Clinical neurophysiology in GJA12-related hypomyelination vs Pelizaeus-Merzbacher disease.

BACKGROUND: Among the hypomyelinating leukoencephalopathies with onset in childhood, Pelizaeus-Merzbacher disease (PMD) and Pelizaeus-Merzbacher-like disease (PMLD) constitute a large subgroup with almost indistinguishable clinical and neuroradiologic features. Whereas PMD is due to X-linked PLP1 mutations, PMLD is genetically heterogeneous, with about 8% of patients carrying autosomal recessive GJA12/GJC2 mutations. The aim of this study was to evaluate whether neurophysiologic testing may separate PMD from GJA12/GJC2-associated PMLD. METHODS: Retrospective data collection study with reevaluation of evoked potentials (EP) and nerve conduction studies (NCS) in 10 patients from 7 families with PMLD due to various GJA12/GJC2 mutations and 8 boys from 7 families with classic PMD caused by a PLP1 duplication or missense mutation. RESULTS: In brainstem auditory EP, waves III-V were absent in all patients with PMD, but clearly recordable in 11 of 13 investigations in 8 patients with PMLD. Visual evoked potentials and somatosensory evoked potentials revealed conduction delay in both PMD and PMLD, without significant difference. NCS were normal in all patients with PMD and indicated mild peripheral neuropathy in only 2 of 10 patients with PMLD. CONCLUSION: In a patient with clinical and neuroradiologic features of Pelizaeus-Merzbacher disease/Pelizaeus-Merzbacher-like disease and a pedigree consistent with both conditions, brainstem auditory evoked potentials provide good selectivity between these disorders and point in the right direction for identifying the primary genetic defect.

In vivo proton MR spectroscopy findings specific for adenylosuccinate lyase deficiency.

Adenylosuccinate lyase (ADSL) deficiency is an inherited metabolic disorder affecting predominantly the central nervous system. The disease is characterized by the accumulation of succinylaminoimidazolecarboxamide riboside and succinyladenosine (S-Ado) in tissue and body fluids. Three children presented with muscular hypotonia, psychomotor delay, behavioral abnormalities, and white matter changes on brain MRI. Two of them were affected by seizures. Screening for inborn errors of metabolism including in vitro high resolution proton MRS revealed an ADSL deficiency that was confirmed genetically in all cases. All patients were studied by in vivo proton MRS. In vitro high resolution proton MRS of patient cerebrospinal fluid showed singlet resonances at 8.27 and 8.29 ppm that correspond to accumulated S-Ado. In vivo proton MRS measurements also revealed a prominent signal at 8.3 ppm in gray and white matter brain regions of all patients. The resonance was undetectable in healthy human brain. In vivo proton MRS provides a conclusive finding in ADSL deficiency and represents a reliable noninvasive diagnostic tool for this neurometabolic disorder.

GJA12 mutations are a rare cause of Pelizaeus-Merzbacher-like disease.

BACKGROUND: Pelizaeus-Merzbacher-like disease (PMLD) is a genetically heterogeneous disorder within the group of hypomyelinating leukoencephalopathies. Mutations of the gap junction protein alpha 12 (GJA12) gene are known to cause one autosomal recessive PMLD form. Few patients with GJA12 mutated PMLD have been reported, and to date, the frequency as well as the genotypic and phenotypic spectrum of GJA12 related PMLD is unclear. METHODS: We report mutation analysis of the GJA12 gene in a clinical and radiologic well-characterized multiethnic cohort of 193 patients with PMLD from 182 families. RESULTS AND CONCLUSIONS: Only 16 patients (8.3%) from 14 families (7.7%) carry GJA12 mutations including five families where we detected only one mutated allele. Among those, we identified 11 novel alterations. Thus, GJA12 mutations are a rather rare cause for Pelizaeus-Merzbacher-like disease. The clinical phenotype of patients with a GJA12 mutation was evaluated and is overall comparable to the clinical features seen in mild forms of proteolipid protein 1 (PLP1) related disorder but with better cognition and earlier signs of axonal degeneration.

Hypomyelination with atrophy of the basal ganglia and cerebellum: follow-up and pathology.

