Halley, D.J.J.

Multiplex ligation-depending probe amplification is not suitable for detection of low-grade mosaicism (Article)

2011-09-01T00:00:00Z

Apparent non-penetrance occurs in several genetic disorders, including tuberous sclerosis complex and neurofibromatosis type 1: clinically unaffected parents may have multiple affected offspring. Germ line or somatic mosaicism in one of the parents of the index patient is the probable cause and results in an enhanced recurrence risk. Therefore, it is of great importance to use the most sensitive technology for testing DNA of the parents of the index patient for the presence/absence of the familial mutation. To detect large rearrangements multiplex ligation-depending probe amplification (MLPA) is often used. Here we show that MLPA is less sensitive in detecting low-grade somatic mosaicism than fluorescence in situ hybridization (FISH) or a mutation-specific PCR test. Therefore, we recommend FISH (if possible) or PCR analysis for the analysis of parental DNA.

N -acetylaspartylglutamate in CNS hypomyelination (Article)

2011-07-05T00:00:00Z

CSF N-acetylaspartylglutamate (NAAG) has been found to be elevated in some hypomyelinating disorders. This study addressed the question whether it could be used as a marker for hypomyelination and as a means to distinguish between hypomyelinating disorders biochemically. We have measured CSF NAAG in a cohort of 28 patients with hypomyelination with known and unknown aetiology. NAAG was found to be elevated in 7 patients, but was normal in the majority, including patients with defined hypomyelinating disorders. CSF NAAG is not a universal marker of hypomyelination, and the mechanism of its elevation remains poorly understood.

A novel GPR56 mutation causes bilateral frontoparietal polymicrogyria (Article)

2011-07-01T00:00:00Z

Bilateral frontoparietal polymicrogyria is an autosomal recessive inherited human brain malformation with abnormal cortical lamination. The affected cortex appears to consist of numerous small gyri, with scalloping of the cortical-white matter junction. There are associated white matter, brain stem, and cerebellar changes. Affected individuals manifest mental retardation, language impairment, motor developmental delay, and seizure disorder. GPR56 is the causative gene. Here we report a novel missense mutation of GPR56, E496K, identified in a consanguineous pedigree with bilateral frontoparietal polymicrogyria. GPR56 protein is cleaved at the G-protein-coupled receptor proteolytic site into an N- and a C-terminal fragment, named GPR56Nand GPR56C, respectively. E496K is located in GPR56C. Further biochemical studies reveal that this mutation affects GPR56Ccell surface expression similar to the effect of a previously reported mutation, R565W. These results provide further insights into how GPR56 mutation causes neurologic disease.

Long-term follow-up of type 1 lissencephaly: Survival is related to neuroimaging abnormalities (Article)

2011-05-01T00:00:00Z

Aim: To evaluate survival, clinical, and genetic characteristics of all patients with classic or type 1 lissencephaly born between 1972 and 1990 in the Netherlands, who at the time were enrolled in an observational study. Method: We re-evaluated 24 patients (11 males, 13 females) for long-term follow-up and survival information. Results: Mean length of follow-up was 14years (SD 9y 8mo). Eleven patients were alive at follow-up. All patients showed severe intellectual disability, intractable epilepsy, and complete dependency on care. Life expectancy was related to the severity of the lissencephaly on neuroimaging. Molecular analysis of the LIS1 gene was not possible at the time of the original study and was now requested by eight parents. This revealed a pathogenic nonsense mutation or deletion in seven patients. Interpretation Our study provides information about the long-term course of lissencephaly and the relationship between lissencephaly severity and prognosis. It also shows that renewed attention to genetic counselling remains valued by families of patients with a severe congenital neurological disease. © The Authors. Developmental Medicine & Child Neurology

Functional assessment of variants in the TSC1 and TSC2 genes identified in individuals with Tuberous Sclerosis Complex (Article)

2011-04-01T00:00:00Z

The effects of missense changes and small in-frame deletions and insertions on protein function are not easy to predict, and the identification of such variants in individuals at risk of a genetic disease can complicate genetic counselling. One option is to perform functional tests to assess whether the variants affect protein function. We have used this strategy to characterize variants identified in the TSC1 and TSC2 genes in individuals with, or suspected of having, Tuberous Sclerosis Complex (TSC). Here we present an overview of our functional studies on 45 TSC1 and 107 TSC2 variants. Using a standardized protocol we classified 16 TSC1 variants and 70 TSC2 variants as pathogenic. In addition we identified eight putative splice site mutations (five TSC1 and three TSC2). The remaining 24 TSC1 and 34 TSC2 variants were classified as probably neutral.

