Cerebral folate deficiency and CNS inflammatory markers in Alpers disease

We describe a 3.5-year-old female with Alpers disease with a POLG genotype of p.A467T/p.G848S and with a lethal outcome. Laboratory investigation revealed elevated CSF neopterin, IL-6, IL-8, IFN-gamma, reduced CSF 5-methyltetrahydrofolate (5MTHF), and increased serum as well as CSF folate receptor blocking autoantibodies. Treatment with oral Leucovorine (5-formyl-tetrahydrofolate) was initiated at 0.25mg/kg bid, and later increased to 4mg/kg bid. Under treatment CSF levels of 5MTHF, seizure frequency and communicative abilities improved. Over a time span of 17months, CSF levels of IL-6 and IFN-gamma decreased, levels of folate receptor blocking autoantibodies continued to raise, whereas CSF IL-8 remained elevated 1500-fold above normal. The child died without apparent stress at the age of 5.5years. Alpers disease, a neurodegenerative disease usually presents in the first years of life as a progressive encephalopathy with multifocal myoclonic seizures, developmental regression, cortical blindness and early death. The underlying genetic defect has been attributed to mutations of the catalytic subunit of the mitochondrial DNA polymerase-gamma leading to an organ-specific mitochondrial DNA depletion syndrome with reduced activity of respiratory chain enzyme complexes in the brain and the liver. A curative therapy is not available. This case report of Alpers disease provides new insights into the pathophysiology of Alpers disease, where mitochondrial dysfunction in conjunction with inflammatory cytokines and blocking folate receptor autoantibodies may lead to a secondary cerebral folate deficiency syndrome. The treatment of the latter provides relief to the patient without stopping the underlying disease.

POLG1Mutations Associated With Progressive Encephalopathy in Childhood

We have identified compound heterozygous missense mutations in POLG1, encoding the mitochondrial DNA polymerase gamma (Pol gamma), in 7 children with progressive encephalopathy from 5 unrelated families. The clinical features in 6 of the children included psychomotor regression, refractory seizures, stroke-like episodes, hepatopathy, and ataxia compatible with Alpers-Huttenlocher syndrome. Three families harbored a previously reported A467T substitution, which was found in compound with the earlier described G848S or the W748S substitution or a novel R574W substitution. Two families harbored the W748S change in compound with either of 2 novel mutations predicted to give an R232H or M1163R substitution. Muscle morphology showed mitochondrial myopathy with cytochrome c oxidase (COX)-deficient fibers in 4 patients. mtDNA analyses in muscle tissue revealed mtDNA depletion in 3 of the children and mtDNA deletions in the 2 sibling pairs. Neuropathologic investigation in 3 children revealed widespread cortical degeneration with gliosis and subcortical neuronal loss, especially in the thalamus, whereas there were only subcortical neurodegenerative findings in another child. The results support the concept that deletions as well as depletion of mtDNA are involved in the pathogenesis of Alpers-Huttenlocher syndrome and add 3 new POLG1 mutations associated with an early-onset neurodegenerative disease.

Tissue preconditioning may explain concentric lesions in Baló's type of multiple sclerosis

Lesions of Baló's concentric sclerosis are characterized by alternating layers of myelinated and demyelinated tissue. The reason for concentric demyelination in this variant of multiple sclerosis is unclear. In the present study we investigated the immunopathology in autopsy tissue of 14 patients with acute multiple sclerosis or fulminant exacerbations of chronic multiple sclerosis with Baló-type lesions in the CNS, focusing on the patterns of tissue injury in actively demyelinating lesions. We found that all active concentric lesions followed a pattern of demyelination that bears resemblances to hypoxia-like tissue injury. This was associated with high expression of inducible nitric oxide synthase in macrophages and microglia. At the edge of active lesions and, less consistently, in the outermost layer of preserved myelin, proteins involved in tissue preconditioning, such as hypoxia-inducible factor 1alpha and heat-shock protein 70, were expressed mainly in oligodendrocytes and to a lesser degree also in astrocytes and macrophages. Due to their neuroprotective effects, the rim of periplaque tissue, where these proteins are expressed, may be resistant to further damage in an expanding lesion and may therefore remain as a layer of preserved myelinated tissue.

Mitochondrial DNA depletion in Alpers syndrome

Mitochondrial dysfunction of the energy generating system was suggested in two infants with progressive infantile poliodystrophy characterised by hypotonia, refractory epilepsy, visual impairment, psychomotor retardation, profound brain atrophy, hepatopathy, and increased levels of lactate in blood and cerebrospinal fluid. Histochemical and electron microscopic analyses of liver biopsies revealed cytochrome c oxidase deficiency, microvesicular steatosis, and enormous multiplication of mitochondria of various sizes. In the first patient, the quantitative Southern blot analyses in tissues obtained at autopsy demonstrated reduced content of mtDNA in the liver, brain, and fibroblasts (11 %, 15 %, and 25 % of the mean values in controls) while a normal content of mtDNA was found in muscle and heart. In the second patient, a reduced content of mtDNA was found in the muscle, liver, and brain (15 %, 10 %, and 30 %, respectively, of the mean values in controls). Biochemical studies in the first patient revealed decreased activities of all respiratory chain complexes except complex II in isolated liver mitochondria and decreased amounts of respiratory chain complexes I, III, IV and ATP synthase in liver and frontal cortex, but not in muscle, heart, and fibroblasts. In conclusions, mtDNA depletion associated with Alpers syndrome may be tissue specific.

A mutation in mitochondrial DNA-encoded cytochrome c oxidase II gene in a child with Alpers-Huttenlocher-like disease

OBJECTIVE

Cytochrome c oxidase (COX) deficiency has been demonstrated in some patients with Alpers-Huttenlocher disease, but no genetic background has been identified. Our objective was to determine the molecular defect underlying the mitochondrial respiratory chain deficiency in a child with Alpers-Huttenlocher-like progressive cerebrohepatic disease.

METHODS

The entire coding region of mitochondrial DNA was analyzed by conformation-sensitive gel electrophoresis and sequencing. Biochemical and morphologic investigations were performed on tissue biopsy material, including oximetric and spectrophotometric analyses of oxidative phosphorylation, histochemistry, and electron microscopy.

