data on selected prenatal malformations in the EUROCAT study. Results of Zurich Canton from 1988 to 1997].

In the context of the EUROCAT study, data on selected congenital malformations and chromosome aberrations were collected from the Canton of Zurich (1988-1997). It was found that the major proportion of severe and early malformations, such as anencephalus and holoprosencephaly, were detected prenatally; for oral clefts and meningomyeloceles this was not the case, at any rate in regard to isolated (non-syndromic) malformations. However, if these defects occur in combination with a chromosome aberration, the likelihood of such a case being registered is higher. For the same reason, i.e. due to abnormal ultrasound findings and intrauterine growth retardation, trisomies 13 and 18 were more often detected prenatally than trisomy 21.

Congenital Abnormalities↗
PubMed2000

[Hereditary hearing loss due to mutations in the connexin-26 gene].

Hearing loss is a frequent disease with an estimated incidence of 1:1000 in children. Hereditary hearing loss is characterised by enormous genetic heterogeneity, which makes diagnosis difficult. Approximately 50% of the Caucasian patients with autosomal recessive inherited hearing loss carry mutations in the connexin-26 gene on chromosome 13. Standard screening procedures such as SSCP (single strand conformation polymorphism) analysis, DHPLC (denaturing high performance liquid chromatography) and subsequent sequencing are used to investigate this gene. A genetic test is thus available which can be offered to probands in genetic counselling. We investigated 11 patients with hearing loss and found sequence aberrations in 7 patients, which is causative for the hearing loss in at least 5 patients. The first application of DHPLC in Switzerland is also documented.

Child↗
PubMed2000

Phenotypic heterogeneity of growth and psychometric intelligence in Prader-Willi syndrome: variable expression of a contiguous gene syndrome or parent-child resemblance?

Phenotypic variability in children with Prader-Willi syndrome (PWS) was investigated with respect to variable expression of the contiguous gene syndrome and trait variance. In a prospective study, parent/child resemblance of anthropometric and psychometric measures was analyzed in 22 children with PWS (11 females and 11 males; 18 deletions, 4 uniparental disomy (UPD)) and in a control group (88 females and 88 males). The average child-midparent Z-score difference for height in females was -1.9 and in males -0.9, head circumference -1.7 and -1.0, and body mass index (BMI) 2.3 and 2.7, respectively. Intellectual performance of females and males was, on average, -2.7 and -2.6 below maternal performance. Range and standard deviation were moderately increased for height and head circumference, doubled for BMI, and unchanged for IQ. Parent/child correlations for anthropometric and psychometric measurements in the study group did not significantly differ from those of the control group. Exceptions were higher correlations between mothers and daughters for height (P < 0.05) and BMI (P < 0.01), and lower correlations for head circumference between midparent values and daughters (P < 0.05) than in the control group. In conclusion, parent-child resemblance in growth and intellectual development among children with PWS was found to be comparable to that noted in the normal population, indicating a strong determination by trait variance. Children with PWS differed significantly with respect to a lower trait level and-with the exception of IQ-a larger variability. The latter may indicate a variable expression of the contiguous gene syndrome.

Adolescent↗
PubMed2000

Schizophrenia and smoking: evidence for a common neurobiological basis?

Several previous investigations have suggested that the gene for the alpha 7-nicotinic receptor may play a role in the pathogenesis of schizophrenia and may be responsible for the heavy smoking among schizophrenic patients. In a study of 129 healthy controls and 127 schizophrenic, schizoaffective, and bipolar patients we have aimed 1) to confirm the potential association between schizophrenia and the alpha 7-nicotinic receptor, 2) to test the diagnostic specificity of alpha 7-receptor subunits with respect to psychiatric diagnoses, and 3) to investigate potential receptor differences between smokers and nonsmokers in the general population. Our analysis included the two dinucleotide polymorphisms D15S1360 and L76630 that are localized in a genomic fragment containing the alpha 7-nicotinic receptor gene CHRNA7. Highly significant differences (P < 0.0001) between the allele distributions of patients and controls were detected for these two markers with all three diagnostic subgroups contributing to the discrimination. An independently ascertained replication sample of 24 patients confirmed this finding. Our results suggested an unspecific vulnerability that depended on the severity of overall psychopathology in terms of the co-occurrence of psychopathology with no clear-cut boundary between the diagnostic entities. In comparison with healthy controls, this vulnerability was lowest among schizophrenics, intermediate among bipolars, and highest among schizoaffectives. As to the question of alpha 7-receptor differences between smokers and nonsmokers among the healthy control subjects, our analysis revealed no significant differences, thus indicating that the differences between patients and controls are more than just a smoker/nonsmoker distinction. Am. J. Med. Genet. (Neuropsychiatr. Genet.) 96:173-177, 2000.

