Anti-CV2 autoantibodies and paraneoplastic neurological syndromes

Predicting disability and mortality in CV2/CRMP5-IgG associated paraneoplastic neurologic disorders

BACKGROUND

We aimed to investigate the prognostic factors associated with clinical outcomes in CV2/Collapsin response-mediator protein 5 (CRMP5)-IgG paraneoplastic neurologic disorders (PND).

METHODS

This is a retrospective study of patients with CV2/CRMP5-IgG PND evaluated between 2002-2022. We examined the association of clinical variables (including age, clinical phenotype [autoimmune encephalopathy, myelopathy, polyneuropathy/radiculopathy, MG, cerebellar ataxia, chorea, optic neuropathy], cancer) with three clinical outcomes (wheelchair dependence, modified Rankin Scale [mRS], mortality) using univariate logistic regression and Cox proportional hazards modeling. Kaplan-Meier estimates were used to determine the probability of survival.

RESULTS

Twenty-seven patients (56% female) with CV2/CRMP5-IgG PND were identified with a median follow-up of 54 months (IQR = 11-102). An underlying tumor was identified in 15 patients (56%) including small cell lung cancer (SCLC) (8, [53%]), thymoma (4, [27%]), and other histologies (3, [20%]). At last follow-up, 10 patients (37%) needed a wheelchair for mobility and this outcome was associated with myelopathy (HR = 7.57, 95% CI = 1.87-30.64, P = 0.005). Moderate-severe mRS = 3-5 was associated with CNS involvement (encephalopathy, myelopathy, or cerebellar ataxia) (OR = 7.00, 95% CI = 1.18-41.36, P = 0.032). The probability of survival 4 years after symptom onset was 66%. Among cancer subtypes, SCLC (HR = 18.18, 95% CI = 3.55-93.04, P < 0.001) was significantly associated with mortality, while thymoma was not.

INTERPRETATION

In this retrospective longitudinal study of CV2/CRMP5-IgG PND, patients with CNS involvement, particularly myelopathy, had higher probability of disability. SCLC was the main determinant of survival in this population.

An overview on CV2/CRMP5 antibody-associated paraneoplastic neurological syndromes

Paraneoplastic neurological syndrome refers to certain malignant tumors that have affected the distant nervous system and caused corresponding dysfunction in the absence of tumor metastasis. Patients with this syndrome produce multiple antibodies, each targeting a different antigen and causing different symptoms and signs. The CV2/collapsin response mediator protein 5 (CRMP5) antibody is a major antibody of this type. It damages the nervous system, which often manifests as limbic encephalitis, chorea, ocular manifestation, cerebellar ataxia, myelopathy, and peripheral neuropathy. Detecting CV2/CRMP5 antibody is crucial for the clinical diagnosis of paraneoplastic neurological syndrome, and anti-tumor and immunological therapies can help to alleviate symptoms and improve prognosis. However, because of the low incidence of this disease, few reports and no reviews have been published about it so far. This article intends to review the research on CV2/CRMP5 antibody-associated paraneoplastic neurological syndrome and summarize its clinical features to help clinicians comprehensively understand the disease. Additionally, this review discusses the current challenges that this disease poses, and the application prospects of new detection and diagnostic techniques in the field of paraneoplastic neurological syndrome, including CV2/CRMP5-associated paraneoplastic neurological syndrome, in recent years.

Paraneoplastic myelitis associated with durvalumab treatment for extensive-stage small cell lung cancer

