An autopsy case of GM1 gangliosidosis type II in a patient who survived a long duration with artificial respiratory support.

GM1 gangliosidosis is a storage disorder with autosomal recessive inheritance caused by deficiency of ß-galactosidase (GLB1), which is a lysosomal hydrolase, due to mutations in GLB1. We describe here an autopsy case of GM1 gangliosidosis in a female patient who survived for 38 years with a long period of artificial respiratory support (ARS). She was born after a normal pregnancy and delivery. Although development was normal until one year old, she was unable to walk at two years old and started having seizures by nine years old. At 21 years old, she became unable to communicate and was bed-ridden. At 36 years old, she suffered from pneumonia and required ARS. She died of pneumonia at 40 years old. Neuropathological examination revealed severe atrophy, predominantly found in the frontal lobes. Microscopically, severe gliosis and neuronal loss were observed in the cerebral cortex, putamen, cerebellum, the latter including Purkinje cell and granule cell layers. The hippocampus was relatively preserved. Severe neuronal swelling was observed in the limbic regions and stored a material in these neurons negative for periodic acid-Schiff (PAS). A PAS-positive granular storage material in neurons and macrophages was mainly observed in the brainstem and limbic regions. Exome analysis showed a known c.152T>C (p.I51T) variant that has been described in type III patients and a novel c.1348-2A>G variant in GLB1. Detailed analysis of reverse transcription-polymerase chain reaction products of GLB1 mRNA revealed that these variants were present in a compound heterozygous state. In our case, clinical features and neuropathological findings were most consistent with type II, although the entire course was longer than any previously reported cases. This may be explained by the residual enzyme activity in this patient whose severity lay between types II and III. Our finding of relative preservation of the limbic regions suggests that neuronal loss in GM1 gangliosidosis has regional selectivity.

Adult-onset cerebello-brainstem dominant form of X-linked adrenoleukodystrophy presenting as multiple system atrophy: case report and literature review.

X-linked adrenoleukodystrophy (X-ALD) is the most common peroxisomal disorder and is caused by ABCD1 mutations. A cerebello-brainstem dominant form that mainly involves the cerebellum and brainstem is summarized in a review of the literature, with autopsy-confirmed cases exceedingly rare. We report a 69-year-old White man who was diagnosed with this rare disorder and describe neuropathologic, ultrastructural and genetic analyses. He did not have adrenal insufficiency or a family history of X-ALD or Addison's disease. His initial symptom was temporary loss of eyesight at age 34 years. His major symptoms were chronic and progressive gait disorder, weakness in his lower extremities and spasticity, as well as autonomic failure and cerebellar ataxia suggesting possible multiple system atrophy (MSA). He also had seizures, hearing loss and sensory disturbances. His brain MRI showed no obvious atrophy or significant white matter pathology in cerebrum, brainstem or cerebellum. He died at age 69 years with a diagnosis of MSA. Microscopic analysis showed mild, patchy myelin rarefaction with perivascular clusters of PAS-positive, CD68-positive macrophages in the white matter most prominent in the cerebellum and occipital lobe, but also affecting the optic tract and internal capsule. Electron microscopy of cerebellar white matter showed cleft-like trilamellar cytoplasmic inclusions in macrophages typical of X-ALD, which prompted genetic analysis that revealed a novel ABCD1 mutation, p.R163G. Given the relatively mild pathological findings and long disease duration, it is likely that the observed pathology was the result of a slow and indolent disease process. We described a patient who had sporadic cerebello-brainstem dominant form of X-ALD with long clinical course, mild pathological findings, and an ABCD1 p.R163G substitution. We also review a total of 34 cases of adult-onset cerebello-brainstem dominant form of X-ALD. Although rare, X-ALD should be considered in the differential diagnosis of MSA.

A new mouse allele of glutamate receptor delta 2 with cerebellar atrophy and progressive ataxia.

