Hereditary Neuropathy Research Articles

HEREDITARY NEUROPATHIES & ALS: P.114 DNAJB2 mutation causes dominant neuromyopathy

DNAJB2 is a J-domain cochaperone best known for its role in proteasomal turnover of client proteins. Two isoforms are produced through alternative splicing: DNAJB2a shows soluble cytosolic and nuclear localization, whereas DNAJB2b is anchored to the ER by a geranylgeranyl anchor. Recessive loss-of-function mutations in DNAJB2 have so far been shown to cause hereditary neuropathy manifesting as distal hereditary motor neuropathy or Charcot–Marie–Tooth disease type 2. We report here molecular characterization of the DNAJB2 mutation c.832T>G (p.Ter278Glyext*83), which was found to segregate with clinically variable neuromyopathy in a single family.

HEREDITARY NEUROPATHIES & ALS: P.116 Determining the utility of the GAITRite walkway to assess foot drop in subjects with CMT1A

Charcot Marie Tooth (CMT) is an inherited progressive peripheral neuropathy characterized by prominent muscle weakness and sensory loss. Typical presentation includes high medial arches and tibialis anterior muscle weakness, which results in foot drop and leads to an increased frequency of falls. For this reason, foot drop is frequently the target of intervention. Reliably quantifying severity of foot drop and tibialis anterior muscle weakness is difficult through observational gait analysis and strength testing.

HEREDITARY NEUROPATHIES & ALS: P.105 An unusual clinical presentation of CTBP1-related syndrome associating muscle dystrophy, cerebellar ataxia and paralytic ileus

Heterozygous CTBP1gene mutation is responsible for autosomal dominant hypotonia, ataxia, developmental delay, and tooth enamel defect syndrome (HADDTS; MIM: 617915). Reports on the detailed phenotype remain scarce. CTBP1 codes a protein that binds to the C-terminus of adenovirus E1A proteins, and it plays a role in genetic regulation during development, serving in chromatin modifying enzymes recruitment to specific areas of the genome. Describing an unusual phenotype including muscle dystrophy we aim to extend the genotype-phenotype correlation in CTBP1-related syndrome.

HEREDITARY NEUROPATHIES & ALS: P.112 Description of muscular involvement in a NEFL-caused neurological disease

Neurofilament light chain (NEFL) protein is one of the neurofilament-core-subunits, forming heterodimers. Toxic neurofilament-accumulation is a hallmark of many neurodegenerative disorders and the potential of NEFL to serve as a serum biomarker in different neurological disorders was investigated. NEFL mutations cause demyelinating, axonal and intermediate forms of Charcot-Marie-Tooth disease (CMT), whereby most of the mutations are dominant missense variants functioning through a gain-of-function mechanism by perturbing neurofilament assembly and organelle transportation in axons. Muscular involvement is described as a clinical feature in CMT2E patients mostly recognized as a secondary effect but overlapping myopathic and neurogenic findings were described in some cases suggesting that NEFL-mutations might be also causative for heterogeneous neuromuscular diseases. However, studies focusing on NEFL-based myopathological changes are still rare. Molecular genetic testing, histopathological, ultra-morphological and muscle proteome studies were done in an 8-year-old boy presenting with muscle weakness, myalgia and cramps. Phenotyping revealed reduced endurance (walking distance <500m), muscle stiffness accompanied by slowly progressive gait disturbances, brisk reflex levels, sensory ataxia, pes cavus, small CMAP, slightly reduced NCV and prolonged distal latencies. CK was 205 U/l. A heterozygous de novo NEFL variant (c310.T>G, p.Phe104Val) was identified. Electron microscopy showed focal Z-band alterations and minicores in some myofibers indicative for myofibrillar disintegration. Proteomic findings are indicative for a vulnerability of proteins beyond cytoskeleton. Our findings provide new morphological and biochemical insights into vulnerability of (proximal) muscle upon the presence of a dominant NEFL missense mutation and support the concept that NEFL might be causative for heterogeneous neuromuscular diseases.

HEREDITARY NEUROPATHIES & ALS: P.115 Analysis of off-target effects of antisense sequence inducing exon skipping in SOD1-linked amyotrophic lateral sclerosis

Mutations in superoxide dismutase 1 (SOD1) are responsible for 20% of familial amyotrophic lateral sclerosis (ALS). Given the toxic gain-of-function role of SOD1, suppressing SOD1 mRNA and protein in the affected tissues is predicted as a promising therapeutic approach. We have previously shown the high efficiency of an adeno-associated virus serotype rh10 vector (AAV10) to mediate exon skipping of the hSOD1 pre-mRNA by expression of exon-2-targeted antisense sequences (AS) embedded in a modified U7 small-nuclear RNA (AAV10-U7-hSOD1) (Biferi et al., 2017).

