Genetic Myelopathies

OBJECTIVE

This article provides an overview of genetic myelopathies, a diverse group of inherited, degenerative conditions that may be broadly categorized as motor neuron disorders, disorders of spinocerebellar degeneration, leukodystrophies, and hereditary spastic paraplegia. Clinical examples from each category are provided to illustrate the spectrum of genetic myelopathies and their distinguishing features that aid in differentiating genetic myelopathies from potentially treatable acquired causes of myelopathy.

LATEST DEVELOPMENTS

Advances in genetic testing have vastly enhanced current knowledge of genetic myelopathies and the ability to diagnose and provide appropriate counseling to patients and their families. However, potential health care disparities in access to genetic testing is a topic that must be further explored. Although treatment for most of these conditions is typically supportive, there have been recent therapeutic breakthroughs in treatments for amyotrophic lateral sclerosis, spinal muscular atrophy, and Friedreich ataxia.

ESSENTIAL POINTS

Genetic myelopathies may present with chronic and progressive symptoms, a family history of similar symptoms, and involvement of other structures outside of the spinal cord. Imaging often shows spinal cord atrophy, but cord signal change is rare. Exclusion of reversible causes of myelopathy is a key step in the diagnosis. There are many different causes of genetic myelopathies, and in some cases, symptoms may overlap, which underscores the utility of genetic testing in confirming the precise underlying neurologic condition.

Negative Selection on a SOD1 Mutation Limits Canine Degenerative Myelopathy While Avoiding Inbreeding

Several hundred disease-causing mutations are currently known in domestic dogs. Breeding management is therefore required to minimize their spread. Recently, genetic methods such as direct-to-consumer testing have gained popularity; however, their effects on dog populations are unclear. Here, we aimed to evaluate the influence of genetic testing on the frequency of mutations responsible for canine degenerative myelopathy and assess the changes in the genetic structure of a Pembroke Welsh corgi population from Japan. Genetic testing of 5,512 dogs for the causative mutation in superoxide dismutase 1 (SOD1) (c.118G>A (p.E40K)) uncovered a recent decrease in frequency, plummeting from 14.5% (95/657) in 2019 to 2.9% (24/820) in 2022. Weir and Cockerham population differentiation (FST) based on genome-wide single-nucleotide polymorphism (SNP) of 117 selected dogs detected the SNP with the highest FST located in the intron of SOD1 adjacent to the c.118G>A mutation, supporting a selection signature on SOD1. Further genome-wide SNP analyses revealed no obvious changes in inbreeding levels and genetic diversity between the 2019 and 2022 populations. Our study highlights that genetic testing can help inform improved mating choices in breeding programs to reduce the frequency of risk variants and avoid inbreeding. This combined strategy could decrease the genetic risk of canine degenerative myelopathy, a fatal disease, within only a few years.

Association of the FGF4L2 retrogene with fibrocartilaginous embolic myelopathy in dogs

BACKGROUND

Fibrocartilaginous embolic myelopathy (FCE) is a well-documented condition in dogs although rarely reported in chondrodystrophic breeds. Genetic associations have not been defined.

OBJECTIVES

Define the association of the chondrodystrophy-associated FGF4L2 retrogene with histopathologically confirmed cases of FCE.

ANIMALS

Ninety-eight dogs with a histopathologic diagnosis of FCE.

METHODS

Retrospective multicenter study. Dogs were genotyped for the FGF4L2 and FGF4L1 retrogenes using DNA extracted from formalin-fixed, paraffin-embedded tissue. Associations between breed, FCE and retrogene status were investigated with reference to a hospital population and known breed and general population allele frequencies.

RESULTS

FGF4L2 genotype was defined in 89 FCE cases. Fibrocartilaginous embolic myelopathy was present in 22 dogs from FGF4L2-segregating breeds with allele frequencies of ≥5%; however, all dogs were wild type. Two Labrador retrievers with FCE carried FGF4L2 alleles. Frequency of the FGF4L2 allele was significantly (P < .001) and negatively associated with FCE relative to predicted hospital-population dogs. FCE was overrepresented in Boxer, Great Dane, Yorkshire Terrier, Bernese Mountain Dog, Miniature Schnauzer, Rottweiler, and Shetland Sheepdog breeds.

CONCLUSIONS AND CLINICAL IMPORTANCE

Study data based on genotypically and histopathologically defined cases support the historical observation that FCE is uncommon in chondrodystrophic dog breeds. FGF4 plays an important role in angiogenesis and vascular integrity; anatomical studies comparing chondrodystrophic and non-chondrodystrophic dogs might provide insight into the pathogenesis of FCE.

Prevalence of SOD1 allele associated with degenerative myelopathy in canine population in Greece

Canine degenerative myelopathy (CDM) is a late-onset fatal disorder associated with a point mutation of the superoxide dismutase 1 (SOD1) gene (c.118G > A). The purpose of this study was to determine the genotype and allele frequencies of this mutation in 108 dogs, mainly in Belgian Malinois and German Shepherd dogs with (CDM-affected group) and without CDM clinical symptoms (control group) in Greece. Genotyping of the c.118G > A mutation was possible by Sanger sequencing and PCR-RFLP. The observed genotype frequencies for the control group were 89.4% for the homozygous (G/G), 9.6% for the heterozygous (A/G), and 0.96% for the homozygous mutant (A/A) allele. The mutant allele was not common in the Belgian Malinois dogs (allele frequency = 0.029), but quite common in the German Shepherd dogs (allele frequency = 0.138). In the CDM affected group, all 4 dogs were homozygous for the mutant allele. These frequencies were close to those expected, indicating no significant departure from Hardy-Weinberg equilibrium. A strong but not statistically significant association between the mutant allele and CDM was observed. A previously identified deletion upstream of the mutation of interest was found at a high frequency (0.361) in the population.

Neoplastic Myelopathies

PURPOSE OF REVIEW

This article reviews the current classification system of primary spinal cord tumors and explores evolving diagnostic and therapeutic strategies for both primary tumors and metastatic tumors to various compartments of the spinal cord.

RECENT FINDINGS

The 2016 World Health Organization classification system allows for more precise prognostication of and therapy for spinal cord tumors and has identified new entities, such as the diffuse midline glioma, H3 K27M mutant. Whole-exome sequencing reveals that the genetic background of primary glial spinal cord neoplasms differs from that of their intracranial histologic counterparts in ways that can potentially influence therapy. Targeted and immune checkpoint therapies have improved survival for patients with melanoma and lung cancer and have simultaneously produced novel complications by enhancing radiation toxicity in some cases and by facilitating the emergence of novel autoimmune and paraneoplastic syndromes involving the spinal cord, such as neuromyelitis optica spectrum disorder and syndromes associated with anti-Hu and collapsin response mediator protein-5 (CRMP-5) antibodies. These conditions must be distinguished from tumor or infection. Epidural spinal cord compression treatment paradigms have changed with the advent of robotic surgery and advances in radiation therapy.