Paraneoplastic neurologic syndromes(PNSs) caused by immune checkpoint inhibitors(ICIs) is rare and requires clinicians to differentiate between disease progression and immune-related adverse effects(irAEs). We hereby report the case of immune-related myelitis accompanied by positive paraneoplastic autoantibodies following durvalumab treatment for extensive-stage small cell lung cancer (ES-SCLC). A 70-year-old Chinese woman with ES-SCLC was administered durvalumab with etoposid-platinum(EP) as first-line treatment. Four cycles after treatment with EP plus ICI, she developed immune-related myelitis with positive paraneoplastic autoantibodies (CV2, SOX1, ZIC4). Spinal MRI showed diffuse abnormal signal shadow in the cervicothoracic spinal cord. She was discontinued for chemotherapy, and treated with high-dose steroids, intravenous immunoglobulin and plasmapheresis, maintenance therapy with steroids resulted in a favorable neurologic outcome. This is the first report of durvalumab-related PNSs. We supposed that the development of paraneoplastic myelitis was causally related to immune activation by durvalumab. Prompt diagnosis and therapeutic intervention are essential for the effective treatment of paraneoplastic myelitis.

Paraneoplastic optic neuropathy secondary to adenocarcinoma of the lung

We describe an uncommon cause of paraneoplastic optic neuropathy in adenocarcinoma of the lung. A 45-year-old healthy woman presented with seizure and encephalitis, followed by an acute visual loss in both eyes for 1 week. Her visual acuity was no perception of light in the right eye and hand movement in the left eye. There was a generalised restriction of extraocular muscle movements in both eyes. Funduscopy showed a bilateral pale optic disc. A paraneoplastic antigen autoimmune profile showed a positive anti-CV2/CRMP-5 antibody. CT of the thorax revealed the presence of right apical lung mass, confirmed to be adenocarcinoma through a biopsy. She was scheduled for lung lobectomy and chemotherapy. Unfortunately, her health deteriorated and she passed away eventually.

Serum Biomarkers in Neuro-Ophthalmology: When to Test

Discovery and characterization of serologic biomarkers has revolutionized the diagnostic framework of systemic and paraneoplastic autoimmune neuro-ophthalmic diseases. Expanding recognition of the multiple ocular and visual manifestations of these conditions highlights the important role of the referring provider in identifying potential cases. Increasing ease of access to serologic testing also enables these practitioners to initiate the diagnostic work-up in suspected cases. We aimed to provide an update on the current knowledge surrounding and use of relevant autoimmune biomarkers by correlating specific clinical neuro-ophthalmic manifestations with autoantibody biomarkers. The utility of select biomarkers for myasthenia gravis, neuromyelitis optica spectrum disorder, myelin oligodendrocyte glycoprotein-IgG-associated disorder, opsoclonus-myoclonus syndrome, anti-collapsin-response mediator protein-5 optic neuropathy, and glial fibrillary acidic protein-IgG-associated disease are discussed with particular focus on the clinical contexts in which to consider testing.

Anti-CV2/CRMP5 antibody-associated hemorrhagic leukoencephalomyelitis treated with steroids, intravenous immunoglobulin, plasmapheresis, and cyclophosphamide

Anti-CV2 or anti-collapsing response-mediator protein-5 (CRMP5) autoantibodies (anti-CV2/CRMP5-Ab) are associated with various paraneoplastic neurological disorders. The best therapy is typically removal of the underlying cancer. We describe a previously healthy elderly male who had no known malignancy. He presented with a demyelinating encephalomyelitis and later developed hemorrhagic changes on neuroimaging. He was treated with intravenous immunoglobulin (IVIG), intravenous steroids, and plasmapheresis; however, sustained clinical and radiographic stabilization and improvement only occurred following cyclophosphamide. He unexpectedly died of a cardiac arrest. postmortem, his serum paraneoplastic screen was found to be weakly positive for anti-CV2/CRMP5-Ab.

Collapsin Response-Mediator Protein 5-Associated Retinitis, Vitritis, and Optic Disc Edema

PURPOSE

Collapsin response-mediator protein 5 (CRMP5) immunoglobulin G (IgG) has been associated with paraneoplastic optic neuritis, vitritis, retinitis, or a combination thereof, but few reports of these findings exist in the literature. We reviewed the neuro-ophthalmic findings and visual outcomes in a large series of CRMP5 IgG-positive patients to characterize further its clinical phenotype and response to treatment.

DESIGN

Retrospective case series.

PARTICIPANTS

Seventy-six patients with CRMP5 autoimmunity examined at the Mayo Clinic, Rochester, Minnesota.