HEREDITARY NEUROPATHIES & ALS: P.108 First-in-human intrathecal gene transfer study for giant axonal neuropathy: Three-year interim evaluation of safety and efficacy

GAN is a rare pediatric neurodegenerative hereditary neuropathy affecting the central and peripheral nervous system. Recessive GAN mutations cause dysfunction of gigaxonin, a cytoskeletal regulatory protein, leading to progressive sensorimotor and optic neuropathy, CNS involvement and respiratory failure with death by the 2nd to 3rd decade of life. We are conducting a first-in-human intrathecal (IT) AAV9 mediated gene transfer trial for GAN (NCT02362438). This is a single site, phase I, non-randomized, open label dose escalation study.

HEREDITARY NEUROPATHIES & ALS: P.117 The relationship between upper and lower limb function in a cohort of children with Charcot-Marie-Tooth (CMT) disease

Charcot-Marie-Tooth (CMT) is a progressive disease with clinical signs presenting first in the distal lower extremities. Upper limb function in this population is also affected at a later stage of life but it is poorly researched and little is known about hand function limitations and loss of manual dexterity. The purpose of this study is to investigate the possible relationship between upper and lower limb function in a group of children and adolescents. The CMT natural history study at Great Ormond Street Hospital in London has been collecting longitudinal data of more than 120 children and adolescents with CMT (age range 4 to 21 years).

HEREDITARY NEUROPATHIES & ALS: P.110 Development and characterization of in vitro models to test the efficiency of gene therapy approaches in SOD1-linked Amyotrophic lateral sclerosis

Amyotrophic lateral sclerosis (ALS) is a fatal neurodegenerative disease of motor neurons (MNs) that causes skeletal muscle (SM) paralysis. Familial forms of ALS are caused by mutations in superoxide dismutase-1 (SOD1) gene, in 20% of cases. A therapeutic approach for SOD1-linked ALS is to suppress mutant SOD1 mRNA and protein in the affected tissues. We have previously shown that an adeno-associated virus serotype rh10 (AAV10) vector mediating exon skipping of the human SOD1 (hSOD1) pre-mRNA significantly reduces mutant SOD1 expression in SOD1G93A-ALS mice (Biferi et al., 2017). Viral particles were delivered through combined intra-cerebroventricular and systemic injections, efficiently reducing hSOD1 levels in MNs and SM. This approach prolonged survival and restored neuromuscular functions in vivo. In order to understand the tissue-specific contribution to the disease and to characterize the effects of the gene therapy approach in the human pathological context, we have generated in vitro models from patient's dermal fibroblasts (expressing SOD1 mutations: A4V, L144F and G93D). Primary fibroblasts were immortalized and trans-differentiated into myoblasts upon conditional MyoD over-expression, using established protocol. We analyzed SOD1 mRNA and protein expression under physiological condition or upon proteasome inhibition in fibroblasts and differentiated myotubes. We observed a statistical increase of hSOD1 mRNA and protein in patient cells relative to controls, after treatment with the proteasome inhibitor MG132. Proliferation and differentiation properties in myotubes were impaired in SOD1-mutant cells, with more striking effects in the A4V cell line (determining an aggressive disease progression in patients). We are currently testing the AAV-10 mediated gene therapy effects in these in vitro models. Our results will contribute to develop in vitro cellular models to investigate ALS physiopathology and gene therapy approaches.

HEREDITARY NEUROPATHIES & ALS: P.109 Expanding the phenotype of ATP7A-related copper transport diseases: Understanding the pathophysiology of neuropathy and copper metabolism