Mucopolysaccharidosis type IIIB may predominantly present with an attenuated clinical phenotype (Article)

2010-12-01T00:00:00Z

Mucopolysaccharidosis type IIIB (MPS IIIB, Sanfilippo syndrome type B) is a lysosomal storage disorder caused by deficiency of the enzyme N-acetyl-α-D-glucosaminidase (NAGLU). Information on the natural course of MPS IIIB is scarce but much needed in view of emerging therapies. To improve knowledge on the natural course, data on all 52 MPS IIIB patients ever identified by enzymatic studies in the Netherlands were gathered. Clinical data on 44 patients could be retrieved. Only a small number (n=9; 21%) presented with a classical MPS III phenotype; all other patients showed a much more attenuated course of the disease characterized by a significantly slower regression of intellectual and motor abilities. The majority of patients lived well into adulthood. First signs of the disease, usually mild developmental delay, were observed at a median age of 4 years. Subsequently, patients showed a slowing and eventually a stagnation of development. Patients with the attenuated phenotype had a stable intellectual disability for many years. Molecular analysis was performed in 24 index patients. The missense changes p.R643C, p.S612G, p.E634K, and p.L497V were exclusively found in patients with the attenuated phenotype. MPS IIIB comprises a remarkably wide spectrum of disease severity, and an unselected cohort including all Dutch patients showed a large proportion (79%) with an attenuated phenotype. MPS IIIB must be considered in patients with a developmental delay, even in the absence of a progressive decline in intellectual abilities. A key feature, necessitating metabolic studies, is the coexistence of behavioral problems.

Mucopolysaccharidosis type IIIA: Clinical spectrum and genotype-phenotype correlations (Article)

2010-12-01T00:00:00Z

Objective: Mucopolysaccharidosis (MPS) IIIA (Sanfilippo syndrome type A) is a lysosomal storage disorder caused by deficiency of the enzyme sulfamidase. Information on the natural course of MPS IIIA is scarce, but is much needed in view of emerging therapies. Methods Clinical history and molecular defects of all 110 MPS IIIA patients identified by enzymatic studies in the Netherlands were collected and included in this study. Results First clinical signs, mainly consisting of delayed speech development and behavioral problems, were noted between the ages of 1 and 6 years. Other symptoms included sleeping and hearing problems, recurrent upper airway infections, diarrhea, and epilepsy. The clinical course varied remarkably and could be correlated with the molecular defects. The frequent pathogenic mutations p.R245H, p.Q380R, p.S66W, and c.1080delC were associated with the classical severe phenotype. Patients compound heterozygous for the p.S298P mutation in combination with 1 of the mutations associated with the classical severe phenotype had a significantly longer preservation of psychomotor functions and a longer survival. Two patients homozygous for the p.S298P mutation, and 4 patients from 3 families heterozygous for 3 missense variants not reported previously (p.T421R, p.P180L, and p.L12Q), showed a remarkably attenuated phenotype. Interpretation We report the natural history and mutational analysis in a large unbiased cohort of MPS IIIA patients. We demonstrate that the clinical spectrum of MPS IIIA is much broader than previously reported. A significant genotype-phenotype correlation was established in this cohort. Copyright

Combined cardiological and neurological abnormalities due to filamin A gene mutation (Article)

