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H W Moser

Publications and source records attributed to H W Moser.

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

Adrenoleukodystrophy: incidence, new mutation rate, and results of extended family screening.

Utilizing the plasma very long chain fatty acid assay, supplemented by mutation analysis and immunofluorescence assay, we determined the number of X-linked adrenoleukodystrophy (X-ALD) hemizygotes from the United States identified each year in the two laboratories that perform most of the assays in this country: the Kennedy Krieger Institute between 1981 and 1998 and the Mayo Clinic Rochester from 1996 to 1998. The minimum frequency of hemizygotes identified in the United States is estimated to be 1:42,000 and that of hemizygotes plus heterozygotes 1:16,800. Our studies involved 616 pedigrees with a total of 12,787 identified at-risk members. Diagnostic assays were performed in 4,169 at-risk persons (33%) and included members of the extended family. Only 5% of male probands and 1.7% of X-ALD hemizygotes were found to have new mutations. The extended family testing led to the identification of 594 hemizygotes and 1,270 heterozygotes. Two hundred fifty of the newly identified hemizygotes were asymptomatic and represent the group in which therapy has the greatest chance of success. Identification of heterozygotes provides the opportunity for disease prevention through genetic counseling. Diagnostic tests should be offered to all at-risk relatives of X-ALD patients and should include members of the extended family.

Adrenoleukodystrophy↗
PubMed2000

Molecular genetics of peroxisomal disorders.

Twenty five human peroxisomal disorders have been defined at this time. They are subdivided into two major categories: 1) the disorders of peroxisome biogenesis, in which the organelle fails to form normally, and there are defects that involve multiple peroxisomal functions; and 2) disorders that affect single peroxisomal enzymes. During the last five years the molecular defects have been identified in nearly all. These recent advances have several important implications. They have facilitated diagnosis of affected patients. The improved capacity to provide prenatal diagnosis and heterozygote identification has been of great value for genetic counseling and disease prevention. Study of genotype-phenotype correlations has led to a new and more rational classification system. The identification of the molecular defects and the development of animal models have increased understanding of pathogenetic mechanisms, and have led to novel therapeutic approaches.

Adrenoleukodystrophy↗
PubMed2000

Determination of 30 X-linked adrenoleukodystrophy mutations, including 15 not previously described.

X-linked Adrenoleukodystrophy (X-ALD) is the most frequent peroxisomal disease. It mainly involves the nervous system white matter, adrenal cortex and testes. Several distinct clinical phenotypes are known. The principal biochemical abnormality is the accumulation of saturated very-long-chain fatty acids (VLCFAs : > C22:0, mainly C26:0), which is due to impaired capacity for beta-oxidation in peroxisomes. Diagnosis is usually based on the VLCFA levels in plasma or cultured skin fibroblasts in both patients and carriers. In 0.1% of affected males, however, the plasma C26:0 level is borderline normal, and 15% of obligate female carriers have normal results. Effective mutation detection in these families is therefore fundamental to unambiguously determine the genetic status of each individual at risk. Of particular concern are female members of kindreds segregating X-ALD mutations, because normal VLCFA levels do not guarantee lack of carrier status. We describe a fast method for detection of X-ALD mutations. The method is based on SSCP analysis of nested PCR fragments followed by sequence-determination reactions. Using this methodology we have found X-ALD mutations in 30 kindreds, including 15 not previously reported.

Adrenoleukodystrophy↗
PubMed2000

Peroxisomal ghosts are intracellular structures distinct from lysosomal compartments in Zellweger syndrome: a confocal laser scanning microscopy study.

