X-linked adrenoleukodystrophy: clinical, biochemical and pathogenetic aspects

X-linked adrenoleukodystrophy (X-ALD) is a clinically heterogeneous disorder ranging from the severe childhood cerebral form to asymptomatic persons. The overall incidence is 1:16,800 including hemizygotes as well as heterozygotes. The principal molecular defect is due to inborn mutations in the ABCD1 gene encoding the adrenoleukodystrophy protein (ALDP), a transporter in the peroxisome membrane. ALDP is involved in the transport of substrates from the cytoplasm into the peroxisomal lumen. ALDP defects lead to characteristic accumulation of saturated very long-chain fatty acids, the diagnostic disease marker. The pathogenesis is unclear. Different molecular mechanisms seem to induce inflammatory demyelination, neurodegeneration and adrenocortical insufficiency involving the primary ABCD1 defect, environmental factors and modifier genes. Important information has been derived from the X-ALD mouse models; species differences however complicate the interpretation of results. So far, bone marrow transplantation is the only effective long-term treatment for childhood cerebral X-ALD, however, only when performed at an early-stage of disease. Urgently needed novel therapeutic strategies are under consideration ranging from dietary approaches to gene therapy.     

Identification of new mutations in Israeli patients with X-linked adrenoleukodystrophy

X-linked adrenoleukodystrophy (ALD) is a peroxisomal disorder characterized by impaired peroxisomal betaoxidation of very-long-chain fatty acids (VLCFAs). This is probably due to reduced activation of the VLCFAs and results in demyelination of the nervous system and adrenocortical insufficiency. The ALD gene is localized on Xq28, has 10 exons and encodes a protein of 745 amino acids with significant homology to the membrane peroxisomal protein PMP70. Characterizing the disease causing mutations is of importance in prenatal diagnosis because 12-20% of women who are obligatory carriers show false-negative results when tested for VLCFA in plasma. We have analyzed DNA from blood samples of 7 Jewish (5 Sephardi and 2 Ashkenazi) and 3 Arab Israeli families suffering from ALD. Five missense-type mutations were identified: R104H, Y174C, L229P, R401Q, and G512C. A single mutation, R464X, was nonsense, and two, Y171 frameshift and E471 frameshift, were frameshift. Interestingly, a single mutation was identified in three families of Moroccan Jewish descent, probably due to a founder effect.     

Evidence that oxidative stress is increased in patients with X-linked adrenoleukodystrophy

X-linked adrenoleukodystrophy (X-ALD) is a hereditary disorder of peroxisomal metabolism biochemically characterized by the accumulation of very long chain fatty acids (VLCFA), particularly hexacosanoic acid (C26:0) and tetracosanoic acid (C24:0) in different tissues and in biological fluids. The disease is clinically characterized by central and peripheral demyelination and adrenal insufficiency, which is closely related to the increased concentrations of these fatty acids. However, the mechanisms underlying the brain damage in X-ALD are poorly known. Considering that free radical generation is involved in various neurodegenerative disorders, like Parkinson disease, multiple sclerosis and Alzheimer's disease, in the present study we evaluated various oxidative stress parameters, namely chemiluminescence, thiobarbituric acid reactive species (TBA-RS), total radical-trapping antioxidant potential (TRAP), and total antioxidant reactivity (TAR) in plasma of X-ALD patients, as well as the activities of the antioxidant enzymes catalase (CAT), superoxide dismutase (SOD) and glutathione peroxidase (GPx) in erythrocytes and fibroblasts from these patients. It was verified a significant increase of plasma chemiluminescence and TBA-RS, reflecting induction of lipid peroxidation, as well as a decrease of plasma TAR, indicating a deficient capacity to rapidly handle an increase of reactive species. We also observed a significant increase of erythrocytes GPx activity and of catalase and SOD activities in fibroblasts from the patients studied. It is therefore proposed that oxidative stress may be involved in pathophysiology of X-ALD.     

Mutational and protein analysis of patients and heterozygous women with X-linked adrenoleukodystrophy.