2010-01-01T00:00:00Z

Background: Cardiac defects can be the presenting symptom in patients with mutations in the X-linked gene FLNA. Dysfunction of this gene is associated with cardiac abnormalities, especially in the left ventricular outflow tract, but can also cause a congenital malformation of the cerebral cortex. We noticed that some patients diagnosed at the neurogenetics clinic had first presented to a cardiologist, suggesting that earlier recognition may be possible if the diagnosis is suspected. Methods and results: From the Erasmus MC cerebral malformations database 24 patients were identified with cerebral bilateral periventricular nodular heterotopia (PNH) without other cerebral cortical malformations. In six of these patients, a pathogenic mutation in FLNA was present. In five a cardiac defect was also found in the outflow tract. Four had presented to a cardiologist before the cerebral abnormalities were diagnosed. Conclusions: The cardiological phenotype typically consists of aortic or mitral regurgitation, coarctation of the aorta or other left-sided cardiac malformations. Most patients in this category will not have a FLNA mutation, but the presence of neurological complaints, hyperlaxity of the skin or joints and/or a family history with similar cardiac or neurological problems in a possibly X-linked pattern may alert the clinician to the possibility of a FLNA mutation.

Identification of a region required for TSC1 stability by functional analysis of TSC1 missense mutations found in individuals with tuberous sclerosis complex (Article)

2009-09-11T00:00:00Z

Background: Tuberous sclerosis complex (TSC) is an autosomal dominant disorder characterised by the development of hamartomas in a variety of organs and tissues. The disease is caused by mutations in either the TSC1 gene on chromosome 9q34, or the TSC2 gene on chromosome 16p13.3. The TSC1 and TSC2 gene products, TSC1 and TSC2, form a protein complex that inhibits signal transduction to the downstream effectors of the mammalian target of rapamycin (mTOR). Recently it has been shown that missense mutations to the TSC1 gene can cause TSC. Methods: We have used in vitro biochemical assays to investigate the effects on TSC1 function of TSC1 missense variants submitted to the Leiden Open Variation Database. Results: We identified specific substitutions between amino acids 50 and 190 in the N-terminal region of TSC1 that result in reduced steady state levels of the protein and lead to increased mTOR signalling. Conclusion: Our results suggest that amino acid residues within the N-terminal region of TSC1 are important for TSC1 function and for maintaining the activity of the TSC1-TSC2 complex.

A high incidence of MSH6 mutations in Amsterdam criteria II-negative families tested in a diagnostic setting (Article)

2008-11-01T00:00:00Z

Background and aims: In Lynch syndrome, the clinical phenotype in MSH6 mutation families differs from that in MLH1 and MSH2 families. Therefore, MSH6 mutation families are less likely to fulfil diagnostic criteria such as the Amsterdam II criteria (AC II) and the revised Bethesda guidelines (rBG), and will be underdiagnosed. The aim of the present study was to evaluate the contribution of MSH6 gene mutations in families that were analysed for Lynch syndrome in a diagnostic setting. Methods: Families that had molecular analysis for Lynch syndrome were included in this study. Complete molecular screening of the MLH1, MSH2 and MSH6 genes was performed in all families. Microsatellite instability (MSI) and immunohistochemical (IHC) analysis was performed in almost all families. Clinical data were collected from medical records and family pedigrees. Results: A total of 108 families were included. MSI and IHC analysis was performed in 97 families, and in 40 an MSI-high phenotype with absent protein expression was found. Germline mutation analysis detected mutations in 23 families (7 MLH1, 4 MSH2 and 12 MSH6). The majority of MSH6 families were AC II negative, but fulfilled the rBG. Conclusions: There is a high incidence of MSH6 mutations in families tested for Lynch syndrome in a diagnostic setting. Many of these families remain underdiagnosed using the AC II. The rBG are more useful to select these families for further analysis. However, to optimise the detection of MSH6 families, MSI and IHC analysis should also be performed in families with clustering of late-onset endometrial carcinoma.