SUMMARY

Neoplastic myelopathies subsume a wide spectrum of pathologies. Neoplastic cord involvement may be primary or secondary and may be approached diagnostically by the particular spinal cord compartment localization. Primary spinal cord tumors account for only 2% to 4% of primary central nervous system tumors, ranging from low-grade glial neoplasms to malignant tumors. Metastatic malignancy to the epidural or leptomeningeal spaces is more common than primary cord tumors. Differential diagnoses arising in the course of evaluation for cord tumors include myelopathies related to radiation or chemotherapy and paraneoplastic syndromes, all of which are sources of significant morbidity. Knowledge of genetic syndromes and the biologic behavior of diverse histologies together with selective application of surgery, radiation, and targeted therapies can facilitate diagnosis, minimize surgical morbidity, and prolong quality of life.

Hereditary Myelopathies

PURPOSE OF REVIEW

This article guides clinicians in the clinical recognition and differential diagnosis of hereditary myelopathies.

RECENT FINDINGS

Rather than a disease, a disease process, or relating to specific cellular vulnerability, the term hereditary myelopathy refers to diverse inherited disorders in which major aspects of the clinical syndrome reflect disturbance of elements within the spinal cord (specifically, the dorsal columns and dorsal root ganglia, corticospinal tracts, and anterior horn cells). It is important to note that the clinical features of almost all hereditary myelopathies reflect not only disturbance of elements within the spinal cord but also disturbance of extraspinal structures (particularly, but not limited to, peripheral nerves and the cerebellum) and that these extraspinal clinical features can be very helpful in recognizing specific myelopathy syndromes. The value of classifying disorders as inherited myelopathies lies primarily in facilitating their clinical recognition and differential diagnosis. It is useful to recognize that many hereditary myelopathies conform to one of four clinical paradigms: (1) spinocerebellar ataxia, (2) motor neuron disorder, (3) leukodystrophy, or (4) distal motor-sensory axonopathy predominantly affecting the central nervous system. Although they are myelopathies, spinal dysraphisms such as spina bifida and myelomeningocele are not included in this context because they are not usually due to single-gene mutation and have low hereditability.

SUMMARY

This article illustrates clinical paradigms of hereditary myelopathy with clinical examples emphasizing the spectrum, clinical recognition, and differential diagnosis of hereditary myelopathies.

Downregulation of microRNA-199a-5p alleviated lidocaine-induced sensory dysfunction and spinal cord myelin lesions in a rat model

Lidocaine induces neurotoxicity in the spinal cord, but the underlying mechanisms remain unclear. In this study, we evaluated the effects of miR-199a-5p on 10 % lidocaine neurotoxicity. Increased expression of miR-199a-5p in the spinal cord of rats treated with 10 % lidocaine was assessed by qRT-PCR. Furthermore, after miR-199a-5p antagomir administration, the sensory dysfunction and myelin sheath lesions (evaluated by semithin sections stained with toluidine blue, electron microscopy, g-ratios and myelin thickness) induced by 10 % lidocaine were alleviated. Myelin regulatory factor (MYRF), a key molecule of myelin sheath development, was predicted to be a target gene of miR-199a-5p by the TargetScan and miRBase databases. MYRF and its downstream factors myelin basic protein (MBP), proteolipid protein (PLP) and myelin oligodendrocyte glycoprotein (MOG) were significantly decreased after intrathecal 10 % lidocaine administration. Moreover, these changes were reversed after miR-199a-5p antagomir administration. FISH-immunofluorescence showed coexpression of miR-199a-5p and MYRF in the spinal cord white matter of rats. A luciferase reporter assay further demonstrated the functional association between miR-199a-5p and MYRF. Overall, miR-199a-5p upregulation is involved in 10 % lidocaine-induced spinal cord toxicity through regulation of MYRF. Therefore, downregulating miR-199a-5p expression may be a potential strategy to ameliorate spinal cord neurotoxicity induced by 10 % lidocaine.

Degenerative Myelopathy in Hovawart Dogs: Molecular Characterization, Pathological Features and Accumulation of Mutant Superoxide Dismutase 1 Protein

Degenerative myelopathy (DM) is an adult-onset, progressive neurological disease affecting several breeds of dog. Homozygosity or compound heterozygosity for the canine superoxide dismutase 1 (SOD1) gene mutations, possibly modulated by the modifier SP110 locus, are associated with a high risk for DM. Although the pathophysiological mechanisms are largely unknown, a role for mutant SOD1 in causing neuronal degeneration has been postulated. Three Hovawart dogs, 9-12 years of age, developed slowly progressive incoordination and weakness of the pelvic limbs leading to non-ambulatory flaccid paraparesis and muscle atrophy. Neuropathological lesions comprised axonal degeneration and loss of ascending and descending spinal pathways, which were most severe in the mid- to caudal thoracic segments. Accumulation of mutant SOD1 protein in neurons and reactive astrocytes was demonstrated by immunolabelling with the 16G9 antibody against the mutant SOD1 protein (p.E40K amino acid substitution). All three dogs were homozygous for the c.118A allele, but none had the SP110 'risk' haplotype, suggesting a weak association of SP110 with the onset of DM in this breed. Our data suggest that the Hovawart breed is predisposed to the SOD1:c.118G>A mutation, which is associated with the development of DM. Prevention of DM could be achieved with the help of strategies based on epidemiological and genetic testing.

Molecular screening for the mutation associated with canine degenerative myelopathy (SOD1:c.118G > A) in German Shepherd dogs in Brazil

Canine Degenerative Myelopathy is a late onset recessive autosomal disease characterized by a progressive ascending degeneration of the spinal cord. Two causal mutations are associated with this disease: a transition (c.118G>A) in exon 2 of the SOD1 that was described in several breeds and a transversion (c.52A>T) in exon 1 of the same gene described in Bernese Mountain dogs. The aim of this study was to understand the impact of the SOD1:c.118G > A mutation by genotyping a population of German Shepherd dogs in Brazil. A PCR-RFLP approach was used to genotype 97 healthy individuals belonging from the Northeast (Bahia and Pernambuco states) and South (Santa Catarina state) regions of Brazil. A total of 95 individuals were successfully genotyped resulting in an observed genotype frequency (with 95% confidence interval) of: 0.758 (0.672–0.844), 0.242 (0.156–0.328) and 0.000 (0.000–0.000) for “GG”, “AG” and “AA” genotypes, respectively. To our knowledge, this is the first attempt to describe the presence of the “A” allele associated with CDM (SOD1:c.118G > A) in German Shepherd dogs in Brazil and, as such, these results contribute toward important epidemiological data in this country and to the knowledge of the distribution of the aforementioned mutation worldwide.