Genetic disorders related to ATP7A copper transporter includes classical Menkes disease (MD) and its milder form occipital horn syndrome (OHS), and ATP7A-related distal motor neuropathy (DMN). The DMN phenotype was recently described and is thought to be a distinct and clinical isolate phenotype of ATP7A related disorders, with different pathophysiology of MD and OHS. We describe clinical, biochemical, radiological characteristics and functional studies in fibroblast of two patients with a novel ATP7Agene mutation. Two related patients, nephew (patient 1) and uncle (patient 2) with the diagnosis of OHS. Patient 2 presents clinical manifestations of OHS and DMN and worsening of the neuropathy after copper treatment and functional motor recovery after a few weeks of treatment withdrawal. Genetic studies: The patients are hemizygous for c.4236delA (p.K1412NFsX15) in the exon 23 of the ATP7Agene (NM_000052.4). Pathogenic mutations of neuropathies-related genes were ruled out in a genetic panel. Mutations in the ATP7Agene presenting with the association of motor distal neuropathy and clinical features of MD or OHS have not been reported previously. It has been hypothesized that the ATP7A mutations leading to DNM may have a different impact on the function of the protein than those mutations causing MD or OHS phenotype. Further studies in the evaluation of the biological mechanisms of this novel mutation could contribute to a better understanding of the complex pathophysiology of ATP7A related disorders. Supplementation with copper-histidinate seems plausible when plasma copper is low, however, exogenous copper could be also dangerous and lead to cellular intoxication. Treatment with copper-histidinate in patients with OHS and DMN should be cautiously considered and monitored, since different repercussion of mutations in ATPA7 function may determine the copper treatment effect.

AUTOPHAGIC MYOPATHIES / MYOFIBRILLAR MYOPATHIES / DISTAL MYOPATHIES / POMPE DISEASE: P.10 Distal myopathy associated with two novel variants in SPTAN1

The phenotypic spectrum associated with autosomal dominant SPTAN1 variants has evolved since the initial 2008 description of infantile epileptic encephalopathy due to non-truncating mutations. Loss of function variants were reported in association with a central nervous system phenotype without epilepsy in 2018, and with a juvenile onset hereditary motor neuropathy in 2019. Here we report novel SPTAN1 variants in two patients seen in our clinic. The first presented at 9 years old with a history of mild motor and cognitive delays, dysmorphic features and abnormal gait. Examination showed distal leg muscle atrophy and weakness most significant in the ankles. Serum CK was normal; limited EMG was unremarkable but showed no evidence for neuropathy. His family history was non-contributory, and standard genetic testing was non-diagnostic. Whole exome sequencing (WES) at age 11 identified a SPTAN1 variant (c.6657delC/p.Asn2220ThrfsTer44) that was not maternally inherited (father unavailable to test). The second presented to our clinic at age 15, with reported first symptoms of abnormal standing posture and delayed motor milestones noted at 20 months. Based on symptoms of bilateral distal atrophy, pes cavus and foot drop, he was thought to have a distal motor neuropathy. An EMG at age 15 years showed evidence of distal myopathy without evidence of neuropathy; serum CK was normal. There was no family history of similar symptoms, and genetic testing including MYH7 sequencing, FSHD testing and a neuromuscular gene panel, was all negative. Examination at age 22 showed distal weakness with preserved EDB bulk, and WES identified a de novo pathogenic truncating SPTAN1 variant (c.2613delG; p.Lys871AsnfsTer5). Additional follow-up studies (including more extensive EMG and muscle biopsy) are planned, and will be reported. These patients suggest that SPTAN1 variants may be associated with a distal myopathy, expanding the clinical heterogeneity associated with mutations in this gene.

A novel histone deacetylase 6 inhibitor improves myelination of Schwann cells in a model of Charcot-Marie-Tooth disease type 1A.

Charcot-Marie-Tooth (CMT) disease is the most common hereditary peripheral neuropathy. CMT type 1A (CMT1A) accounts for approximately 50% of CMT patients and is linked to PMP22 gene duplication. Histone deacetylase-6 (HDAC6) has pleiotropic effects, such as regulating lipid homeostasis and cellular stress. Although HDAC6 has been regarded as a promising drug target for neurodegenerative diseases, its inhibition has not yet been tested in CMT1A. Here we have tested the therapeutic potential of CKD-504, a clinical stage HDAC6 inhibitor, in a mouse model of CMT1A EXPERIMENTAL APPROACH: The potency and selectivity of CKD-504 was evaluated, using a HDAC enzyme panel assay and western blots. The therapeutic potential of CKD-504 was evaluated using behavioural testing and electrophysiological assessments in the C22 mouse model of CMT1A. PMP22 protein expression and aggregation were analysed in mesenchymal stem cell-derived Schwann cells from CMT1A patients and sciatic nerves from C22 mice. The HDAC6 inhibitor, CKD-504, modulated molecular chaperon proteins such as HSP90 and HSP70, which are involved in the folding/refolding of proteins such as PMP22. CKD-504 treatment restored myelination in both mesenchymal stem cell-derived Schwann cells from CMT1A patients and sciatic nerves of C22 mice and improved the axonal integrity of the sciatic nerve, leading to behavioural, electrophysiological, and histological improvements in C22 mice. A novel HDAC6 inhibitor, CKD-504, has potent therapeutic efficacy for CMT1A.