Multiple familial trichoepithelioma and familial cylindroma: One cause! (Article)

2008-11-01T00:00:00Z

Identification and characterization of the interaction between tuberin and 14-3-3zeta. (Article)

2002-10-18T00:00:00Z

Tuberous sclerosis is caused by mutations to either the TSC1 or TSC2 tumor suppressor gene. The disease is characterized by a broad phenotypic spectrum that includes seizures, mental retardation, renal dysfunction, and dermatological abnormalities. TSC1 encodes a 130-kDa protein called hamartin, and TSC2 encodes a 200-kDa protein called tuberin. Although it has been shown that hamartin and tuberin form a complex and mediate phosphoinositide 3-kinase/Akt-dependent phosphorylation of the ribosomal protein S6, it is not yet clear how inactivation of either protein leads to tuberous sclerosis. Therefore, to obtain additional insight into tuberin and hamartin function, yeast two-hybrid screening experiments were performed to identify proteins that interact with tuberin. One of the proteins identified was 14-3-3zeta, a member of the 14-3-3 protein family. The interaction between tuberin and 14-3-3zeta was confirmed in vitro and by co-immunoprecipitation; multiple sites within tuberin for 14-3-3zeta binding were identified; and it was determined that 14-3-3zeta associated with the tuberin-hamartin complex. Finally, it was shown that the tuberin/14-3-3zeta interaction is regulated by Akt-mediated phosphorylation of tuberin, providing insight into how tuberin may regulate phosphorylation of S6.

Genetic risk factors in infertile men with severe oligozoospermia and azoospermia (Article)

2002-01-01T00:00:00Z

BACKGROUND: Male infertility due to severe oligozoospermia and azoospermia has been associated with a number of genetic risk factors. METHODS: In this study 150 men from couples requesting ICSI were investigated for genetic abnormalities, such as constitutive chromosome abnormalities, microdeletions of the Y chromosome (AZF region) and mutations in the cystic fibrosis transmembrane conductance regulator (CFTR) gene. RESULTS: Genetic analysis identified 16/150 (10.6%) abnormal karyotypes, 8/150 (5.3%) AZFc deletions and 14/150 (9.3%) CFTR gene mutations. An abnormal karyotype was found both in men with oligozoospermia and azoospermia: 9 men had a sex-chromosomal aneuploidy, 6 translocations were identified and one marker chromosome was found. Y chromosomal microdeletions were mainly associated with male infertility, due to testicular insufficiency. All deletions identified comprised the AZFc region, containing the Deleted in Azoospermia (DAZ) gene. CFTR gene mutations were commonly seen in men with congenital absence of the vas deferens, but also in 16% of men with azoospermia without any apparent abnormality of the vas deferens. CONCLUSIONS: A genetic abnormality was identified in 36/150 (24%) men with extreme oligozoospermia and azoospermia. Application of ICSI in these couples can result in offspring with an enhanced risk of unbalanced chromosome complement, male infertility due to the transmission of a Y-chromosomal microdeletion, and cystic fibrosis if both partners are CFTR gene mutation carriers. Genetic testing and counselling is clearly indicated for these couples before ICSI is considered.

Chloride conductance and genetic background modulate the cystic fibrosis phenotype of Delta F508 homozygous twins and siblings (Article)

2001-01-01T00:00:00Z

To investigate the impact of chloride (Cl(-)) permeability, mediated by residual activity of the cystic fibrosis transmembrane conductance regulator (CFTR) or by other Cl(-) channels, on the manifestations of cystic fibrosis (CF), we determined Cl(-) transport properties of the respiratory and intestinal tracts in Delta F508 homozygous twins and siblings. In the majority of patients, cAMP and/or Ca(2+)-regulated Cl(-) conductance was detected in the airways and intestine. Our finding of cAMP-mediated Cl(-) conductance suggests that, in vivo, at least some Delta F508 CFTR can reach the plasma membrane and affect Cl(-) permeability. In respiratory tissue, the expression of basal CFTR-mediated Cl(-) conductance, demonstrated by 30% of Delta F508 homozygotes, was identified as a positive predictor of milder CF disease. In intestinal tissue, 4,4'-diisothiocyanatostilbene-2,2'-disulfonic acid-insensitive (DIDS-insensitive) Cl(-) secretion, which is indicative of functional CFTR channels, correlated with a milder phenotype, whereas DIDS-sensitive Cl(-) secretion was observed mainly in more severely affected patients. The more concordant Cl(-) secretory patterns within monozygous twins compared with dizygous pairs imply that genes other than CFTR significantly influence the manifestation of the basic defect.