Inhibition of ABL1 tyrosine kinase reduces HTLV-1 proviral loads in peripheral blood mononuclear cells from patients with HTLV-1-associated myelopathy/tropical spastic paraparesis

Human T-cell leukemia virus type 1 (HTLV-1) causes incurable adult T-cell leukemia and HTLV-1-associated myelopathy/tropical spastic paraparesis (HAM/TSP). Patients with HAM/TSP have increased levels of HTLV-1-infected cells compared with asymptomatic HTLV-1 carriers. However, the roles of cellular genes in HTLV-1-infected CD4+ T cells await discovery. We performed microarray analysis of CD4+ T cells from HAM/TSP patients and found that the ABL1 is an important gene in HAM/TSP. ABL1 is a known survival factor for T- and B-lymphocytes and is part of the fused gene (BCR-ABL) known to be responsible for chronic myelogenous leukemia (CML). ABL1 tyrosine kinase inhibitors (TKIs), including imatinib, nilotinib, and dasatinib, are used clinically for treating CML. To evaluate whether ABL1 is indeed important for HAM/TSP, we investigated the effect of TKIs on HTLV-1-infected cells. We developed a propidium monoazide-HTLV-1 viability quantitative PCR assay, which distinguishes DNA from live cells and dead cells. Using this method, we were able to measure the HTLV-1 proviral load (PVL) in live cells alone when peripheral blood mononuclear cells (PBMCs) from HAM/TSP cases were treated with TKIs. Treating the PBMCs with nilotinib or dasatinib induced significant reductions in PVL (21.0% and 17.5%, respectively) in live cells. Furthermore, ABL1 siRNA transfection reduced cell viability in HTLV-1-infected cell lines, but not in uninfected cell lines. A retrospective survey based on our clinical records found a rare case of HAM/TSP who also suffered from CML. The patient showed an 84.2% PVL reduction after CML treatment with imatinib. We conclude that inhibiting the ABL1 tyrosine kinase specifically reduced the PVL in PBMCs from patients with HAM/TSP, suggesting that ABL1 is an important gene for the survival of HTLV-1-infected cells and that TKIs may be potential therapeutic agents for HAM/TSP.

Hereditary Myelopathies

PURPOSE OF REVIEW

Hereditary myelopathies are very diverse genetic disorders, and many of them represent a widespread neurodegenerative process rather than isolated spinal cord dysfunction. This article reviews various types of inherited myelopathies, with emphasis on hereditary spastic paraplegias and spastic ataxias.

RECENT FINDINGS

The ever-growing number of myelopathy-causing genes and broadening of phenotype-genotype correlations makes the molecular diagnosis of inherited myelopathies a daunting task. This article emphasizes the main phenotypic clusters among inherited myelopathies that can facilitate the diagnostic process. This article focuses on newly identified genetic causes and the most important identifying clinical features that can aid the diagnosis, including the presence of a characteristic age of onset and additional neurologic signs such as leukodystrophy, thin corpus callosum, or amyotrophy.

SUMMARY

The exclusion of potentially treatable causes of myelopathy remains the most important diagnostic step. Syndromic diagnosis can be supported by molecular diagnosis, but the genetic diagnosis at present does not change the management. Moreover, a negative genetic test does not exclude the diagnosis of a hereditary myelopathy because comprehensive molecular testing is not yet available, and many disease-causing genes remain unknown.

Pathogenicity of novel ABCD1 variants: The need for biochemical testing in the era of advanced genetics

X-linked adrenoleukodystrophy (ALD), a progressive neurodegenerative disease, is caused by mutations in ABCD1 and characterized by very-long-chain fatty acids (VLCFA) accumulation. In male patients, an increased plasma VLCFA levels in combination with a pathogenic mutation in ABCD1 confirms the diagnosis. Recent studies have shown that many women with ALD also develop myelopathy. Correct diagnosis is important for management including genetic counseling. Diagnosis in women can only be confirmed when VLCFA levels are elevated or when a known pathogenic ABCD1 mutation is identified. However, in 15-20% of women with ALD VLCFA plasma levels are not elevated. Demonstration that a novel sequence variant is pathogenic can be a challenge when VLCFA levels are in the normal range. Here we report two women with a clinical presentation compatible with ALD, an ABCD1 variation (p.Arg17His and p.Ser358Pro) of unknown significance, but with normal VLCFA levels. We developed a diagnostic test that is based on generating clonal cell lines that express only one of the two alleles. Subsequent biochemical studies enabled us to show that the two sequence variants were not pathogenic, thereby excluding the diagnosis ALD in these women. We conclude that the clonal approach is an important addition to the existing diagnostic array.

Clinical pattern, mutations and in vitro residual activity in 33 patients with severe 5, 10 methylenetetrahydrofolate reductase (MTHFR) deficiency

BACKGROUND

Severe methylenetetrahydrofolate reductase (MTHFR) deficiency is a rare inborn defect disturbing the remethylation of homocysteine to methionine (<200 reported cases). This retrospective study evaluates clinical, biochemical genetic and in vitro enzymatic data in a cohort of 33 patients.

METHODS

Clinical, biochemical and treatment data was obtained from physicians by using a questionnaire. MTHFR activity was measured in primary fibroblasts; genomic DNA was extracted from cultured fibroblasts.

RESULTS

Thirty-three patients (mean age at follow-up 11.4 years; four deceased; median age at first presentation 5 weeks; 17 females) were included. Patients with very low (<1.5%) mean control values of enzyme activity (n = 14) presented earlier and with a pattern of feeding problems, encephalopathy, muscular hypotonia, neurocognitive impairment, apnoea, hydrocephalus, microcephaly and epilepsy. Patients with higher (>1.7-34.8%) residual enzyme activity had mainly psychiatric symptoms, mental retardation, myelopathy, ataxia and spasticity. Treatment with various combinations of betaine, methionine, folate and cobalamin improved the biochemical and clinical phenotype. During the disease course, patients with very low enzyme activity showed a progression of feeding problems, neurological symptoms, mental retardation, and psychiatric disease while in patients with higher residual enzyme activity, myelopathy, ataxia and spasticity increased. All other symptoms remained stable or improved in both groups upon treatment as did brain imaging in some cases. No clear genotype-phenotype correlation was obvious.

DISCUSSION

MTHFR deficiency is a severe disease primarily affecting the central nervous system. Age at presentation and clinical pattern are correlated with residual enzyme activity. Treatment alleviates biochemical abnormalities and clinical symptoms partially.