Peroxisome ghosts are aberrant peroxisomal structures found in cultured skin fibroblasts from patients affected by Zellweger Syndrome (ZS), a genetic disorder of peroxisomal assembly. They contain peroxisomal integral membrane proteins (PxIMPs) and they lack most of the matrix enzymes that should be inside the organelle (Santos et al., Science 239 (1988) 1536-1538). Considerable evidence indicates that these ghosts result from genetic defects in the cellular machinery for importing newly-synthesized peroxisomal proteins into the organelle. In contrast to these observations, (Heikoop et al., Eur. J. Cell Biol. 57 (1992) 165-171) report that in Zellweger Syndrome, peroxisomal membranes are located within lysosomes and/or contain lysosomal enzymes. We have undertaken a more detailed and systematic investigation of this matter, employing confocal laser scanning microscopy (CLSM). In fibroblasts derived from ZS patients belonging to different complementation groups, peroxisomes were labeled with antibodies against PxIMPs and lysosomes were labeled with an antibody against a lysosome associated membrane protein (LAMP-2) or with LysoTracker. The results unambiguously demonstrated no appreciable colocalization of PxIMPs and LAMPs (or LysoTracker), indicating that peroxisomal ghosts are distinct subcellular structures, occupying separate subcellular locations.

Antigens, CD↗
PubMed2000

Therapy of X-linked adrenoleukodystrophy: prognosis based upon age and MRI abnormality and plans for placebo-controlled trials.

Evaluation of the therapy of X-linked adrenoleukodystrophy (X-ALD) is hampered by its rarity and by the striking and unpredictable variation in phenotypic expression. We present two approaches that may facilitate therapy evaluation. (1) We have analysed data on 377 X-ALD patients who have been followed at the Kennedy Krieger Institute for a mean period of 38 months and have subdivided them into 18 subgroups on the basis of age and the degree of abnormality in brain magnetic resonance imaging (MRI) as assessed by the Loes score (Am. J. Neuroradrol 1994; 15: 1761). We find that grouping on the basis of age and MRI score provides information that is of significant prognostic value. (2) We present plans for the development of a placebo-controlled multicentre international study that will have sufficient biostatistical power to provide objective evaluation of new therapeutic interventions.

Adrenoleukodystrophy↗
PubMed2000

Bone marrow transplantation for infantile ceramidase deficiency (Farber disease).

Infantile ceramidase deficiency (Farber disease) is an uncommon, progressive lysosomal storage disease characterized by multiple ceramide-containing nodules (lipogranulomata) in the subcutaneous tissue and upper aerodigestive tract, painful periarticular swelling, psychomotor retardation, and varying degrees of ocular, pulmonary or hepatic involvement. Management of Farber disease has been limited to symptomatic supportive care, and few affected infants survive beyond 5 years of age. We performed an allogeneic bone marrow transplant (BMT) from an HLA-identical heterozygous sister in a 9.5-month-old female with minimally symptomatic Farber disease who received a pre-transplant regimen of busulfan and cyclophosphamide. Ceramidase activity in peripheral blood leukocytes increased from 6% before transplant to 44% (donor heterozygote level) by 6 weeks after BMT. By 2 months after transplant, the patient's subcutaneous lipogranulomata, pain on joint motion, and hoarseness had resolved. Despite modest gains in cognitive and language development, hypotonia and delayed motor skills persisted. Gradual loss of circulating donor cells with autologous hematopoietic recovery occurred; VNTR analyses showed 50% donor DNA in peripheral blood cells at 8.5 months after BMT and only 1% at 21 months after transplant. Interestingly, leukocyte ceramidase activity consistently remained in the heterozygous range despite attrition of donor cells in peripheral blood. This novel observation indicates ongoing hydrolase production by non-circulating donor cells, possibly in the mononuclear phagocytic system, and uptake by recipient leukocytes. Although lipogranulomata and hoarseness did not recur, the patient's neurological and neurocognitive status progressively declined. She died 28 months after BMT (age 37.5 months) with pulmonary insufficiency caused by recurrent aspiration pneumonias. Allogeneic BMT improves the peripheral manifestations of infantile ceramidase deficiency, but may not prevent the progressive neurological deterioration, even when carried out in minimally symptomatic patients.

