Mutations in a newly identified GTPase gene cause autosomal dominant hereditary spastic paraplegia.

The hereditary spastic paraplegias (HSPs; Strümpell-Lorrain syndrome, MIM number 18260) are a diverse class of disorders characterized by insidiously progressive lower-extremity spastic weakness (reviewed in refs. 1-3). Eight autosomal dominant HSP (ADHSP) loci have been identified, the most frequent of which is that linked to the SPG4 locus on chromosome 2p22 (found in approximately 42%), followed by that linked to the SPG3A locus on chromosome 14q11-q21 (in approximately 9%). Only SPG4 has been identified as a causative gene in ADHSP. Its protein (spastin) is predicted to participate in the assembly or function of nuclear protein complexes. Here we report the identification of mutations in a newly identified GTPase gene, SPG3A, in ADHSP affected individuals.

Systematic isolation and characterization of cDNAs encoding AAA proteins from human brain.

BACKGROUND: The AAA (ATPases Associated with various cellular Activities) domain characterizes a diverse superfamily of proteins. Mutations in genes encoding AAA-domains cause a variety of human diseases including cystic fibrosis, Zellweger syndrome, adrenomyeloneuropathy, and dystonia. Recently, mutations in two AAA-containing proteins paraplegin and spastin have been shown to cause two types of hereditary spastic paraplegia (HSP). The HSPs are genetically heterogeneous degenerative spinal cord disorders characterized by lower extremity weakness and spasticity. Clinical similarity between various genetic types of HSP led us to propose that different genetic types of HSP were due to common biochemical abnormalities including disturbances in related proteins. For this reason, we sought to identify novel AAA-containing proteins as potential candidates for HSP and related neurodegnerative disorders. We used degenerative PCR, based on the conserved AAA peptide sequence to systematically clone and characterize AAA genes expressed in human brain. RESULTS: We analyzed 646 clones and identified 19 known AAA-containing proteins including spastin and paraplegin, AAA-containing genes that cause HSP. In addition, we identified 14 unique DNA inserts representing novel putative AAA-containing proteins. Four of these novel genes are hypothetical AAA proteins and the rest of novel clones matched sequences of yet uncharacterized expressed sequence tags (ESTs). CONCLUSION: Fourteen novel AAA-containing proteins are potential candidates for human diseases including degenerative neurologic disorders, and their further analysis is ongoing (Tab. 1, Fig. 1, Ref. 22).

Expression of human glucocerebrosidase in long-term reconstituted mice following retroviral-mediated gene transfer into hematopoietic stem cells.

A retroviral vector (GTN) in which the glucocerebrosidase (GCase) cDNA is driven by the Moloney murine leukemia virus (Mo-MuLV) long terminal repeat (LTR) was tested for transfer efficiency and expression of the GCase gene in long-term reconstituted mice. Eleven W/Wv mice were transplanted with unselected GTN-infected bone marrow cells and 10 of these mice were analyzed 3 months later. Seven of these 10 mice (70%) contained the intact proviral genome in bone marrow, spleen, and thymus. Of these 7,3 mice contained a high-copy number of the provirus in all the hematopoietic tissues tested. The mice contained anywhere from one to four proviral integration sites that were the same in all three tissues, indicating that these mice have been repopulated by one or more transduced multipotential hematopoietic stem cells. Five months after transplantation, bone marrow from the eleventh mouse was transplanted into secondary recipient animals. The secondary recipients contained the intact proviral genome in the bone marrow, spleen, thymus, and macrophages 4 months after the secondary transplantation. This further supports the conclusion that hematopoietic stem cells have indeed been targeted. Human GCase RNA was detected in all 7 mice containing the proviral DNA. These results demonstrate expression of the human GCase gene in the progeny of repopulating hematopoietic stem cells of mice following gene transfer.

Acid-sensing ion channel (ASIC) 4 gene: physical mapping, genomic organisation, and evaluation as a candidate for paroxysmal dystonia.

