Molecular and phenotypic characteristics of metachromatic leukodystrophy patients from Poland.

The occurrence and genotype-phenotype correlations of the eight most common mutations in the arylsulfatase A (ARSA) gene were studied in 43 unrelated Polish patients suffering from different types of metachromatic leukodystrophy (MLD). Screening for mutations p.R84Q, p.S96F, c.459+1G>A, p.I179S, p.A212V, c.1204+1G>A, p.P426L, and c.1401-1411del allowed the identification of 53.5% of the mutant alleles. In the whole investigated group of patients, mutations c.459+1G>A and p.P426L were the most frequent, 19 and 17%, respectively. The prevalence of the third most frequent mutation, i.e. p.I179S (13%), seems to be higher than that in other populations. The incidence of c.1204+1G>A was 5%, which is higher than reported earlier (2%). It seems that p.I179S and c.1204+1G>A are more prevalent in MLD patients from Poland than from other countries. In the group examined by us, mutations p.R84Q, p.S96F, p.A212V, and c.1401-1411del were not detected; thus, 46.5% of MLD alleles remained unidentified. This indicates that other, novel or already described, but rare, mutations exist in Polish population. In late infantile homozygotes for c.459+1G>A and one homozygote for c.1204+1G>A, first clinical symptom was motor deterioration. In adult homozygotes for p.P426L, the disease onset manifested as gait disturbances, followed by choreoathetotic movements, difficulties in swallowing, dysarthria, tremor, and nystagmus. In the carriers of the p.I179S mutation, the hallmark of the clinical picture was psychotic disturbances.

Co-expression of mutated and normal adrenoleukodystrophy protein reduces protein function: implications for gene therapy of X-linked adrenoleukodystrophy.

Inherited defects in the X-chromosomal adrenoleukodystrophy (ALD; ABCD1) gene are the genetic cause of the severe neurodegenerative disorder X-linked adrenoleukodystrophy (X-ALD). Biochemically the accumulation of very long-chain fatty acids, caused by impaired peroxisomal beta-oxidation, is the pathognomonic characteristic of the disease. Due to the X-chromosomal inheritance of X-ALD no data are available to clarify the question whether mutated adrenoleukodystrophy proteins (ALDPs) can negatively influence normal ALDP function. Here we show that restoration of beta-oxidation in X-ALD fibroblasts following transient transfection with normal ALD cDNA is more effective in ALDP-deficient fibroblasts compared with fibroblasts expressing normal amounts of mutated ALDP. Furthermore, we utilized the HeLa Tet-on system to construct a stable HeLa cell line expressing a constant level of endogenous ALDP and doxycycline-inducible levels of mutated ALDP. The induction was doxycycline dosage-dependent and the ALDP correctly localized. Interestingly, although mutated ALDP increased >6-fold in a dosage-dependent manner the total amount of ALDP (mutated and normal) remained approximately even as demonstrated by western blot and flow cytometric analyses. Thus, apparently mutated and normal ALDP compete for integration into a limited number of sites in the peroxisomal membrane. Consequently, increased amounts of mutated ALDP resulted in decreased peroxisomal beta-oxidation and accumulation of very long-chain fatty acids. These findings have direct implications on future gene therapy approaches for treatment of X-ALD, since in some patients a non-functional endogenous protein could act in a dominant negative way or displace the introduced, normal protein.

Rolipram does not normalize very long-chain fatty acid levels in adrenoleukodystrophy protein-deficient fibroblasts and mice.

In its severe form, X-linked adrenoleukodystrophy (X-ALD) is a lethal neurodegenerative disorder with inflammatory demyelination, in which defective peroxisomal beta-oxidation causes accumulation of very long-chain fatty acids (VLCFA) in tissues and plasma, in particular in the nervous system and adrenal glands. Recently, several drugs have been reported to reduce VLCFA in cultured human fibroblasts of X-ALD patients, and therefore to be potential candidates for novel therapeutic treatments in X-ALD. Among the most promising of these substances is the antidepressant rolipram, because of favourable adverse event profile in clinical studies and its additionally reported anti-inflammatory action. To further elucidate the effects of rolipram on peroxisomal beta-oxidation and VLCFA accumulation, we administered rolipram orally in the diet to ALD protein-deficient mice and ALD protein-deficient cultured human and mouse fibroblasts and assayed the accumulation of VLCFA. In contrast to the previously reported reduction of VLCFA, our data did not demonstrate a decrease in VLCFA content either in vivo or in vitro. NMR spectroscopic analysis verified the structural integrity and purity of the rolipram used here, thus excluding inauthenticity as a reason for the discrepancy. We therefore suggest that rolipram should be excluded from the current list of potential therapeutic agents for X-ALD.