Spinocerebellar degenerations (SCDs) are a large class of sporadic or hereditary neurodegenerative disorders characterized by progressive motion defects and degenerative changes in the cerebellum and other parts of the CNS. Here we report the identification and establishment from a C57BL/6J mouse colony of a novel mouse line developing spontaneous progressive ataxia, which we refer to as ts3. Frequency of the phenotypic expression was consistent with an autosomal recessive Mendelian trait of inheritance, suggesting that a single gene mutation is responsible for the ataxic phenotype of this line. The onset of ataxia was observed at about three weeks of age, which slowly progressed until the hind limbs became entirely paralyzed in many cases. Micro-MRI study revealed significant cerebellar atrophy in all the ataxic mice, although individual variations were observed. Detailed histological analyses demonstrated significant atrophy of the anterior folia with reduced granule cells (GC) and abnormal morphology of cerebellar Purkinje cells (PC). Study by ultra-high voltage electron microscopy (UHVEM) further indicated aberrant morphology of PC dendrites and their spines, suggesting both morphological and functional abnormalities of the PC in the mutants. Immunohistochemical studies also revealed defects in parallel fiber (PF)-PC synapse formation and abnormal distal extension of climbing fibers (CF). Based on the phenotypic similarities of the ts3 mutant with other known ataxic mutants, we performed immunohistological analyses and found that expression levels of two genes and their products, glutamate receptor delta2 (grid2) and its ligand, cerebellin1 (Cbln1), are significantly reduced or undetectable. Finally, we sequenced the candidate genes and detected a large deletion in the coding region of the grid2 gene. Our present study suggests that ts3 is a new allele of the grid2 gene, which causes similar but different phenotypes as compared to other grid2 mutants.

A mutation in the saposin C domain of the sphingolipid activator protein (Prosaposin) gene causes neurodegenerative disease in mice.

Saposins A, B, C, and D are small amphiphatic glycoproteins that are encoded in tandem within a precursor protein (prosaposin, PSAP), and are required for in vivo degradation of sphingolipids. Humans with saposin C deficiency exhibit the clinical presentation of Gaucher-like disease. We generated two types of saposin C mutant mice, one carrying a homozygous missense mutation (C384S) in the saposin C domain of prosaposin (Sap-C(-/-)) and the other carrying the compound heterozygous mutation with a second null Psap allele (Psap(-/C384S)). During early life stages, both Sap-C(-/-) and Psap(-/C384S) mice grew normally; however, they developed progressive motor and behavioral deficits after 3 months of age and the majority of affected mice could scarcely move by about 15 months. They showed no signs of hepatosplenomegaly throughout their lives. No accumulation of glucosylceramide and glucosylsphingosine was detected in the brain or liver of both Sap-C(-/-) and Psap(-/C384S) mice. Neuropathological analyses revealed patterned loss of cerebellar Purkinje cells, widespread axonal spheroids filled with membrane-derived concentric or lamellar electron-dense bodies, and lipofuscin-like deposition in the neurons. Soap-bubble-like inclusion bodies were detected in the trigeminal ganglion cells and the vascular endothelial cells. Compound heterozygous Psap(-/C384S) mice showed qualitatively identical but faster progression of the neurological phenotypes than Sap-C(-/-) mice. These results suggest the in vivo role of saposin C in axonal membrane homeostasis, the disruption of which leads to neurodegeneration in lysosomal storage disease.

Novel mutation and the first prenatal screening of cathepsin D deficiency (CLN10).

The neuronal ceroid lipofuscinoses (NCLs) are autosomal recessively inherited disorders collectively considered to be one among the most common pediatric neurodegenerative lysosomal storage diseases. Four main clinical subtypes have been described based on the age at presentation: infantile, late infantile, juvenile and adult types. In addition, rare congenital cases of NCL have been reported in the literature. Previously, a homozygous mutation in the cathepsin D gene has been shown to cause congenital NCL in a patient of Pakistani origin. We report a case of a 39-week estimated gestational age female infant with severe microcephaly and hypertonia, whereas MRI showed generalized hypoplasia of the cerebral and cerebellar hemispheres. The infant died on day two after birth. Postmortem examination revealed a small, firm brain with extensive neuronal loss and gliosis. Remaining neurons, astrocytes and macrophages contained PAS-positive storage material with granular ultrastructure and immunoreactivity against sphingolipid activator protein D. A diagnosis of congenital NCL was rendered with a novel mutation, c.299C > T (p.Ser100Phe) in exon 3 of the cathepsin D gene. In the patient fibroblasts, cathepsin D activity was marginal, but the protein appeared stable and normally processed. This was confirmed in overexpression studies. Importantly, by identification of the mutation in the family, we were able to confirm the first prenatal diagnosis excluding cathepsin D deficiency in the younger sibling of the patient.