Bone Marrow Transplantation↗
PubMed2000

X-Linked adrenoleukodystrophy: overview and prognosis as a function of age and brain magnetic resonance imaging abnormality. A study involving 372 patients.

The phenotypic expression of X-linked adrenoleukodystrophy (X-ALD) ranges from the rapidly progressive childhood cerebral form to the milder adrenomyeloneuropathy (AMN) in adults. It is not possible to predict phenotype by mutation analysis or biochemical assays. This study reports on 372 patients ranging in age from less than 3 years to adulthood, who have been followed at the Kennedy Krieger Institute. With the aim of determining whether a method could be developed to predict clinical course by analysis of data available at time of first contact, the patients were subdivided into 18 subgroups on the basis of age and the extent of brain magnetic resonance (MRI) abnormality utilizing the MRI scoring system devised by Loes et al. Scores to grade degree of neurologic and neuropsychologic impairment were also developed. There was strong correlation between MRI and the neurology and neuropsychology scores at baseline. Information based exclusively on age and MRI score at time of first contact was highly predictive of future clinical course and should aid the evaluation of the effects of bone marrow transplantation and the selection of patients for this procedure, as well as the evaluation of other therapies that may be developed in the future.

Adrenoleukodystrophy↗
PubMed2000

Dendritic anomalies in disorders associated with mental retardation.

Dendritic abnormalities are the most consistent anatomical correlates of mental retardation (MR). Earliest descriptions included dendritic spine dysgenesis, which was first associated with unclassified MR, but can also be found in genetic syndromes associated with MR. Genetic disorders with well-defined dendritic anomalies involving branches and/or spines include Down, Rett and fragile-X syndromes. Cytoarchitectonic analyses also suggest dendritic pathology in Williams and Rubinstein-Taybi syndromes. Dendritic abnormalities appear to have syndrome-specific pathogenesis and evolution, which correlate to some extent with their cognitive profile. The significance of dendritic pathology in synaptic circuitry and the role of animal models in the study of MR-associated dendritic abnormalities are also discussed. Finally, a model of genotype to neurologic phenotype pathway in MR, centered in dendritic abnormalities, is postulated.

Animals↗
PubMed2000

Adrenomyeloneuropathy: a neuropathologic review featuring its noninflammatory myelopathy.

The neuropathologic features of adrenomyeloneuropathy (AMN) are reviewed by supplementing those few previously published cases with 5 additional cases collected over the years. The endocrine involvement in AMN is briefly presented to serve as a pathogenetic backdrop and to emphasize that most of the lesions in AMN, as in adreno-leukodystrophy (ALD), are noninflammatory in the traditional sense of the word. The myeloneuropathy is emphasized, but the dysmyelinative/inflammatory demyelinative lesions also are presented. The preponderance of available data indicates that the myeloneuropathy of AMN is a central-peripheral distal (dying-back) axonopathy, as was originally proposed. The severity of the myeloneuropathy does not appear to correlate with the duration or severity of endocrine dysfunction. Microglia are the dominant participating cells in the noninflammatory myelopathy. Abnormalities in the ALD gene, which encodes a peroxisomal ABC half-transporter, do not correlate with clinical phenotypes. The relationship of the gene product, ALDP, to the peroxisomal very long chain fatty acid (VLCFA) synthetase, the activity of which is deficient in ALD/AMN, is unclear. An ALD-knockout mouse model has developed axonal degeneration, particularly in spinal cord, and is therefore more reminiscent of AMN than ALD. We continue to postulate that the fundamental defect in the myeloneuropathy of AMN is an axonal or neuronal membrane abnormality perhaps due to the incorporation of VLCFA-gangliosides, which perturbs the membrane's microenvironment and leads to dysfunction and atrophy.

Adrenoleukodystrophy↗
PubMed2000

X-linked adrenoleukodystrophy: the role of contrast-enhanced MR imaging in predicting disease progression.