BACKGROUND AND OBJECTIVE: Hypomyelination with atrophy of the basal ganglia and cerebellum is a recently defined disorder. Only a few patients have been described. We report on 11 additional patients and new MRI findings and provide histopathologic confirmation of the MRI interpretation. METHODS: We reviewed the patients' clinical history and present findings. We scored the MRI abnormalities. The histopathology of one patient was re-examined. RESULTS: The patients' early psychomotor development was normal or delayed, followed by increasing extrapyramidal movement abnormalities, ataxia, and spasticity. Mental capacities were variably affected. MRI showed hypomyelination with, on follow-up, evidence of further myelin loss and variable white matter atrophy. The putamen was small or, more often, absent; the head of the caudate nucleus was decreased in size. In contrast, the thalamus and globus pallidus remained normal. Cerebellar atrophy was invariably present. Histopathology confirmed the myelin deficiency, probably related to both lack of deposition and low-grade further loss. The degeneration of putamen was subtotal. The cerebellar cortex was affected, particularly the granular layer. CONCLUSION: Hypomyelination with atrophy of the basal ganglia and cerebellum is a syndrome diagnosed by distinctive MRI findings. Histopathology confirms hypomyelination, low-grade further myelin loss, subtotal degeneration of the putamen, and cerebellar cortical atrophy. All known patients are sporadic, and the mode of inheritance is unclear.

Pitfall in metabolic screening in a patient with fatal peroxisomal beta-oxidation defect.

We present a rare case of peroxisomal acyl-CoA oxidase deficiency that was not detected by the common metabolic screening program for peroxisomal disorders. The patient presented with a typical MRI pattern showing pachygyria, perisylvian polymicrogyria, cerebral and cerebellar white matter abnormalities, and facial dysmorphia, progressive psychomotor retardation, deafness, retinopathy, peripheral neuropathy, and infantile seizures strongly indicative for a peroxisomal disorder. Yet, repetitive measurements of very long-chain fatty acids (VLCFAs) and phytanic acid in serum and plasma as well as plasmalogens in erythrocytes revealed normal values apparently excluding a peroxisomal defect (methods of measurement published by Moser and co-workers in 1980 [4 ] and 1981 [2 ]). Subsequent biochemical investigation in cultured skin fibroblasts of the patient, however, revealed elevated concentrations of VLCFAs, deficient oxidation of C26:0, but normal oxidation of both phytanic acid and pristanic acid and normal DE NOVO plasmalogen synthesis, indicative for a defect in the peroxisomal beta-oxidation system. Enzymatic studies in these fibroblasts pointed to peroxisomal acyl-CoA oxidase deficiency and subsequent molecular analyses revealed a homozygous acceptor splice site mutation IVS3-1G>A in the ACOX1 gene (MIM *609751).

Cystic leukoencephalopathy without megalencephaly: a distinct disease entity in 15 children.

OBJECTIVE: To describe a distinctive syndrome of nonprogressive encephalopathy, normo- or microcephaly, and early onset of severe psychomotor impairment in 15 white patients, including two siblings and two first cousins. METHODS AND RESULTS: MRI revealed bilateral cysts in the anterior part of the temporal lobe and white matter abnormalities with pericystic abnormal myelination and symmetric lesions in frontal and occipital periventricular regions. None of the usual inborn errors of metabolism/infectious diseases associated with leukoencephalopathy and bilateral anterior temporal lobe cysts were detected. CONCLUSIONS: These patients' clinical signs and cranial MRI abnormalities are strikingly similar and may represent a distinctive disease with autosomal-recessive inheritance: cystic leukoencephalopathy without megalencephaly.

Maple syrup urine disease: mutation analysis in Turkish patients.

Maple syrup urine disease (MSUD), the most frequently occurring organic acidaemia in Turkey, is caused by a deficiency of the activity of branched-chain keto acid dehydrogenase enzyme (BCKAD) complex. Mutation analysis of the E1alpha, E1beta, and E2 genes of the BCKAD complex in 12 Turkish MSUD patients yielded three disease-specific mutations and a polymorphism in the E1alpha gene, none in the E1beta gene and one mutation in the E2 gene. Among them, three missense mutations (Q80E, C213Y, T106M) and the F280F polymorphism occurring in the E1alpha gene and the splice site mutation (IVS3 - 1G>A) in the E2 gene were novel. Three of the missense mutations and the splicing mutation occurred homozygously and caused classical MSUD. One patient carried the splicing mutation homozygously and the T106M mutation in the heterozygous state; this patient is the first case having simultaneously two different mutations in two different genes in the BCKAD complex. IVS3 - IG>A splicing mutation detected on the E2 gene causes deletion of the first 14 bp of exon 3 in the mutant mRNA extending between 190 and 204 nt. The deletion spans the cleavage point between mitochondrial targeting and lipoyl-bearing site of the E2 protein.

Induction of neutralizing antibodies by poliovirus capsid polypeptides VP1, VP2 and VP3.