METHODS

Single academic medical center chart review of all CRMP5 IgG-positive (serum titer, >1:240) patients seen between 2001 and 2017.

MAIN OUTCOME MEASURES

Neuro-ophthalmic manifestations and outcomes of CRMP5 autoimmunity, coexisting neural autoantibody presence and paraneoplastic associations, and the impact of immunosuppressant therapy.

RESULTS

Twenty-nine of 76 patients (38%) demonstrated neuro-ophthalmic manifestations. Of the 29 patients with neuro-ophthalmic findings, the median age was 67 years (range, 33-88 years) and 20 (69%) were women. Cancer was diagnosed in 62% of the patients (small-cell carcinoma in 83%). Neuro-ophthalmic symptoms occurred before the diagnosis of cancer in 72%. Seventeen of 29 patients (59%) showed ocular (i.e., anterior visual pathway or intraocular) manifestations; presenting median visual acuity was 20/50 (range, 20/20-counting fingers) and the final median visual acuity was 20/40 (range, 20/20-hand movements). Fourteen of 17 patients (82%) demonstrated optic neuropathy, with 12 of these patients also showing retinitis or uveitis. Three of 17 patients (18%) showed retinitis or uveitis without optic neuropathy. All 12 patients with optic neuropathy and a documented fundus examination at visual symptom onset demonstrated optic disc edema. No patients showed optic nerve enhancement on magnetic resonance imaging. Twelve of 29 patients (41%) demonstrated ocular motility dysfunction consisting of central nystagmus and diplopia. Among those receiving immunosuppressive therapy, visual function improved in 50%.

CONCLUSIONS

In our cohort of 29 CRMP5 IgG-positive patients with neuro-ophthalmic manifestations, optic neuropathy presented with optic disc edema, often associated with uveitis, retinitis, or both. The combination of retinitis, vitritis, and optic disc edema without optic nerve enhancement should prompt serologic testing for CRMP5 IgG to expedite vision-sparing immunosuppressant therapy and a targeted search for a systemic cancer.

Diagnosing autoimmune encephalitis based on clinical features and autoantibody findings

INTRODUCTION

Autoimmune encephalitides have been accepted as a reproducible and treatable new group of diseases. At present, there is concern that such diagnoses might be made too liberally. Areas covered: This article suggests how to make valid diagnoses. They should consist of three elements: the clinical syndrome, the associated antibody and the presumed cause or predisposition. Recently, an international consortium published formal clinical criteria for autoimmune encephalitides to enable diagnoses even if antibody testing is not (immediately) available and to prevent overinterpretation of questionable antibody results. Antibody testing has greatly benefitted from the introduction of cell-based assays for the demonstration of antibodies against surface antigens. Paraneoplastic or post-infectious situations, side effects of tumor therapies or genetic predispositions help to explain why a patient develops autoimmune encephalitis. Expert opinion: With the application of this three-fold diagnostic system, clinicians can counsel patients regarding therapy and prognosis, while researchers can form meaningful patient cohorts. An operationalization of criteria would be advantageous.

Immune-mediated ataxias

Immune-mediated cerebellar ataxia (CA) comprises a group of rare diseases that are still incompletely described, and are probably underdiagnosed. Both acute and progressive progressions are possible. Different syndromes have been identified, including CA associated with anti-GAD antibodies, the cerebellar type of Hashimoto encephalopathy, primary autoimmune CA, gluten ataxia, opsoclonus-myoclonus syndrome, and paraneoplastic cerebellar degenerations. Most of these syndromes are associated with autoantibodies targeting neuronal antigens. Additionally, autoimmune CA can be triggered by infections, especially in children, and in rare cases occur in the context of an autoimmune multisystem disease, such as systemic lupus erythematosus, sarcoidosis, or Behçet disease. A careful workup is needed to distinguish autoimmune CA from other causes. In adults, a paraneoplastic origin must be ruled out, especially in cases with subacute onset. Neurologic outcome in adults is frequently poor, and optimal therapeutic strategies remain ill defined. The outcome in children is in general good, but children with a poor recovery are on record. The precise pathophysiologic mechanisms even in the presence of detectable autoantibodies are still largely unknown. Further research is needed on both the clinical and mechanistic aspects of immune-mediated CA, and to determine optimal therapeutic strategies.

