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Biomedical subjects

Marjo S van der Knaap

Publications and source records attributed to Marjo S van der Knaap.

At least 19 recordsLinked to original sources
PubMed2006

Glutaric aciduria type 1: clinical, biochemical and molecular findings in patients from Israel.

Glutaric aciduria type 1 (GA1) is a rare cerebral organic aciduria which typically manifests as an acute encephalopathic crisis followed by profound long-term neurological handicap. We report the diagnosis of 12 new patients from a single laboratory in Israel during a 5-year period. Eleven of the 12 were of Palestinian origin, and only two were related. One patient was asymptomatic whilst one was mildly, one moderately and nine severely affected, two of whom had unusual MRI findings. Two patients had normal glutaric acid excretion and normal blood glutarylcarnitine levels yet glutarylcarnitine excretion was increased, indicating its utility as a diagnostic marker. Four novel GCDH mutations (Thr193_Arg194insHis, Asn329Ser, Thr341Pro, Met405Val) and five previously reported mutations (Ser119Leu, Leu283Pro, Ala293Thr, Gly390Arg and Thr416Ile) were identified. Severely and mildly affected or even asymptomatic patients shared the same genotypes (Thr416Ile/Thre416Ile and Aal293Thr/Thr193_Arg194insHis). Knowledge of the responsible mutation enabled successful prenatal diagnosis on chorionic villous DNA in three families. In conclusion, GA1 is genetically heterogeneous and has a relatively high incidence in the Palestinian population, reflecting the historical tradition of marriages within extended kindreds, particularly in isolated villages. Additional genetic and/or environmental factors must account for the phenotypic heterogeneity in patients with the same genotype. The diagnosis was not suspected in the majority of cases despite typical clinical and/or neuroimaging features, suggesting that glutaric aciduria may be under-diagnosed. Greater awareness of glutaric aciduria amongst pediatricians, neonatologists and radiologists is the key to identifying the disorder in the presymptomatic phase and preventing its catastrophic consequences.

Adolescent↗
PubMed2006

Deficiency of hyccin, a newly identified membrane protein, causes hypomyelination and congenital cataract.

We describe a new autosomal recessive white matter disorder ('hypomyelination and congenital cataract') characterized by hypomyelination of the central and peripheral nervous system, progressive neurological impairment and congenital cataract. We identified mutations in five affected families, resulting in a deficiency of hyccin, a newly identified 521-amino acid membrane protein. Our study highlights the essential role of hyccin in central and peripheral myelination.

Animals↗
PubMed2006

Defective translation initiation causes vanishing of cerebral white matter.

Leukoencephalopathy with vanishing white matter (VWM) is one of the most prevalent inherited white-matter disorders, especially in Caucasian populations. VWM is unusual because of its sensitivity to febrile infections and minor head trauma. The basic defect of this enigmatic brain disease resides in the regulation of initiation of protein synthesis. Recently, undue activation of the unfolded-protein response has emerged as an important factor in the pathophysiology of VWM. Here, we discuss the mechanisms that might be responsible for the selective involvement of the brain white matter in VWM. At present, VWM research is in need of an animal model to study disease mechanisms and therapeutic interventions.

Animals↗
PubMed2006

Neonatal porencephaly and adult stroke related to mutations in collagen IV A1.

OBJECTIVE: The objective of this study was to describe leukoencephalopathy, lacunar infarcts, microbleeds and macrobleeds in the context of a collagen IV A1 mutation. METHODS: We examined a family with autosomal dominant porencephaly, in whom a defect in collagen IV A1 was detected recently. The patients underwent neurological, ophthalmological, and cardiological examinations and magnetic resonance imaging of the brain. Electron microscopy of a skin biopsy was performed. Extensive laboratory screening was performed for thrombophilia and increased bleeding tendency. RESULTS: The porencephaly was symptomatic in the infantile period in two patients, whereas it led to only minor neurological dysfunction in their affected mother. However, she experienced development of recurrent strokes in her 40s. In addition to the porencephaly, all patients had a leukoencephalopathy, which was most severe in the mother. Her magnetic resonance imaging results also showed lacunar infarcts, macrobleeds and a multitude of microbleeds. No other risk factors for recurrent stroke were found. Electron microscopy showed interruptions of the basement membrane of skin capillaries and inhomogeneous thickening of the basement membrane with pools of basement membrane fragments. INTERPRETATION: Leukoencephalopathy, ischemic infarcts, microbleeds, and macrobleeds are indicative of an underlying microangiopathy, of which the best-known causes are hypertension, cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy, and cerebral amyloid angiopathy. Mutations in collagen IV A1, a major component of the vascular basement membrane, appear to be another risk factor.