Acid-sensing ion channels (ASICs) are protongated Na(+) channels. They have been implicated with synaptic transmission, pain perception as well as mechanoperception. ASIC4 is the most recent member of this gene family. It shows expression throughout the central nervous system with strongest expression in pituitary gland. ASIC4 is inactive by itself and its function is unknown. Mutations in ion channel subunits, which are homologues of ASICs lead to neurodegeneration in Caenorhabditis elegans. It has, therefore, been speculated that similar mutations in ASICs may be responsible for neurodegeneration in humans. Here, we show that ASIC4 maps to the long arm of chromosome 2 in close proximity to the locus for paroxysmal dystonic choreoathetosis (PDC), a movement disorder with unknown cause. Ion channel genes have been shown to cause several other paroxysmal neurologic disorders and are important candidate genes for PDC. We established the genomic organisation of the ASIC4 gene and screened a PDC pedigree for mutations in the coding region. Although we identified three polymorphisms in the Cterminal part of the ASIC4 protein, these were not present in each affected subject in the PDC kindred we analysed. Therefore, although the ASIC4 gene is physically mapped to the PDC locus, our data indicates that ASIC4 gene mutation is not the cause of PDC. It remains to be established if mutations in ASIC4 or other ASIC subunits may cause neurological disorders.

Clinical and genetic analysis of progressive dystonia with diurnal variation.

We examined 17 patients with progressive dystonia with diurnal variation, a dominantly inherited, generalized dystonia that begins in childhood. Dystonia was typically least severe in the morning, increased as the day continued, and markedly improved with low doses of carbidopa-levodopa. We also studied the patient's parents, children, and siblings from seven families. We observed a spectrum of neurologic involvement, phenotypic variability among siblings, and incomplete genetic penetrance. Progression of motor impairment over several years, which reaches a plateau during late adolescence, is useful in distinguishing progressive dystonia with diurnal variation from cerebral palsy and degenerative disorders. It is important to recognize the subtle, as well the extreme, manifestations of progressive dystonia with diurnal variation because it is treatable. Genetic counseling must consider that mildly affected parents with little or no disability may have profoundly affected children. Appreciation of the phenotypic variability and degree of genetic penetrance will permit detailed genetic and biochemical analyses.

Neurologic complications in long-standing nephropathic cystinosis.

The central nervous system has been considered to be uninvolved in nephropathic cystinosis. Survival into adulthood, following renal dialysis and transplantation, has brought attention to the sequelae of long-standing cystinosis. We examined 14 patients with cystinosis, 12 of whom had undergone renal transplantation. Two patients had neurologic symptoms. One patient had progressive bradykinesia, dementia, and spasticity with computed tomographic scan evidence of cerebral atrophy and multifocal mineralization in bilateral internal capsules and periventricular white matter. One patient had behavioral and, to a lesser extent, cognitive disturbance and computed tomographic scan evidence of marked, progressive cerebral atrophy. Although the remaining patients had normal results of neurologic examinations, 11 had roentgenographic evidence of generalized cerebral atrophy; 2 of these had abnormal electroencephalograms, 1 had borderline-deficient intellectual function, and 2 had computed tomographic scan evidence of multifocal, intracerebral mineralization. The patients with nervous system abnormalities were not distinguished by patterns of medication use, demographic or laboratory features, or the relative severity of cystinosis. Although the neurologic involvement in these patients suggests that cystinosis may eventually involve the central nervous system, the differential diagnosis must include other complications from renal failure, dialysis, and immunosuppression.

Treatment of Wilson disease with ammonium tetrathiomolybdate. II. Initial therapy in 33 neurologically affected patients and follow-up with zinc therapy.

OBJECTIVE: To test the efficacy and toxic effects of ammonium tetrathiomolybdate in the initial treatment of a relatively large series of patients with neurologic symptoms and signs caused by Wilson disease. Two key aspects of efficacy are to preserve the neurologic function present at the onset of therapy and to maximize the opportunity for long-term recovery. DESIGN: An open study of 33 patients treated for 8 weeks each, including further follow-up data on the original 17 patients. Neurologic function was evaluated by frequent quantitative neurologic and speech pathology examinations. Several copper-related variables were studied to evaluate the effect of the drug on copper, and several biochemical and clinical variables were studied to evaluate potential toxic effects. Patients were then followed up at yearly intervals, with follow-up periods of 1 to 8 years reported. SETTING: A university hospital referral setting. INTERVENTION: Patients were generally treated for 8 weeks with tetrathiomolybdate, followed by zinc maintenance therapy. MAIN OUTCOME MEASURES: Neurologic function was evaluated by quantitative neurologic and motor speech examinations and magnetic resonance imaging scans of the brain. RESULTS: During the 8 weeks of tetrathiomolybdate administration, only 1 of the 33 patients showed deterioration in neurologic function. Copper status and potential further toxic effects were generally well controlled quickly. Evaluation of data from individual patients revealed evidence of a toxic side effect in only 1 patient, who exhibited reversible anemia. During the ensuing period of follow-up of 1 to 6 years, neurologic recovery in most patients was good to excellent. CONCLUSIONS: Tetrathiomolybdate appears to be an excellent form of initial treatment in patients with Wilson disease who present with neurologic symptoms and signs. In contrast to penicillamine therapy, initial treatment with tetrathiomolybdate rarely allows further, often irreversible, neurologic deterioration.