MHC class II exacerbates demyelination in vivo independently of T cells.

We have shown previously the importance of MHC class II for central nervous system remyelination; however, the function of MHC class II during cuprizone-induced demyelination has not been examined. Here, we show that I-A(beta)-/- mice exhibit significantly reduced inflammation and demyelination. RAG-1(1/1) mice are indistinguishable from controls, indicating T cells may not play a role. The role of MHC class II depends on an intact cytoplasmic tail that leads to the production of IL-1beta, TNF-alpha, and nitric oxide, and oligodendrocyte apoptosis. Thus, the function of MHC class II cytoplasmic tail appears to increase microglial proliferation and activation that exacerbates demyelination.

Peripheral neuropathy in the twitcher mouse: accumulation of extracellular matrix in the endoneurium and aberrant expression of ion channels.

Globoid cell leukodystrophy (GLD; Krabbe's disease), caused by a genetic galactosylceramidase deficiency, affects both the central and peripheral nervous systems (CNS and PNS). Allogenic hematopoietic stem-cell transplantation (HSCT) has been beneficial for clinical improvement of this disease. However, recent reports by Siddiqi et al. suggested that none of their transplanted patients achieved complete normalization of their peripheral nerve function, despite the well-documented remyelination of the CNS and PNS in the treated patients. We hypothesized that the PNS dysfunction in GLD is due to altered Schwann cell-axon interactions, resulting in structural abnormalities of the node of Ranvier and aberrant expression of ion channels caused by demyelination and that the persistence of this altered interaction is responsible for the dysfunction of the PNS after HSCT. Since there has not been any investigation of the Schwann cell-axonal relationship in twitcher mice, an authentic model of GLD, we first investigated structural abnormalities, focusing on the node of Ranvier in untreated twitcher mice, and compared the results with those obtained after receiving bone marrow transplantation (BMT). As expected, we found numerous supernumerary Schwann cells that formed structurally abnormal nodes of Ranvier. Similar findings, though at somewhat variable extent, were detected in mice treated with BMT. Activated supernumerary Schwann cells expressed GFAP immunoreactivity and generated Alcian blue-positive extracellular matrix (ECM) in the endoneurial space. The processes of these supernumerary Schwann cells often covered and obliterated the nodal regions. Furthermore, the distribution of Na(+) channel immunoreactivity was diffuse without the concentration at the nodes of Ranvier as seen in wild-type mice. Neither K(+) channels nor Neurexin IV/ Caspr/ Paranoidin (NCP-1) were detected in the twi/twi sciatic nerve. The results of our study suggest the importance of normalization of the Schwann cell-axon relationship for the functional recovery of peripheral nerves, when one considers therapeutic strategies for PNS pathology in GLD.

Postmortem diagnosis of Fabry disease with acromegaly and a unique vasculopathy.

A 44-year-old Japanese man with elevated growth hormone levels and gradual deterioration of mental and renal function was admitted to the hospital. With his deteriorated general condition and renal failure, the patient developed pulmonary thromboembolism and died of respiratory failure. Autopsy examination was conducted, which revealed abnormal accumulation or intracytoplasmic storage of lipid-rich material in the small blood vessels, kidney, heart, and nervous system. After postmortem pathologic studies, including light-microscopic histochemistry, electron microscopy, and biochemical analysis of the stored lipid contents, a final diagnosis of Fabry disease was made. Histopathologic examination revealed a unique vasculopathy characterized by the presence of abnormal intracytoplasmic lipid inclusions and vascular remodeling. With regard to the clinical presentation of acromegaly, hyperplasia but not adenomatous transformation of the acidophils of the anterior pituitary gland with immunohistochemical detection of growth hormone within the cells was noted. In this case, the complication of acromegaly with hyperplasia of the acidophilic cells of the anterior pituitary gland and the unique vasculopathy causing significant organ failure, mainly of the kidney, heart, and central nervous systems, possibly as a result of microcirculatory failure, are considered to be not incidental findings but to be intimately involved in the pathogenesis of Farby disease.

Hematopoietic prostaglandin D synthase and DP1 receptor are selectively upregulated in microglia and astrocytes within senile plaques from human patients and in a mouse model of Alzheimer disease.