RESULTS

Postmortem histologic examination revealed a marked loss of neurons in the olivary nuclei and a spongy change in the calcarine cortex, fatty infiltration and micronodular cirrhosis of the liver, and atrophic ovaries. A novel heteroplasmic 7706G>A mutation was found in the COX II gene. The median degree of the mutant heteroplasmy was 90% in 5 tissues examined but was lower in the blood of asymptomatic maternal relatives. The distribution of the mutant heteroplasmy was skewed to the left in single muscle fibers of the proband and her mother. The 7706G>A mutation converts a hydrophobic alanine in a conserved transmembrane segment to hydrophilic threonine.

CONCLUSIONS

The 7706G>A mutation is pathogenic and may lead to impaired dioxygen transfer to the active site of COX. The clinical phenotype of this patient resembled that in Alpers-Huttenlocher disease, suggesting that analysis of mitochondrial DNA is worthwhile in patients with a progressive cerebrohepatic disease.

Diagnostic criteria for respiratory chain disorders in adults and children

BACKGROUND

Respiratory chain (RC) disorders are clinically, biochemically, and molecularly heterogeneous. The lack of standardized diagnostic criteria poses difficulties in evaluating diagnostic methodologies.

OBJECTIVE

To assess proposed adult RC diagnostic criteria that classify patients into "definite," "probable," or "possible" categories.

METHODS

The authors applied the adult RC diagnostic criteria retrospectively to 146 consecutive children referred for investigation of a suspected RC disorder. Data were collected from hospital, genetics, and laboratory records, and the diagnoses predicted by the adult criteria were compared with the previously assigned assessments.

RESULTS

The authors identified three major difficulties in applying the adult criteria:lack of pediatric-specific criteria; difficulty in segregating continuous data into circumscribed major and minor criteria; and lack of additivity of clinical features or enzyme tests. They therefore modified the adult criteria to allow for pediatric clinical and histologic features and for more sensitive coding of RC enzyme and functional studies. Reanalysis of the patients' data resulted in congruence between the diagnostic certainty previously assigned by the authors' center and that defined by the new general RC diagnostic criteria in 99% of patients.

CONCLUSIONS

These general diagnostic criteria appear to improve the sensitivity of the adult criteria. They need further assessment in prospective clinical and epidemiologic studies.

MR spectroscopic findings in a case of Alpers-Huttenlocher syndrome

Alpers-Huttenlocher syndrome, considered a mitochondrial disease, combines encephalopathy and liver failure. An 11-year-old boy with Alpers-Huttenlocher syndrome underwent conventional MR imaging, diffusion-weighted imaging, and proton MR spectroscopy. Diffusion-weighted imaging showed cytotoxic edema interpreted as acute-phase encephalopathy. MR spectroscopy revealed a lactate peak in the cortex that appeared abnormal on diffusion-weighted images, possibly representing respiratory deficiency with anaerobic metabolism. MR spectroscopy proved to be more sensitive regarding lactate detection than did neurometabolic examination of serum and CSF. A reduced N-acetylaspartate-creatine ratio was detected in both the cortex that appeared abnormal and the cortex that appeared normal on the diffusion-weighted images, indicating neuronal damage that was widespread, even beyond the boundaries of conventional MR imaging changes.

Inducible nitric oxide synthase and nitrotyrosine are found in monocytes/macrophages and/or astrocytes in acute, but not in chronic, multiple sclerosis

We have examined the localization of inducible nitric oxide synthase (iNOS) and nitrotyrosine (the product of nitration of tyrosine by peroxynitrite, a highly reactive derivative of nitric oxide [NO]) in demyelinating lesions from (i) two young adult patients with acute multiple sclerosis (MS), (ii) a child with MS (consistent with diffuse sclerosis), and (iii) five adult patients with chronic MS. Previous reports have suggested a possible correlation between iNOS, peroxynitrite, related nitrogen-derived oxidants, and the demyelinating processes in MS. We have demonstrated iNOS-immunoreactive cells in both acute-MS and diffuse-sclerosis-type lesions. In acute-MS lesions, iNOS was localized in both monocytes/macrophages and reactive astrocytes. However, foamy (myelin-laden) macrophages and the majority of reactive astrocytes were iNOS negative. In specimens from the childhood MS patient, iNOS protein was present only in a subpopulation of reactive or hypertrophic astrocytes. In contrast, no iNOS staining was detected in chronic-MS lesions. Immunohistochemical staining of acute-MS lesions with an antibody to nitrotyrosine revealed codistribution of iNOS- and nitrotyrosine-positive cells, although nitrotyrosine staining was more widespread in cells of the monocyte/macrophage lineage. In diffuse-sclerosis-type lesions, nitrotyrosine staining was present in hypertrophic astrocytes, whereas it was absent in chronic-MS lesions. These results suggest that NO and nitrogen-derived oxidants may play a role in the initiation of demyelination in acute-MS lesions but not in the later phase of the disease.

Overexpression of DM20 messenger RNA in two brothers with Pelizaeus-Merzbacher disease

Pelizaeus-Merzbacher disease is a rare, sex-linked recessive, dysmyelinating disease of the central nervous system that has been associated with mutations in the myelin proteolipid protein (PLP) gene. Only 25% of patients studied with Pelizaeus-Merzbacher disease have exonic mutations in this gene, the underlying cause of the disease in the remaining patients is unknown. The PLP gene encodes two major alternatively spliced transcripts called PLP and DM20. PLP messenger RNA is specifically expressed in central nervous system tissue, whereas DM20 messenger RNA is found in central nervous system, cardiac, and other tissues. We studied cultured skin fibroblasts from 2 brothers with Pelizaeus-Merzbacher disease who exhibited no detectable exonic mutation of the PLP gene. Examination of RNA from these cells showed that the level of DM20 messenger RNA is elevated sixfold relative to male control skin fibroblasts. An unrelated female carrier, also with no detectable exonic mutation, showed a threefold increase in DM20 messenger RNA in cultured skin fibroblasts. Our findings suggest that in some patients, Pelizaeus-Merzbacher disease is caused by overexpression of PLP gene transcripts, and that in these families a 50% increase of DM20 messenger RNA in females, relative to the increase in affected males, can identify a female carrier.