Structural and functional annotation of PR/SET Domain (PRDM) protein family: In-silico study elaborating role of PRDM12 mutation in congenital insensitivity to pain

Congenital insensitivity to pain (CIP), classified as a type of hereditary sensory and autonomic neuropathies, is a rare disease in which the affected individuals fail to perceive sensation of pain. One of the PR/SET Domain Proteins, PRDM12, has been identified in recent past as a candidate gene for congenital insensitivity to pain. In the present study, we performed whole exome sequencing in a Pakistani family with CIP phenotype to ascertain the causative mutation. We identified a previously described alanine repeat duplication in PRDM12 (Ala353_Ala359dup) in this family. After this, we performed structural annotations for PR/SET Domain (PRDM) containing protein family to prognosticate the potential hypothetical structure of PRDM proteins with physical and chemical parameters. Out of nineteen members of this family, four members (PRDM5, PRDM8, PRDM12 and PRDM13) were specially focused because of their role in neurological disorders. Predictions about structure and interactions of these proteins revealed novel interacting molecules and pathways. Detailed in silico analysis of PRDM12 was performed to elaborate importance of its domain structure in interaction with other proteins and its role in pain insensitivity phenotype. These results have substantially enhanced our understanding regarding the etiology of congenital pain insensitivity and would stimulate further research on therapy and prevention.

Orphan Peripheral Neuropathies.

Objectives:Generally, neuropathies of peripheral nerves are a frequent condition (prevalence 2–3%) and most frequently due to alcoholism, diabetes, renal insufficiency, malignancy, toxins, or drugs. However, the vast majority of neuropathies has orphan status. This review focuses on the etiology, frequency, diagnosis, and treatment of orphan neuropathies.Methods:Literature reviewResults:Rareness of diseases is not uniformly defined but in the US an orphan disease is diagnosed if the prevalence is <1:200000, in Europe if <5:10000. Most acquired and hereditary neuropathies are orphan diseases. Often the causative variant has been reported only in a single patient or family, particularly the ones that are newly detected (e.g. SEPT9, SORD). Among the complex neuropathies (hereditary multisystem disorders with concomitant neuropathies) orphan forms have been reported among mitochondrial disorders (e.g. NARP, MNGIE, SANDO), spinocerebellar ataxias (e.g. TMEM240), hereditary spastic paraplegias (e.g UBAP1), lysosomal storage disease (e.g. Schindler disease), peroxisomal disorders, porphyrias, and other types (e.g. giant axonal neuropathy, Tangier disease). Orphan acquired neuropathies include the metabolic neuropathies (e.g. vitamin-B1, folic acid), toxic neuropathies (e.g. copper, lithium, lead, arsenic, thallium, mercury), infectious neuropathies, immune-mediated (e.g. Bruns-Garland syndrome), and neoplastic/paraneoplastic neuropathies.Conclusions:Though orphan neuropathies are rare per definition they constitute the majority of neuropathies and should be considered as some of them are easy to identify and potentially treatable, as clarification of the underlying cause may contribute to the knowledge about etiology and pathophysiology of these conditions, and as the true prevalence may become obvious only if all ever diagnosed cases are reported.

De Novo and Inherited Variants in GBF1 are Associated with Axonal Neuropathy Caused by Golgi Fragmentation