Prostaglandin (PG) D2 is produced in activated microglia by the action of hematopoietic PGD synthase (HPGDS) and plays important roles in neuroinflammation. Because the fact that neuroinflammation accelerates progression of Alzheimer disease (AD) has been documented, we investigated whether PGD2 is also involved in the pathology of AD. Here, we report that the level of the mRNA of the receptor for PGD2 (DP1) was increased in AD brains compared with the level in non-AD brains. Immunocytochemical analysis showed HPGDS expression to be localized in the microglia surrounding senile plaques. In situ hybridization studies revealed that DP1 mRNA was specifically localized in microglia and reactive astrocytes within senile plaques of AD brains. In the brain of Tg2576 mice, a model of AD, HPGDS and DP1 proteins were mainly localized immunocytochemically in microglia and astrocytes in the plaques, and the levels of their mRNAs increased in parallel with amyloid beta deposition. These results indicate that PGD2 may act as a mediator of plaque-associated inflammation in AD brain and may explain the pharmacologic mechanisms underlying the favorable response of patients with AD to nonsteroidal anti-inflammatory drugs.

Neuropathology of developmental abnormalities.

Varieties of neuropathological disorders are caused by a perturbation of normal developmental processes, resulting from insults by heterogeneous etiologic factors. These factors trigger the sequence of molecular, biochemical, and morphologic alterations of the brain, resulting morphologically and/or functionally abnormal brain. The resulting brain contains basic components of the normal brain but is assembled in an abnormal way. The developmental stage when the insults occur appears to largely dictate the outcome of the pathological processes. Depending on the developmental stage involved, the morphology of the brain may be grossly abnormal or is apparently normal but functionally abnormal. The brain development progresses in an orderly fashion and can be divided into several major developmental stages; the neurulation (neural tube formation), ventral induction (formation of prosencephalon), neuroepithelial cell proliferation and migration, neuroglial differentiation and establishment of neuronal circuits. The perturbation of these developmental stages results in uniquely specific pathological outcome, regardless of the etiologic factors/agents. In this review, I will briefly discuss the normal pattern of brain development and neuropathology of the representative disorders resulting from the deviation of normal developmental processes in the individual developmental stage.

Pregnane X receptor (PXR) activation: a mechanism for neuroprotection in a mouse model of Niemann-Pick C disease.

Niemann-Pick type C1 (NPC1) disease is a fatal neurodegenerative disease characterized by neuronal lipid storage and progressive Purkinje cell loss in the cerebellum. We investigated whether therapeutic approaches to bypass the cholesterol trafficking defect in NPC1 disease might delay disease progression in the npc1(-/-) mouse model. We show that the neurosteroid allopregnanolone (ALLO) and T0901317, a synthetic oxysterol ligand, act in concert to delay onset of neurological symptoms and prolong the lifespan of npc1(-/-) mice. ALLO and T0901317 therapy preserved Purkinje cells, suppressed cerebellar expression of microglial-associated genes and inflammatory mediators, and reduced infiltration of activated microglia in the cerebellar tissue. To establish whether the mechanism of neuroprotection in npc1(-/-) mice involves GABA(A) receptor activation, we compared treatment of natural ALLO and ent-ALLO, a stereoisomer that has identical physical properties of natural ALLO but is not a GABA(A) receptor agonist. ent-ALLO provided identical functional and survival benefits as natural ALLO in npc1(-/-) mice, strongly supporting a GABA(A) receptor-independent mechanism for ALLO action. On the other hand, the efficacy of ALLO, ent-ALLO, and T0901317 therapy correlated with the ability of these compounds to activate pregnane X receptor-dependent pathways in vivo. These findings suggest that treatment with pregnane X receptor ligands may be useful clinically in delaying the progressive neurodegeneration in human NPC disease.

A de novo deafwaddler mutation of Pmca2 arising in ES cells and hitchhiking with a targeted modification of the Pparg gene.