Bungarotoxins↗
PubMed2000

Prenatal diagnosis of mosaicism for a del(22)(q13).

A case of prenatally detected mosaicism for a del(22)(q13) is reported. CVS was performed because of abnormal fetal ultrasound findings: cystic 'tumour' in the fetal neck and the upper thoracic aperture. Karyotypes from chorionic villi were suspicious of an aberration concerning the long arm of one chromosome 22. FISH analysis demonstrated mosaicism for a distal 22q deletion in fetal fibroblasts. The deletion was postnatally confirmed by FISH with a chromosome-specific 22q probe. The 'tumour' on autopsy turned out to be cystic thymic tissue. Apart from this, no other obvious fetal anomalies were found.

Adult↗
PubMed2000

Isolated central form of tetrahydrobiopterin deficiency associated with hemizygosity on chromosome 11q and a mutant allele of PTPS.

6-Pyruvoyl-tetrahydropterin synthase (PTS or PTPS) is involved in tetrahydrobiopterin (BH(4)) biosynthesis, the cofactor for various enzymes including the aromatic amino acid hydroxylases. Inherited PTPS deficiency is a heterogeneous disease with different phenotypes leading to BH(4) depletion. The severe form of PTPS deficiency causes hyperphenylalaninemia and monoamine neurotransmitter deficiency, whereas the mild form gives rise to hyperphenylalaninemia only. From 228 patients with PTPS deficiency at least 32 different mutant alleles have been identified on its corresponding gene, located on chromosome 11q22.3-q23.3. Here we describe a new allele from a child with PTPS deficiency who exhibited a mild but transient form of hyperphenylalaninemia, yet was deficient in CSF monoamines. The patient was found to carry, on her genomic DNA and cDNA, a homozygous A>G transition, leading to PTPS codon alteration Tyr99 to Cys (Y99C). The mother and several members of the maternal family were carriers of the Y99C allele, also verified by the reduced PTPS enzyme activity in erythrocytes. By cytogenetic, molecular, and FISH analyses, a de novo deletion spanning from 11q14 to 11q23.3 on the patient's paternal chromosome was mapped, establishing hemizygosity of the Y99C allele. The PTPS mutation observed in this patient generates a novel phenotype with an apparently isolated central form of BH(4) deficiency.

Alleles↗
PubMed2000

Maternal uniparental disomy 7--review and further delineation of the phenotype.

UNLABELLED: Uniparental disomy (UPD) is defined as the inheritance of both homologous chromosomes from only one parent. So far, maternal UPD 7 has been described in 28 cases. Here, we report 4 new cases, present clinical information of 5 cases previously reported by us, and review the clinical and molecular findings of all 32 cases. We found a phenotype characterized by pre- and postnatal growth retardation, occipitofrontal head circumference in the lower normal range, a triangular face, and retarded bone maturation. Findings of the facial gestalt included a high and broad forehead and a pointed chin. A broad mouth with down-turned corners, prominent ears, café-au-lait spots, hemihypotrophy, or clinodactyly were rarely present. Psychomotor development was delayed in 6 cases. The clinical findings strikingly resemble the phenotype of the heterogeneous Silver-Russell syndrome (SRS). Other anomalies were less frequently found than in SRS. Molecular investigations revealed 11 cases with isodisomy and 17 cases with heterodisomy. In 4 cases this information was not available. From the allelic distribution of the microsatellites investigated, 9 cases might be the consequence of an error at maternal meiosis I, and 6 cases might be due to non-disjunction at maternal meiosis II. Three of the 17 heterodisomic cases had trisomy 7 in chorionic villi, in the remaining cases no prenatal diagnosis through chorionic villus sampling was reported. CONCLUSION: Maternal UPD 7 should investigated in children with pre- and postnatal growth retardation anda facial gestalt characterized by a high and broad forehead and a pointed chin, as well as in cofined placental mosaicism for trisomy 7.