Identification of HOXD4 Mutations in Spinal Extradural Arachnoid Cyst

Spinal extradural arachnoid cyst (SEDAC) is a cyst in the spinal canal that protrudes into the epidural space from a defect in the dura mater and leads to neurological disturbances. We previously showed that familial SEDAC is caused by FOXC2 mutation; however, the causal gene of sporadic SEDAC has not been identified. To identify the causal gene of sporadic SEDAC, we performed whole exome sequencing for 12 subjects with sporadic SEDAC and identified heterozygous HOXD4 loss-of-function mutations in three subjects. HOXD4 haplo-insufficiency causes SEDAC and a transcriptional network containing HOXD4 and FOXC2 is involved in the development of the dura mater and the etiology of SEDAC.

Progression rate of myelopathy in X-linked adrenoleukodystrophy heterozygotes

X-linked adrenoleukodystrophy heterozygote women can present adult onset myeloneuropathy and little is known about its natural history. We aimed to describe the progression rate of the neurological impairment in the prospective follow-up of our cohort and to look for prognostic factors. The neurological scales Japanese Orthopaedic Association (JOA) and Severity Score System for Progressive Myelopathy (SSPROM) were applied at baseline in 29 symptomatic carriers and in follow-up visits. Age at onset, disease duration, X inactivation pattern, determination of the allele expressed, plasma levels of the very long chain fatty acids and of the neuron-specific enolase, and somato-sensory evoked potentials, were taken at baseline. The slope of the linear regression of both JOA and SSPROM versus disease duration since the first symptom was estimated using mixed modeling. JOA and SSPROM decreased 0.42 and 1.87 points per year, respectively (p < 0.001). None of the parameters under study influenced these rates. We estimated that the number of carriers per arm needed in a future 12 month trial with 80% power and a 50% reduction in disease progression would be 225 women for JOA and 750 for SSPROM. The progression rates of the studied neurological scales were small, did not depend on any modifier factor known, and reflected the characteristically slow worsening of symptoms in X-ALD heterozygotes. Better biomarkers are still necessary for future studies.

A case of myelopathy, myopathy, peripheral neuropathy and subcortical grey matter degeneration associated with recessive compound heterozygous POLG1 mutations

This 54year old woman presented with symptoms of sensory ataxic neuropathy, with cerebellar features. She developed further weakness, visual disturbances with diplopia, dysarthria and dysphasia. After her death at 66years, she was found to have compound heterozygous mutations of POLG1 gene in muscle, and Southern blot showed low levels of multiple deletions of mitochondrial DNA. Neuropathological examination showed profound dorsal column and dorsal spinocerebellar tract degeneration, degeneration of dorsal root ganglia and Clarke's nucleus in spinal cord and severe predominantly sensory peripheral neuropathy. The brain showed severe neuronal loss and gliosis in substantia nigra, medial posterior thalamus and head of caudate. Excess numbers of COX-negative fibres and "ragged-red" fibres were found in five skeletal muscles sampled.

Genome-wide association studies for multiple diseases of the German Shepherd Dog

The German Shepherd Dog (GSD) is a popular working and companion breed for which over 50 hereditary diseases have been documented. Herein, SNP profiles for 197 GSDs were generated using the Affymetrix v2 canine SNP array for a genome-wide association study to identify loci associated with four diseases: pituitary dwarfism, degenerative myelopathy (DM), congenital megaesophagus (ME), and pancreatic acinar atrophy (PAA). A locus on Chr 9 is strongly associated with pituitary dwarfism and is proximal to a plausible candidate gene, LHX3. Results for DM confirm a major locus encompassing SOD1, in which an associated point mutation was previously identified, but do not suggest modifier loci. Several SNPs on Chr 12 are associated with ME and a 4.7 Mb haplotype block is present in affected dogs. Analysis of additional ME cases for a SNP within the haplotype provides further support for this association. Results for PAA indicate more complex genetic underpinnings. Several regions on multiple chromosomes reach genome-wide significance. However, no major locus is apparent and only two associated haplotype blocks, on Chrs 7 and 12 are observed. These data suggest that PAA may be governed by multiple loci with small effects, or it may be a heterogeneous disorder.

[Effect of acupotomy lysis on hypothalamic POMC mRNA and PPE mRNA expression in rats with 3rd lumbar vertebrae transverse process syndrome]

OBJECTIVE

To observe the effect of acupotomy lysis (AL) on hypothalamic proopiomelanocortin (POMO) mRNA and preproenkephalin (PPE) mRNA expression in rats with the third lumbar vertebrae transverse process syndrome (TLVTPS) so as to study its underlying mechanism in relieving symptoms of lumbar muscle strain.

METHODS

Twenty-four SD rats were randomly divided into normal control group, model group, AL group and electroacupunture (EA) group. The TLVTPS model was established by inserting a piece of gelatin sponge into the posterior of the left 3rd lumbar vertebrae transverse process. AL and EA were applied to the left "Shenshu"(BL 23) and "Yaoyangguan" (GV 3) respectively. The POMC mRNA and PPE mRNA expression levels in the hypothalamus were detected by in situ hybridization.

RESULTS

In comparison with the normal group, the integrated optical density (IOD) values of hypothalamic POMC mRNA and PPE mRNA positive cells in the model group were increased significantly (P < 0.01); while compared with the model group, those of POMC mRNA and PPE mRNA positive cells in both left and right hypothalamus were increased further considerably in both AL and EA groups (P < 0.01). No significant differences were found between AL and EA groups in POMC mRNA and PPE mRNA expression levels (P > 0.05).

CONCLUSION

AL and EA therapies can increase the expression of POMC mRNA and PPE mRNA in hypothalamus in rats with TLVTPS, which may contribute to its effect in relieving pain in the treatment of lumbar muscle strain.

Drosophila melanogaster as a model organism of brain diseases

Drosophila melanogaster has been utilized to model human brain diseases. In most of these invertebrate transgenic models, some aspects of human disease are reproduced. Although investigation of rodent models has been of significant impact, invertebrate models offer a wide variety of experimental tools that can potentially address some of the outstanding questions underlying neurological disease. This review considers what has been gleaned from invertebrate models of neurodegenerative diseases, including Alzheimer’s disease, Parkinson’s disease, metabolic diseases such as Leigh disease, Niemann-Pick disease and ceroid lipofuscinoses, tumor syndromes such as neurofibromatosis and tuberous sclerosis, epilepsy as well as CNS injury. It is to be expected that genetic tools in Drosophila will reveal new pathways and interactions, which hopefully will result in molecular based therapy approaches.