Treatment of Wilson's disease with ammonium tetrathiomolybdate. I. Initial therapy in 17 neurologically affected patients.

OBJECTIVE: To test the efficacy and toxicity of a new drug, ammonium tetrathiomolybdate, in the initial treatment of a relatively large series of patients presenting with neurologic signs and symptoms caused by Wilson's disease. The key aspect of efficacy was to preserve the neurologic function present at the onset of therapy. DESIGN: An open study of 17 patients treated for 8 weeks each. Neurologic function was evaluated by frequent quantitative neurologic and speech examinations. Several copper-related variables were studied to evaluate the effect of the drug on copper, and a large number of biochemical and clinical variables were studied to evaluate potential toxicity. Patients were then followed up at yearly intervals, with follow-up periods of 1 to 5 years reported. SETTING: A university hospital referral setting INTERVENTION: Patients were generally treated for 8 weeks with tetrathiomolybdate, followed by zinc maintenance therapy. MAIN OUTCOME MEASURES: Neurologic function was evaluated by quantitative neurologic and speech examinations. RESULTS: None of the patients suffered a loss of neurologic function. Copper status and potential further toxic effects were generally well controlled quickly. No toxic effects resulted from administration of tetrathiomolybdate. During the ensuing period of follow-up of 1 to 5 years, neurologic recovery in most patients was good to excellent. CONCLUSIONS: Tetrathiomolybdate appears to be an excellent form of initial treatment in patients with Wilson's disease presenting with neurologic signs and symptoms. In contrast to penicillamine therapy, initial treatment with tetrathiomolybdate does not result in further, often irreversible neurologic deterioration.

ApoE epsilon 4 allelic association with Alzheimer's disease: independent confirmation using denaturing gradient gel electrophoresis.

There is intriguing evidence associating apolipoprotein E (ApoE) with Alzheimer's disease (AD). ApoE is deposited with beta-amyloid in senile plaques and binds to beta-amyloid in vitro. We used denaturing gradient gel electrophoresis to identify ApoE epsilon 2, epsilon 3, and epsilon 4 alleles in 135 control subjects and 57 AD patients. We observed a marked increase in ApoE epsilon 4 allele frequency (0.40) in AD patients compared with control subjects (0.14) (p < 0.0001). Our independent finding of a marked association of ApoE epsilon 4 allele with AD further supports a possible role of ApoE in the pathogenesis of AD and confirms the study of Saunders et al (Neurology 1993;43:1467-1472).

Paroxysmal dystonic choreoathetosis linked to chromosome 2q: clinical analysis and proposed pathophysiology.

We describe clinical features of a large Polish-American kindred in which autosomal-dominant, paroxysmal dystonic choreoathetosis (PDC) was linked to a locus on chromosome 2q. Episodes of generalized dystonia and choreoathetosis involving the face and all extremities began in early childhood, lasted for 30 minutes to several hours, and occurred up to several times each week. There was no interruption of consciousness and EEGs were normal during the episodes. Paroxysmal dyskinesia occurred at rest both spontaneously and following caffeine or alcohol consumption. Neurologic examinations were normal between attacks. The cause of PDC is unknown. We deduced a model of PDC pathophysiology from analyzing neurophysiologic effects of alcohol and caffeine (which provoke attacks of PDC), the variably beneficial effects of levodopa-carbidopa, and the occurrence of dystonia and paroxysmal dyskinesia in biopterin synthesis disorders. We propose that nigrostriatal neurons in PDC patients have either marginally deficient dopamine synthesis or excessive alcohol- and caffeine-induced dopamine release; and that following alcohol- and caffeine-induced dopamine release, PDC patients experience a period of dopamine deficiency.

Dystonia with marked diurnal variation associated with biopterin deficiency.

