Effectiveness of valproate for the treatment of manic-like behavior in X-linked adrenoleukodystrophy

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Preferential expression of mutant ABCD1 allele is common in adrenoleukodystrophy female carriers but unrelated to clinical symptoms

<p>Abstract</p> <p>Background</p> <p>Approximately 20% of adrenoleukodystrophy (X-ALD) female carriers may develop clinical manifestations, typically consisting of progressive spastic gait, sensory deficits and bladder dysfunctions. A skewing in X Chromosome Inactivation (XCI), leading to the preferential expression of the X chromosome carrying the mutant <it>ABCD1 </it>allele, has been proposed as a mechanism influencing X-linked adrenoleukodystrophy (X-ALD) carrier phenotype, but reported data so far are conflicting.</p> <p>Methods</p> <p>To shed light into this topic we assessed the XCI pattern in peripheral blood mononuclear cells (PBMCs) of 30 X-ALD carriers. Since a frequent problem with XCI studies is the underestimation of skewing due to an incomplete sample digestion by restriction enzymes, leading to variable results, we developed a pyrosequencing assay to identify samples completely digested, on which to perform the XCI assay. Pyrosequencing was also used to quantify <it>ABCD1 </it>allele-specific expression. Moreover, very long-chain fatty acid (VLCFA) levels were determined in the same patients.</p> <p>Results</p> <p>We found severely (≥90:10) or moderately (≥75:25) skewed XCI in 23 out of 30 (77%) X-ALD carriers and proved that preferential XCI is mainly associated with the preferential expression of the mutant <it>ABCD1 </it>allele, irrespective of the manifestation of symptoms. The expression of mutant <it>ABCD1 </it>allele also correlates with plasma VLCFA concentrations.</p> <p>Conclusions</p> <p>Our results indicate that preferential XCI leads to the favored expression of the mutant <it>ABCD1 </it>allele. This emerges as a general phenomenon in X-ALD carriers not related to the presence of symptoms. Our data support the postulated growth advantage of cells with the preferential expression of the mutant <it>ABCD1 </it>allele, but argue against the use of XCI pattern, <it>ABCD1 </it>allele-specific expression pattern and VLCFA plasma concentration as biomarkers to predict the development of symptoms in X-ALD carriers.</p

Molecular Genetic Analysis of the PLP1 Gene in 38 Families with PLP1-related disorders: Identification and Functional Characterization of 11 Novel PLP1 Mutations

<p>Abstract</p> <p>Background</p> <p>The breadth of the clinical spectrum underlying Pelizaeus-Merzbacher disease and spastic paraplegia type 2 is due to the extensive allelic heterogeneity in the X-linked <it>PLP1 </it>gene encoding myelin proteolipid protein (PLP). <it>PLP1 </it>mutations range from gene duplications of variable size found in 60-70% of patients to intragenic lesions present in 15-20% of patients.</p> <p>Methods</p> <p>Forty-eight male patients from 38 unrelated families with a PLP1-related disorder were studied. All DNA samples were screened for <it>PLP1 </it>gene duplications using real-time PCR. <it>PLP1 </it>gene sequencing analysis was performed on patients negative for the duplication. The mutational status of all 14 potential carrier mothers of the familial <it>PLP1 </it>gene mutation was determined as well as 15/24 potential carrier mothers of the <it>PLP1 </it>duplication.</p> <p>Results and Conclusions</p> <p><it>PLP1 </it>gene duplications were identified in 24 of the unrelated patients whereas a variety of intragenic <it>PLP1 </it>mutations were found in the remaining 14 patients. Of the 14 different intragenic lesions, 11 were novel; these included one nonsense and 7 missense mutations, a 657-bp deletion, a microdeletion and a microduplication. The functional significance of the novel <it>PLP1 </it>missense mutations, all occurring at evolutionarily conserved residues, was analysed by the <it>MutPred </it>tool whereas their potential effect on splicing was ascertained using the <it>Skippy </it>algorithm and a neural network. Although <it>MutPred </it>predicted that all 7 novel missense mutations would be likely to be deleterious, <it>in silico </it>analysis indicated that four of them (p.Leu146Val, p.Leu159Pro, p.Thr230Ile, p.Ala247Asp) might cause exon skipping by altering exonic splicing elements. These predictions were then investigated <it>in vitro </it>for both p.Leu146Val and p.Thr230Ile by means of RNA or minigene studies and were subsequently confirmed in the case of p.Leu146Val. Peripheral neuropathy was noted in four patients harbouring intragenic mutations that altered RNA processing, but was absent from all <it>PLP1</it>-duplication patients. Unprecedentedly, family studies revealed the <it>de novo </it>occurrence of the <it>PLP1 </it>duplication at a frequency of 20%.</p