Impairments in fast axonal transport and motor neuron deficits in transgenic mice expressing familial Alzheimer's disease-linked mutant presenilin 1

Presenilins (PS) play a central role in gamma-secretase-mediated processing of beta-amyloid precursor protein (APP) and numerous type I transmembrane proteins. Expression of mutant PS1 variants causes familial forms of Alzheimer's disease (FAD). In cultured mammalian cells that express FAD-linked PS1 variants, the intracellular trafficking of several type 1 membrane proteins is altered. We now report that the anterograde fast axonal transport (FAT) of APP and Trk receptors is impaired in the sciatic nerves of transgenic mice expressing two independent FAD-linked PS1 variants. Furthermore, FAD-linked PS1 mice exhibit a significant increase in phosphorylation of the cytoskeletal proteins tau and neurofilaments in the spinal cord. Reductions in FAT and phosphorylation abnormalities correlated with motor neuron functional deficits. Together, our data suggests that defects in anterograde FAT may underlie FAD-linked PS1-mediated neurodegeneration through a mechanism involving impairments in neurotrophin signaling and synaptic dysfunction.

Interferon beta-1b exacerbates multiple sclerosis with severe optic nerve and spinal cord demyelination

To evaluate the effect of interferon beta-1b (IFNB-1b) on multiple sclerosis (MS) with severe optic nerve and spinal cord demyelination, we examined the relationship between IFNB-1b treatment outcome and the clinical and genetic characteristics of three types of demyelinating diseases of the central nervous system, i.e., neuromyelitis optica (NMO), MS and MS with severe optic-spinal demyelination. Japanese MS frequently carried HLA DPB1*0501, which is associated with NMO. MS with DPB1*0501 showed severe optic-spinal demyelination represented by longitudinally extensive spinal cord lesion, blindness and CSF pleocytosis. IFNB-1b treatment did not succeed in these patients because of the increase of optic nerve and spinal cord relapse and other severe side effects. IFNB-1b should not be administered to demyelinating patients with genetic and clinical characteristics mimicking NMO such as HLA DPB1*0501 allele, longitudinally extensive spinal cord lesion, blindness and CSF pleocytosis even if they have symptomatic cerebral lesions as typically seen in MS. The present study strongly suggests that these patients should be diagnosed as having NMO.

Comparative analysis of cytokine gene expression in cerebrospinal fluid of horses without neurologic signs or with selected neurologic disorders

OBJECTIVE

To determine gene transcription for cytokines in nucleated cells in CSF of horses without neurologic signs or with cervical stenotic myelopathy (CSM), West Nile virus (WNV) encephalitis, equine protozoal myeloencephalitis (EPM), or spinal cord trauma.

ANIMALS

41 horses (no neurologic signs [n = 12], CSM [8], WNV encephalitis [9], EPM [6], and spinal cord trauma [6]).

PROCEDURES

Total RNA was extracted from nucleated cells and converted into cDNA. Gene expression was measured by use of real-time PCR assay and final quantitation via the comparative threshold cycle method.

RESULTS

Cytokine genes expressed by nucleated cells of horses without neurologic signs comprised a balance between proinflammatory tumor necrosis factor-alpha (TNF-alpha), anti-inflammatory cytokines (interleukin [IL]-10 and transforming growth factor [TGF]-beta), and Th1 mediators (interferon [IFN]-gamma). Cells of horses with CSM mainly expressed genes for TNF-alpha, TGF-beta, and IL-10. Cells of horses with WNV encephalitis mainly expressed genes for IL-6 and TGF-beta. Cells of horses with EPM mainly had expression of genes for IL-6, IL-8, IL-10, TNF-alpha, IFN-gamma, and TGF-beta. Cells from horses with spinal cord trauma had expression mainly for IL-6; IFN-gamma; TGF-beta; and less frequently, IL-2, IL-10, and TNF-alpha. Interleukin-8 gene expression was only detected in CSF of horses with infectious diseases.

CONCLUSIONS AND CLINICAL RELEVANCE

Despite the small number of CSF samples for each group, results suggest distinct gene signatures expressed by nucleated cells in the CSF of horses without neurologic signs versus horses with inflammatory or traumatic neurologic disorders.

Progressive white matter pathology in the spinal cord of transgenic mice expressing mutant (P301L) human tau

Transgenic mice expressing mutant (P301L) tau develop paresis, neurofibrillary tangles and neuronal loss in spinal motor neurons beginning at 4 to 6 months of age. Astrocytes and oligodendrocytes acquire filamentous tau inclusions at later ages. Here we report pathology in the spinal white matter of these animals. Progressive white matter pathology, detected as early as 2 months of age, was most marked in lateral and anterior columns, with sparing of posterior columns until late in the disease. Early changes in Luxol fast blue/periodic acid Schiff (LFB/PAS) and toluidine blue stained sections were vacuolation of myelin followed by accumulation of myelin figures within previous axonal tubes and finally influx of PAS-positive macrophages. Myelin debris and vacuoles were found in macrophages. At the ultrastructural level, myelinated axons showed extensive vacuolation of myelin sheaths formed by splitting of myelin lamellae at the intra-period line, while axons were atrophic and contained densely packed neurofilaments. Other axons were lost completely, resulting in collapse and phagocytosis of myelin sheaths. Also present were spheroids derived from swollen axons with thin myelin sheaths containing neurofilaments, tau filaments and degenerating organelles. Many oligodendrocytes had membrane-bound cytoplasmic bodies composed of tightly stacked lamellae capped by dense material. The vacuolar myelopathy in this model to some extent resembles that reported in acquired immune deficiency syndrome and vitamin B12 deficiency. The progressive axonal pathology is most consistent with a dying-back process caused by abnormal accumulation of tau in upstream neurons, while vacuolar myelinopathy may be a secondary manifestation of neuroinflammation.

Reversible nitrous oxide myelopathy and a polymorphism in the gene encoding 5,10-methylenetetrahydrofolate reductase

We present a case of a patient who received nitrous oxide on two occasions within a period of 8 weeks and who subsequently developed a diffuse myelopathy, characterized by upper extremity paresis, lower extremity paraplegia and neurogenic bladder. Laboratory testing revealed hyperhomocysteinaemia and low levels of vitamin B(12). Because of this uncommon clinical presentation, we analysed the patient's DNA, and found a polymorphism in the MTHFR gene that is associated with the thermolabile isoform of the 5,10-methylenetetrahydrofolate reductase enzyme, which explained the myelopathy experienced by the patient after being exposed to nitrous oxide. Soon after initiating supplementary therapy with folic acid and vitamin B(12), the neurological symptoms subsided.