BACKGROUND AND PURPOSE: Early assignment of disease progression among patients with X-linked adrenoleukodystrophy (ALD) is critical for the appropriate selection of effective therapy. We evaluated the association between contrast enhancement on T1-weighted spin-echo MR images and disease progression. METHODS: Clinical charts of patients with X-linked ALD were reviewed for age, availability of MR images of the brain, severity of neurologic impairment, and duration and number of follow-up evaluations. Forty-three male patients with X-linked ALD had undergone multiple MR imaging examinations of the brain that consisted of at least sagittal and axial T1-weighted spin-echo, axial double-echo spin-echo, and contrast-enhanced axial T1-weighted spin-echo imaging. The MR images were reviewed for the presence of contrast enhancement. In addition, global disease burden, as shown by the double-echo spin-echo images, was assessed using a visual scoring method (Loes score). RESULTS: Enhancement was seen on the initial T1-weighted spin-echo MR images of 21 (49%) patients; 18 (86%) of the 21 patients had disease progression revealed by the follow-up evaluations based on MR imaging (Loes) and neurologic scores. No enhancement was seen on the initial T1-weighted spin-echo MR images of 22 (51%) patients; for 18 (82%) of the 22 patients, no evidence of disease progression was revealed by the follow-up evaluations. CONCLUSION: There is a very strong association between the presence of contrast enhancement on T1-weighted MR images and X-linked ALD progression based on clinical evaluation and MR imaging.

Adolescent↗
PubMed1999

Prenatal diagnosis of rhizomelic chondrodysplasia punctata due to isolated alkyldihydroacetonephosphate acyltransferase synthase deficiency.

Current practices in prenatal diagnosis of rhizomelic chondrodysplasia punctata (RCDP) are reviewed. A case is presented with a family having one daughter affected with RCDP due to alkyldihydroacetonephosphate acyltransferase synthase (DHAPAT synthase) deficiency, and three subsequent pregnancies. Biochemical test values are presented for the pregnancies and daughter. Post-mortem tests of one fetus of a terminated pregnancy showed that radiologic examination could not make the diagnosis of RCDP. We conclude that biochemical or molecular testing is necessary to accurately diagnose this type of RCDP prenatally.

Adult↗
PubMed1999

Genomic structure and identification of 11 novel mutations of the PEX6 (peroxisome assembly factor-2) gene in patients with peroxisome biogenesis disorders.

The PEX6 (peroxisome assembly factor-2, PAF-2) gene encodes a member of the AAA protein (ATPases associated with diverse cellular activities) family and restores peroxisome assembly in fibroblasts from peroxisome biogenesis disorder patients belonging to complementation group C (group 4 in the United States). We have now clarified the genomic DNA structure of human PEX6 and identified mutations in patients from various ethnic groups. The human PEX6 gene consists of 17 exons and 16 introns, spanning about 14kb. The largest exon, exon 1, has at least 952 bp nucleotides. Eleven novel mutations (18 alleles) were identified by direct sequencing of the PEX6 cDNA from 10 patients. All these mutations have been confirmed in the corresponding genomic DNA. There was no common mutation, but an exon skip was identified in two unrelated Japanese patients. Most of the mutations led to premature termination or large deletions of the PEX6 protein and resulted in the most severe peroxisome biogenesis disorder phenotype of Zellweger syndrome. A patient with an atypical Zellweger syndrome had a missense mutation that was shown to disrupt the cell's ability to form peroxisomes. This mutation analysis will aid in understanding the functions of the PEX6 protein in peroxisomal biogenesis. Hum Mutat 13:487-496, 1999.

ATPases Associated with Diverse Cellular Activitie↗
PubMed1999

Plasma very long chain fatty acids in 3,000 peroxisome disease patients and 29,000 controls.