X-linked adrenoleukodystrophy (ALD), a neurodegenerative disorder associated with impaired beta-oxidation of very-long-chain fatty acids (VLCFA), is due to mutations in a gene encoding a peroxisomal ATP-binding cassette (ABC) transporter (ALD protein [ALDP]). We analyzed the open reading frame of the ALD gene in 44 French ALD kindred by using SSCP or denaturing gradient-gel electrophoresis and studied the effect of mutations on ALDP by immunocytofluorescence and western blotting of fibroblasts and/or white blood cells. Mutations were detected in 37 of 44 kindreds and were distributed over the whole protein-coding region, with the exception of the C terminus encoded in exon 10. Except for two mutations (delAG1801 and P560L) observed four times each, nearly every ALD family has a different mutation. Twenty-four of 37 mutations were missense mutations leading to amino acid changes located in or close to putative transmembrane segments (TMS 2, 3, 4, and 5), in the EAA-like motif and in the nucleotide fold of the ATP-binding domain of ALDP. Of 38 ALD patients tested, 27 (71%) lacked ALDP immunoreactivity in their fibroblasts and/or white blood cells. More than half of missense mutations studied (11 of 21) resulted in a complete lack of ALDP immunoreactivity, and six missense mutations resulted in decreased ALDP expression. The fibroblasts and/or white blood cells of 15 of 15 heterozygous carrier from ALD kindred with no ALDP showed a mixture of positive- and negative-ALDP immunoreactivity due to X-inactivation. Since 5%-15% of heterozygous women have normal VLCFA levels, the immunodetection of ALDP in white blood cells can be applicable in a majority of ALD kindred, to identify heterozygous women, particularly when the ALD gene mutation has not yet been identified.     

Mutations in btk in patients with presumed X-linked agammaglobulinemia.

In 1993, two groups showed that X-linked agammaglobulinemia (XLA) was due to mutations in a tyrosine kinase now called Btk. Most laboratories have been able to detect mutations in Btk in 80%-90% of males with presumed XLA. The remaining patients may have mutations in Btk that are difficult to identify, or they may have defects that are phenotypically similar to XLA but genotypically different. We analyzed 101 families in which affected males were diagnosed as having XLA. Mutations in Btk were identified in 38 of 40 families with more than one affected family member and in 56 of 61 families with sporadic disease. Excluding the patients in whom the marked decrease in B cell numbers characteristic of XLA could not be confirmed by immunofluorescence studies, mutations in Btk were identified in 43 of 46 patients with presumed sporadic XLA. Two of the three remaining patients had defects in other genes required for normal B cell development, and the third patient was unlikely to have XLA, on the basis of results of extensive Btk analysis. Our techniques were unable to identify a mutation in Btk in one male with both a family history and laboratory findings suggestive of XLA. DNA samples from 41 of 49 of the mothers of males with sporadic disease and proven mutations in Btk were positive for the mutation found in their son. In the other 8 families, the mutation appeared to arise in the maternal germ line. In 20 families, haplotype analysis showed that the new mutation originated in the maternal grandfather or great-grandfather. These studies indicate that 90%-95% of males with presumed XLA have mutations in Btk. The other patients are likely to have defects in other genes.     

Diagnostic patterns of very-long-chain fatty acids in plasma of patients with X-linked adrenoleukodystrophy

Pattern recognition analysis on the levels of the very-long-chain fatty acids (VLCFAs) in plasma is described for the visual discrimination of X-linked adrenoleukodystrophy (X-ALD) patients from normal healthy group. Plasma VLCFA compositions of 58 normal subjects and 16 X-ALD patients were examined by gas chromatography as their methyl esters to determine the area percentages of behenic acid (C22:0), lignoceric acid (C24:0) and hexacosanoic acid (C26:0) in the total fatty acids, and the concentration (μg/ml) of C26:0. When star symbol plotting was applied to the VLCFA values of C22:0 (%), C24:0 (%), C26:0 (%), C24:0/C22:0, C26:0/C22:0 and C26:0 (μg/ml) after normalization to the corresponding median values in normal group, the resulting deformed hexagonal star pattern was characteristic of each patient. Therefore, simple visual comparison with the equilateral hexagon of normal group average as the control pattern enabled one readily to discriminate X-ALD patients from the normal group. Additionally, canonical discriminant analysis performed on the six unnormalized VLCFA values correctly classified 74 plasma specimens into two separate clusters according to normal subject or X-ALD patient in the canonical plot.     