Mutational screening of theCYP26A1 gene in patients with caudal regression syndrome

BACKGROUND

The retinoic acid (RA)-catabolizing enzyme Cyp26a1 plays an important role in protecting tailbud tissues from inappropriate exposure to RA. Cyp26a1-null animals exhibit caudal agenesis and spina bifida, imperforate anus, agenesis of the caudal portions of the digestive and urogenital tracts, and malformed lumbosacral skeletal elements. This phenotype closely resembles the most severe form of caudal agenesis in humans. In view of these findings, we investigated a potential involvement of the human CYP26A1 gene in the pathogenesis of caudal regression syndrome (CRS).

METHODS

Mutational screening of 49 CRS patients and 132 controls was performed using denaturing high-performance liquid chromatography and sequencing. Differences in the genotype and allele frequency of each SNP were evaluated by chi(2) analysis. The biological significance of the intronic variants was investigated by transfection assays of mutant constructs and by analysis of the splicing patterns with RT-PCR.

RESULTS

Mutational screening allowed us to identify 6 SNPs, 4 of which (447 C>G, 1134 G>A, IVS 1+10 G>C, and IVS 4+8 AG>GA) are new. In addition, we describe a novel 2-site haplotype consisting of the 2 intronic SNPs. Both single-locus and haplotype analyses revealed no association with increased risk for CRS. The consequences of the 2 intronic polymorphisms on the mRNA splicing process were also investigated. Moreover, using functional and computational methods we demonstrated that both of these intronic polymorphisms affect the intron splicing efficiency.

CONCLUSIONS

Our research did not provide evidence that CYP26A1 has implications for the pathogenesis of human CRS. However, the relationship between CRS risk and the CYP26A1 genotype requires further study with a larger number of genotyped subjects.

Aspartoacylase gene knockout results in severe vacuolation in the white matter and gray matter of the spinal cord in the mouse

Canavan disease (CD) is a neurodegenerative disorder characterized by the spongy degeneration of the white matter of the brain. Aspartoacylase (ASPA) gene mutation resulting enzyme deficiency is the basic cause of CD. Whether the ASPA defect in CD affects the spinal cord has been investigated using the ASPA gene knockout mouse. Luxol fast blue-hematoxylin and eosin staining in the spinal cord of the knockout mouse showed vacuolation in both white matter and gray matter areas of cervical, thoracic, lumbar, and sacral segments of the spinal cord. However, more vacuoles were seen in the gray matter than the white matter of the spinal cord. ASPA activity in the cervical, thoracic, lumbar, and sacrococcygeal regions of the spinal cord was significantly lower in the knockout mouse compared to the wild type. The enzyme defect in the knockout mouse was also confirmed using the Western blot method. These observations suggest that the ASPA gene defect in the mouse leads to spinal cord pathology, and that these changes may be partly involved in the cause of the physiological/behavioral abnormalities seen in the knockout mouse, if documented also in patients with CD.

Analysis of the mitochondrial genome of cheetahs (Acinonyx jubatus) with neurodegenerative disease

The complete mitochondrial genome of Acinonyx jubatus was sequenced and mitochondrial DNA (mtDNA) regions were screened for polymorphisms as candidates for the cause of a neurodegenerative demyelinating disease affecting captive cheetahs. The mtDNA reference sequences were established on the basis of the complete sequences of two diseased and two nondiseased animals as well as partial sequences of 26 further individuals. The A. jubatus mitochondrial genome is 17,047-bp long and shows a high sequence similarity (91%) to the domestic cat. Based on single nucleotide polymorphisms (SNPs) in the control region (CR) and pedigree information, the 18 myelopathic and 12 non-myelopathic cheetahs included in this study were classified into haplotypes I, II and III. In view of the phenotypic comparability of the neurodegenerative disease observed in cheetahs and human mtDNA-associated diseases, specific coding regions including the tRNAs leucine UUR, lysine, serine UCN, and partial complex I and V sequences were screened. We identified a heteroplasmic and a homoplasmic SNP at codon 507 in the subunit 5 (MTND5) of complex I. The heteroplasmic haplotype I-specific valine to methionine substitution represents a nonconservative amino acid change and was found in 11 myelopathic and eight non-myelopathic cheetahs with levels ranging from 29% to 79%. The homoplasmic conservative amino acid substitution valine to alanine was identified in two myelopathic animals of haplotype II. In addition, a synonymous SNP in the codon 76 of the MTND4L gene was found in the single haplotype III animal. The amino acid exchanges in the MTND5 gene were not associated with the occurrence of neurodegenerative disease in captive cheetahs.

Gene therapy: a primer for neurosurgeons

Gene therapy involves the transfer of genes into cells with therapeutic intent. Although several methods can accomplish this, vectors based on viruses still provide the most efficient approach. For neurosurgical purposes, preclinical and clinical applications in the areas of glioma therapy, spinal neurosurgery, and neuroprotection for treatment of Parkinson's disease and cerebral ischemia are reviewed. In general, therapies applied in the neurosurgical realm have proven relatively safe, despite occasional, well-publicized cases of morbidity and death in non-neurosurgical trials. However, continued clinical and preclinical research in this area is critical, to fully elucidate potential toxicities and to generate truly effective treatments that can be applied in neurological diseases.

Molecular genetic and expression analysis of alpha-tocopherol transfer protein mRNA in German shepherd dogs with degenerative myelopathy

Degenerative Myelopathy (DM) is a progressive neurological disorder of the spinal cord preferentially occurring in German shepherd dogs. The pathogenesis of the disease is unknown. However, there are indications that vitamin E deficiency may be involved in the pathogenesis of DM. Therefore, we analyzed the expression and the nucleotide sequence of the canine alpha-tocopherol transfer protein (alpha Ttp) of German shepherd dogs with DM in order to determine whether a deficiency or a defect of the alpha Ttp could be a primary factor in the pathogenesis of DM, as found in human patients with Ataxia with vitamin E deficiency (AVED). The cDNA of the coding region of the canine alpha Ttp-mRNA was generated from total liver RNA using RT-PCR and 5' RACE technique. We determined the sequence of 707 out of 834 base pairs or 84.8% of the canine alpha Ttp coding region. Sequence comparison of canine alpha Ttp between affected and control dogs revealed no differences in either nucleotide or predicted amino acid sequence. Using Northern blot analysis alpha Ttp-mRNA expression was solely found in the liver of the dogs, rats and humans, while various other organs showed no alpha Ttp-mRNA expression. No significant differences in expression levels of canine alpha Ttp mRNA were found between DM and control dogs. Our data suggest that the canine alpha Ttp gene is unlikely to be involved in the pathogenesis of DM in German shepherd dogs.