We observed severe ataxia in mice homozygous for modification of the Pparg locus. Genetic analysis and nucleotide sequencing revealed that ataxia is caused by a T692K substitution in plasma membrane calcium ATPase 2 (Pmca2), which is tightly linked to Pparg, but not by modified PPARgamma itself. We traced this mutation and found that it arose spontaneously during clonal expansion of the targeted embryonic stem (ES) cells. Consistent with the deafwaddler phenotype in other Pmca2 mutants, homozygous T692K Pmca2 mutants exhibit severe balance disorder, impaired neurologic reflexes, and motor coordination, and have profound hearing loss. Heterozygous mutants have normal movement and motor function but are severely deficient in hearing. Our findings represent a cautionary example since, although rare, spontaneous mutations do arise in ES cells during culture and hitchhike onto the targeted gene mutation.

Prostaglandin D2-mediated microglia/astrocyte interaction enhances astrogliosis and demyelination in twitcher.

Prostaglandin (PG) D2 is well known as a mediator of inflammation. Hematopoietic PGD synthase (HPGDS) is responsible for the production of PGD2 involved in inflammatory responses. Microglial activation and astrogliosis are commonly observed during neuroinflammation, including that which occurs during demyelination. Using the genetic demyelination mouse twitcher, a model of human Krabbe's disease, we discovered that activated microglia expressed HPGDS and activated astrocytes expressed the DP1 receptor for PGD2 in the brain of these mice. Cultured microglia actively produced PGD2 by the action of HPGDS. Cultured astrocytes expressed two types of PGD2 receptor, DP1 and DP2, and showed enhanced GFAP production after stimulation of either receptor with its respective agonist. These results suggest that PGD2 plays an important role in microglia/astrocyte interaction. We demonstrated that the blockade of the HPGDS/PGD2/DP signaling pathway using HPGDS- or DP1-null twitcher mice, and twitcher mice treated with an HPGDS inhibitor, HQL-79 (4-benzhydryloxy-1-[3-(1H-tetrazol-5-yl)-propyl]piperidine), resulted in remarkable suppression of astrogliosis and demyelination, as well as a reduction in twitching and spasticity. Furthermore, we found that the degree of oligodendroglial apoptosis was also reduced in HPGDS-null and HQL-79-treated twitcher mice. These results suggest that PGD2 is the key neuroinflammatory molecule that heightens the pathological response to demyelination in twitcher mice.

Lipocalin-type prostaglandin D synthase is up-regulated in oligodendrocytes in lysosomal storage diseases and binds gangliosides.

Lipocalin-type prostaglandin (PG) D synthase (L-PGDS) is a dually functional protein, acting both as a PGD2-synthesizing enzyme and as an extracellular transporter of various lipophilic small molecules. L-PGDS is expressed in oligodendrocytes (OLs) in the central nervous system and is up-regulated in OLs of the twitcher mouse, a model of globoid cell leukodystrophy (Krabbe's disease). We investigated whether up-regulation of L-PGDS is either unique to Krabbe's disease or is a more generalized phenomenon in lysosomal storage disorders (LSDs), using LSD mouse models of Tay-Sachs disease, Sandhoff disease, GM1 gangliosidosis and Niemann-Pick type C1 disease. Quantitative RT-PCR revealed that L-PGDS mRNA was up-regulated in the brains of all these mouse models. In addition, strong L-PGDS immunoreactivity was observed in OLs, but not in either astrocytes or microglia in these models. Thus, up-regulation of L-PGDS appears to be a common response of OLs in LSDs. Moreover, surface plasmon resonance analyses revealed that L-PGDS binds GM1 and GM2 gangliosides, accumulated in neurons in the course of LSD, with high affinities (KD = 65 and 210 nm, respectively). This suggests that L-PGDS may play a role in scavenging harmful lipophilic substrates in LSD.

Hematopoietic cell transplantation ameliorates clinical phenotype and progression of the CNS pathology in the mouse model of late onset Krabbe disease.

Krabbe disease is a genetic demyelinating disease caused by a deficiency of galactosylceramidase. The majority of cases are of infantile onset with rapid clinical course. A rare late onset form with milder clinical symptoms also exists. The latter form has been reported to respond well to the bone marrow transplantation (BMT) therapy. We tested whether the BMT could be an effective therapy for the mouse model of the late onset form, saposin-A-/- (SAP-A-/-) mice. We used green fluorescent protein transgenic mice as the donors. Chimeric SAP-A-/- mice that received BMT showed very little evidence of neurologic symptoms. At postnatal day 190 when severe demyelination was evident in naive SAP-A-/- mice, demyelination was virtually absent in the brain of chimeric SAP-A-/- mice. Presence of residual enzyme activity, at the time of rapid myelination in SAP-A-/- mice, appears to limit initial inflammatory responses and macrophage infiltration, thereby preventing progression of demyelination in the CNS in SAP-A-/- mice. In contrast, the peripheral nerves showed features of hypertrophic neuropathy with hypomyelination and onion bulb formation, suggesting that there are different cellular responses to the BMT in the CNS and PNS.