The antigenic and immunogenic properties of poliovirus capsid polypeptides (VPs) have been investigated in vivo and in vitro. VPs were isolated from infectious and formalin inactivated virus. Upon immunization VPs from infectious virus did not induce neutralizing antibodies in laboratory animals after two or three injections. Monomeric VP1, VP2 and VP3 from formalin inactivated virus all induced high titres of neutralizing antibodies generally already after two injections. Some anti-VP sera neutralized heterologous virus types. All anti-VP sera reacted with the corresponding capsid polypeptides from the homologous and heterologous virus strains in an immunoblotting assay. The anti-VP sera reacted equally well with D- and C-antigen in ELISA. Our results indicate that not only VP1, but also VP2 and VP3 are involved in the induction of neutralizing antibodies.

Antigenicity and immunogenicity of poliovirus capsid proteins.

Poliovirus capsid proteins (VP's) were isolated by DEAE-Sepharose chromatography in the presence of RNA-se and 9 M urea or by preparative SDS-polyacrylamide gelelectrophoresis (SDS-PAGE). With the first method, several, but not all, capsid proteins, from the three different virus types could be isolated in pure form, probably because of incomplete dissociation of the virus particles in 9 M urea. With SDS-PAGE all capsid proteins could be isolated in pure form. Immunization of rats and rabbits with the three largest VP's (VP1, VP2 and VP3) isolated by both methods, resulted in the induction of neutralizing antibodies already after 2-3 injections, provided the capsid proteins were isolated from formalin inactivated virus. Apparently formalin treatment stabilized the antigenic determinants, which are responsible for induction of neutralizing antibodies, against denaturation upon VP-isolation. In contrast to several other picornaviruses, where only one of the VP's induces neutralizing antibodies, for poliovirus both VP1, VP2 and VP3 are able to induce neutralizing antibodies. VP's isolated from live virus did not induce neutralizing antibodies, but were able to "prime" the animals. Primary vaccination with any of the VP's, followed by a second injection with a low dose of vaccine (D-antigen) resulted in a boosterlike production of neutralizing antibodies against the D-antigen, even D-antigen of a heterotypic virus. This indicates the occurrence of common antigenic regions on the different capsid polypeptides.(ABSTRACT TRUNCATED AT 250 WORDS)

Subunit composition of mitochondrial F1-ATPase isolated from Saccharomyces carlsbergensis.

1. The subunit stoicheiometry of mitochondrial F1-ATPase from yeast (Saccharomyces carlsbergensis), grown in the presence of [3H]leucine and uniformly labelled [14C]glucose, has been determined. 2. The stoicheiometry on the basis of radioactivity is : alpha: beta: gamma: epsilon = 3 : 3 : 1 : 1. The amount of the smallest subunit, epsilon, could not be measured by this method. 3. The molecular weights of the subunits, determined by urea-SDS gel electrophoresis, are 53 000, 50 000, 33 000, 12 500 and 6500, respectively. The calculated molecular weight of the ATPase is 360 000, assuming the presence of one epsilon subunit per F1. 4. The amino acid composition of the total ATPase and of the individual subunits has been determined. 5. The aurovertin-binding properties of F1 are discussed in relation to the subunit stoicheiometry.

Studies on the structure and conformation of yeast mitochondrial ATPase using aurovertin and methanol as probes.

1. The isolation of the mitochondrial ATPase F1 and its beta-subunit from commercial baker's yeast (Saccharomyces cerevisiae) is described. 2. The molecular weight determined by ultracentrifugation is 340000 +/- 30000. Gel chromatography indicates a molecular weight of 300000 +/- 20000. 3. Fluorimetric titration of the isolated enzyme with aurovertin reveals two binding sites per molecule. The isolated beta-subunit binds aurovertin in a 1 : 1 stoicheiometry. It is concluded that the ATPase molecule contains two aurovertin-binding beta-subunits. 4. The stabilizing agent methanol influences both the measured Kd and the concentration of binding sites for aurovertin. These results fit a model in which both F1 and aurovertin are distributed between aqueous and methanol phases. 5. The effect of methanol on the ATPase activity can be described in terms of the model proposed by Recktenwald and Hess (Recktenwald, D. and Hess, B. (1977) FEBS Lett. 76, 25-28). It is proposed that methanol enhances the affinity of the regulatory site for ATP, but at higher concentrations prevents the interaction between the regulatory and catalytic sites. 6. Since HSO(-3), a typical effector of the assumed regulatory site of F1, has no effect on the binding of aurovertin, it is concluded that the binding site of aurovertin is not correlated with the regulatory site. 7. The inhibition of ATPase activity by aurovertin is slowly (t 1/2 = 70 s) induced during turnover conditions. 8. From the effect of methanol on the inhibition of ATPase activity by aurovertin it is concluded that under turnover conditions the conformation is such that the aurovertin-binding sites have a 6-fold higher affinity for methanol than under resting conditions.