Gene therapy for spinal cord injury and disease

An incomplete understanding of the pathological processes involved in neurodegeneration and dysfunction of spinal cord injuries and diseases makes these disorders difficult to treat. Repair of damaged or genetically impaired spinal cord also has been limited by the complexity, cellular heterogeneity, and relative inaccessibility of the tissue. Thus, therapeutic options for the treatment of either chronic spinal cord diseases such as amyotrophic lateral sclerosis or acute spinal cord injuries have been rather limited. Potential new therapeutic targets are being identified as our understanding of the molecular pathology involved in neural injury and regeneration increases. Recent advances in gene transfer techniques have made gene therapy a more realistic and viable strategy for the treatment of a broad range of spinal cord disorders. This review summarizes the current state of knowledge regarding the limitations and recent advances in gene therapy and potential application of this technology toward spinal cord injury and disease.

A new millenium for spinal cord regeneration: growth-associated genes

INTRODUCTION

Neurons surviving spinal cord injury undergo extensive reorganization that may result in the formation of functional synaptic contacts. Many neurons, however, fail to activate the necessary mechanisms for successful regeneration. In this review, we discuss the implications of growth cone genes that we have correlated with successful spinal cord axonal regeneration.

METHOD

Factors that inhibit regeneration, and activation of genes that promote it are discussed.

RESULTS/DISCUSSION

The early progress n understanding mechanisms that seem to promote or inhibit regeneration in the central nervous system may have significant clinical utility in the future.

Mapping of the dysmyelinating murine Hindshaker mutation to a 1.2-cM interval on chromosome 3

Hindshaker (hsh) is a novel, spontaneous, autosomal recessive mouse mutation displaying a myelin deficit, predominantly in the spinal cord. It is characterized by developmentally dependent hypomyelination, first evident at postnatal day (P) 10, followed by progressive but incomplete recovery by P42. Hypomyelination is associated with a decreased number of mature oligodendrocytes, which fail to form complete myelin sheaths. Heterozygotes are phenotypically normal, and the hsh mutation shows considerable variation in penetrance and expression depending on genetic background, indicating the influence of modifying loci. Here, we followed an outcross/backcross breeding strategy in conjunction with genotyping for microsatellites and a novel marker for the gene S100a4. We describe the genomic mapping of the hsh mutation to within a 1.2-cM region near the centromere of mouse chromosome 3. We found that hsh is flanked between D3Mit187 proximally and S100a4 distally. The area containing hsh is gene-rich, with a high proportion of the genes specific to nervous tissue. Identification of the hsh mutation will aid our understanding of processes important in regional control of oligodendrocyte development and myelination.

Differential expression of apoptotic markers in jimpy and in Plp overexpressors: evidence for different apoptotic pathways

Point mutations and duplications of proteolipid protein (PLP) gene in mammals cause dysmyelination and oligodendrocyte cell death. The jimpy mouse, which has a lethal Plp point mutation, is the best characterized of the mutants; transgenic mice, which have additional copies of Plp gene, are less characterized. While oligodendrocyte death is a prominent feature in jimpy, the pathways leading to death have not been investigated in jimpy and Plp overexpressors. Using immunohistochemistry and immunobloting, we examined expression of cleaved caspase-3, Poly (ADP-ribose) polymerase (PARP), caspase-12, and mitochondrial apoptotic markers in spinal cord in jimpy males and Plp overexpressors. Compared to controls, cleaved caspase-3 is increased 10x in jimpy white matter spinal cord, and 3x in Plp overexpressor. In jimpy, the number of cleaved caspase-3 cells far exceeds the number of TUNEL(+) cells. The majority of cleaved caspase-3(+) cells were not TUNEL(+) and these cells exhibited staining in perikarya and in processes. Only 30% of the cleaved caspase-3(+) cells were TUNEL(+) and exhibited both nuclear and perinuclear staining. This observation suggests that activation of caspase-3 begins earlier and overlaps for a period of time with DNA fragmentation. In both Plp mutants, quantitative immunobloting of PARP showed a 45% increase in total as well as cleaved form, indicating that oligodendrocytes die via apoptosis. Most interestingly, cleavage of caspase-12, a caspase associated with unfolded protein response, is dramatically increased in jimpy but not at all in Plp overexpressors. Mitochondrial markers cytochrome c and Bcl-X(L) are upregulated in both Plp mutants but levels of expression are different between mutants, suggesting that apoptosis in these two Plp mutants follows different pathways. In jimpy, mitochondrial apoptotic markers may play a role in amplifying the apoptotic signal. Our data shows for the first time, in vivo, that mutations in Plp gene increase oligodendrocyte death by activating the caspase cascade but the trigger to upregulate this cascade follows different pathways.

[Neurodegenerative diseases of the spinal cord]

Numerous classifications have been applied to describe degenerative diseases of the spinal cord before the era of molecular analysis. The present challenge is to match in an appropriate manner old and new clinical classifications with the results of genetic analysis. This work is now well advanced for spinocerebellar degeneration but needs to be developed for hereditary spastic paraplegia, spinal muscular atrophies and amyotrophic lateral sclerosis. The widening of clinical spectrum observed in hereditary neurodegenerative diseases of the spinal cord raises the question of modulating factors (environmental or genetic). Clinicians in charge of patients with progressive spinal cord signs should bear in mind that the field of degenerative diseases is a moving one and that a degenerative aetiology has to be suspected more widely than in the past.

RNA processing and human disease

Gene expression involves multiple regulated steps leading from gene to active protein. Many of these steps involve some aspect of RNA processing. Diseases caused by mutations that directly affect RNA processing are relatively rare compared with mutations that disrupt protein function. The vast majority of diseases of RNA processing result from loss of function of a single gene due to mutations in cis-acting elements required for pre-messenger RNA (mRNA) splicing. However, a few diseases are caused by alterations in the trans-acting factors required for RNA processing and in the vast majority of cases it is the pre-mRNA splicing machinery that is affected. Clearly, alterations that disrupt splicing of pre-mRNAs from large numbers of genes would be lethal at the cellular level. A common theme among these diseases is that only subsets of genes are affected. This is consistent with an emerging view that different subsets of exons require different sets of cis-acting elements and trans-acting factors.

Spinal xanthomatosis: a variant of cerebrotendinous xanthomatosis

We describe seven Dutch patients from six families with a slowly progressive, mainly spinal cord syndrome that remained for many years the sole expression of cerebrotendinous xanthomatosis (CTX). MRI demonstrated white matter abnormalities in the lateral and dorsal columns of the spinal cord. Post-mortem examination of one of the patients showed extensive myelin loss in these columns. An array of genotypes was found in these patients. We conclude that 'spinal xanthomatosis' is a clinical and radiological separate entity of CTX that should be included in the differential diagnosis of 'chronic myelopathy'.