MR findings in Leigh syndrome with COX deficiency and SURF-1 mutations

In a large number of patients with Leigh syndrome (LS) and cytochrome c oxidase (COX) deficiency, mutations of the SURF-1 gene were recently identified. The aim of the present study was to review the MR findings in patients with LS to verify if the genetically homogeneous patients with LS and SURF-1 mutations (LS SURF-1 patients) had a homogeneous MR pattern that could be used to differentiate them from other patients with LS (LS non-SURF-1 patients)

Severe X-Linked Mitochondrial Encephalomyopathy Associated with a Mutation in Apoptosis-Inducing Factor

We investigated two male infant patients who were given a diagnosis of progressive mitochondrial encephalomyopathy on the basis of clinical, biochemical, and morphological features. These patients were born from monozygotic twin sisters and unrelated fathers, suggesting an X-linked trait. Fibroblasts from both showed reduction of respiratory chain (RC) cIII and cIV, but not of cI activities. We found a disease-segregating mutation in the X-linked AIFM1 gene, encoding the Apoptosis-Inducing Factor (AIF) mitochondrion-associated 1 precursor that deletes arginine 201 (R201 del). Under normal conditions, mature AIF is a FAD-dependent NADH oxidase of unknown function and is targeted to the mitochondrial intermembrane space (this form is called AIFmit). Upon apoptogenic stimuli, a soluble form (AIFsol) is released by proteolytic cleavage and migrates to the nucleus, where it induces “parthanatos,” i.e., caspase-independent fragmentation of chromosomal DNA. In vitro, the AIFR201 del mutation decreases stability of both AIFmit and AIFsol and increases the AIFsol DNA binding affinity, a prerequisite for nuclear apoptosis. In AIFR201 del fibroblasts, staurosporine-induced parthanatos was markedly increased, whereas re-expression of AIFwt induced recovery of RC activities. Numerous TUNEL-positive, caspase 3-negative nuclei were visualized in patient #1's muscle, again indicating markedly increased parthanatos in the AIFR201 del critical tissues. We conclude that AIFR201 del is an unstable mutant variant associated with increased parthanatos-linked cell death. Our data suggest a role for AIF in RC integrity and mtDNA maintenance, at least in some tissues. Interestingly, riboflavin supplementation was associated with prolonged improvement of patient #1's neurological conditions, as well as correction of RC defects in mutant fibroblasts, suggesting that stabilization of the FAD binding in AIFmit is beneficial

Impaired complex III assembly associated with BCS1L gene mutations in isolated mitochondrial encephalopathy

We investigated two unrelated children with an isolated defect of mitochondrial complex III activity. The clinical picture was characterized by a progressive encephalopathy featuring early-onset developmental delay, spasticity, seizures, lactic acidosis, brain atrophy and MRI signal changes in the basal ganglia. Both children were compound heterozygotes for novel mutations in the human bc1 synthesis like (BCS1L) gene, which encodes an AAA mitochondrial protein putatively involved in both iron homeostasis and complex III assembly. The pathogenic role of the mutations was confirmed by complementation assays, using a Delta Bcs1 strain of Saccharomyces cerevisiae. By investigating complex III assembly and the structural features of the BCS1L gene product in skeletal muscle, cultured fibroblasts and lymphoblastoid cell lines from our patients, we have demonstrated, for the first time in a mammalian system, that a major function of BCS1L is to promote the maturation of complex III and, more specifically, the incorporation of the Rieske iron-sulfur protein into the nascent complex. Defective BCS1L leads to the formation of a catalytically inactive, structurally unstable complex III. We have also shown that BCS1L is contained within a high-molecular-weight supramolecular complex which is clearly distinct from complex III intermediates