Abnormalities, Multiple↗
PubMed2000

No evidence of uniparental disomy 2, 6, 14, 16, 20, and 22 as a major cause of intrauterine growth retardation.

Intrauterine growth retardation (IUGR) is defined as length and/or weight below the 10th percentile. Etiology and, consequently, long-term outcome are extremely heterogeneous with chromosomal abnormalities found in up to 7%. Recently, uniparental disomy (UPD), i.e. the inheritance of both homologues of one pair of chromosomes from only one parent, was found in an increasing number of children with IUGR. Particularly, UPD of chromosome 7 was found in up to 10% of patients with IUGR and/or a phenotype of primordial growth retardation or Silver-Russell syndrome (SRS), but also UPD of chromosomes 2, 6, 14, 16, 20, and 22 was reported in single cases with IUGR. To evaluate impact and relevance of UPD in children with IUGR we investigated 23 sporadic cases with IUGR subsequently diagnosed as primordial growth retardation (n = 13) or SRS (n = 10) by molecular methods for UPD of chromosomes 2, 6, 14, 16, 20, and 22. No instance of UPD was found. Inheritance of all chromosomes investigated was biparental in all cases. Therefore, we conclude that UPD of these chromosomes is not a major cause of IUGR.

Adult↗
PubMed2000

An autosomal dominant form of hereditary hypotrichosis simplex maps to 18p11.32-p11.23 in an Italian family.

We report on a three-generation Italian family with dominant transmission of a form of hereditary hypotrichosis simplex (HHS). The nine affected adults presented with sparse, thin and short hair. Somewhat less sparse and longer hair was observed in the two affected young children in the third generation. Reduced hair growth affected the scalp and body, although normal eyelashes, eyebrows and growth of men's beards were observed. No associated abnormality was detected and the overall psychomotor development of the affected individuals was normal. A phenotypic variation was observed amongst the family members and is suggestive of a reduced penetrance of the trait or the effect of a modifying factor. After exclusion, in our family, of linkage to loci previously described in other forms of atrichia or hypotrichosis, we performed a genome-wide linkage analysis, which resulted in a positive lod score at 18p11.32-p11.23. We defined a critical region of about 35 cM flanked by markers D18S853 and D18S40. The highest two-point lod score was obtained with the microsatellite markers D18S1376, D18S53 and D18S453 (lod score of 3.31 at theta = 0.00). The 18p11.32-p11.23 locus represents the first chromosome region shown to be associated with hereditary hypotrichosis simplex.

Adult↗
PubMed2000

Paternal meiotic origin of der(21;21)(q10;q10) mosaicism [46,XX/46, XX,der(21;21)(q10;q10),+21] in a girl with mild Down syndrome.

Mosaicism for a derivative 21, der(21;21)(q10;q10), is a rare chromosomal abnormality. Since a normal cell line is present, mitotic origin is considered. Chromosome examination of a female with developmental delay and dysmorphic features compatible with mosaic trisomy 21 revealed a normal cell line and a second cell line with a der(21;21)(q10;q10) [46,XX/46,XX,der(21;21)(q10;q10),+21]. Molecular investigation with a panel of highly polymorphic microsatellites mapping to chromosome 21 demonstrated three different alleles, two of paternal and one of maternal origin. Therefore, either formation of the der(21;21)(q10;q10) during paternal meiosis with subsequent loss of the der(21;21)(q10;q10) and mitotic reduplication of the maternal homologue in the normal cell line, or more likely a zygote with paternally derived trisomy 21 and subsequent mitotic formation of the der(21;21)(q10;q10) have to be considered. This case again shows that mammalian chromosome aberrations may have a more complex mechanism of formation than was previously thought.

Age Determination by Skeleton↗