Posterior column ataxia with retinitis pigmentosa (AXPC1) maps to chromosome 1q31-q32

OBJECTIVE

To establish a genetic linkage between highly polymorphic microsatellite loci and the disease locus responsible for an autosomal recessive neurodegenerative syndrome that causes posterior column ataxia and retinitis pigmentosa.

BACKGROUND

The authors reported previously a genetic syndrome that causes visual impairment, proprioceptive loss, sensory ataxia, and areflexia in affected individuals from a large, inbred family belonging to a sectarian population that has been genetically semi-isolated from mainstream society for several centuries.

METHODS

To find the disease locus responsible for this condition, the authors performed a genome-wide search using genetic loci spaced at 10 to 20-cM intervals spanning human chromosomes (chr) 1-22. Pairwise linkage analysis, multipoint linkage analysis, and haplotype reconstruction were used to delineate the candidate region containing the disease gene.

RESULTS

After testing 226 loci that covered the entire genome, the authors identified a maximum lod score of 8.94 at a recombination fraction of 0.00 for locus D1S2692. Additional analyses placed the disease gene, AXPC1, in an 8.3-cM interval flanked by markers D1S2692 and D1S414 on chr 1q31-q32.

CONCLUSIONS

This study suggests that a single genetic mutation can cause selective degeneration of the posterior columns of the spinal cord and retina. Finding the gene responsible for this syndrome may increase our understanding of the molecular basis of diseases that affect sensory neurons.

[Clinical and molecular genetic analysis of 4 Swiss families with the pure form of hereditary spastic spinal paralysis]

Hereditary spastic paraplegia (HSP) is a rare neurodegenerative disease of the spinal cord with a progressive gait disorder, associated with other neurological abnormalities in the complicated form. A cluster of families with this disorder in the central part of the country has long been known to Swiss neurologists. In the present report, we describe our clinical and molecular findings in four large families originating from this region and suffering from a pure HSP form. Clinical presentation was similar in the four families. The age of onset varied widely from 2 to 70 years with the appearance of a gait disorder, which slowly progressed to wheelchair confinement after 30-70 years. No other neurological abnormality was found except for impairment of the vibration sense and sphincter abnormalities. In three families an association with markers of the SPG4 locus on chromosome 2 was found. In the fourth, the largest one, no linkage could be found with either SPG4, or with the other two known loci, SPG3 on chromosome 14 and SPG6 on chromosome 15. These data demonstrate the genetic heterogeneity in HSP, even in families from the same region. They also suggest the presence of at least one additional locus for the pure form.

An autosomal recessive disorder with posterior column ataxia and retinitis pigmentosa

We report an autosomal recessive form of ataxia that is not allelic to Friedreich's disease in six individuals from a large kindred with family origins traced to a common founder of German-Swiss descent. The disorder begins during early childhood with a concentric contraction of the visual fields and proprioceptive loss. Eventually blindness, a severe sensory ataxia, achalasia, scoliosis, and inanition develop by third decade. Inversion recovery MRIs of the spinal cord in affected individuals demonstrate a hyperintense signal in the posterior columns. Finding the gene responsible for this disorder may aid in our understanding of the mechanisms that cause sensory neuronal degeneration.

Hindshaker, a novel myelin mutant showing hypomyelination preferentially affecting the spinal cord

Animals with spontaneous mutations affecting myelin formation have provided useful information about the genetic and cellular mechanisms regulating normal and abnormal myelination. In this paper we describe a novel murine mutation termed hindshaker (hsh), which is inherited in an autosomal recessive manner. Affected mice are characterised by a variable tremor of the hind end which commences at about 2 weeks of age and largely disappears in animals older than 6 weeks. There is hypomyelination affecting predominantly the spinal cord, although the optic nerves and brain are involved to a much lesser degree. The defect of thinly myelinated and naked axons is maximal at 20 days of age and largely resolves with time so that in the adult most axons are myelinated. The myelin structure appears normal and immunostains for the major proteins. Although the distribution of oligodendrocytes in the spinal cord is similar to normal during the period of hypomyelination, there are fewer mature cells. The hsh mutation appears to delay the maturation of oligodendrocytes, particularly in the spinal cord. Additionally, there is a considerable variation in phenotypic expression and in penetrance when the mutation is expressed on different genetic backgrounds, suggesting the hsh locus is subject to the influence of modifying gene(s). Identification of the hsh gene should identify a factor important in the development of oligodendrocytes, particularly those in the spinal cord.

Vacuolar myelopathy in transgenic mice expressing human immunodeficiency virus type 1 proteins under the regulation of the myelin basic protein gene promoter

Vacuolar myelopathy is a common neurological complication in AIDS patients. The pathogenesis of this spinal cord white matter disease remains unclear and it is still debated whether infection of spinal cord with the human immunodeficiency virus type 1 (HIV-1) is causing the disease. We have generated transgenic mice expressing the entire HIV-1 genome under the regulation of an oligodendrocyte-specific promoter. These mice develop spinal cord vacuolar lesions similar to those found in AIDS patients. This animal model provides in vivo evidence linking the expression of HIV-1 proteins in oligodendrocytes to the spinal cord damage found in vacuolar myelopathy.

Atypical vitamin B12-unresponsive methylmalonic aciduria in sibship with severe progressive encephalomyelopathy: a new genetic disease?

We report on two siblings, a girl of 7 years and a boy of 2 years, who presented in infancy with hypotonia, athetoid movements, myopathy and severe developmental delay. The progressive clinical course was characterized by ophthalmoplegia, pyramidal tract signs, loss of visual contact and failure to thrive. The older sister died at the age of 7 years. The younger brother followed an almost identical clinical course. MRI of the brain revealed bilateral hypodensities and atrophy of the putamen. Neurophysiological investigations were consistent with peripheral neuropathy. Investigations for neurometabolic disorders in urine, plasma and CSF of both patients revealed a consistent increase of methylmalonic acid in urine, plasma and CSF as well as borderline low free GABA in CSF. Except for an inconstant elevation of lactate in the boy, metabolic acidosis, hypoglycaemia, episodic ketoacidosis, or hyperammonaemia, the usual concomitants of organoacidopathies, were absent in both children. Homocystinuria was excluded. Methylmalonic aciduria did not respond to antibiotic treatment, vitamin B12 therapy nor dietary protein restriction. Incorporation of [14C]propionate into protein in cultured fibroblasts was pathologically but inconsistently decreased. Both patients' cell lines showed only minimal response to hydroxocobalamin and normal methylmalonyl-CoA mutase activity.

CONCLUSION

Even though the definitive underlying enzymatic defect in this sibship remains obscure our results suggest a new genetic disorder. This report illustrates that hitherto undescribed metabolic disorders remain to be elucidated even in long investigated areas of intermediary metabolism such as methylmalonic aciduria.