The assay of plasma very long chain fatty acids (VLCFAs), developed in our laboratory in 1981, has become the most widely used procedure for the diagnosis of X-linked adrenoleukodystrophy (X-ALD) and other peroxisomal disorders. We present here our 17 years' experience with this assay. Three VLCFA parameters, the level of hexacosanoic acid (C26:0), the ratio of C26:0 to tetracosanoic acid (C24:0), and of C26:0 to docosanoic acid (C22:0), were measured in 1,097 males (hemizygotes) with X-ALD, 1,282 women heterozygous for this disorder, including 379 obligate heterozygotes, 797 patients with other peroxisomal disorders, and 29,600 control subjects. All X-ALD hemizygotes who had not previously received Lorenzo's oil or a diet with a high erucic acid content had increased VLCFA levels, but the application of a discriminant function based on all three measurements is required to avoid the serious consequences of a false-negative result. VLCFA levels are increased at day of birth, thus providing the potential for neonatal mass screening, are identical in the childhood and adult forms, and do not change with age. Eighty-five percent of obligate heterozygotes had abnormally high VLCFA levels, but a normal result does not exclude carrier status. VLCFA levels were increased in all patients homozygous for Zellweger syndrome, neonatal adrenoleukodystrophy, infantile Refsum's disease, and in patients with deficiencies of peroxisomal acyl-coenzyme A oxidase, bifunctional enzyme, and 3-oxoacyl-coenzyme A thiolase. In these patients the degree of VLCFA excess correlated with clinical severity.

Adolescent↗
PubMed1999

Accurate DNA-based diagnostic and carrier testing for X-linked adrenoleukodystrophy.

X-linked adrenoleukodystrophy is a serious and often fatal disorder, affecting the white matter of the nervous system, the adrenal cortex, and the testis. The gene mutated in X-ALD encodes a peroxisomal membrane protein, ALDP. The presence of very long chain fatty acids in plasma is highly diagnostic for affected males and carrier females, but exclusion of carrier status biochemically is unreliable. Molecular analysis of the X-ALD gene has the potential to either identify or rule out carrier status accurately, but is complicated by the existence of autosomal paralogs. We have developed and validated a robust DNA diagnostic test for this disorder involving nonnested genomic amplification of the X-ALD gene, followed by fluorescent dye-primer sequencing and analysis. This protocol provides a highly reliable means of determining carrier status in women at risk for transmitting X-ALD and is applicable to a clinical diagnostic laboratory.

ATP Binding Cassette Transporter, Subfamily D, Mem↗
PubMed1999

Genotype-phenotype correlations in disorders of peroxisome biogenesis.

Genetically determined human peroxisomal disorders are subdivided into two major categories: disorders of peroxisome biogenesis (PBD), in which the organelle is not formed normally, and those that involve a single peroxisomal enzyme. Twelve PBD have been identified, and the molecular defects have been defined in 10. All involve defects in the import of proteins into the organelle. Factors required for this import are now referred to as peroxins (PEX) and form the basis of a new and preferred classification system. The PBD are associated with four clinical phenotypes, named before their association with the organelle was recognized: Zellweger syndrome (ZS), neonatal adrenoleukodystrophy (NALD), infantile Refsum disease (IRD), and rhizomelic chondrodysplasia punctata (RCDP). The first three are associated with 9 of the 10 PEX defects that have been defined so far, and represent a clinical continuum with variant severity, with ZS the most severe, NALD intermediate, and IRD the least severe. RCDP is associated with PEX7. Genotype-phenotype correlations are complicated by the fact that the clinical manifestations of the ZS-NALD-IRD continuum can be mimicked by disorders that affect single enzymes of peroxisomal fatty acid oxidation, and PEX7 by disorders of plasmalogen synthesis enzymes. Furthermore, clinical manifestations of each of the PEX disorders may vary. Phenotypic expression varies with the nature of the mutation, the milder phenotypes being associated with mutations that do not abolish function completely, or with mosaicism. Definition of the molecular defects is of great value for genetic counseling and may be of aid in establishing prognosis.

Genotype↗