Adult↗
PubMed2006

Microphthalmia and brain atrophy: a novel neurodegenerative disease.

OBJECTIVE: To delineate the features of a novel neurodegenerative disease. METHODS: We report three children of three related families with congenital microphthalmia and blindness, and progressive spasticity, microcephaly, seizures, and profound mental retardation. RESULTS: A magnetic resonance imaging scan was normal at birth. However, follow-up studies showed progressive atrophy involving the cerebral white matter and cortex, cerebellum, brainstem, and corpus callosum. The white matter changes extended into the subcortical region leaving only small islands of remaining cortical tissue. Known metabolic conditions involving white matter degeneration were excluded. INTERPRETATION: We propose this to be a novel autosomal recessive neurodegenerative disorder to be coined MOBA (microphthalmia brain atrophy) disease.

Atrophy↗
PubMed2006

Megalencephalic leukoencephalopathy with subcortical cysts: an update and extended mutation analysis of MLC1.

Megalencephalic leukoencephalopathy with subcortical cysts (MLC) is an autosomal recessive cerebral white matter disorder in children. This disease is histopathologically characterized by myelin splitting and intramyelinic vacuole formation. MLC is caused by mutations in the gene MLC1, which encodes a novel protein, MLC1. Since the first report, 50 mutations in this gene have been found. Mutations occur throughout the entire coding region and include all different types: 11 splice-site mutations; one nonsense mutation; 24 missense mutations; and 14 deletions and insertions. Until now, six polymorphisms within the coding sequence of MLC1 had been reported. In about 20% of the patients with a typical clinical and MRI picture, no mutations in the MLC1 gene are found. Several of the families, in which no mutations are found, also do not show linkage with the MLC1 locus, which suggests a second gene involved in MLC. The absence of mutations may also be the consequence of performing standard mutation analysis that can miss heterozygous deletions, mutations in the promoter, 3' and 5' untranslated regions (UTRs), and intron mutations, which may influence the amino acid composition of the end product. In this work we describe 13 novel mutations, including those found with extended mutation analysis on MLC patients. This study shows that extended mutation analysis is a valuable tool to identify at least some of the missing mutations. Therefore, we suggest extended mutation analysis for the MLC1 gene, if no mutations are found during standard analysis.

Base Sequence↗
PubMed2006

Vanishing white matter disease: a review with focus on its genetics.

Leukoencephalopathy with vanishing white matter (VWM) is an autosomal recessive brain disorder, most often with a childhood onset. Magnetic resonance imaging and spectroscopy indicate that, with time, increasing amounts of cerebral white matter vanish and are replaced by fluid. Autopsy confirms white matter rarefaction and cystic degeneration. The process of localization and identification of the first two genes related to VWM, EIF2B5 and EIF2B2, was facilitated by two founder effects in the Dutch population. EIF2B5 and EIF2B2 encode the epsilon and beta subunits of translation initiation factor eIF2B. Soon it was shown that mutations in all five eIF2B subunit genes can cause VWM. EIF2B is essential for the initiation of translation of RNA into protein and is involved in regulation of the process, especially under stress conditions, which may explain the sensitivity to stress conditions observed in VWM patients. The pathophysiology of the disease is still poorly understood.

Brain↗
PubMed2006

Vanishing white matter disease.