ABCD1 mutations and phenotype distribution in Chinese patients with X-linked adrenoleukodystrophy

X-linked adrenoleukodystrophy (X-ALD) is a neurodegenerative disorder resulting from mutations within the ABCD1 gene. Adrenomyeloneuropathy (AMN) and childhood cerebral ALD (CCALD) are most common phenotypes in the Western ALD patients. Here we performed mutation analysis of ABCD1 in 10 Chinese ALD families and identified 8 mutations, including one novel deletion (c.1477_1488 + 11del23) and 7 known mutations. Mutations c.1772G>A and c.1816T>C were first reported in the Chinese patients. Mutations c.1661G>A and c.1679C>T were demonstrated to be de novo mutations. The dinucleotide deletion 1415_16delAG, described as a mutational hotspot in different ethnic groups, was identified in two families. In addition, we performed a retrospective nation-wide mutation study of X-linked ALD in China based on a literature review. The retrospective study further confirmed the hypothesis that exon 6 is a potential mutation cluster region in the Asian populations. Furthermore, it suggested that CCALD is the most common phenotype in China.     

X-linked adrenoleukodystrophy (X-ALD): clinical presentation and guidelines for diagnosis, follow-up and management

Background

Pompe disease (Glycogen storage disease type II, GSD II, acid alpha-glucosidase deficiency, acid maltase deficiency, OMIM # 232300) is an autosomal-recessive lysosomal storage disorder due to a deficiency of acid alpha-glucosidase (GAA, acid maltase, EC 3.2.1.20, Swiss-Prot P10253). Clinical manifestations are dominated by progressive weakness of skeletal muscle throughout the clinical spectrum. In addition, the classic infantile form is characterised by hypertrophic cardiomyopathy.

Methods

In a cross-sectional single-centre study we clinically assessed 3 patients with classic infantile Pompe disease and 39 patients with non-classic presentations, measured their acid alpha-glucosidase activities and analysed their GAA genes.

Results

Classic infantile patients had nearly absent residual enzyme activities and a typical clinical course with hypertrophic cardiomyopathy until the beginning of therapy. The disease manifestations in non-classic patients were heterogeneous. There was a broad variability in the decline of locomotive and respiratory function. The age of onset ranged from birth to late adulthood and correlated with enzyme activities. Molecular analysis revealed as many as 33 different mutations, 14 of which are novel. All classic infantile patients had two severe mutations. The most common mutation in the non-classic group was c.-32-13?T?>?G. It was associated with a milder course in this subgroup.

Conclusions

Disease manifestation strongly correlates with the nature of the GAA mutations, while the variable progression in non-classic Pompe disease is likely to be explained by yet unknown modifying factors. This study provides the first comprehensive dataset on the clinical course and the mutational spectrum of Pompe disease in Germany.     

X-linked adrenoleukodystrophy (X-ALD): clinical presentation and guidelines for diagnosis, follow-up and management

ABSTRACT: X-linked adrenoleukodystrophy (X-ALD) is the most common peroxisomal disorder. The disease is caused by mutations in the ABCD1 gene that encodes the peroxisomal membrane protein ALDP which is involved in the transmembrane transport of very long-chain fatty acids (VLCFA; >C22). A defect in ALDP results in elevated levels of VLCFA in plasma and tissues. The clinical spectrum in males with X-ALD ranges from isolated adrenocortical insufficiency and slowly progressive myelopathy to devastating cerebral demyelination. The majority of heterozygous females will develop symptoms by the age of 60 years. In individual patients the disease course remains unpredictable. This review focuses on the diagnosis and management of patients with X-ALD and provides a guideline for clinicians that encounter patients with this highly complex disorder.     