Autoimmune CRMP5 neuropathy phenotype and outcome defined from 105 cases

Objective

To establish the phenotype and clinical outcomes of collapsin response-mediator protein-5 (CRMP5) autoimmune neuropathy in comparison with anti-neuronal nuclear antibody type 1 (ANNA1)–immunoglobulin G (IgG) neuropathy.

Methods

Patients with CRMP5-IgG and/or ANNA1-IgGs were identified in our service-line testing, and medical records were reviewed.

Results

One hundred five patients with CRMP5-IgG neuropathy (88% smokers; 69% having cancer, most commonly small cell lung cancer [75%]) were identified and compared to 51 patients with ANNA1-IgG neuropathy, 27 with coexisting CRMP5-IgG. Patients with CRMP5 had painful axonal polyradiculoneuropathy (65%), mostly asymmetric onset (84%), with neuropathy predating cancer diagnosis by 185 days (range 60–540 days). Most cases (79%) had moderate to severe neuropathic pain, all on neuropathic medications (median 2, range 1–4), opioids in 39%. Nerve biopsies (n = 2) showed microvascular inflammation with axonal degeneration. Compared to ANNA1 alone, CRMP5 neuropathy has a higher prevalence of pain (79% vs 46%, p = 0.008), asymmetric polyradiculoneuropathy (54% vs 12%, p < 0.001), and inflammatory spinal fluids (elevated CSF protein or nucleated cell count 92% vs 60%, p = 0.022). Cerebellar ataxia (21%), myelopathy (19%), and optic neuritis and/or retinitis (11%) were common neurologic accompaniments. CRMP5 cases had significant pain reduction by immunotherapy (p < 0.001). Specifically, high-dose corticosteroid administration was associated with improvement/stabilization in neuropathy impairment scores (p = 0.012) (Class IV). Patients with CRMP5 had better 5-year survival than patients with ANNA1 (67% vs 32%, p = 0.012).

Conclusion

Painful axonal asymmetric polyradiculoneuropathy is established as the major CRMP5 autoimmune neuropathy presentation and is distinguishable from other paraneoplastic neuropathies, including by ANNA1 autoimmunity. Patients with this phenotype should be prompted for CRMP5-IgG testing to assist in early cancer diagnosis.

Anti-collapsin response mediator protein 5 encephalitis masquerading as a low-grade brain tumour

A 71-year-old woman presented acutely with seizures; her MRI suggested a low-grade glioma of the right temporal lobe. Over the preceding 18 months, she had developed progressive limb chorea and orofacial dyskinesia. Examination showed a predominantly amnestic cognitive profile. Initial investigations were normal, but later she was found to have antibodies to collapsin response mediator protein 5 (also called CV2). Her symptoms and neuroimaging abnormalities gradually improved without treatment. Four months later, surveillance imaging with (18)F-fluorodeoxyglucose-positron-emission tomography revealed a lesion confirmed by biopsy as a TX, N2, M0 small-cell lung cancer. This case is unusual for the strikingly unilateral neuroimaging abnormalities, which led to an initial misdiagnosis, and the spontaneous symptomatic improvement without treatment. In retrospect, the co-occurrence of paraneoplastic chorea, limbic encephalitis and neuropathy in the presence of an occult lung tumour make this almost a 'full house' of symptoms associated with antibodies to collapsin response mediator protein 5. It underlines the importance in clinical reasoning of avoiding the cognitive errors of premature closure and anchoring.

A case of severe chronic progressive axonal polyradiculoneuropathy temporally associated with anti-CV2/CRMP5 antibodies

OBJECTIVES

The involvement of the peripheral nervous system by anti-CV2/CRMP5 paraneoplastic antibodies is typically encountered as a mixed sensorimotor polyneuropathy. We report a fatal case of severe chronic progressive axonal polyradiculoneuropathy in association with this antibody.