TSC2 missense mutations inhibit tuberin phosphorylation and prevent formation of the tuberin-hamartin complex (Article)

2001-01-01T00:00:00Z

Tuberous sclerosis (TSC) is an autosomal dominant disorder characterized by a broad phenotypic spectrum that includes seizures, mental retardation, renal dysfunction and dermatological abnormalities. Inactivating mutations to either of the TSC1 and TSC2 tumour suppressor genes are responsible for the disease. TSC1 and TSC2 encode two large novel proteins called hamartin and tuberin, respectively. Hamartin and tuberin interact directly with each other and it has been reported that tuberin may act as a chaperone, preventing hamartin self-aggregation and maintaining the tuberin-hamartin complex in a soluble form. In this study, the ability of tuberin to act as a chaperone for hamartin was used to investigate the tuberin-hamartin interaction in more detail. A domain within tuberin necessary for the chaperone function was identified, and the effects of TSC2 missense mutations on the tuberin-hamartin interaction were investigated to allow specific residues within the central domain of tuberin that are important for the interaction with hamartin to be pin-pointed. In addition, the results confirm that phosphorylation may play an important role in the formation of the tuberin-hamartin complex. Although mutations that prevent tuberin tyrosine phosphorylation also inhibit tuberin-hamartin binding and the chaperone function, our results indicate that only hamartin is phosphorylated in the tuberin-hamartin complex.

An unbalanced submicroscopic translocation t(8;16)(q24.3;p13.3)pat associated with tuberous sclerosis complex, adult polycystic kidney disease, and hypomelanosis of Ito (Article)

2000-01-01T00:00:00Z

We report on a familial submicroscopic translocation involving chromosomes 8 and 16. The proband of the family had a clinical picture suggestive of a large deletion in the chromosome 16p13.3 area, as he was affected with tuberous sclerosis complex (TSC) and had alpha thalassaemia trait, and his half brother, who also had TSC, may have suffered additionally from polycystic kidney disease (PKD). FISH studies provided evidence for a familial translocation t(8;16)(q24.3;p13.3) with an unbalanced form in the proband and a balanced form in the father and in a paternal aunt. The unbalanced translocation caused the index patient to be deleted for the chromosome 16p13.3-pter region, with the most proximal breakpoint described to date for terminal 16p deletions. In addition, FISH analysis showed a duplication for the distal 8q region. Since the index patient also had hypomelanosis of Ito (HI), either of the chromosomal areas involved in the translocation may be a candidate region for an HI determining gene. Furthermore, it is noteworthy that both carriers of the balanced translocation showed a nodular goitre, while the proband has hypothyroidism.

The complex relationships between cystic fibrosis and congenital bilateral absence of the vas deferens: clinical, electrophysiological and genetic data (Article)

1999-01-01T00:00:00Z

Congenital bilateral absence of the vas deferens (CBAVD) is found in 1-2% of infertile males and in most male cystic fibrosis (CF) patients. CF and some of the CBAVD cases were found to share the same genetic background. In this study, 21 males with CBAVD had extensive physical and laboratory testing for symptoms of CF. Possible defective cellular chloride transport was measured by interstitial current measurement of rectal suction biopsies. Cystic fibrosis transmembrane conductance regulator (CFTR) gene mutation analysis was performed for 10 common CFTR mutations. CF-related symptoms were found in six men. On laboratory testing slightly abnormal liver and pancreatic function was found in seven patients. The sweat test was found to be abnormal in four patients; interstitial current measurement showed defective chloride excretion in 11 patients. CFTR gene mutations were found in 66% of the patients: eight were compound heterozygotes; in six, only one common mutation could be detected. The 5T allele in one copy of intron 8 was found in four men. CBAVD appears to be a heterogeneous clinical and genetic condition. A CFTR gene mutation was found in both copies of the allele or interstitial current measurement showed defective chloride excretion in 14/21 cases. Genetic counselling is clearly indicated for couples seeking pregnancy through epididymal or testicular sperm aspiration and intracytoplasmic sperm injection.