Prevalence of arylsulfatase A pseudodeficiency allele in metachromatic leukodystrophy patients from Poland.

Arylsulfatase A (ASA) pseudodeficiency (PD) allele was searched for in 22 patients originating from Poland and suffering from different types of metachromatic leukodystrophy (MLD). Four of them carried the PD allele in a heterozygous state. The prevalence of the PD allele among investigated MLD patients was revealed to be 9%, while the frequency of the PD allele in healthy controls was estimated at 6-7%. One of the examined MLD patients was additionally a carrier of an isolated mutation leading to the loss of the N-glycosylation site. The question arises whether and how MLD mutations create a convenient milieu for PD mutations to occur (or inversely).

Adrenoleukodystrophy-related protein can compensate functionally for adrenoleukodystrophy protein deficiency (X-ALD): implications for therapy.

Inherited defects in the peroxisomal ATP-binding cassette (ABC) transporter adrenoleukodystrophy protein (ALDP) lead to the lethal peroxisomal disorder X-linked adrenoleukodystrophy (X-ALD), for which no efficient treatment has been established so far. Three other peroxisomal ABC transporters currently are known: adrenoleukodystrophy-related protein (ALDRP), 70 kDa peroxisomal membrane protein (PMP70) and PMP70- related protein. By using transient and stable overexpression of human cDNAs encoding ALDP and its closest relative ALDRP, we could restore the impaired peroxisomal beta-oxidation in fibroblasts of X-ALD patients. The pathognomonic accumulation of very long chain fatty acids could also be prevented by overexpression of ALDRP in immortalized X-ALD cells. Immunofluorescence analysis demonstrated that the functional replacement of ALDP by ALDRP was not due to stabilization of the mutated ALDP itself. Moreover, we were able to restore the peroxisomal beta-oxidation defect in the liver of ALDP-deficient mice by stimulation of ALDRP and PMP70 gene expression through a dietary treatment with the peroxisome proliferator fenofibrate. These results suggest that a correction of the biochemical defect in X-ALD could be possible by drug-induced overexpression or ectopic expression of ALDRP.

Coincidence of two novel arylsulfatase A alleles and mutation 459+1G>A within a family with metachromatic leukodystrophy: molecular basis of phenotypic heterogeneity.

In a family with three siblings, one developed classical late infantile metachromatic leukodystrophy (MLD), fatal at age 5 years, with deficient arylsulfatase A (ARSA) activity and increased galactosylsulfatide (GS) excretion. The two other siblings, apparently healthy at 12(1/2) and 15 years, respectively, and their father, apparently healthy as well, presented ARSA and GS values within the range of MLD patients. Mutation screening and sequence analysis disclosed the involvement of three different ARSA mutations being the molecular basis of intrafamilial phenotypic heterogeneity. The late infantile patient inherited from his mother the frequent 0-type mutation 459+1G>A, and from his father a novel, single basepair microdeletion of guanine at nucleotide 7 in exon 1 (7delG). The two clinically unaffected siblings carried the maternal mutation 459+1G>A and, on their paternal allele, a novel cytosine to thymidine transition at nucleotide 2435 in exon 8, resulting in substitution of alanine 464 by valine (A464V). The fathers genotype thus was 7delG/A464V. Mutation A464V was not found in 18 unrelated MLD patients and 50 controls. A464V, although clearly modifying ARSA and GS levels, apparently bears little significance for clinical manifestation of MLD, mimicking the frequent ARSA pseudodeficiency allele. Our results demonstrate that in certain genetic conditions MLD-like ARSA and GS values need not be paralleled by clinical disease, a finding with serious diagnostic and prognostic implications. Moreover, further ARSA alleles functionally similar to A464V might exist which, together with 0-type mutations, may cause pathological ARSA and GS levels, but not clinical outbreak of the disease.