The neonatal progeroid syndrome (Wiedemann-Rautenstrauch) and its relationship to Pelizaeus-Merzbacher's disease

The neuropathology of a clinically well-documented case of the neonatal progeroid syndrome Wiedemann-Rautenstrauch is described. The most striking feature was a nearly complete absence of mature myelin in the brain. When immunohistochemistry for myelin basic protein was applied, some subcortical nerve fibres were accompanied by immature myelin sheaths. The neuropathology corresponds exactly to that of Pelizaeus-Merzbacher disease (Seitelberger type). Furthermore, this morphology, with the presence of myelin basic protein in the absence of mature myelin sheaths is reminiscent of the early stages of myelination in the newborn. From a brief review of the literature on Wiedemann-Rautenstrauch syndrome, we conclude, that the neuropathology of the syndrome is heterogeneous, and that there is relationship between the progeroid aspect and pathological myelination.

A case of Pelizaeus-Merzbacher disease showing increased dosage of the proteolipid protein gene

Clinical, neuropathological and molecular genetic studies in a 9 month old boy with Pelizaeus-Merzbacher disease are described. The principal clinical features were developmental delay, nystagmus, stridor and seizures. Both brain and spinal cord showed almost complete absence of stainable central myelin, while cranial and spinal root myelin was preserved. Probes for cDNA in the boy and his asymptomatic mother indicated an increase in the dosage of proteolipid protein gene (of at least twofold) compared with controls.

Biochemical diagnosis of Canavan disease

Canavan disease (CD) is a rare autosomal recessive disorder characterized by macrocephaly and progressive leukodystrophy. Up to now biopsy or necropsy were required to define the diagnosis. Recently the disease has been related to N-acetylaspartic aciduria and deficiency of aspartoacylase, an enzyme possibly involved in the myelin synthesis. These biochemical findings have provided a diagnostic marker for the disease. We report a new case of infantile CD in which the demonstration of N-acetylaspartic aciduria and a marked deficiency of aspartoacylase activity confirmed the diagnosis.

Accumulation of alpha B-crystallin in brains of patients with Alexander's disease is not due to an abnormality of the 5'-flanking and coding sequence of the genomic DNA

alpha B-Crystallin is a major protein component of Rosenthal fibers, which massively accumulate in the brains of patients suffering from Alexander's disease. To examine whether or not accumulation of alpha B-crystallin is due to any abnormality of the gene structures, we determined the sequence of the alpha B-crystallin gene in two cases of pathologically confirmed Alexander's disease. Direct sequencing of the promoter and coding regions of the alpha B-crystallin gene in patients revealed them to have a normal sequence. Northern blotting showed a single alpha B-crystallin mRNA species expressed in the Alexander's disease brain.

Phosphorylation of alpha-crystallin B in Alexander's disease brain

The phosphorylation of alpha-crystallin B was studied in homogenates of autopsy samples of brain tissue from patients with Alexander's disease, a condition characterized by over-expression of this protein. After incubation in the presence of [gamma-32P]ATP and cAMP the homogenates were analyzed by two-dimensional electrophoresis, (isoelectric focusing followed by SDS-PAGE). Three major polypeptides having the same molecular weight as bovine lens alpha-crystallin B and pIs 7.1, 6.9 and 6.7 were detected in the Coomassie blue stained gels. These three polypeptides were recognized by an alpha-crystallin B-specific antiserum in Western blots. The polypeptides with pIs 7.1 and 6.7 co-migrated in isoelectric focusing gels with bovine lens alpha B and its phosphorylated form alpha Bp, respectively. Radioautography of the two-dimensional gels demonstrated the presence of 32P in the most acidic polypeptide. The results demonstrate the occurrence of alpha B phosphorylation in Alexander's disease brain tissue.

[Demyelinating elements of demyelinated encephalopathy]

The myelin basic protein (MBPi) accounts for the main encephalitogenic antigen of the demyelinating encephalopathy, but other myelin elements also be noted by some articles. We tried to determine the relationship between W1 protein and the demyelinating encephalopathies. The 2',3'-cyclic nucleotide 3'-phospho-diesterase(CNPase, a gift from Dr. Yasuzo Tuskada) monoclonal antibody was used as a probe to study the W1 protein level in 5 different demyelinating encephalopathies and 2 normal adult brains with immunocytochemical technique. Two different demyelinating types of W1 protein level were found out. Type 1 showed the W1 protein level parallel with demyelinated feature in general pathology whereas the type 2 showed demyelinated in the general pathology but the W1 protein level was normal in the immunocytochemical study. Multiple system degeneration, Binswanger's disease and postvaccinal encephalopathy of type B encephalitis belong to type 1 and multiple sclerosis and Balo's concentric sclerosis belong to type 2. These results might indicate the different pathogenesis of demyelinating encephalopathies.

Liver involvement in Alpers disease

Alpers disease consists of diffuse cerebral degeneration manifested as developmental delay, seizures, vomiting, and progressive neuromuscular deterioration, with liver disease and death. We report the clinical course of the liver disease, histologic progression of the hepatic lesions, and etiologic investigations in five patients (four girls, three kinships). All had grown and developed normally until seen at 6 to 36 months of age (mean 20 months), with vomiting (n = 5), progressive hypotonia (n = 3), or seizures (n = 2). All had been given anticonvulsants, including valproic acid in three. Liver disease was noted at a mean age of 35 months (range 9 to 67 months), with hepatomegaly (two patients), abnormal hepatic synthetic function (three) or transaminase values (three), and cirrhosis in one. Patients survived for a mean of 4.6 weeks (range 1 to 8 weeks) after the identification of liver disease; all died of hepatic failure. Results of evaluation for infectious and metabolic causes of liver disease and causes of degenerative neuromuscular disease were negative in all patients. Premortem liver biopsy specimens (n = 3) demonstrated an early lesion consisting of lobular disarray, microvesicular steatosis, periportal acute and chronic inflammation, and individual hepatocyte necrosis. Autopsy findings (n = 5) consisted of macrovesicular steatosis, massive hepatocyte dropout, and proliferation of bile ductular elements, with almost complete replacement of hepatocytes by proliferating bile ductular elements in two patients. Brain showed characteristic neuronal degeneration. We conclude that Alpers disease can be a cause of rapidly progressive liver failure in early childhood. Although the cause of this autosomal recessive disease is not known, it does not appear to be related to peroxisomal dysfunction.