Vanishing white matter disease (VWM) is one of the most prevalent inherited childhood leucoencephalopathies. The classical phenotype is characterised by early childhood onset of chronic neurological deterioration, dominated by cerebellar ataxia. VWM is unusual because of its clinically evident sensitivity to febrile infections, minor head trauma, and acute fright, which may cause rapid neurological deterioration and unexplained coma. Most patients die a few years after onset. The phenotypic variation is extremely wide, including antenatal onset and early demise and adult-onset, slowly progressive disease. MRI findings are diagnostic in almost all patients and are indicative of vanishing of the cerebral white matter. The basic defect of this striking disease resides in either one of the five subunits of eukaryotic translation initiation factor eIF2B. eIF2B is essential in all cells of the body for protein synthesis and its regulation under different stress conditions. Although the defect is in housekeeping genes, oligodendrocytes and astrocytes are predominantly affected, whereas other cell types are surprisingly spared. Recently, undue activation of the unfolded-protein response has emerged as important in the pathophysiology of VWM, but the selective vulnerability of glia for defects in eIF2B is poorly understood.

Age of Onset↗
PubMed2006

Glia-specific activation of all pathways of the unfolded protein response in vanishing white matter disease.

Leukoencephalopathy with vanishing white matter (VWM) is a childhood white matter disorder with an autosomal-recessive mode of inheritance. The clinical course is chronic progressive with episodes of rapid neurologic deterioration after febrile infections. The disease is caused by mutations in the genes encoding the subunits of eukaryotic initiation factor 2B (eIF2B), a protein complex that is essential for protein synthesis. In VWM, mutations in the eIF2B genes are thought to impair the ability of cells to regulate protein synthesis under normal and stress conditions. It has been suggested that the pathophysiology of VWM involves inappropriate activation of the unfolded protein response (UPR). The UPR is a protective mechanism activated by an overload of unfolded or malfolded proteins in the endoplasmic reticulum. Activation of one pathway of the UPR, in which eIF2B is involved, has already been described in brain tissue of patients with VWM. In the present study, we demonstrate activation of all 3 UPR pathways in VWM brain tissue using real-time quantitative polymerase chain reaction and immunohistochemistry. We show that activation occurs exclusively in the white matter, predominantly in oligodendrocytes and astrocytes. The selective involvement of these cells suggests that inappropriate UPR activation may play a key role in the pathophysiology of VWM.

Activating Transcription Factor 6↗
PubMed2006

Childhood white matter disorders: quantitative MR imaging and spectroscopy.

PURPOSE: To prospectively investigate whether quantitative magnetic resonance (MR) parameters, including magnetization transfer ratio (MTR), apparent diffusion coefficient (ADC), fractional anisotropy (FA), and MR spectroscopic metabolite concentrations, allow for discrimination between different types of pathologic conditions that underlie signal intensity abnormalities in white matter. MATERIALS AND METHODS: Institutional review board approval and informed consent were obtained. Forty-one patients (19 male, 22 female; mean age, 15.4 years) and 41 control subjects (25 male, 16 female; mean age, 11.3 years) were included. Twelve patients had a hypomyelinating disorder; 14, a demyelinating disorder; five, a disorder characterized by myelin vacuolation; and 10, a disorder characterized by cystic degeneration. Regions of interest were selected within the parietal white matter and were transferred to the corresponding sections of the generated ADC, FA, and MTR maps to extract quantitative measurements. Linear discriminant analysis and univariate analysis of covariance were used for statistical evaluation. RESULTS: Linear discriminant analysis showed that 95% of patients were correctly classified by using total creatine, choline-containing compounds, myo-inositol, MTR, and ADC. In the hypomyelination group, all MR parameters were close to normal, with the exception of elevated total creatine (P = .03) and myo-inositol (P < .001) levels and decreased MTR values (P < .001). In the demyelination group, the levels of choline-containing compounds (P = .02) and myo-inositol (P < .001) were highly elevated. In the myelin vacuolation and cystic degeneration groups, high ADC values (P < .001) and variable decreases in all MR spectroscopic metabolites were seen. MTR was significantly reduced (P < .001) in the cystic degeneration group. CONCLUSION: Quantitative MR techniques can be used to discriminate between different types of white matter disorders and to classify white matter lesions of unknown origin with respect to underlying pathologic conditions.