Elevated sulfatide excretion in compound heterozygotes of metachromatic leukodystrophy and ASA-pseudodeficiency allele.

OBJECTIVE: Use of sulfatide excretion in differentiating MLD/PD-heterozygotes from MLD-patients and PD/PD-homozygotes. DESIGN AND METHODS: Sulfatide was extracted from urine sediment with chlorotom/methanol (2:1, v/v). The quantity of sulfatide was measured densitometrically (lambda = 580 nm) after thin-layer chromatography. ASA and beta-galactosidase activities were assayed enzymatically. RESULTS: MLD/PD-heterozygotes excreted sulfatide in the range of 4.8-36.3 nmol/mg lipid (mean +/- SD = 17.8 +/- 10.7), whereas sulfatide in MLD-patients ranged from 74.3-411.6 nmol/mg lipid (mean +/- SD = 184.5 +/- 130.8) and in PD/PD-hormozygotes sulfatide excretion remained in normal range of 0.0-5.9 nmol/mg lipid (mean +/- SD = 1.64 +/- 2.12). ASA activities in these groups were very low or lowered. CONCLUSIONS: The quantitative measurement of sulfatide in urine allows differentiation between MLD/PD-heterozygotes and MLD-heterozygotes, as well as between MLD/PD-heterozygotes with very low ASA activity and MLD-patients or PD/PD-hormozygotes. The quantitative measurement of sulfatide in urine differs between MLD-carriers and controls.

[Adrenoleukodystrophy]. / Adrenoleukodystrophia.

7-year-old boy with adrenoleukodystrophy is presented with the typical clinical picture, biochemical findings and review of the literature. The obligate carrier status of the mother and the asymptomatic adrenoleukodystrophy of the 5-year-old brother are biochemically proved. Therapeutic regime of Lorenzo's oil has been introduced to the young brother, and the question of bone marrow transplantation is discussed.

Occurrence, distribution, and phenotype of arylsulfatase A mutations in patients with metachromatic leukodystrophy.

Occurrence, distribution, and phenotype of arylsulfatase A (ASA) mutations were investigated in 27 patients with metachromatic leukodystrophy (MLD) from Central Europe, mainly from Austria (n = 15) and Poland (n = 9). Genomic DNA from leukocytes, fibroblasts, or paraffin-embedded, formalin-fixed brain or nerve tissue, respectively, was tested by natural or mutated primer-modulated PCR restriction, fragment length polymorphism for the eight most common European mutations: R84Q, S96F, 459+1G > A, I179S, A212V, 1204+1G > A, P426L, and 1401del11bp. The overall identification rate of unrelated MLD alleles was the highest, in adult (90%), medium in juvenile (50%), and lowest in late infantile (36%) MLD patients. The two common alleles, 459+1G > A and P426L, together accounted for 42% of all 50 unrelated MLD alleles investigated; I179S was observed in 6 of 50 MLD alleles (12%). Thus, I179S was far more frequent than hitherto thought and appears to be a third common mutation in Europe. Moreover, a different allelic distribution between Austrian and Polish juvenile patients was disclosed, indicating genetic heterogeneity of MLD even within Central Europe. The genotype-phenotype correlation suggested by Polten et al. [N Engl J Med 324:18-22, 1991] was not followed by all of our MLD patients. Moreover, some MLD patients with identical ASA mutations presented with different phenotypes. This may be due, at least in some cases, to the presence of an additional mutation on individual mutant alleles. Therefore, prediction of the clinical course from single mutation analysis is not possible.

Targeted inactivation of the X-linked adrenoleukodystrophy gene in mice.