X-linked adrenoleukodystrophy: Clinical, metabolic, genetic and pathophysiological aspects

X-linked adrenoleukodystrophy (X-ALD) is the most frequent peroxisomal disease. The two main clinical phenotypes of X-ALD are adrenomyeloneuropathy (AMN) and inflammatory cerebral ALD that manifests either in children or more rarely in adults. About 65% of heterozygote females develop symptoms by the age of 60years. Mutations in the ABCD1 gene affect the function of the encoded protein ALDP, an ATP-binding-cassette (ABC) transporter located in the peroxisomal membrane protein. ALDP deficiency impairs the peroxisomal beta-oxidation of very long-chain fatty acids (VLCFA) and facilitates their further chain elongation by ELOVL1 resulting in accumulation of VLCFA in plasma and tissues. While all patients have mutations in the ABCD1 gene, there is no general genotype-phenotype correlation. Environmental factors and a multitude of modifying genes appear to determine the clinical manifestation in this monogenetic but multifactorial disease. This review focuses on the clinical, biochemical, genetic and pathophysiological aspects of X-ALD. This article is part of a Special Issue entitled: Metabolic Functions and Biogenesis of Peroxisomes in Health and Disease.     

Cholesterol-deprivation increases mono-unsaturated very long-chain fatty acids in skin fibroblasts from patients with X-linked adrenoleukodystrophy

X-linked adrenoleukodystrophy (X-ALD) is the most common peroxisomal disorder and is characterized by a striking and unpredictable variation in phenotypic expression. It ranges from a rapidly progressive and fatal cerebral demyelinating disease in childhood (CCALD), to the milder slowly progressive form in adulthood (AMN). X-ALD is caused by mutations in the ABCD1 gene that encodes a peroxisomal membrane located ABC half-transporter named ALDP. Mutations in ALDP result in reduced beta-oxidation of very long-chain fatty acids (VLCFA, >22 carbon atoms) in peroxisomes and elevated levels of VLCFA in plasma and tissues. Previously, it has been shown that culturing skin fibroblasts from X-ALD patients in lipoprotein-deficient medium results in reduced VLCFA levels and increased expression of the functionally redundant ALD-related protein (ALDRP). The aim of this study was to further resolve the interaction between cholesterol and VLCFA metabolism in X-ALD. Our data show that the reduction in 26:0 in X-ALD fibroblasts grown in lipoprotein-deficient culture medium (free of cholesterol) is offset by a significant increase in both the level and synthesis of 26:1. We also demonstrate that cholesterol-deprivation results in increased expression of stearoyl-CoA-desaturase (SCD) and increased desaturation of 18:0 to 18:1. Finally, there was no increase in [1-(14)C]-26:0 beta-oxidation. Taken together, we conclude that cholesterol-deprivation reduces saturated VLCFA, but increases mono-unsaturated VLCFA. These data may have implications for treatment of X-ALD patients with lovastatin.     

CD1 gene polymorphisms and phenotypic variability in X-linked adrenoleukodystrophy

X-linked adrenoleukodystrophy (X-ALD) is characterized by marked phenotypic variation ranging from adrenomyeloneuropathy (AMN) to childhood cerebral ALD (CCALD). X-ALD is caused by mutations in the ABCD1 gene, but no genotype-phenotype correlation has been established so far and modifier gene variants are suspected to modulate phenotypes. Specific classes of lipids, enriched in very long-chain fatty acids that accumulate in plasma and tissues from X-ALD patients are suspected to be involved in the neuroinflammatory process of CCALD. CD1 proteins are lipid- antigen presenting molecules encoded by five CD1 genes in human (CD1A-E). Association studies with 23 tag SNPs covering the CD1 locus was performed in 52 patients with AMN and 87 patients with CCALD. The minor allele of rs973742 located 4-kb downstream from CD1D was significantly more frequent in AMN patients (χ² = 7.6; P = 0.006). However, this association was no longer significant after Bonferroni correction for multiple testing. The other polymorphisms of the CD1 locus did not reveal significant association. Further analysis of other CD1D polymorphisms did not detect stronger association with X-ALD phenotypes. Although the association with rs973742 warrants further investigations, these results indicate that the genetic variants of CD1 genes do not contribute markedly to the phenotypic variance of X-ALD.     