METHODS

Review of the patient's chart, nerve conduction/electromyographic studies, and nerve biopsy.

RESULTS

A 51-year-old man presented with a progressive quadriparesis over a 4-month period. Extensive evaluation for potential etiologies was significant only for positive anti-CV2/CRMP5 antibodies without detection of an underlying neoplasm. Despite multiple immunomodulatory therapies, the patient progressed and demonstrated electrodiagnostic evidence for a chronic axonal polyradiculoneuropathy with ongoing denervation. The patient eventually died of respiratory failure.

CONCLUSIONS

This case adds to the clinical spectrum of the peripheral nervous system involvement in patients with paraneoplastic anti-CV2/CRMP5 antibodies.

Paraneoplastic disorders of the central and peripheral nervous systems

Paraneoplatic neurologic syndromes (PNS) have been seminally defined as acute or subacute neurological syndromes resulting from nervous system dysfunction that is remote from the site of a malignant neoplasm or its metastases. However, in respect to our current understanding of their pathogenesis we may redefine these disorders as cancer-related dysimmune neurologic syndromes. We first deal with the epidemiology and the pathogenesis of PNS, then the different classic PNS are reviewed with clinical features according to the associated onconeuronal antibodies. Finally, therapeutic approaches are discussed.

Insights into the oligomerization of CRMPs: crystal structure of human collapsin response mediator protein 5

Collapsin response mediator protein-5 (CRMP-5) is the latest identified member of the CRMP cytosolic phosphoprotein family, which is crucial for neuronal development and repair. CRMPs exist as homo- and/or hetero-tetramers in vivo and participate in signaling transduction, cytoskeleton rearrangements, and endocytosis. CRMP-5 antagonizes many of the other CRMPs' functions either by directly interacting with them or by competing for their binding partners. We determined the crystal structures of a full length and a truncated version of human CRMP-5, both of which form a homo-tetramer similar to those observed in CRMP-1 and CRMP-2. However, solution studies indicate that CRMP-5 and CRMP-1 form weaker homo-tetramers compared with CRMP-2, and that divalent cations, Ca(2+) and Mg(2+), destabilize oligomers of CRMP-5 and CRMP-1, but promote CRMP-2 oligomerization. On the basis of comparative analysis of the CRMP-5 crystal structure, we identified residues that are crucial for determining the preference for hetero-oligomer or homo-oligomer formation. We also show that in spite of being the CRMP family member most closely related to dihydropyrimidinase, CRMP-5 does not have any detectable amidohydrolase activity. The presented findings provide new detailed insights into the structure, oligomerization, and regulation of CRMPs.

Pathogenic and physiological autoantibodies in the central nervous system

In this article, we review the current knowledge on pathological and physiological autoantibodies directed toward structures in the central nervous system (CNS) with an emphasis on their regulation and origin. Pathological autoantibodies in the CNS that are associated with autoimmunity often lead to severe neurological deficits via inflammatory processes such as encephalitis. In some instances, however, autoantibodies function as a marker for diagnostic purposes without contributing to the pathological process and/or disease progression. The existence of naturally occurring physiological autoantibodies has been known for a long time, and their role in maintaining homeostasis is well established. Within the brain, naturally occurring autoantibodies targeting aggregated proteins have been detected and might be promising candidates for new therapeutic approaches for neurodegenerative disorders. Further evidence has demonstrated the existence of naturally occurring antibodies targeting antigens on neurons and oligodendrocytes that promote axonal outgrowth and remyelination. The numerous actions of physiological autoantibodies as well as their regulation and origin are summarized in this review.