Metabolism of saturated and polyunsaturated very-long-chain fatty acids in fibroblasts from patients with defects in peroxisomal beta-oxidation

The metabolism of [1-14C]lignoceric acid (C24:0) and [1-14C]tetracosatetraenoic acid (C24:4, n-6) was studied in normal skin fibroblast cultures and in cultures from patients with defects in peroxisomal beta-oxidation (but normal peroxisomal numbers). Cells from X-linked adrenoleukodystrophy (ALD) patients with a presumed defect in a peroxisomal acyl-CoA synthetase, specific for fatty acids of carbon chain lengths greater than 22 (very-long-chain fatty acids; VLCFA), showed a relatively normal production of radiolabelled CO2 and water-soluble metabolites from [1-14C]C24:0. However, the products of synthesis from acetate de novo (released by beta-oxidation), i.e. C16 and C18 fatty acids, were decreased, and carbon chain elongation of the fatty acid was increased. In contrast, cell lines from two patients with an unidentified lesion in peroxisomal beta-oxidation (peroxisomal disease, PD) showed a marked deficiency in CO2 and water-soluble metabolite production, a decreased synthesis of C16 and C18 fatty acids and an increase in carbon chain elongation. The relatively normal beta-oxidation activity of ALD cells appears to be related to low uptake of substrate, as a defect in beta-oxidation is apparent when measurements are performed on cell suspensions under high uptake conditions. Oxidation of [1-14C]C24:4 was relatively normal in ALD cells and in the cells from one PD patient but abnormal in those from the other. Our data suggest that, despite the deficiency in VLCFA CoA synthetase, ALD cells retain a near normal ability to oxidize both saturated and polyunsaturated VLCFA under some culture conditions. However, acetate released by beta-oxidation of the saturated VLCFA and, to a much lesser degree, the polyunsaturated VLCFA, appears to be used preferentially for the production of CO2 and water-soluble products, and acetate availability for fatty acid synthesis in other subcellular compartments is markedly decreased. It is likely that the increased carbon chain elongation of the saturated VLCFA which is also observed reflects the increased availability of substrate (C24:0) and/or an increase in microsomal elongation activity in ALD cells.

Cellular oxidation of lignoceric acid is regulated by the subcellular localization of lignoceroyl-CoA ligases

The acyl-CoA ligases convert free fatty acids to acyl-CoA derivatives, and these enzymes have been shown to be present in mitochondria, peroxisomes, and endoplasmic reticulum. Because their activity is obligatory for fatty acid metabolism, it is important to identify their substrate specificities and subcellular distributions to further understand the cellular regulation of these pathways. To define the role of the enzymes and organelles involved in the metabolism of very long chain (VLC) fatty acids, we studied human genetic cell mutants impaired for the metabolism of these molecules. Fibroblast cell lines were derived from patients with X-linked adrenoleukodystrophy (X-ALD) and Zellweger's cerebro-hepato-renal syndrome (CHRS). While peroxisomes are present and morphologically normal in X-ALD, they are either greatly reduced in number or absent in CHRS. Palmitoyl-CoA ligase is known to be present in mitochondria, peroxisomes, and endoplasmic reticulum (microsomes). We found enzyme-dependent formation of lignoceroyl-CoA in these same organelles (specific activities were 0.32 +/- 0.12, 0.86 +/- 0.12, and 0.78 +/- 0.07 nmol/h per mg protein, respectively). However, lignoceroyl-CoA synthesis was inhibited by an antibody to palmitoyl-CoA ligase in isolated mitochondria while it was not inhibited in peroxisomes or endoplasmic reticulum (ER). This suggests that palmitoyl-CoA ligase and lignoceroyl-CoA are different enzymes and that mitochondria lack lignoceroyl-CoA ligase. This conclusion is further supported by data showing that oxidation of lignoceric acid was found almost exclusively in peroxisomes (0.17 nmol/h per mg protein) but was largely absent from mitochondria and the finding that monolayers of CHRS fibroblasts lacking peroxisomes showed a pronounced deficiency in lignoceric acid oxidation in situ (1.8% of control). In spite of the observation that lignoceroyl-CoA ligase activity is present on the cytoplasmic surface of ER, our data indicate that lignoceroyl-CoA synthesized by ER is not available for oxidation in mitochondria. This organelle plays no physiological role in the beta-oxidation of VLC fatty acids. Furthermore, the normal peroxisomal oxidation of lignoceroyl-CoA but deficient oxidation of lignoceric acid in X-ALD cells indicates that cellular VLC fatty acid oxidation is dependent on peroxisomal lignoceroyl-CoA ligase. These studies allow us to propose a model for the subcellular localization of various acyl-CoA ligases and to describe how these enzymes control cellular fatty acid metabolism.

[X-linked adrenoleukodystrophy and other peroxisomal diseases caused by a failing peroxisomal beta-oxidation system: clinical expression, diagnosis and treatment]

X-linked adrenoleukodystrophy (ALD) is a sex-linked, neurodegenerative disorder which in its most stereotypic form manifests itself in a boy who progresses normally for the first years of life and then presents with CNS signs and symptoms such as behavioural abnormalities, visual and auditory disturbances and an abnormal gait. The course of the disease is progressive, culminating within a few years in dementia, blindness, quadriplegia and death. Recently it has become clear that ALD is caused by an impairment in the peroxisomal beta-oxidation system leading to the accumulation of very-long-chain fatty acids. Accumulation occurs not only in plasma but also in brain giving rise to increasing myelin instability and subsequent demyelination. Apart from X-linked ALD there are a number of other disorders all characterized by a deficient peroxisomal beta-oxidation activity. It is remarkable that the clinical presentation of these different inborn errors of peroxisomal beta-oxidation differs markedly. In this paper the inborn errors of peroxisomal beta-oxidation known at present will be discussed with particular emphasis on ALD.