Anti-inflammatory therapy by ibudilast, a phosphodiesterase inhibitor, in demyelination of twitcher, a genetic demyelination model.

BACKGROUND: Twitcher mouse (twi/twi) is an authentic murine model of Krabbe's disease. Accumulation of psychosine, resulting in apoptosis of oligodendrocytes and subsequent demyelination, is a cardinal event to the pathogenesis of this disease. Moreover, recruitment of inflammatory cells plays a significant role in the pathological process in the twi/twi central and peripheral nervous systems. In this study, we investigated the 1) the relationship between tumor necrosis factor-alpha (TNFalpha), pro-inflammatory cytokine, and the progression of this disease and 2) effect of the anti-inflammatory therapy by ibudilast, a phosphodiesterase inhibitor. METHODS: We quantified the expression level of TNFalpha and TNF-receptor mRNA in twi/twi using semi-quantitative RT-PCR. The relationship between TNFalpha expression, apoptosis of oligodendrocytes and demyelination was studied with immunohistochemistry and TUNEL method. We then treated twi/twi with a daily intraperitoneal injection of ibudilast (10 mg/kg), which suppress TNFalpha production in the brain. RESULTS: We found that TNFalpha-immunoreactive microglia/macrophages appeared in the twi/twi brain and that the mRNA levels of TNFalpha and TNF-receptor 1 was increased with the progression of demyelination. The distribution profile of TNFalpha-immunoreactive microglia/macrophages overlapped that of TUNEL-positive oligodendrocytes in the twi/twi brain. When twi/twi was treated with ibudilast from PND30, the number of oligodendrocytes undergoing apoptosis was markedly reduced and demyelination was milder. Obvious improvement of clinical symptom was noted in two of five. The failure of constant clinical improvement by ibudilast may result from hepatotoxicity and/or the inhibition of proliferation of NG2-positive oligodendrocyte precursors. CONCLUSION: We conclude that anti-inflammatory therapy by a phosphodiesterase inhibitor can be considered as a novel alternative therapy for Krabbe's disease.

Apoptosis accompanied by up-regulation of TNF-alpha death pathway genes in the brain of Niemann-Pick type C disease.

Niemann-Pick disease type C (NP-C) is an autosomal recessive neurovisceral storage disease with neurodegeneration caused by mutations in either the NPC-1 or NPC-2 gene. The murine ortholog of NPC-1 is mutated in BALB/c npc(nih) and this mutant mouse shows equally conspicuous neurodegeneration and loss of neurons. However, the molecular mechanisms causing neurodegeneration in NP-C remain elusive. Here, we report the presence of apoptotic cells detected by both TUNEL staining and electron microscopy in the cerebrum and cerebellum of human patients and the mouse model. Moreover, we found that with progression of the disease process leading to neuronal cell death, an up-regulation of genes involved in the TNF-alpha death pathway caspase-8, FADD, TNFRp55, TRADD, and RIP-by an RNA protection assay. Furthermore, RT-PCR showed that TNF-alpha mRNA expression level also increased up to 30-50-fold in the cerebellum of 7- and 9-week-old NP-C mice compared with wild-type mice. Elevated expression of TNF-alpha was detected in both neurons and astrocytes with TNF-alpha-expressing astrocytes distributed in the affected brain regions. Collectively, our results suggest that the cell death in the brain of NP-C disease occurs through apoptosis and it is mediated by the TNF receptor superfamily pathway.

Consequences of NPC1 and NPC2 loss of function in mammalian neurons.