In its severe form, X-linked adrenoleukodystrophy (ALD) is a lethal neurologic disease of children, characterized by progressive cerebral demyelination and adrenal insufficiency. Associated with a biochemical defect of peroxisomal beta-oxidation, very long-chain fatty acids (VLCFA) build up in tissues that have a high turnover of lipids, such as central nervous system (CNS) white matter, adrenal cortex, and testis. Whether the abnormal accumulation of VLCFA is the underlying cause of demyelination or merely an associated biochemical marker is unknown. ALD is caused by mutations in the gene for a peroxisomal membrane protein (ALDP) that shares structural features with ATP-binding-cassette (ABC) transporters. To analyze the cellular function of ALDP and to obtain an animal model of this debilitating disease, we have generated transgenic mice with a targeted inactivation of the ald gene. Motor functions in ALDP-deficient mice developed at schedule, and unexpectedly, adult animals appeared unaffected by neurologic symptoms up to at least 6 months of age. Biochemical analyses demonstrated impaired beta-oxidation in mutant fibroblasts and abnormal accumulation of VLCFAs in the CNS and kidney. In 6-month-old mutants, adrenal cortex cells displayed a ballooned morphology and needle-like lipid inclusions, also found in testis and ovaries. However, lipid inclusions and demyelinating lesions in the CNS were not a feature. Thus, complete absence of ALDP expression results in a VLCFA storage disease but does not impair CNS function of young adult mice by pathologic and clinical criteria. This suggests that additional genetic or environmental conditions must be fulfilled to model the early-onset and lethality of cerebral ALD in transgenic mice.

Late juvenile metachromatic leukodystrophy (MLD) in three patients with a similar clinical course and identical mutation on one allele.

Metachromatic leukodystrophy (MLD) is an autosomal, recessively inherited, lysosomal storage disease caused by arylsulfatase A (ASA) activity deficit. Arylsulfatase A initiates the degradation of sulfatide (cerebroside sulfate), which is an essential component of myelin. The main clinical symptoms are caused by progressive demyelination. At least 34 MLD-related ASA mutations are known to date. I179S (E3P799) is a disease-related mutation, described for the first time by Fluharty in 1991. This aberration appears to substantially reduce, but not completely eliminate ASA activity, and was detected in individuals with late-onset (juvenile or adult) forms of MLD. This paper deals with the peculiar clinical course in three unrelated juveniles with late-onset MLD carrying the I179S mutations on one allele. In the three described patients with the I179S mutation, psychiatric disturbances and intellectual impairment dominated the clinical picture, while the neurological lesions progressed more slowly. Although the symptoms appeared rather early, making it possible to classify this as the juvenile type of MLD, the clinical picture was more that of the adult type. Although the mutations on the second allele in our patients are unknown, one can speculate, that the mutation I179S plays an important role in the characteristic clinical course (psychiatric impairment, slower neurological deterioration, but relatively early onset). It seems that I179S mutation on one allele with another mutation on the other allele reduces ASA activity, but the enzyme can still cope with a part of the substrate influx, leading to late-juvenile-onset MLD with such strikingly similar phenotypes remaining a little bit of the adult (psychiatric) type. This could be one more argument in favour of phenotype-genotype correlation in patients with MLD.

A new polymorphism of arylsulfatase A within the coding region.

A 10-year-old boy with juvenile metachromatic leukodystrophy (MLD) presented with the 459 + 1G-->A arylsulfatase A (ASA) mutation on one allele. To detect his complete genotype, the other ASA allele was sequenced and a T-to-C transition at nucleotide 376 in exon 2 was identified. This missense mutation results in a substitution of leucine 76 by proline. Of 20 MLD unrelated controls, 18 carried the L/P76 mutation either in the homozygous (n = 6) or heterozygous (n = 12) state. The presence or absence of L/P76 did not influence leukocyte ASA activity or urinary sulfatide excretion. Apparently, the substitution of leucine 76 by proline is a common ASA polymorphism, neither being related to MLD nor creating ASA pseudodeficiency. However, because of its frequency and location, L/P76 may be of particular importance in genetic studies requiring the differentiation of the ASA alleles within a kindred. Further studies are directed to the as yet unresolved genotype of the index case with juvenile MLD.

Association of X-linked adrenoleukodystrophy with HLA DRB1 alleles.