Pelizaeus-Merzbacher disease: an X-linked neurologic disorder of myelin metabolism with a novel mutation in the gene encoding proteolipid protein

The nosology of the inborn errors of myelin metabolism has been stymied by the lack of molecular genetic analysis. Historically, Pelizaeus-Merzbacher disease has encompassed a host of neurologic disorders that present with a deficit of myelin, the membrane elaborated by glial cells that encircles and successively enwraps axons. We describe here a Pelizaeus-Merzbacher pedigree of the classical type, with X-linked inheritance, a typical clinical progression, and a pathologic loss of myelinating cells and myelin in the central nervous system. To discriminate variants of Pelizaeus-Merzbacher disease, a set of oligonucleotide primers was constructed to polymerase-chain-reaction (PCR) amplify and sequence the gene encoding proteolipid protein (PLP), a structural protein that comprises half of the protein of the myelin sheath. The PLP gene in one of two affected males and the carrier mother of this family exhibited a single base difference in the more than 2 kb of the PLP gene sequenced, a C----T transition that would create a serine substitution for proline at the carboxy end of the protein. Our results delineate the clinical features of Pelizaeus-Merzbacher disease, define the possible molecular pathology of this dysmyelinating disorder, and address the molecular classification of inborn errors of myelin metabolism. Patients with the classical form (type I) and the more severely affected, connatal variant of Pelizaeus-Merzbacher disease (type II) would be predicted to display mutation at the PLP locus. The other variants (types III-VI), which have sometimes been categorized as Pelizaeus-Merzbacher disease, may represent mutations in genes encoding other structural myelin proteins or proteins critical to myelination.

Adrenoleukodystrophy: impaired oxidation of fatty acids due to peroxisomal lignoceroyl-CoA ligase deficiency

Very long chain fatty acids (lignoceric acid) are oxidized in peroxisomes and pathognomonic amounts of these fatty acids accumulate in X-adrenoleukodystrophy (X-ALD) due to a defect in their oxidation. However, in cellular homogenates from X-ALD cells, lignoceric acid is oxidized at a rate of 38% of control cells. Therefore, to identify the source of this residual activity we raised antibody to palmitoyl-CoA ligase and examined its effect on the activation and oxidation of palmitic and lignoceric acids in isolated peroxisomes from control and X-ALD fibroblasts. The normalization of peroxisomal lignoceric acid oxidation in the presence of exogenously added acyl-CoA ligases and along with the complete inhibition of activation and oxidation of palmitic and lignoceric acids in peroxisomes from X-ALD by antibody to palmitoyl-CoA ligase provides direct evidence that lignoceroyl-CoA ligase is deficient in X-ALD and demonstrates that the residual activity for the oxidation of lignoceric acid was derived from the activation of lignoceric acid by peroxisomal palmitoyl-CoA ligase. This antibody inhibited the activation and oxidation of palmitic acid but had little effect on these activities for lignoceric acid in peroxisomes from control cells. Furthermore, these data provide evidence that peroxisomal palmitoyl-CoA and lignoceroyl-CoA ligases are two different enzymes.

Alpha B-crystallin is expressed in non-lenticular tissues and accumulates in Alexander's disease brain

Rosenthal fibers (RFs) are abnormal inclusions within astrocytes, characteristic of Alexander's disease. We have previously isolated a 22 kd protein component of RFs from Alexander's disease brain. By Western blotting, we detected its equivalent in several rat organs, with the highest level in heart, and in a human astrocytoma cell line (U-373MG). A cDNA library established from U-373MG was screened with an anti-RF protein antibody. A partial cDNA clone encoding the lens protein alpha B-crystallin was isolated. The anti-RF protein antibodies react with lens alpha B-crystallin. Furthermore, the distribution of alpha B-crystallin mRNA in rat organs is consistent with the Western blots. Therefore, alpha B-crystallin is not lens-specific and it can accumulate in large amounts in astrocytes in pathological conditions.

Adrenoleukodystrophy. The chain shortening of erucic acid (22:1(n-9)) and adrenic acid (22:4(n-6)) is deficient in neonatal adrenoleukodystrophy and normal in X-linked adrenoleukodistrophy skin fibroblasts

The metabolism of long chain unsaturated fatty acids was studied in cultured fibroblasts from patients with X-linked adrenoleukodystrophy (ALD) and with neonatal ALD. By using [14-14C] erucic acid (22:1(n-9)) as substrate it was shown that the peroxisomal beta-oxidation, measured as chain shortening, was impaired in cells from patients with neonatal ALD. The beta-oxidation of adrenic acid (22:4(n-6)), measured as acid-soluble products, was also reduced in the neonatal ALD cells. The peroxisomal beta-oxidation of [14-14C]erucic acid (22:1(n-9)) and [2-14C]adrenic acid (22:4(n-6)) was normal in cells from X-ALD patients. The beta-oxidation, esterification and chain elongation of [1-14C]arachidonic acid (20:4(n-6)) and [1-14C]eicosapentaenoic acid (20:5(n-3)) was normal in both X-linked ALD and in neonatal ALD. Previous studies suggest that the activation of very long chain fatty acids by a lignoceryl (24:0)-CoA ligase is deficient in X-linked ALD, while the peroxisomal beta-oxidation enzymes are deficient in neonatal ALD. The present results suggest that the peroxisomal very long-chain acyl-CoA ligase is not required for activation of unsaturated C20 and C22 fatty acids and that these fatty acids can be efficiently activated by the long chain acyl-(palmityl)-CoA ligase.

Adrenoleukodystrophy and other peroxisomal disorders that affect the nervous system, including new observations on L-pipecolic acid oxidase in primates

Impaired nervous system function in childhood is encountered in 10 separate disorders of the peroxisome. Peroxisomal disorders are subdivided into three major groups. In group 1 there is failure to form the organelle and impairment of multiple peroxisomal functions. In group 3 peroxisome structure is intact and the defect involves a single enzyme. In group 2 (rhizomelic chondrodysplasia punctata) peroxisome structure is probably intact, but at least 2 peroxisomal enzymes fail to function normally. We present an overview of this newly recognized field which is so pertinent to brain development. In addition, we present recent and new data about the biochemical defect, genetics and therapy of X-linked adrenoleukodystrophy; about the normal metabolism of L-pipecolic acid in primates and its disturbance in the Zellweger syndrome, and about the prenatal diagnosis of peroxisomal disorders.