Immunological markers in neurological disorders

Neurological dysfunction results from vascular, inflammatory, degenerative, neoplastic, metabolic or genetic causes. Of particular interest is a group of neurological symptoms thought to be linked to an underlying tumour, the so-called paraneoplastic syndromes. It is considered to be due to an attempt by the immune system to subjugate the growth of the tumour by triggering an antibody response against the neuronal antigens expressed by the neoplasm. The unfortunate consequence of this is an assault by the immune components on the nervous tissue, thereby rapidly precipitating a variety of neurological deficits. Every level of the nervous system is potentially vulnerable, with the disability being considered as irreversible due to the lack of regenerative capacity of the neurons. This phenomenon is rare, occurring at an approximate frequency of less than 1% of all tumours and often accompanied by the presence of specific high-titre autoantibodies in both the cerebrospinal fluid and blood. This group of antibodies are non-pathogenic markers for paraneoplastic neurological syndromes, which have expanded to almost 20 since the discovery, in 1986, of the first clinically relevant syndrome. More recently, a new generation of antineuronal antibodies against cell surface antigens, having a direct pathogenic role in causing the disease, has emerged to complement the existing repertoire. Neuronal antibodies are useful diagnostic markers of the brain disease and also, in some cases, may reveal an underlying malignancy, thus facilitating faster diagnosis and earlier treatment with consequently better prognosis.

Onco-neural antibodies and tumour type determine survival and neurological symptoms in paraneoplastic neurological syndromes with Hu or CV2/CRMP5 antibodies

OBJECTIVE

Anti-Hu antibodies (Hu-Ab) and anti-CV2/CRMP5 antibodies (CV2/CRMP5-Ab) have been identified in association with paraneoplastic neurological disorders. However, it is not clear whether these antibodies are associated with specific neurological symptoms or are only markers of anti-cancer immune reaction.

METHODS

To address this question, 37 patients with CV2/CRMP5-Ab and 324 patients with Hu-Ab were compared.

RESULTS

Whereas the age and sex ratio were the same between the two groups, the distribution of neurological symptoms was not. Patients with CV2/CRMP5-Ab presented more frequently cerebellar ataxia, chorea, uveo/retinal symptoms and myasthenic syndrome (Lambert-Eaton myasthenic syndrome LEMS or myasthenia gravis). They also had a better Rankin score. In contrast, dysautonomia, brainstem encephalitis and peripheral neuropathy were more frequent in patients with Hu-Ab. Limbic encephalitis occurred similarly in both groups. Small-cell lung cancer was the most frequently associated tumour in both groups of patients, while malignant thymoma was observed only in patients with CV2/CRMP5-Ab. In particular, patients with CV2/CRMP5-Ab and thymoma developed myasthenic syndrome more frequently, while patients with SCLC developed neuropathies more frequently. Chorea and myasthenic syndrome were only seen in patients with CV2/CRMP5-Ab. The median survival time was significantly longer in patients with CV2/CRMP5-Ab, and this effect was not dependent on the type of tumour.

INTERPRETATION

The data demonstrate that in patients with paraneoplastic neurological syndromes, the neurological symptoms and survival vary with both the type of associated onco-neural antibody and the type of tumour.

Cells, Cells, and More Cells

A 64-year-old woman presented with bilateral optic nerve swelling, vitreous cells, and cerebrospinal fluid monocytic pleocytosis. A chest radiograph and computed tomography demonstrated a lesion in the left lung, which histologically was confirmed to be a small-cell lung carcinoma. The serum was positive for the anti-CV2 (anti-CRMP-5) antibody. Following treatment with chemoradiation the optic nerve swelling and vitritis resolved. The differential diagnosis of uveal-meningeal diseases is discussed and the pathophysiology and clinical manifestations of paraneoplastic syndromes reviewed.

Geriatric Chorea

The differential diagnosis, diagnostic evaluation, and treatment of late-onset chorea are reviewed. Late-onset chorea is rare and has a heterogeneous causation. A systematic approach to geriatric chorea greatly enhances a correct diagnosis. An accurate diagnosis is important because many causes of chorea are treatable or or, when heritable, may have significant implications for subsequent generations. Most late-onset chorea is either nonlimiting, requiring no treatment, has a spontaneous remission, or responds to medication. In a minority of patients, chorea is medically refractory or manifestation of an untreatable disorder.