SummaryDistal hereditary motor neuropathies (HMNs) and axonal Charcot-Marie-Tooth neuropathy (CMT2) are clinically and genetically heterogeneous diseases characterized primarily by motor neuron degeneration and distal weakness. The genetic cause for about half of the individuals affected by HMN/CMT2 remains unknown. Here, we report the identification of pathogenic variants in GBF1 (Golgi brefeldin A-resistant guanine nucleotide exchange factor 1) in four unrelated families with individuals affected by sporadic or dominant HMN/CMT2. Genomic sequencing analyses in seven affected individuals uncovered four distinct heterozygous GBF1 variants, two of which occurred de novo. Other known HMN/CMT2-implicated genes were excluded. Affected individuals show HMN/CMT2 with slowly progressive distal muscle weakness and musculoskeletal deformities. Electrophysiological studies confirmed axonal damage with chronic neurogenic changes. Three individuals had additional distal sensory loss. GBF1 encodes a guanine-nucleotide exchange factor that facilitates the activation of members of the ARF (ADP-ribosylation factor) family of small GTPases. GBF1 is mainly involved in the formation of coatomer protein complex (COPI) vesicles, maintenance and function of the Golgi apparatus, and mitochondria migration and positioning. We demonstrate that GBF1 is present in mouse spinal cord and muscle tissues and is particularly abundant in neuropathologically relevant sites, such as the motor neuron and the growth cone. Consistent with the described role of GBF1 in Golgi function and maintenance, we observed marked increase in Golgi fragmentation in primary fibroblasts derived from all affected individuals in this study. Our results not only reinforce the existing link between Golgi fragmentation and neurodegeneration but also demonstrate that pathogenic variants in GBF1 are associated with HMN/CMT2.

Resveratrol Treatment Reduces Neuromotor Impairment and Hearing Loss in a Mouse Model of Diabetic Neuropathy and Nerve Injury

Schwann cells produce myelin sheath around peripheral nerve axons. Myelination is critical for rapid propagation of action potentials, as illustrated by the large number of acquired and hereditary peripheral neuropathies, such as diabetic neuropathy or Charcot-Marie-Tooth diseases, that are commonly associated with a process of demyelination.

FLVCR1-related disease as a rare cause of retinitis pigmentosa and hereditary sensory autonomic neuropathy

FLVCR1 encodes for a transmembrane heme exporter protein and it is known to cause a rare form of syndromic retinitis pigmentosa: posterior column ataxia with retinitis pigmentosa. Recently, the FLVCR1-associated phenotype has been expanded with sporadic reports of hereditary sensory-autonomic neuropathy or non-syndromic retinitis pigmentosa. Here, we report a 23-year- old female with early onset hypomyelinating sensory-autonomic neuropathy and retinitis pigmentosa. Both features were present since childhood. The patient developed signs of advanced retinitis pigmentosa by the age of 10 years leading to legal blindness after the age of 18. Following candidate gene panel testing, which was negative, whole exome sequencing revealed compound heterozygous pathogenic FLVCR1 variants: NM_014053.3: c.3G > T; p.(Met1?) and NM_014053.3: c.730G > A; p.(Gly244Ser), the latter variant is novel. In this report we highlight the association of retinitis pigmentosa with hypomyelinating sensory-autonomic neuropathy, which could be underdiagnosed due to variable severity. To summarize, the phenotypic heterogeneity of FLVCR1 variants is broad and should include retinitis pigmentosa along with range of neurological features.

Altered Sensory Neuron Development in CMT2D Mice Is Site-Specific and Linked to Increased GlyRS Levels.

Dominant, missense mutations in the widely and constitutively expressed GARS1 gene cause peripheral neuropathy that usually begins in adolescence and principally impacts the upper limbs. Caused by a toxic gain-of-function in the encoded glycyl-tRNA synthetase (GlyRS) enzyme, the neuropathology appears to be independent of the canonical role of GlyRS in aminoacylation. Patients display progressive, life-long weakness and wasting of muscles in hands followed by feet, with frequently associated deficits in sensation. When dysfunction is observed in motor and sensory nerves, there is a diagnosis of Charcot-Marie-Tooth disease type 2D (CMT2D), or distal hereditary motor neuropathy type V if the symptoms are purely motor. The cause of this varied sensory involvement remains unresolved, as are the pathomechanisms underlying the selective neurodegeneration characteristic of the disease. We have previously identified in CMT2D mice that neuropathy-causing Gars mutations perturb sensory neuron fate and permit mutant GlyRS to aberrantly interact with neurotrophin receptors (Trks). Here, we extend this work by interrogating further the anatomy and function of the CMT2D sensory nervous system in mutant Gars mice, obtaining several key results: (1) sensory pathology is restricted to neurons innervating the hindlimbs; (2) perturbation of sensory development is not common to all mouse models of neuromuscular disease; (3) in vitro axonal transport of signaling endosomes is not impaired in afferent neurons of all CMT2D mouse models; and (4) Gars expression is selectively elevated in a subset of sensory neurons and linked to sensory developmental defects. These findings highlight the importance of comparative neurological assessment in mouse models of disease and shed light on key proposed neuropathogenic mechanisms in GARS1-linked neuropathy.