Histopathologic and biochemical analysis of classic Pelizaeus-Merzbacher disease

An autopsy study of an 11-year-old boy with the classic type of Pelizaeus-Merzbacher disease is presented. He developed normally until 5 years of age when he began to deteriorate with scanning speech and gait abnormality. Auditory brainstem responses were normally preserved. At the age of 11 years, 8 months, he died of pneumonia while in a vegetative state. The neuropathologic findings suggested a typical classic type of Pelizaeus-Merzbacher disease and biochemical analysis of cerebral white matter demonstrated a decreased ratio of long-chain fatty acids (greater than or equal to C19) to short- and medium-chain fatty acids (less than C19). These findings suggested defective myelin synthesis as the etiology of Pelizaeus-Merzbacher disease; comprehensive classifications of the disease are expected to include both pathologic and biochemical parameters.

Direct demonstration that the deficient oxidation of very long chain fatty acids in X-linked adrenoleukodystrophy is due to an impaired ability of peroxisomes to activate very long chain fatty acids

A method was developed to prepare peroxisome-enriched fractions depleted of microsomes and mitochondria from cultured skin fibroblasts. The method consists of differential centrifugation of a postnuclear supernatant followed by density gradient centrifugation on a discontinuous Metrizamide gradient. The activity of hexacosanoyl-CoA synthetase was subsequently measured in postnuclear supernatants and peroxisome-enriched fractions prepared from cultured skin fibroblasts from control subjects and patients with X-linked adrenoleukodystrophy. Whereas the hexacosanoyl-CoA synthetase activity in postnuclear supernatants of X-linked adrenoleukodystrophy fibroblasts was only slightly decreased (77.8 +/- 4.4% of control (n = 15], enzyme activity was found to be much more markedly reduced in peroxisomal fractions isolated from the mutant fibroblasts (19.6 +/- 6.7% of control (n = 5]. This is a direct demonstration that the defect in X-linked adrenoleukodystrophy is at the level of a deficient ability of peroxisomes to activate very long chain fatty acids, as first suggested by Hashmi et al. [Hashmi, M., Stanley, W. and Singh, I. (1986) FEBS Lett. 86, 247-250].

Comparative immunocytochemistry of Pelizaeus-Merzbacher disease, the jimpy mouse, and the myelin-deficient rat

Patients with Pelizaeus-Merzbacher disease (PM), hemizygous mice with the jimpy mutation (jp/Y), and hemizygous rats with X-linked myelin deficiency (md/Y) share a profound lack of proteolipid protein (PLP) in their central nervous systems (CNS). The peripheral nervous system is normal. These X-linked disorders are associated with or actually caused by the lack of normal oligodendrocytes. Vibratome sections of brain were incubated with antisera to myelin basic protein (MBP), myelin-associated glycoprotein (MAG), 2':3'-cyclic-nucleotide 3'-phosphodiesterase (CNP) (EC 3.1.4.37), PLP, a synthetic PLP-peptide, glial fibrillary acidic protein (GFAP), and transferrin. Reaction product was developed by sequential incubation with biotinylated second antibodies, the avidin-biotin-peroxidase complex (ABC), and diaminobenzidine (DAB) plus hydrogen peroxide as chromogenic substrates. In PM, jp/Y and md/Y, islands of myelin-like structures were revealed by antisera to MBP, MAG, and CNP. Reaction product after application of anti-PLP was absent. Reaction product after anti-PLP-peptide was restricted to infrequent bizarre cells possibly representing abnormal oligodendroglia. The lack of oligodendrocytes in jp/Y and md/Y could also be confirmed by immunocytochemistry for transferrin.

Polarizing inclusions in some organs of children with congenital peroxisomal diseases (Zellweger's, Refsum's, chondrodysplasia punctata (rhizomelic form), X-linked adrenoleukodystrophy)

Polarizing material has been reported in the liver of children with infantile Refsum's disease (IRD) and was absent in two patients with the cerebro-hepato-renal syndrome of Zellweger (CHRS). We examined in polarized light 15 liver biopsy and autopsy samples from six other patients with the cerebro-hepato-renal syndrome of Zellweger, two with the rhizomelic form of chondrodysplasia punctata (rCDP) and two with X-linked adrenoleukodystrophy (ALD), all conditions with deficient peroxisomes. Two types of birefringent inclusions were found in CHRS only: the first is transparent in bright field, the second appears as brown granules or rods, similar to lipofuscins. As in IRD large PAS-positive macrophage-like cells contain the transparent type. Electron microscopical investigation of these cells shows trilaminar structures within membrane-bound organelles. The two types were also seen in kidney and brown adipose tissue, the first type in pancreas, the second type in adrenal gland; no such was observed in myocardium or in thyroid gland (CHRS). No birefringent inclusions were present in rCDP and ALD. The nature of the inclusions is still unclear. An accumulation of the transparent polarizing material with increasing age of the patients is most likely.

Peroxisomal integral membrane proteins in livers of patients with Zellweger syndrome, infantile Refsum's disease and X-linked adrenoleukodystrophy

Livers from seven patients with peroxisome disorders, three with Zellweger syndrome, one with infantile Refsum's syndrome and three with X-linked adrenoleukodystrophy, were analysed by immunoblotting. The bifunctional protein catalysing two peroxisomal beta-oxidation reactions was deficient in all Zellweger livers and in the infantile Refsum's liver, consistent with the absence of morphologically recognizable peroxisomes. Three peroxisomal integral membrane proteins (IMPs) (69, 53 and 22 kDa) were present in normal amounts in all the Zellweger and adrenoleukodystrophy samples and they sedimented in a membrane fraction. These membrane proteins were also present in the infantile Refsum's liver. We suggest, on the basis of these results, that aberrant peroxisomal membranes may be present in Zellweger syndrome and that the defect is in the transport of matrix proteins into the organelle.