Collapsin response mediator proteins (CRMPs): involvement in nervous system development and adult neurodegenerative disorders

The members of the collapsin response mediator protein (CRMP) family-five cytosolic phosphoproteins -are highly expressed throughout brain development. The first member to be cloned, CRMP2, was identified as an intracellular messenger required for the growth cone-collapse induced by semaphorin 3A (Sema3A). A rapidly expanding body of study indicates that the functions of CRMPs are not solely limited to the signaling transduction of the Sema3A guidance cue. They are probably involved in multiple cellular and molecular events involved in apoptosis/proliferation, cell migration, and differentiation. In the adult brain, the expression of CRMPs is dramatically downregulated. However, they remain expressed in structures that retain their capacity for differentiation and plasticity and also in a subpopulation of oligodendrocytes (CRMP2 and CRMP5). Moreover, the expression of CRMPs is altered in neurodegenerative diseases, and these proteins may be of key importance in the physiopathology of the adult nervous system.

Paraneoplastic chorea associated with CRMP-5 neuronal antibody and lung carcinoma

Paraneoplastic chorea is described in 16 patients: 11 with limited small-cell carcinoma, 2 with lung cancer revealed by imaging, 1 with renal cell carcinoma, and 1 with lymphoma. All had CRMP-5-IgG; 6 also had ANNA-1 (anti-Hu), including 1 without evident cancer. Chorea was the initial and most prominent symptom in 11 patients, asymmetric or unilateral in 5 patients, and part of a multifocal syndrome in 14 patients. Basal ganglia abnormalities were revealed by magnetic resonance imaging and at autopsy (as perivascular inflammation and microglial activation). Four patients improved with chemotherapy, and 2 improved with intravenous methylprednisolone.

Isolation and expression pattern of human Unc-33-like phosphoprotein 6/collapsin response mediator protein 5 (Ulip6/CRMP5): coexistence with Ulip2/CRMP2 in Sema3a- sensitive oligodendrocytes

The Unc-33-like phosphoprotein/collapsin response mediator protein (Ulip/CRMP) family consists of four homologous phosphoproteins considered crucial for brain development. Autoantibodies produced against member(s) of this family by patients with paraneoplastic neurological diseases have made it possible to clone a fifth human Ulip/CRMP and characterize its cellular and anatomical distribution in developing brain. This protein, referred to as Ulip6/CRMP5, is highly expressed during rat brain development in postmitotic neural precursors and in the fasciculi of fibers, suggesting its involvement in neuronal migration/differentiation and axonal growth. In the adult, Ulip6/CRMP5 is still expressed in some neurons, namely in areas that retain neurogenesis and in oligodendrocytes in the midbrain, hindbrain, and spinal cord. Ulip2/CRMP2 and Ulip6/CRMP5 are coexpressed in postmitotic neural precursors at certain times during development and in oligodendrocytes in the adult. Because Ulip2/CRMP2 has been reported to mediate semaphorin-3A (Sema3A) signal in developing neurons, in studies to understand the function of Ulip6/CRMP5 and Ulip2/CRMP2 in the adult, purified adult rat brain oligodendrocytes were cultured in a Sema3A-conditioned medium. Oligodendrocytes were found to have Sema3A binding sites and to express neuropilin-1, the major Sema3A receptor component. In the presence of Sema3A, these oligodendrocytes displayed a dramatic reduction in process extension, which was reversed by removal of Sema3A and prevented by anti-neuropilin-1, anti-Ulip6/CRMP5, anti-Ulip2/CRMP2 antibodies, or VEGF-165, another neuropilin-1 ligand. These results indicate the existence in the adult brain of a Sema3A signaling pathway that modulates oligodendrocyte process extension mediated by neuropilin-1, Ulip6/CRMP5, and Ulip2/CRMP2, and they open new fields of investigation of neuron/oligodendrocyte interactions in the normal and pathological brain.