Mutational spectrum of the TSC1 gene in a cohort of 225 tuberous sclerosis complex patients: no evidence for genotype-phenotype correlation (Article)

1999-01-01T00:00:00Z

Tuberous sclerosis complex is an inherited tumour suppressor syndrome, caused by a mutation in either the TSC1 or TSC2 gene. The disease is characterised by a broad phenotypic spectrum that can include seizures, mental retardation, renal dysfunction, and dermatological abnormalities. The TSC1 gene was recently identified and has 23 exons, spanning 45 kb of genomic DNA, and encoding an 8.6 kb mRNA. After screening all 21 coding exons in our collection of 225 unrelated patients, only 29 small mutations were detected, suggesting that TSC1 mutations are under-represented among TSC patients. Almost all TSC1 mutations were small changes leading to a truncated protein, except for a splice site mutation and two in frame deletions in exon 7 and exon 15. No clear difference was observed in the clinical phenotype of patients with an in frame deletion or a frameshift or nonsense mutation. We found the disease causing mutation in 13% of our unrelated set of TSC patients, with more than half of the mutations clustered in exons 15 and 17, and no obvious under-representation of mutations among sporadic cases. In conclusion, we find no support for a genotype-phenotype correlation for the group of TSC1 patients compared to the overall population of TSC patients.

High rate of mosaicism in tuberous sclerosis complex (Article)

1999-01-01T00:00:00Z

Six families with mosaicism are identified in a series of 62 unrelated families with a mutation in one of the two tuberous sclerosis complex (TSC) genes, TSC1 or TSC2. In five families, somatic mosaicism was present in a mildly affected parent of an index patient. In one family with clinically unaffected parents, gonadal mosaicism was detected after TSC was found in three children. The detection of mosaicism has consequences for genetic counseling of the families involved, as changed risks apply to individuals with mosaicism, both siblings and parents. Clinical investigation of parents of patients with seemingly sporadic mutations is essential to determine their residual chance of gonadal and/or somatic mosaicism, unless a mosaic pattern is detected in the index patient, proving a de novo event. In our data set, the exclusion of signs of TSC in the parents of a patient with TSC reduced the chance of one of the parents to be a (mosaic) mutation carrier from 10% to 2%. In the five families with somatic mosaicism, the parent was given the diagnosis after the diagnosis was made in the child.

Characterization of the cytosolic tuberin-hamartin complex. Tuberin is a cytosolic chaperone for hamartin (Article)

1999-01-01T00:00:00Z

Tuberous sclerosis (TSC) is an autosomal dominant disorder characterized by a broad phenotypic spectrum that includes seizures, mental retardation, renal dysfunction and dermatological abnormalities. Mutations to either the TSC1 or TSC2 gene are responsible for the disease. The TSC1 gene encodes hamartin, a 130-kDa protein without significant homology to other known mammalian proteins. Analysis of the amino acid sequence of tuberin, the 200-kDa product of the TSC2 gene, identified a region with limited homology to GTPase-activating proteins. Previously, we demonstrated direct binding between tuberin and hamartin. Here we investigate this interaction in more detail. We show that the complex is predominantly cytosolic and may contain additional, as yet uncharacterized components alongside tuberin and hamartin. Furthermore, because oligomerization of the hamartin carboxyl-terminal coiled coil domain was inhibited by the presence of tuberin, we propose that tuberin acts as a chaperone, preventing hamartin self-aggregation.

17Beta-hydroxysteroid dehydrogenase-3 deficiency: diagnosis, phenotypic variability, population genetics, and worldwide distribution of ancient and de novo mutations (Article)