Adolescent↗
PubMed2006

Leukoencephalopathy with vanishing white matter due to homozygous EIF2B2 gene mutation. First Polish cases.

Leukoencephalopathy with vanishing white matter (VWM), also called childhood ataxia with central nervous system hypomyelination (CACH), is an autosomal recessive disease caused by mutations in any of the five genes encoding subunits of the eukaryotic translation initiation factor eIF2B. Neuropathological findings comprise a severe, cavitating orthochromatic leukodystrophy with only small amounts of myelin breakdown products, and predominantly involving the cerebral hemispheric white matter. Within the white matter abnormal oligodendroglial cells are present with abundant "foamy" cytoplasm. In some regions oligodendroglial cells are increased in numbers. We present three sisters, 18, 11 and 8 years old, with the early to late childhood phenotype. The first signs of the disease were gait disturbances at 4, 2 and 6 years of age, respectively. Neurological examination showed mild tremor of hands and head, truncal ataxia, dysarthria, and hypotonia, after several years followed by spasticity. The course of the disease was slowly progressive. Intellectual abilities are relatively spared. The MRI showed diffusely abnormal white matter of the cerebral hemispheres. The FLAIR images revealed rarefaction of the affected white matter with some stripe-like structures, suggesting the presence of remaining tissue strands. The abnormalities were most pronounced with the middle sister, who had the earliest onset of the disease. A homozygous point mutation in the EIF2B2 gene was found, 638A>G. Both the parents were found to be carriers of this mutation. This is the first description of a Polish family with VWM.

Adolescent↗
PubMed2005

Propensity for paternal inheritance of de novo mutations in Alexander disease.

De novo dominant mutations in the GFAP gene have recently been associated with nearly all cases of Alexander disease, a rare but devastating neurological disorder. These heterozygous mutations must occur very early in development and be present in nearly all cells in order to be detected by the sequencing methods used. To investigate whether the mutations may have arisen in the parental germ lines, we determined the parental chromosome bearing the mutations for 28 independent Alexander disease cases. These cases included 17 different missense mutations and one insertion mutation. To enable assignment of the chromosomal origin of the mutations, six new single nucleotide polymorphisms in the GFAP gene were identified, bringing the known total to 26. In 24 of the 28 cases analyzed, the paternal chromosome carried the GFAP mutation (P < 0.001), suggesting that they predominantly arose in the parental germ line, with most occurring during spermatogenesis. No effect of paternal age was observed. There has been considerable debate about the magnitude of the male to female germ line mutation rate; our ratio of 6:1 is consistent with indirect estimates based on the rate of evolution of the sex chromosome relative to the autosomic chromosomes.

Adult↗
PubMed2005

Regulation of protein synthesis in lymphoblasts from vanishing white matter patients.

Leukoencephalopathy with vanishing white matter (VWM) is an inherited childhood white matter disorder, caused by mutations in the genes encoding eukaryotic initiation factor 2B (eIF2B). The present study showed that, while the eIF2B activity was reduced in VWM lymphoblasts, the expression levels of the eIF2B subunits were similar to control lymphoblast lines. The mutations in eIF2B did not affect the interaction with eIF2. Strikingly, no apparent differences for the regulation of protein synthesis, measured by [35S]-methionine incorporation, were found between control and VWM lymphoblasts. Western blotting showed that, in some VWM cells, exposure to heat shock caused a decrease in the expression of specific eIF2B subunits. Most importantly, the increase in phosphorylation of eIF2alpha in response to heat shock was lower in VWM lymphoblasts than in control cells. These findings could form part of the explanation for the episodes of rapid and severe deterioration in VWM patients that are precipitated by febrile infections.

Blotting, Western↗
PubMed2005

MRI of a family with leukoencephalypathy with vanishing white matter.