Pigmentary type of orthochromatic leukodystrophy (OLD): a new case with ultrastructural and biochemical study

A 34-year-old woman with no family history of orthochromatic leukodystrophy (OLD) developed progressive intellectual deterioration, a frontal syndrome and spastic tetraparesis. She died four years after the onset of the clinical illness. Neuropathological studies included light and electron microscopy of cerebral and nerve biopsies, and a complete postmortem examination. Light microscopy demonstrated OLD with pigmented macrophages and glial cells. Electron microscopy showed electron-dense, membrane-bound intracytoplasmic lamellar inclusions with curved or straight parallel arrangement, or fingerprint pattern, in white matter macrophages, astrocytes and oligodendrocytes. Cortical cells contained lipofuscin which was normal in type and amount. This suggests that the material in white matter glial cells and macrophages is ceroid pigment, however, the distribution is not that seen in ceroid-lipofuscinosis. Similar inclusions have been found in oligodendrocytes in other forms of OLD. Biochemical study did not show evidence of demyelination. Galactolipids were normal. Polyunsaturated fatty acids were decreased. The most striking feature was an increase in plasmalogens.

X-linked adrenoleukodystrophy: defective peroxisomal oxidation of very long chain fatty acids but not of very long chain fatty acyl-CoA esters

We investigated the peroxisomal fatty acid beta-oxidation system in liver and cultured skin fibroblasts from patients with X-linked adrenoleukodystrophy known to accumulate very long chain fatty acids. In order to examine whether the deficient peroxisomal oxidation of very long chain fatty acids in these patients results from a deficiency in one of the peroxisomal beta-oxidation enzyme proteins (acyl-CoA oxidase, bifunctional protein with enoyl-CoA hydratase and 3-hydroxyacyl-CoA dehydrogenase activities and 3-oxoacyl-CoA thiolase) we carried out immunoblotting experiments using antibodies directed against the peroxisomal beta-oxidation enzyme proteins from rat liver. Furthermore, we studied the oxidation of palmitoyl-CoA and lignoceroyl-CoA in homogenates of fibroblasts from the patients. The results indicate that the peroxisomal beta-oxidation enzyme proteins are not only present immunologically but also functionally active which suggests that the defect in X-linked adrenoleukodystrophy is, indeed, as recently suggested by Hashmi and coworkers (FEBS Lett 1986;196:247-250) at the level of a deficient peroxisomal activation of very long chain fatty acids.

Adrenoleukodystrophy: from bedside to molecular biology

Although X-linked adrenoleukodystrophy was first described in 1923, the key advances in understanding the disorder followed discoveries beginning in 1973 that it was characterized by the tissue accumulation of very long chain fatty acids, particularly hexacosanoic acid (C26:0). Very long chain fatty acid assays in plasma, red cells, fibroblasts, or amniocytes permit prenatal and postnatal diagnosis and carrier detection. The phenotype of X-linked adrenoleukodystrophy is varied and ranges from the severe and fatal childhood form, to persons who remain asymptomatic in adult life. The underlying biochemical defect is the impaired capacity to degrade very long chain fatty acids, a reaction which normally takes place in the peroxisome. The locus of the adrenoleukodystrophy gene has been mapped to the terminal (Q28) segment of the long arm of the X-chromosome, in close proximity to the loci of Hemophilia A and red-green color blindness. A DNA probe (St14) for this portion of the X-chromosome is of aid for carrier detection. A new dietary regimen, which combines restricted very long chain fatty acid intake with the administration of a glycerol trioleate oil, is capable of reducing plasma very long chain fatty acid levels, and may offer neurological benefit.

An adult case of adrenoleukodystrophy with features of olivo-ponto-cerebellar atrophy: II. Lipid biochemical studies

Different portions with or without demyelination or degeneration of formalin-fixed brain tissues of a patient with adrenoleukodystrophy and a control subject were applied to analyses of lipids, particularly sphingolipids and cholesteryl ester. Demyelinated area of the white matter in the occipital lobe showed marked decrease in cerebroside and sulfatide except for sphingomyelin and, conversely an accumulation of cholesteryl ester, whereas un-demyelinated white matter in the frontal lobe showed no abnormalities in lipids. Abnormalities of lipids in degenerated lateral nuclei of the thalamus were not so remarkable as the demyelinated white matter, whereas apparently normal dorsomedial nuclei of the thalamus showed no abnormalities in lipids. With regard to the fatty acid composition of abnormal lipids in the demyelinated white matter, all sphingolipids of cerebroside, sulfatide, and sphingomyelin showed remarkable reduction of their longer chain fatty acids and, conversely a significant increment of shorter chain fatty acids. However, these fatty acids in the degenerated lateral nuclei of the thalamus were not so different from those in the undemyelinated and apparently normal areas as well as in control brain. The fatty acids of cholesteryl ester contained mainly C18:1 and C16 acids, and very long chain fatty acids, namely fatty acids with chain length more than 22 carbons, by about 22% of the total fatty acids. In view of the analytical results of the fatty acid composition of brain lipids, it was inconceivable that this ALD patient brain showed especially the accumulation of very long chain fatty acids, and that the biochemical defect in this disease was related to the abnormal oxidation of very long chain fatty acids in peroxisomes. However, the neuropathological findings of demyelination, reactive astrocytosis, and massive infiltration of foam cells well correlated with the abnormalities in myelin lipids and the accumulation of cholesteryl ester. Also, the lower values of urinary 17-ketosteroid and 17-hydroxycorticosteroid suggested that the failure of ACTH to stimulate corticoid secretion seemed to indicate the relationship between the adrenocortical insufficiency and the affected areas of the central nervous system.

Neonatal adrenoleukodystrophy. Impaired plasmalogen biosynthesis and peroxisomal beta-oxidation due to a deficiency of catalase-containing particles (peroxisomes) in cultured skin fibroblasts

Neonatal adrenoleukodystrophy belongs to the newly recognized group of inherited diseases, the peroxisomal disorders. Based on the reported similarities between neonatal adrenoleukodystrophy and the cerebro-hepato-renal (Zellweger) syndrome, we have studied peroxisomal functions in cultured skin fibroblasts from 5 neonatal adrenoleukodystrophy patients. The results indicate that multiple peroxisomal enzyme activities are deficient in fibroblasts from neonatal adrenoleukodystrophy patients. Digitonin titration experiments revealed that peroxisomes are strongly deficient in these fibroblasts as found earlier in fibroblasts from Zellweger patients. These findings not only explain the generalized loss of peroxisomal functions in neonatal adrenoleukodystrophy, but also provide an explanation for the observed resemblance in clinical and biochemical abnormalities between neonatal adrenoleukodystrophy and Zellweger syndrome. The implications for the pre- and postnatal detection of this disease will be discussed.