Isoform-specific loss of dystonin causes hereditary motor and sensory neuropathy.

ObjectiveTo determine the genetic cause of axonal Charcot-Marie-Tooth disease in a small family with 2 affected siblings, one of whom had cerebellar features on examination.MethodsWhole-exome sequencing of genomic DNA and analysis for recessively inherited mutations; PCR-based messenger RNA/complementary DNA analysis of transcripts to characterize the effects of variants identified by exome sequencing.ResultsWe identified compound heterozygous mutations in dystonin (DST), which is alternatively spliced to create many plakin family linker proteins (named the bullous pemphigoid antigen 1 [BPAG1] proteins) that function to bridge cytoskeletal filament networks. One mutation (c.250C>T) is predicted to cause a nonsense mutation (p.R84X) that only affects isoform 2 variants, which have an N-terminal transmembrane domain; the other (c.8283+1G>A) mutates a consensus splice donor site and results in a 22 amino acid in-frame deletion in the spectrin repeat domain of all BPAG1a and BPAG1b isoforms.ConclusionsThese findings introduce a novel human phenotype, axonal Charcot-Marie-Tooth, of recessive DST mutations, and provide further evidence that BPAG1 plays an essential role in axonal health.

Fatigue in patients with hereditary neuropathy with liability to pressure palsies.

ObjectiveHereditary Neuropathy with Liability to Pressure Palsies (HNPP) is caused by a heterozygous deletion of peripheral myelin protein‐22 (PMP22) gene resulting in focal sensorimotor deficits. Our lab has identified a disruption of myelin junctions in excessively permeable myelin that impairs action potential propagation. This mechanism is expected to cause fatigue in patients with HNPP. Therefore, the objective was to characterize fatigue in patients with HNPP and determine the relationship of fatigue to nerve pathology, disability, and quality of life.MethodsNine females with HNPP participated in a single visit that included genotyping, nerve conduction studies, neurological exam, quantitative magnetic resonance imaging, and a physical therapy exam incorporating upper and lower extremity function and survey measures of fatigue. This visit was followed by 2 weeks of ecological momentary assessment (wrist‐worn device) that captured fatigue ratings five times per day.ResultsParticipants demonstrated mild neurological impairment (CMTNS: 5.7 ± 2.8), yet reported high fatigue levels (average fatigue intensity over 2 weeks: 5.9 out of 10). Higher fatigue levels were associated with poorer quality of life and more pain. Higher fatigue was associated with significantly greater distal nerve proton density changes on peripheral nerve MRI, which is in line with hyper‐permeable myelin in HNPP.InterpretationFatigue is common and severe among patients with HNPP whose disabilities are minimal by conventional outcome measures. Therapeutic interventions targeting fatigue have the potential to improve quality of life and may serve as a robust outcome measure to show longitudinal changes for patients with HNPP.

A missense point mutation in nerve growth factor (NGFR100W) results in selective peripheral sensory neuropathy.

The R100W mutation in nerve growth factor is associated with hereditary sensory autonomic neuropathy V in a Swedish family. These patients develop severe loss of perception to deep pain but with apparently normal cognitive functions. To better understand the disease mechanism, we examined a knockin mouse model of HSAN V. The homozygous mice showed significant structural deficits in intra-epidermal nerve fibers (IENFs) at birth. These mice had a total loss of pain perception at ∼2 months of age and often failed to survive to adulthood. Heterozygous mutant mice developed a progressive degeneration of small sensory fibers both behaviorally and functionally: they showed a progressive loss of IENFs starting at the age of 9 months accompanied with progressive loss of perception to painful stimuli such as noxious temperature. Quantitative analysis of lumbar 4/5 dorsal root ganglia revealed a significant reduction in small size neurons, while analysis of sciatic nerve fibers revealed the heterozygous mutant mice had no reduction in myelinated nerve fibers. Significantly, the amount of NGF secreted from mouse embryonic fibroblasts were reduced from both heterozygous and homozygous mice compared to their wild-type littermates. Interestingly, the heterozygous mice showed no apparent structural alteration in the brain: neither the anterior cingulate cortex nor the medial septum including NGF-dependent basal forebrain cholinergic neurons. Accordingly, these animals did not develop appreciable deficits in tests for brain function. Our study has thus demonstrated that the NGFR100W mutation likely affects the structure and function of peripheral sensory neurons.