Persistent failures in gene repair.
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Animals↗
Biomedical subjects
H Scheffer
Publications and source records attributed to H Scheffer.
Best practice guidelines for molecular analysis in spinal muscular atrophy.
With a prevalence of approximately 1/10 000, and a carrier frequency of 1/40-1/60 the proximal spinal muscular atrophies (SMAs) are among the most frequent autosomal recessive hereditary disorders. Patients can be classified clinically into four groups: acute, intermediate, mild, and adult (SMA types I, II, III, and IV, respectively). The complexity and instability of the genomic region at chromosome 5q13 harbouring the disease-causing survival motor neuron 1 (SMN1) gene hamper molecular diagnosis in SMA. In addition, affected individuals with SMA-like phenotypes not caused by SMN1, and asymptomatic individuals with two mutant alleles exist. The SMN gene is present in at least one telomeric (SMN1) and one centromeric copy (SMN2) per chromosome in normal (non-carrier) individuals, although chromosomes containing more copies of SMN1 and/or SMN2 exist. Moreover, the two SMN genes (SMN1 and SMN2) are highly homologous and contain only five base-pair differences within their 3' ends. Also, a relatively high de novo frequency is present in SMA. Guidelines for molecular analysis in diagnostic applications, carrier detection, and prenatal analysis using direct and indirect approaches are described. Overviews of materials used in the molecular diagnosis as well as Internet resources are included.
Cyclic AMP Response Element-Binding Protein↗
Identification of a novel mutation (867delA) in the glucose-6-phosphatase gene in two siblings with glycogen storage disease type Ia with different phenotypes.
We identified a novel mutation (867delA) in the glucose-6-phosphatase gene of two siblings with glycogen storage disease type Ia. Although both siblings share the same mutations, their phenotype regarding adult height and hepatomegaly differs. In glycogen storage disease type Ia, substantial heterogeneity in phenotype is observed. So far, no evidence for a clear genotype-phenotype correlation has been found. Hum Mutat 15:381, 2000.
Adult↗
Use of 23Na MRS to discriminate viable from non viable tissue: experimental studies.
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Animals↗
Glycogen storage disease type Ia: recent experience with mutation analysis, a summary of mutations reported in the literature and a newly developed diagnostic flow chart.
UNLABELLED: We studied the glucose-6-phosphatase (G6Pase) gene of 30 unrelated glycogen storage disease type Ia (GSD Ia) patients using single strand conformational polymorphism (SSCP) prior to automated sequencing of exons revealing an aberrant SSCP pattern. In all patients we could identify mutations on both alleles of the G6Pase gene, indicating that this method is a reliable procedure. A total of 14 different mutations were identified. R83C (16/60), 158delC (12/60), Q347X (7/60), R170X (6/60) and deltaF327 (4/60) were found most frequently. Nine other mutations accounted for the other 15 mutant alleles. Two DNA-based prenatal diagnoses were performed successfully. At present, 56 mutations in the G6Pase gene have been reported in 300 unrelated GSD Ia patients and an overview of these mutations is presented. Evidence for a clear genotype-phenotype correlation could be established neither from our data nor from those in the literature. With increased knowledge about the genetic basis of GSD Ia and GSD Ib and the high detection rate of mutations, it is our opinion that the diagnoses GSD Ia and GSD Ib can usually be based on clinical and biochemical abnormalities combined with mutation analysis instead of enzyme assays in liver tissue obtained by biopsy. A newly developed flowchart for the diagnosis of GSD I is presented. CONCLUSION: Increased knowledge of the genetic basis of glycogen storage disease type I provides a DNA-based diagnosis, prenatal DNA-based diagnosis in chorionic villus samples and carrier detection.
Chorionic Villi Sampling↗
SMA carrier testing--validation of hemizygous SMN exon 7 deletion test for the identification of proximal spinal muscular atrophy carriers and patients with a single allele deletion.
To facilitate the detection of carriers of a hemizygous survival motor neuron (SMN) exon 7 deletion we have modified the quantitative SMN exon 7 assay described by McAndrew et al (1997). The major changes include quantitative analysis of the amount of SMN exon 7-specific fluorescently-labelled PCR product on an automated sequencer, and the monitoring of the completeness of a DraI digestion necessary to distinguish the PCR products of exons 7 of SMN and its copy gene. In our method the amount of SMN exon 7 PCR product is compared with the amount of a co-amplified PCR product of the retinoblastoma (RB1) exon containing a DraI restriction site. By co-amplification using the same primers of plasmids included in the reaction as internal standards containing SMN exon 7 with a 36-nucleotide deletion and RB1 exon 13 with a 19-nucleotide deletion, respectively, the relative amplification efficacy can be monitored. The assay has been validated in 63 ascertained carriers and 28 ascertained non-carriers. The sensitivity of the test is approximately 97%, the specificity approaches 100%. In four out of six SMA patients without a homozygous deletion we detected a hemizygous deletion. The implications of the use of this assay for carrier testing and for confirmation of the clinical diagnosis of SMA are discussed.