Two pairs of siblings with severe dystonia with marked diurnal fluctuation had both reduced CSF concentration of biopterin and marked symptomatic improvement of the dystonia in response to levodopa. Whether the reduced concentration of biopterin reflects focal abiotrophy of biopterin-containing neurons or deficiency of biopterin synthesis is uncertain. A fifth individual, who had a systemic deficiency of biopterin synthesis, shared the features of reduced biopterin in CSF, marked diurnal variation in the degree of dystonia, and clinical improvement in response to levodopa. Generalized dystonia with marked diurnal fluctuation was therefore shared by the four patients in whom biopterin deficiency was limited to the CNS and the patient with systemic deficiency of biopterin.

Multiple sulfatase deficiency.

Multiple sulfatase deficiency is an inherited disorder characterized by a deficiency of several sulfatases and the accumulation of sulfatides, glycosaminoglycans, sphingolipids, and steroid sulfates in tissues and body fluids. The clinical manifestations represent the summation of two diseases: late infantile metachromatic leukodystrophy and mucopolysaccharidosis. We present a 9-year-old girl with a phenotype similar to a mucopolysaccharidosis: short stature, microcephaly, and mild facial dysmorphism, along with dysphagia, retinal degeneration, developmental arrest, and ataxia. We discuss the importance of measuring the sulfatase activities in the leukocytes, and the instability of sulfatases in the cultured skin fibroblasts.

Novel polymorphism in the A4 region of the amyloid precursor protein gene in a patient without Alzheimer's disease.

We found a novel polymorphism in the amyloid precursor protein (APP) gene in a patient with ischemic cerebrovascular disease who had no evidence of Alzheimer's disease (AD). This polymorphism deletes a Fok I restriction enzyme site and causes the substitution of threonine for alanine at codon 673. This is adjacent to the site at which APP is thought to undergo cleavage in AD. Analysis of this polymorphism may provide insight into the basis of APP processing.

Allele-specific sequencing confirms novel prion gene polymorphism in Creutzfeldt-Jakob disease.

We analyzed the prion protein coding sequence in a familial Creutzfeldt-Jakob disease patient who did not have any of the currently recognized prion protein mutations. Denaturing gradient gel electrophoresis indicated that the prion protein coding sequence was heterozygous at least one location. We isolated each allele by denaturing gradient gel electrophoresis and directly sequenced. We found a DNA polymorphism at codon 178 that predicted the amino acid substitution, aspartate----asparagine. Whether this represents a benign polymorphism or pathogenic mutation will depend on analysis of the functional consequences of this change. Denaturing gradient gel electrophoresis and allele-specific sequencing proved to be efficient means of analyzing sequence polymorphisms in this gene.

Late-onset generalized disorder of peroxisomes.

We diagnosed a unique peroxisomal disorder in a 32-year-old man with profound mental retardation, mild facial dysmorphism, retinal pigmentary degeneration, seizures, and sensorineural deafness. Although plasma very-long-chain fatty acid profile suggested X-linked adrenoleukodystrophy, marked reduction in fibroblast lignoceric acid oxidation and the presence of cytosolic catalase were consistent with Zellweger syndrome (ZS). Unlike ZS, functional peroxisomes were present as indicated by the density of peroxisomes (1.175 gm/ml) similar to peroxisomes from control cells and by partial deficiencies of fibroblast phytanic acid oxidation and dihydroxyacetone phosphate acyltransferase activity. These findings indicate that this patient has a previously undescribed group 3 peroxisomal disorder (multiple peroxisomal enzyme deficiencies with preserved peroxisomes).

Hereditary spastic paraplegia linked to chromosome 15q: Analysis of candidate genes.

We previously reported an extended kindred with autosomal dominant uncomplicated hereditary spastic paraplegia (HSP) and found close linkage between the disorder and microsatellite polymorphisms on chromosome 15q. Multipoint linkage analysis reached a maximum LOD score (10.16) between D15S128 and D15S156, a region that includes genes encoding alpha5 and beta3 subunits of GABAA receptor. Theoretically, abnormal GABA-mediated neurotransmission could produce spasticity and possibly other changes of HSP. We used genetic linkage analysis to evaluate these two HSP candidate genes and observed obligate recombinants for polymorphisms immediately adjacent to (or within untranslated regions of) genes encoding alpha5 and beta3 GABAA receptor subunits. Although these genes are linked tightly to the HSP locus, our findings conclusively exclude these genes from being responsible for HSP in this kindred.