Leukoencephalopathy with vanishing white matter (VWM) is a newly described entity with characteristic MRI features. We report the cranial MRI findings in three sisters with slowly progressive neurological deterioration. The MRI showed symmetrical diffuse abnormalities of cerebral white matter with hypointensity on FLAIR images. The diagnosis of leukoencephalopathy with VWM was made on the basis of genetic analysis.

Adolescent↗
PubMed2005

Mutations in Col4a1 cause perinatal cerebral hemorrhage and porencephaly.

Porencephaly is a rare neurological disease, typically manifest in infants, which is characterized by the existence of degenerative cavities in the brain. To investigate the molecular pathogenesis of porencephaly, we studied a mouse mutant that develops porencephaly secondary to focal disruptions of vascular basement membranes. Half of the mutant mice died with cerebral hemorrhage within a day of birth, and approximately 18% of survivors had porencephaly. We show that vascular defects are caused by a semidominant mutation in the procollagen type IV alpha 1 gene (Col4a1) in mice, which inhibits the secretion of mutant and normal type IV collagen. We also show that COL4A1 mutations segregate with porencephaly in human families. Because not all mutant mice develop porencephaly, we propose that Col4a1 mutations conspire with environmental trauma in causing the disease.

Alleles↗
PubMed2005

Quantification of sugar phosphate intermediates of the pentose phosphate pathway by LC-MS/MS: application to two new inherited defects of metabolism.

We describe a liquid chromatography tandem mass spectrometry (LC-MS/MS) method to quantify pentose phosphate pathway intermediates (triose-3-phosphates, tetrose-4-phosphate, pentose-5-phosphate, pentulose-5-phosphates, hexose-6-phosphates and sedoheptulose-7-phosphate (sed-7P)) in bloodspots, fibroblasts and lymphoblasts. Liquid chromatography was performed using an ion pair loaded C(18) HPLC column and detection of the sugar phosphates was carried out by tandem mass spectrometry using an electron ion spray source operating in the negative mode and multiple reaction monitoring. Reference values for the pentose phosphate pathway intermediates in blood spots, fibroblasts and lymphoblasts were established. The method was applied to cells from patients affected with a deficiency of transaldolase. The transaldolase-deficient cells showed an increased concentration of sedoheptulose-7-phosphate. (Bloodspots: 5.19 and 5.43 micromol/L [0.49-3.33 micromol/L]; fibroblasts 7.43 and 26.46 micromol/mg protein [0.31-1.14 micromol/mg protein]; lymphoblasts 16.03 micromol/mg protein [0.61-2.09 micromol/mg protein].) The method was also applied to study enzymes of the pentose phosphate pathway by incubating fibroblasts or lymphoblasts homogenates with ribose-5-phosphate or 6-phosphogluconate and the subsequent analysis of the formed sugar phosphates.

Cells, Cultured↗
PubMed2005

Unusual variants of Alexander's disease.

The purpose of this study was to describe unusual variants of Alexander's disease. We studied 10 patients who did not meet previously established magnetic resonance imaging (MRI) criteria for Alexander's disease, but for whom this diagnosis was considered because of Rosenthal fibers at histological examination or presence of some MRI features suggestive of Alexander's disease. Sequence analysis of the GFAP gene was performed. In eight patients, MRI results showed predominantly posterior fossa lesions, especially multiple tumor-like brainstem lesions. One patient had asymmetrical frontal white matter abnormalities and basal ganglia abnormalities. One patient (Patient 10) developed degeneration of the frontal white matter. In nine patients, a mutation was found that was concluded to be pathogenic, because the mutation was de novo (five patients), a known mutation was found (two patients), or assembly of the glial fibrillary acidic protein was abnormal in cultured cells (two patients). In Patient 10, a DNA variation was found that was also present in the patient's clinically unaffected father and was concluded to be a polymorphism. In conclusion, DNA diagnostics is warranted in patients who display MRI features suggestive of Alexander's disease, even if they do not meet the full set of previously established MRI criteria.

Adolescent↗