Cyclic AMP Response Element-Binding Protein↗
Recommendations for quality improvement in genetic testing for cystic fibrosis. European Concerted Action on Cystic Fibrosis.
These recommendations for quality improvement of cystic fibrosis genetic diagnostic testing provide general guidelines for the molecular genetic testing of cystic fibrosis in patients/individuals. General strategies for testing as well as guidelines for laboratory procedures, internal and external quality assurance, and for reporting the results, including the requirements of minimal services in mutation testing, the nomenclature for describing mutations, procedures to control false-positive amplification reactions and to validate tests, and guidelines to implement a quality system in a molecular diagnostic laboratory are reviewed.
Accreditation↗
Exempting homologous pseudogene sequences from polymerase chain reaction amplification allows genomic keratin 14 hotspot mutation analysis.
In patients with the major forms of epidermolysis bullosa simplex, either of the keratin genes KRT5 or KRT14 is mutated. This causes a disturbance of the filament network resulting in skin fragility and blistering. For KRT5, a genomic mutation detection system has been described previously. Mutation detection of KRT14 on a DNA level is, however, hampered by the presence of a highly homologous but nontranscribed KRT14 pseudogene. Consequently, mutation detection in epidermolysis bullosa simplex has mostly been carried out on cDNA synthesized from KRT5 and KRT14 transcripts in mRNA isolated from skin biopsies. Here we present a genomic mutation detection system for exons 1, 4, and 6 of KRT14 that encode the 1A, L1-2, and 2B domains of the keratin 14 protein containing the mutation hotspots. After cutting the KRT14 pseudogene genomic sequences with restriction enzymes while leaving the homologous genomic sequences of the functional gene intact, only the mutation hotspot-containing exons of the functional KRT14 gene are amplified. This is followed by direct sequencing of the polymerase chain reaction products. In this way, three novel mutations could be identified, Y415H, L419Q, and E422K, all located in the helix termination motif of the keratin 14 rod domain 2B, resulting in moderate, severe, and mild epidermolysis bullosa simplex phenotype, respectively. By obviating the need of KRT14 cDNA synthesis from RNA isolated from skin biopsies, this approach substantially facilitates the detection of KRT14 hotspot mutations.
DNA Mutational Analysis↗
Two novel germline mutations of the retinoblastoma gene (RB1) that show incomplete penetrance, one splice site and one missense.
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Female↗
Transthyretin Val71Ala mutation in a Dutch family with familial amyloidotic polyneuropathy.
A Dutch family with familial amyloidotic polyneuropathy associated with the transthyretin mutation Val71Ala is described. This is the third reported family with this mutation, causing at the protein level an unstable TTR monomer and at the clinical level progressive wasting, polyneuropathy, autonomic dysfunction and vitreous opacities.
Adult↗
Epidermolysis bullosa simplex with mottled pigmentation: clinical aspects and confirmation of the P24L mutation in the KRT5 gene in further patients.
Epidermolysis bullosa simplex with mottled pigmentation (EBS-MP) is a rare dermatologic disorder of autosomal dominant inheritance with intraepidermal blistering after minor trauma, reticular hyperpigmentation unrelated to the blistering, nail dystrophy, and mild palmoplantar keratosis. Keratin 5 and keratin 14 are known to be essential for the basal keratinocyte cytoskeleton and are defective in several forms of epidermolysis bullosa simplex. Recently, a 71C-->T transition in the keratin 5 gene (KRT5) causing a P24L substitution was identified in some patients with EBS-MP. We present a family with three affected members and a sporadic patient with EBS-MP. They exemplify clinically mild expression with intrafamilial variability and the possibility of improvement with time. In all of them, mutation analysis of the KRT5 gene showed the P24L mutation. So far, other mutations in the same or in other genes have not been reported in patients with EBS-MP.
Adult↗
Two cases of maternal uniparental disomy 14 with a phenotype overlapping with the Prader-Willi phenotype.
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Abnormalities, Multiple↗
Glycogen storage disease type Ia: four novel mutations (175delGG, R170X, G266V and V338F) identified. Mutations in brief no. 220. Online.
Deficient activity of glucose-6-phosphatase (G6Pase) causes glycogen storage disease type Ia (GSD Ia). We analysed the G6Pase gene of 16 GSD Ia patients using single strand conformation polymorphism (SSCP) analysis prior to automated sequencing of exon(s) revealing an aberrant SSCP pattern. In all GSD Ia patients we were able to identify mutations on both alleles of the G6Pase gene, indicating that this method is a reliable procedure to identify mutations. Four novel mutations (175delGG, R170X, G266V and V338F) were identified.
Amino Acid Substitution↗
Maternal uniparental disomy for chromosome 14 in a boy with a normal karyotype.