(+)-alpha-[11C]Dihydrotetrabenazine PET imaging in familial paroxysmal dystonic choreoathetosis.

Clinical observations suggest a disturbance of striatal dopaminergic function in familial paroxysmal dystonic choreoathetosis (PDC). The authors used PET with [11C]dihydrotetrabenazine (DTBZ) to study striatal dopaminergic innervation in PDC. The results did not reveal abnormal DTBZ binding potential in PDC striatum. This suggests that dopaminergic abnormalities, if present, may be due to altered regulation of dopamine release or to postsynaptic mechanisms, rather than to an altered density of nigrostriatal innervation.

Phenotypic analysis of autosomal dominant hereditary spastic paraplegia linked to chromosome 8q.

OBJECTIVE: To describe clinical, electrophysiologic, neuroimaging, and muscle biopsy features in a hereditary spastic paraplegia (HSP) kindred linked to a new HSP locus on chromosome 8q. BACKGROUND: HSP is a genetically diverse group of disorders characterized by insidiously progressive spastic weakness in the legs. We recently analyzed a Caucasian kindred with autosomal dominant HSP and identified tight linkage to a novel HSP locus on chromosome 8q23-24. METHODS: Clinical analysis, nerve conduction studies, electromyography, somatosensory evoked potentials, MRI of brain and spinal cord, and muscle biopsy for mitochondrial analysis were performed in members of the first HSP kindred linked to chromosome 8q. RESULTS: Fifteen individuals showed insidiously progressive spastic paraparesis beginning between ages 22 and 60 years (average, 37.2 years). Spinal cord MRI in 1 moderately affected subject showed significant atrophy of the thoracic spinal cord as determined by cross-sectional area measurements. Somatosensory evoked potential recording, electromyography, nerve conduction studies, and muscle biopsy, including histochemical and biochemical analysis of mitochondrial function, were normal. CONCLUSIONS: The phenotype in this family is that of typical, but severe, uncomplicated HSP. Other than apparently increased severity, there were no clinical features that distinguished this family from autosomal dominant HSP linked to loci on chromosomes 2p, 14q, and 15q. This clinical similarity between different genetic types of autosomal dominant HSP raises the possibility that genes responsible for these clinically indistinguishable disorders may participate in a common biochemical cascade. Normal results of muscle histochemical and biochemical analysis suggest that mitochondrial disturbance, a feature of chromosome 16-linked autosomal recessive HSP due to paraplegin gene mutations, is not a feature of chromosome 8q-linked autosomal dominant HSP and may not be a common factor of HSP in general.

Hereditary spastic paraplegia: advances in genetic research. Hereditary Spastic Paraplegia Working group.

Hereditary spastic paraplegia (HSP) is a diverse group of inherited disorders characterized by progressive lower-extremity spasticity and weakness. Insight into the genetic basis of these disorders is expanding rapidly. Uncomplicated autosomal dominant, autosomal recessive, and X-linked HSP are genetically heterogeneous: different genes cause clinically indistinguishable disorders. A locus for autosomal recessive HSP is on chromosome 8q. Loci for autosomal dominant HSP have been identified on chromosomes 2p, 14q, and 15q. One locus (Xq22) has been identified for X-linked, uncomplicated HSP and shown to be due to a proteolipoprotein gene mutation in one family. The existence of HSP families for whom these loci are excluded indicates the existence of additional, as yet unidentified HSP loci. There is marked clinical similarity among HSP families linked to each of these loci, suggesting that gene products from HSP loci may participate in a common biochemical cascade, which, if disturbed, results in axonal degeneration that is maximal at the ends of the longest CNS axons. Identifying the single gene defects that cause HSPs distal axonopathy may provide insight into factors responsible for development and maintenance of axonal integrity. We review clinical, genetic, and pathologic features of HSP and present differential diagnosis and diagnostic criteria of this important group of disorders. We discuss polymorphic microsatellite markers useful for genetic linkage analysis and genetic counseling in HSP.

Carbamazepine in Fabry's disease: effective analgesia with dose-dependent exacerbation of autonomic dysfunction.

Seven patients with Fabry's disease and severe pain received carbamazepine (CMZ). Five of 7 patients had moderate to complete relief based upon self-assessment of pain levels. Preexisting autonomic dysfunction was exacerbated by CMZ in 2. Complications encountered were ileus, urinary retention, and gastrointestinal disturbance. Although CMZ was useful in treatment of pain, caution should be employed in this disease.