1999-01-01T00:00:00Z

17Beta-hydroxysteroid dehydrogenase-3 (17betaHSD3) deficiency is an autosomal recessive form of male pseudohermaphroditism caused by mutations in the HSD17B3 gene. In a nationwide study on male pseudohermaphroditism among all pediatric endocrinologists and clinical geneticists in The Netherlands, 18 17betaHSD3-deficient index cases were identified, 12 of whom initially had received the tentative diagnosis androgen insensitivity syndrome (AIS). The phenotypes and genotypes of these patients were studied. Endocrine diagnostic methods were evaluated in comparison to mutation analysis of the HSD17B3 gene. RT-PCR studies were performed on testicular ribonucleic acid of patients homozygous for two different splice site mutations. The minimal incidence of 17betaHSD3 deficiency in The Netherlands and the corresponding carrier frequency were calculated. Haplotype analysis of the chromosomal region of the HSD17B3 gene in Europeans, North Americans, Latin Americans, Australians, and Arabs was used to establish whether recurrent identical mutations were ancient or had repeatedly occurred de novo. In genotypically identical cases, phenotypic variation for external sexual development was observed. Gonadotropin-stimulated serum testosterone/androstenedione ratios in 17betaHSD3-deficient patients were discriminative in all cases and did not overlap with ratios in normal controls or with ratios in AIS patients. In all investigated patients both HSD17B3 alleles were mutated. The intronic mutations 325 + 4;A-->T and 655-1;G-->A disrupted normal splicing, but a small amount of wild-type messenger ribonucleic acid was still made in patients homozygous for 655-1;G-->A. The minimal incidence of 17betaHSD3 deficiency in The Netherlands was shown to be 1: 147,000, with a heterozygote frequency of 1:135. At least 4 mutations, 325 + 4;A-->T, N74T, 655-1;G-->A, and R80Q, found worldwide, appeared to be ancient and originating from genetic founders. Their dispersion could be reconstructed through historical analysis. The HSD17B3 gene mutations 326-1;G-->C and P282L were de novo mutations. 17betaHSD3 deficiency can be reliably diagnosed by endocrine evaluation and mutation analysis. Phenotypic variation can occur between families with the same homozygous mutations. The incidence of 17betaHSD3 deficiency is 0.65 times the incidence of AIS, which is thought to be the most frequent known cause of male pseudohermaphroditism without dysgenic gonads. A global inventory of affected cases demonstrated the ancient origin of at least four mutations. The mutational history of this genetic locus offers views into human diversity and disease, provided by national and international collaboration.

Interaction between hamartin and tuberin, the TSC1 and TSC2 gene products (Article)

1998-01-01T00:00:00Z

Tuberous sclerosis (TSC) is an autosomal dominant disorder caused by a mutation in either the TSC1 or TSC2 tumour suppressor gene. The disease is characterized by a broad phenotypic spectrum that can include seizures, mental retardation, renal dysfunction and dermatological abnormalities. TSC2 encodes tuberin, a putative GTPase activating protein for rap1 and rab5. The TSC1 gene was recently identified and codes for hamartin, a novel protein with no significant homology to tuberin or any other known vertebrate protein. Here, we show that hamartin and tuberin associate physically in vivo and that the interaction is mediated by predicted coiled-coil domains. Our data suggest that hamartin and tuberin function in the same complex rather than in separate pathways.

A prospective 10 year follow up study of patients with neurofibromatosis type 1 (Article)

1998-01-01T00:00:00Z

OBJECTIVE: To establish the prevalence and incidence of symptoms and complications in children with neurofibromatosis type 1 (NF1) and to assess possible risk factors for the development of complications. DESIGN: A 10 year prospective multidisciplinary follow up study. PATIENTS: One hundred and fifty children diagnosed with NF1 according to criteria set by the National Institutes of Health. RESULTS: In 62 of 150 children (41.3%) complications were present, including 42 (28.0%) children with one complication, 18 (12.0%) with two complications, and two (1.3%) with three complications (mean (SD) duration of follow up 4.9 (3.8) years). Ninety five of the 150 children presented without complications (follow up, 340.8 person-years). The incidence of complications was 2.4/100 person-years in this group. An association was found between behavioural problems and the presence of complications. CONCLUSION: This is the largest single centre case series of NF1 affected children followed until 18 years of age. Children with NF1, including those initially presenting without complications, should have regular clinical examinations.