Linkage analysis in X-linked adrenoleukodystrophy and application in post-and prenatal diagnosis

Summary We have performed linkage analysis with the DNA markers DXS52 and the clotting factor VIII gene (F8C), in several large families with X-linked adrenoleukodystrophy (ALD). The tight linkage to DXS52 could be extended giving a maximal LOD score of 22.5 at 1 cM. F8C was also tightly linked to ALD with a maximal LOD score of 7.8 without recombination. Multipoint linkage analysis with the markers DXS304, DXS52, and F8C indicated that both the gene for ALD and for F8C are distal to DXS52. In four patients with ALD, no major structural rearrangement in the Xqter region was observed; in particular, there were no abnormalities in the vision blindness genes. DNA analysis appeared to be of use in determination of the carrier status of females at risk, for the determination of the origin of the mutation in a particular family, and for prenatal diagnosis.     

Role of ALDP (ABCD1) and mitochondria in X-linked adrenoleukodystrophy

Peroxisomal disorders have been associated with malfunction of peroxisomal metabolic pathways, but the pathogenesis of these disorders is largely unknown. X-linked adrenoleukodystrophy (X-ALD) is associated with elevated levels of very-long-chain fatty acids (VLCFA; C(>22:0)) that have been attributed to reduced peroxisomal VLCFA beta-oxidation activity. Previously, our laboratory and others have reported elevated VLCFA levels and reduced peroxisomal VLCFA beta-oxidation in human and mouse X-ALD fibroblasts. In this study, we found normal levels of peroxisomal VLCFA beta-oxidation in tissues from ALD mice with elevated VLCFA levels. Treatment of ALD mice with pharmacological agents resulted in decreased VLCFA levels without a change in VLCFA beta-oxidation activity. These data indicate that ALDP does not determine the rate of VLCFA beta-oxidation and that VLCFA levels are not determined by the rate of VLCFA beta-oxidation. The rate of peroxisomal VLCFA beta-oxidation in human and mouse fibroblasts in vitro is affected by the rate of mitochondrial long-chain fatty acid beta-oxidation. We hypothesize that ALDP facilitates the interaction between peroxisomes and mitochondria, resulting, when ALDP is deficient in X-ALD, in increased VLCFA accumulation despite normal peroxisomal VLCFA beta-oxidation in ALD mouse tissues. In support of this hypothesis, mitochondrial structural abnormalities were observed in adrenal cortical cells of ALD mice.     

Loss of AMP-activated protein kinase in X-linked adrenoleukodystrophy patient-derived fibroblasts and lymphocytes

X-Adrenoleukodystrophy (X-ALD) is a peroxisomal disorder characterized by accumulation of very-long-chain (VLC) fatty acids, which induces inflammatory disease and alterations in cellular redox, both of which are reported to play a role in the pathogenesis of the severe form of the disease (childhood cerebral ALD). While the mutation defect in ABCD1 gene is common to all forms of X-ALD it fails to account for the spectrum of phenotypic variability seen in X-ALD patients, strongly suggesting a role for as yet unidentified modifier gene(s). Here we report, for the first time, loss of AMP-activated protein kinase alpha1 (AMPKα1) in patient-derived fibroblasts and lymphocytes of the severe cerebral form of X-ALD (ALD), and not in the milder adrenomyeloneuropathy (AMN) form. Decrease in AMPK was observed at both protein and mRNA levels. AMPK loss in ALD patient-derived fibroblasts was associated with increased ubiquitination. Using the Seahorse Bioscience XF^e96 Flux Analyzer for measuring the mitochondrial oxygen consumption and extracellular acidification rate we show that ALD patient-derived fibroblasts have a significantly lower “metabolic state” than AMN fibroblasts. Unstimulated ALD patient-derived lymphocytes had significantly higher proinflammatory gene expression. Selective AMPK loss represents a novel physiopathogenic factor in X-ALD disease mechanism. Strategies aimed at upregulating/recovering AMPK levels might have beneficial therapeutic effects in X-ALD.     