Inflammatory demyelination in the central nervous system in the childhood cerebral phenotype of X-linked adrenoleukodystrophy (X-ALD) bears resemblance to that of multiple sclerosis. With a view to an association of HLA class II genes, specifically HLA-DRB1 subtype DRB1*15 to multiple sclerosis we investigated the HLA class II DR haplotype in 29 unrelated X-ALD patients including 17 childhood cerebral phenotype patients. Our results did not show an association of DRB1*15 and X-ALD, but disclosed a significant association of HLA DRB1*16 alleles and X-ALD in general. This finding suggests that in addition to the X-chromosomal ALD gene an autosomal gene linked to the HLA class II region is involved in the pathogenesis of X-ALD. This gene should affect a pathomechanism common to all ALD variants, such as defective peroxisomal metabolism of very long chain fatty acids.

X-linked adrenoleukodystrophy (ALD): a novel mutation of the ALD gene in 6 members of a family presenting with 5 different phenotypes.

Fragments of the adrenoleukodystrophy (ALD) cDNA from a patient with adolescent ALD were amplified by polymerase chain reaction and subcloned. Bidirectional sequencing of the entire coding ALD gene disclosed a cytosine to guanine transversion at nucleotide 1451 in exon five, resulting in substitution of proline 484 by arginine. Five of nine siblings of the patient, comprising two cerebral ALD, one adrenomyeloneuropathy, one Addison only as well as the symptomatic mother (all accumulating very long chain fatty acids) carried this mutation, which was not found in the unaffected persons, in five unrelated ALD patients, and in twenty controls. We propose that this missense mutation generated the disease per se as well as the metabolic defect; the different phenotypes, however, must have originated by means of additional pathogenetic factors.

Simultaneous detection of the two most frequent metachromatic leukodystrophy mutations.

Metachromatic leukodystrophy (MLD) is an autosomal recessive neurometabolic disorder caused by deficiency of arylsulfatase A (ASA). To detect ASA mutations E2S609 and E8P2382, the two most frequent MLD mutations, a non-radioactive polymerase chain reaction (PCR)-based assay was developed. This assay is a multiple "mutated primer-modulated PCR restriction fragment length polymorphism". The primers related to each mutation mismatch to create an XbaI or PstI restriction site in mutation E2S609 or E8P2382, respectively. The assay was designed to give four fragments of 160, 130, 100, and 70 bp, easy to distinguish. An internal control fragment is not necessary since both primer pairs amplify different regions of the ASA gene and fragments will be obtained in all allelic possibilities. This technique produced clear-cut results when genomic DNA, isolated either from leukocytes, cultured human fibroblasts, or paraffin-embedded autopsy material, was used as template. The assay will be of help in comparative studies on the relation between MLD genotype and phenotype, a problem not yet fully understood. Since our method was shown to work also on DNA from paraffin-embedded autopsy material, genotype/phenotype studies would not be restricted to in vivo investigations but could be done also on post mortem material, thus including investigations on a large group of cases and also studies on the relation between genotype and neuropathological features.

Diagnosis of peroxisomal disorders with neurological involvement.

Peroxisomal disorders are a group of inherited metabolic diseases caused by impairment of one or more peroxisomal functions. Ten disorders with neurological involvement have been recognized. Diagnosis and differentiation of these disorders is based on a number of important biochemical markers. For all disorders elevated values of very long chain fatty acids (VLCFA) and/or phytanic acid (PHYT) are important primary diagnostic parameters. Our results with regard to these two diagnostic markers are presented. VLCFA determined by gaschromatography in 414 samples (plasma, leukocytes or fibroblasts respectively) revealed increased values of hexacosanoic acid in 30 hemizygotes and 10 heterozygotes of adrenoleukodystrophy/adrenomyeloneuropathy and in eight infants with Zellweger disease or neonatal adrenoleukodystrophy. 15 cases with peroxisomal disorders were detected by VLCFA analysis in autopsy material. Gaschromatographic analysis of PHYT in plasma showed in some patients with Zellweger disease or neonatal adrenoleukodystrophy increase. In seven Refsum patients beside gaschromatographic demonstration of PHYT accumulation in plasma, analysis of plasma phytanyltriglycerides by thin-layer chromatography proved to be a rapid and reliable method for detection of patients and monitoring dietary treatment.