Defective biosynthesis of proteolipid protein in Pelizaeus-Merzbacher disease

The brain of an 18-year-old patient with Pelizaeus-Merzbacher disease was examined by standard neuropathological and biochemical methods and by immunocytochemical and immunochemical techniques. Analysis revealed a lack of myelin-specific lipids, but showed a residual immunoreactivity for myelin basic protein, myelin-associated glycoprotein, and 2',3'-cyclic nucleotide-3'-phosphodiesterase. Examination by immunocytochemistry and enzyme-linked immunosorbent assay showed an absence of proteolipid apoprotein (lipophilin). The peripheral nervous system was normal. Pelizaeus-Merzbacher disease in humans shares many neuropathological and biochemical features with X-linked mutations in animals, e.g., the jimpy mouse and myelin-deficient rat. The specificity of this protein deficiency in Pelizaeus-Merzbacher disease gains additional support from the recent mapping of the lipophilin gene to the human X chromosome.

N-acetylaspartic aciduria due to aspartoacylase deficiency--a new aetiology of childhood leukodystrophy

We describe a male infant with psychomotor retardation and leukodystrophy who excretes large quantities of N-acetylaspartate in his urine. A high CSF/plasma concentration ratio of N-acetylaspartate indicates that this substance originates in the brain. Fibroblasts from the patient are deficient in aspartoacylase activity. It is proposed that the dysmyelination in the patient may be due to failure of N-acetylaspartate to serve as a carrier of acetyl groups from mitochondria to the cytosol for lipogenesis.

Peroxisomal disorders

The different types of adrenoleukodystrophy are considered with their clinical and biochemical features, particularly the excess of very-long-chain fatty acids. Then other conditions which show this latter finding are described, including the Zellweger cerebrohepatorenal syndrome, hyperpipecolic acidemia and Refsum disease. The role of peroxisomes is discussed and the different ways in which their functions can be disordered. The possibilities of treating these diseases is at the moment limited but examples are given of research already carried out in this field.

Brain galactolipid content in a patient with pseudoarylsulfatase A deficiency and coincidental diffuse disseminated sclerosis, and in patients with metachromatic, adreno-, and other leukodystrophies

A 4-year old boy died of diffuse disseminated sclerosis (DDS) of the brain and was found to have also pseudoarylsulfatase A deficiency (PASAD) with about 20% residual arylsulfatase A (ASA) and cerebroside sulfatase (CS) activity. The reexamination of lipids did not show any sulfatide accumulation in the patient's organ extracts. Although the residual CS activity in the patient's extracts was clearly demonstrable only after partial purification, it was concluded that this activity protects organ tissues from sulfatide accumulation in PASAD, since in sulfatide lipidosis (metachromatic leukodystrophy, MLD) no residual CS activity was detectable. The study of residual ASA activity in the patient's fibroblasts by gel electrofocusing resulted in an almost normal enzyme microheterogeneity. However, the detailed study of the brain galactolipids in the patient revealed an elevated ratio of sulfatide/galactocerebroside content, despite the decrease of both lipids. In tissues of other patients with severe demyelinating diseases different from DDS and MLD, this galactolipid ratio was also found to be increased, especially in three patients with adrenoleukodystrophy. A general mechanism of this anomaly in severe demyelination is considered.

Very long chain fatty acids in genetic peroxisomal disease fibroblasts: differences between the cerebro-hepato-renal (Zellweger) syndrome and adrenoleukodystrophy variants

Very long chain fatty acids were investigated by gas chromatography in fibroblasts of patients with genetic peroxisomal diseases (cerebro-hepato-renal (Zellweger) syndrome, childhood adrenoleukodystrophy, adrenomyeloneuropathy, neonatal adrenoleukodystrophy) and of controls. Concentrations of C 26:0 were increased to about the same extent in all disorders investigated. C 26:1 concentrations, on the other hand, were considerably elevated only in the cerebro-hepato-renal syndrome. In all control, adrenoleukodystrophy, and adrenomyeloneuropathy cases the C 22:0 concentration was higher than the respective C 26:0 concentration; the reverse was found in the cerebro-hepato-renal syndrome. These differences seem to reflect different impairment of peroxisomes in the cerebro-hepato-renal syndrome and adrenoleukodystrophy variants, respectively. Additional experiments to characterize C 26:1 by thin layer chromatography, gas chromatography and mass spectrometry revealed the presence of two straight-chain C 26:1 isomers with similar fragmentation patterns.

Plasmalogen deficiency in cultured skin fibroblasts from neonatal adrenoleukodystrophy

The plasmalogen ratio (defined as area ratio of lysophosphatidylethanolamine to the diacyl form of phosphatidylethanolamine) was investigated in cultured skin fibroblasts from neonatal adrenoleukodystrophy (N = 4) and X-linked recessive (N = 3) in addition to Zellweger syndrome (N = 3) because plasmalogen was reported to be reduced in Zellweger syndrome. The ratio was markedly decreased in all cases of Zellweger syndrome studied and in three of the four cases of neonatal adrenoleukodystrophy, whereas it was normal in the X-linked cases. This is the first documentation of a plasmalogen deficiency in neonatal adrenoleukodystrophy.

Very long-chain fatty acids in erythrocyte membrane sphingomyelin: detection of ALD hemizygotes and heterozygotes

We used mass fragmentography to analyze a very long-chain fatty acid composition of erythrocyte membrane sphingomyelin. The content of hexacosanoic acid (C26:0), tetracosanoic acid (C24:0) and docosanoic acid (C22:0) in adrenoleukodystrophy (ALD) hemizygotes and heterozygotes was significantly higher than in controls. Although the ratio of C26:0 to C22:0 in 18 of the 46 controls was in the range of ALD heterozygotes, the absolute content of C26:0 and C24:0 in controls did not overlap with ALD hemizygotes or heterozygotes. The content of C26:0 and C24:0 is more reliable for detection of ALD hemizygotes and heterozygotes than the ratio of C26:0 to C22:0 when red cell sphingomyelin is used for diagnosis.