Mutations of the CD40 ligand gene in 13 Japanese patients with X-linked hyper-IgM syndrome

X-linked hyper-IgM syndrome (XHIM) is a rare primary immunodeficiency caused by a defective CD40 ligand. We identified mutations of the CD40 ligand gene in 13 unrelated Japanese XHIM patients. Of the four patients with missense mutations, one had a mutation within the transmembrane domain, and the three others had mutations affecting the TNF homology region of the extracellular domain. Two of the missense mutations resulted in the substitution of amino acids that are highly conserved in TNF family proteins. Three patients had nonsense mutations, all of which resulted in the truncation of the TNF homology domain of the CD40 ligand. Three patients had genomic DNA deletions of 2, 3 or 4 nucleotides, respectively. All of the deletions were flanked by direct repeat sequences, suggesting that these deletions were caused by slipped mispairing. Three patients had mutations within introns resulting in altered splicing, and multiple splicing products were found in one patient. Thus, each of the 13 Japanese patients had different mutations, 9 of them being novel mutations. These results indicate that mutations in XHIM are highly heterogeneous, although codon 140 seems to be a hot spot of the CD40 ligand gene since two additional point mutations were located at Trp 140, bringing the total numbers of mutations affecting codon 140 to six. In one XHIM family with a missense mutation, prenatal diagnosis was performed by single-strand conformation polymorphism analysis of genomic DNA of a male fetus. Received: 20 August 1996     

Paleopathology in South American mummies: a review and new findings

This article is a review of research and additional unpublished diseases that have been discovered and documented in naturally mummified remains recovered from South America. A new impetus in paleopathological studies was the work and discovery of a solution for rehydration of mummified tissues by Sir Marc Armand Ruffer in 1913. This solution allows the paleopathologist, after performing the autopsy, to process the tissues in a manner similar to current practices in pathology. In our studies, the most common diseases were infectious in nature, similar to the diseases that are most prominent today in the same regions.     

X-linked hypophosphatemia in Polish patients. 1. Mutations in the PHEX gene

We present twenty-nine PHEX gene mutations extending our previous work, giving it to a total of 37 different mutations identified in Polish patients with familial or sporadic X-linked hypophosphatemia. Deletions, insertions and nucleotide substitutions leading to frameshift (27%), stop codon (29%), splice site (24%), and missense mutations (20%) were found. The mutations are distributed along the gene; exons 3, 4, 11, 12, 14, 15, 17, 20 and 22 are regions with the most frequent mutation events. Four mutations, P534L, G579R, R549X and IVS15+1nt, recurred in three, four, two and three unrelated patients, respectively. They have also been detected in affected persons from other countries. Twenty-eight mutations are specific for Polish population and almost all of them are unique. Most of the identified mutations are expected to result in major changes in protein structure and/or function.     

Clinical variation in X-linked adrenoleukodystrophy: fatty acid and lipid metabolism in cultured fibroblasts

To determine whether the clinical phenotype of ALD correlates with the extent of metabolic abnormality, we investigated VLFA metabolism in cultured fibroblasts from patients with the clinically severe childhood from of ALD and the milder AMN variant. No differences were seen in the content of neutral lipids or phospholipids, in incorporation of [1-14C]lignocerate into cellular lipids, or in the fatty acid composition of fibroblasts from patients with childhood ALD or AMN. [1-14C]Lignocerate oxidation was deficient to a similar extent (35-40% of normal) in both intact fibroblasts and cell homogenates from patients with childhood ALD and AMN. With the use of fibroblast homogenates, oxidation of lignocerate was partially inhibited by various long-chain fatty acids, and residual activity in ALD homogenates was more susceptible to inhibition by palmitate than normal. In the presence of competing palmitate, residual lignocerate oxidative activity in fibroblast homogenates was reduced to 20 +/- 4% of normal in childhood ALD and 24 +/- 2% of normal in AMN. These results indicate that residual VLFA oxidative activity, fatty acid composition, VLFA metabolism, and lipid content of cultured fibroblasts do not correlate with the clinical expression of the ALD gene.