Screening and diagnosis for the fragile X syndrome among the mentally retarded: an epidemiological and psychological survey. Collaborative Fragile X Study Group (Article)

1997-01-01T00:00:00Z

The fragile X syndrome is an X-linked mental retardation disorder caused by an expanded CGG repeat in the first exon of the fragile X mental retardation (FMR1) gene. Its frequency, X-linked inheritance, and consequences for relatives all prompt for diagnosis of this disorder on a large scale in all affected individuals. A screening for the fragile X syndrome has been conducted in a representative sample of 3,352 individuals in schools and institutes for the mentally retarded in the southwestern Netherlands, by use of a brief physical examination and the DNA test. The attitudes and reactions of (non)consenting parents/guardians were studied by (pre- and posttest) questionnaires. A total of 2,189 individuals (65%) were eligible for testing, since they had no valid diagnosis, cerebral palsy, or a previous test for the FMR1 gene mutation. Seventy percent (1,531/2,189) of the parents/guardians consented to testing. Besides 32 previously diagnosed fragile X patients, 11 new patients (9 males and 2 females) were diagnosed. Scoring of physical features was effective in preselection, especially for males (sensitivity .91 and specificity .92). Major motives to participate in the screening were the wish to obtain a diagnosis (82%), the hereditary implications (80%), and the support of research into mental retardation (81%). Thirty-four percent of the parents/guardians will seek additional diagnostic workup after exclusion of the fragile X syndrome. The prevalence of the fragile X syndrome was estimated at 1/ 6,045 for males (95% confidence interval 1/9,981-1/ 3,851). On the basis of the actual number of diagnosed cases in the Netherlands, it is estimated that >50% of the fragile X cases are undiagnosed at present.

Determinants of mild clinical symptoms in cystic fibrosis patients. Residual chloride secretion measured in rectal biopsies in relation to the genotype (Article)

1994-01-01T00:00:00Z

Previous Ussing chamber measurements of secretagogue-provoked changes in short circuit current in rectal suction biopsies of cystic fibrosis (CF) patients showed that in a minority of patients chloride secretion in response to cholinergic agonists is reduced but not completely absent. To assess a possible relationship between this phenomenon and both the genotype and the phenotype, we performed Ussing chamber experiments on rectal suction biopsies of 51 CF patients. The CF mutation was identified in 89 out of 102 CF alleles. No apparent chloride secretion was found in 30 CF patients (group I). Low residual chloride secretion was found in 11 CF patients (group II), while a relatively high residual secretion appeared in 10 CF patients (group III). Pancreatic function was preserved more frequently in CF patients displaying residual secretion: 0% in group I, 27% in group II, and 60% in group III (P < 0.001). The age at diagnosis (mean +/- SEM) in group III (18.4 +/- 6.6) was significantly different from group I (1.2 +/- 0.4, P < 0.01) and group II (3.5 +/- 1.4, P = 0.05). Residual chloride secretion was found in some of the 28 dF508 homozygous patients (three in group II, and one in group III), disclosing that other factors than the CF gene defect itself affect the transepithelial chloride transport. The age at diagnosis correlates significantly with the magnitude of the secretory response, even within the dF508 homozygous patients (r = 0.4, P < 0.05). We conclude that residual chloride secretion in CF is the pathophysiological basis of preserved pancreatic function and delayed presentation of the disease, which is not exclusively determined by the CF genotype.

Release and uptake of lysosomal enzymes : studied in cultured cells (Doctoral Thesis)

1980-06-11T00:00:00Z

The purpose of the experimental work described in this thesiswas to investigate some aspects of the release and uptake of lysosomal enzymes. The experiments involved the use of normal human and animal fibroblasts and some other cell types such as hepatocytes and hepatoma cells as sources of hydrolytic enzymes, and fibroblasts from patients with lysosomal storage diseases associated with a single lysosomal enzyme deficiency and with "1-cell" disease as recipient cells. In a number of studies co-cultivation of normal and mutant cells was applied. as a means to study the release and uptake of lysosomal enzymes at physiological concentrations. We have also studied some characteristics of released lysosomal enzyme activities in· normal and mutant cell cultures in comparison with the corresponding intracellular activities. Finally, we have used somatic cell hybridization to investigate the genetic background of the metabolic abnormalities in some of the human mutant cells. Our studies have provided information on the normal transport of lysosomal enzymes within the cell and between cells. Furthermore, we hope that more knowledge about recognition and uptake of lysosomal enzymes by deficient cells from patients with lysosomal storage diseases will have future implications for enzyme therapy.