We report on a boy with a maternal uniparental disomy for chromosome 14 (UPD(14)). At 7 years of age he was referred to us by the paediatrician because of symptoms of Prader-Willi syndrome (PWS). He showed short stature, obesity, mild developmental delay, cryptorchidism, and some mild dysmorphic features. The history further indicated intrauterine growth retardation at the end of the pregnancy. His mother was 44 years of age at the time of his birth. After birth he showed hypotonia with poor sucking, for which gavage feeding was needed. Motor development was delayed. After 1 year he became obese despite a normal appetite. Recurrent middle ear infections, a high pain threshold, and a great skill with jigsaw puzzles were reported. There were no behavioural problems or sleep disturbance. Chromosomal analysis was normal (46,XY). DNA analysis for Prader-Willi syndrome showed no abnormalities. Two years later he was re-examined because we thought his features fitted the PWS-like phenotype associated with maternal UPD(14). At that time precocious puberty was evident. DNA analysis showed maternal heterodisomy for chromosome 14. In all the previously described 11 cases with maternal UPD(14), a Robertsonian translocation involving chromosome 14 was detected cytogenetically before DNA analysis. This is the first report of diagnosis of maternal UPD(14) based on clinical features. This finding underlines the importance of DNA analysis for maternal UPD(14) in patients with a similar PWS-like phenotype even without previous identification of a Robertsonian translocation involving chromosome 14.
Child↗
Three novel KCNA1 mutations in episodic ataxia type I families.
Hereditary paroxysmal ataxia, or episodic ataxia (EA), is a rare, genetically heterogeneous neurological disorder characterized by attacks of generalized ataxia. By direct sequence analysis, a different missense mutation of the potassium channel gene (KCNA1) has been identified in three families with EA.
Amino Acid Substitution↗
Relative frequencies of cystic fibrosis mutations in The Netherlands as an illustration of significant regional variation in a small country.
Cystic fibrosis (CF) is one of the most common autosomal recessive disorders in white populations. Significant regional differences in CF mutations among affected individuals have been reported. We have studied the geographic distribution of the relative frequencies of the three most common Dutch CF mutations, deltaF508, A455E, and G542X, by analyzing data on area of residence of CF patients. Significantly higher relative frequencies of the A455E mutation and the G542X mutation were observed in the South-West and the South-East, respectively. A uniform distribution of relative frequencies was found for the deltaF508 mutation. The results of our study show that, even in a small country such as The Netherlands, certain CF mutations may be more common in one region than in another.
Cystic Fibrosis↗
Mutation frequency of cystic fibrosis transmembrane regulator is not increased in oligozoospermic male candidates for intracytoplasmic sperm injection.
OBJECTIVE: To examine the frequency of anomalies of the vas deferens and the frequency of mutations of the cystic fibrosis transmembrane regulator (CFTR) gene in male candidates for intracytoplasmic sperm injection (ICSI) who had severe oligoasthenoteratozoospermia. DESIGN: The clinical data for male candidates for ICSI were studied. The three most frequent cystic fibrosis (CF)-causing CFTR mutations in the Dutch population (deltaF508, A455E, and G542X) and the three most frequent CFTR mutations potentially causing congenital bilateral absence of the vas deferens (CBAVD) in the Dutch population (deltaF508, R117H, and IVS8-5T) were analyzed. Delta I507 is also detected by the deltaF508 test. Samples of DNA from patients identified as CFTR mutation carriers were subjected to denaturing gradient gel electrophoresis analysis with use of a two-dimensional electrophoretic technique. SETTING: University-based center for reproductive medicine and clinical genetics. PATIENT(S): Male candidates for ICSI who had oligoasthenoteratozoospermia and no history of operative sterilization and refertilization. Males with a chromosomal aberration or a Y-chromosome microdeletion were excluded. INTERVENTION(S): Semen and blood samples were collected from the patients at their first visit to the clinic. MAIN OUTCOME MEASURE(S): Frequency of anomalies of the vas deferens and frequency of mutations of the CFTR gene in male candidates for ICSI who had oligoasthenoteratozoospermia. RESULT(S): None of the patients had abnormalities of the vas deferens at physical examination. In 4 of the 150 chromosomes (75 patients), a CFTR mutation was found, yielding a CFTR mutation frequency of 2.7% (95% confidence interval, 1.0-6.7%). None of the patients had two CFTR mutations. CONCLUSION(S): The frequency of congenital abnormalities of the vas deferens in patients with oligoasthenoteratozoospermia is low. The frequencies of the CFTR mutations identified in this cohort did not differ significantly from the frequencies found in the normal Dutch population.
Cystic Fibrosis Transmembrane Conductance Regulato↗
Revertant mosaicism in epidermolysis bullosa caused by mitotic gene conversion.
Mitotic gene conversion acting as reverse mutation has not been previously demonstrated in human. We report here that the revertant mosaicism of a compound heterozygous proband with an autosomal recessive genodermatosis, generalized atrophic benign epidermolysis bullosa, is caused by mitotic gene conversion of one of the two mutated COL17A1 alleles. Specifically, the maternal allele surrounding the mutation site on COL17A1 (1706delA) showed reversion of the mutation and loss of heterozygosity along a tract of at least 381 bp in revertant keratinocytes derived from clinically unaffected skin patches; the paternal mutation (R1226X) remained present in all cell samples. Revertant mosaicism represents a way of natural gene therapy.
Adult↗