Genetic deficiency of NPC1 or NPC2 results in a devastating cholesterol-glycosphingolipidosis of brain and other organs known as Niemann-Pick type C (NPC) disease. While NPC1 is a transmembrane protein believed involved in retroendocytic shuttling of substrate(s) to the Golgi and possibly elsewhere in cells as part of an essential recycling/homeostatic control mechanism, NPC2 is a soluble lysosomal protein known to bind cholesterol. The precise role(s) of NPC1 and NPC2 in endosomal-lysosomal function remain unclear, nor is it known whether the two proteins directly interact as part of this function. The pathologic features of NPC disease, however, are well documented. Brain cells undergo massive intracellular accumulation of glycosphingolipids (lactosylceramide, glucosylceramide, GM2 and GM3 gangliosides) and cholesterol and concomitant distortion of neuron shape (meganeurite formation). In neurons from humans with NPC disease the metabolic defects and storage often lead to extensive growth of new, ectopic dendrites (possibly linked to ganglioside sequestration) as well as formation of neurofibrillary tangles (NFTs) (possibly linked to dysregulation of cholesterol metabolism). Other features of cellular pathology in NPC disease include fragmentation of the Golgi apparatus and neuroaxonal dystrophy, though reasons for these changes remain largely unknown. As the disease progresses, neurodegeneration is also apparent for neurons in some brain regions, particularly Purkinje cells of the cerebellum, but the basis of this selective neuronal vulnerability is unknown. The NPC1 protein is evolutionarily conserved with homologues reported in yeast to humans; NPC2 is reported in C. elegans to humans. While neurons in mammalian models of NPC1 and NPC2 diseases exhibit many changes that are remarkably similar to those in humans (e.g., endosomal/lysosomal storage, Golgi fragmentation, neuroaxonal dystrophy, neurodegeneration), a reduced degree of ectopic dendritogenesis and an absence of NFTs in these species suggest important differences in the way lower mammalian neurons respond to NPC1/NPC2 loss of function.

Comparative clinico-pathological study of saposin-A-deficient (SAP-A-/-) and Twitcher mice.

The Twitcher mouse (twi/twi) has been widely used as an animal model of globoid cell leukodystrophy (GLD; Krabbe disease), a hereditary leukodystrophy due to genetic galactosylceramidase deficiency. Recently, we generated a new mouse model of late-onset, chronic GLD (SAP-A-/- mice) by introducing a mutation (C106F) in the saposin A domain of the sphingolipid activator protein gene. Comparative study of SAP-A-/- and twi/twi mice revealed delay in the onset of neurological symptoms in SAP-A-/- mice (90 days vs 20 to 25 days), milder symptoms, and prolonged average survival (134.4 +/- 29.1 days vs 47.5 +/- 3.9 days). However, in both, the earliest sites of demyelination and macrophage infiltration were in regions of the 8th nerve and the spinal tract of the 5th nerve and spinal-cord, where macrophages could be detected as early as day 30 in asymptomatic SAP-A-/- mice. Furthermore, spacio-temporal pattern of demyelination/macrophage infiltration and the extent of neuropathology at the terminal stage are closely similar in both. These results suggest that peripheral macrophages are readily accessible in these sites and participate in the demyelinating process in the central nervous system.

Perturbed myelination process of premyelinating oligodendrocyte in Niemann-Pick type C mouse.

Niemann-Pick disease type C (NPC) is an autosomal recessive neurovisceral lipid storage disease caused by a loss of NPCI function, which results in perturbation of intracellular cholesterol transport. In BALB/c npc(nih) mice, the murine ortholog of NPCI gene is mutated. In NPC mouse, hypomyelination is conspicuous in the cerebral white matter and corpus callosum in addition to neuronal storage. However, the pathogenesis on hypomyelination is not well elucidated. We hypothesized that the hypomyelination in NPC mice resulted from either defective differentiation of oligodendrocyte lineage cells or a failure of proper axon-glial interaction. Myelin basic protein immunohistochemistry disclosed severe hypomyelination of cerebral cortex as well. NG2- or O4-positive progenitor cells and premyelinating oligodendrocytes (OLs) were abundant. However, pi-glutathione-S-transferase-positive mature OLs were considerably reduced. In hypomyelinated white matter, strong immunoreactivity of polysialylated-neural cell adhesion molecule, a negative regulator of myelination, was observed in axons. Given the fact that neuro-axonal degeneration has been observed in NPC mouse as early as 9 days of age prior to the commencement of myelination in the corpus callosum and that axonal signals are essential for the proper myelination, subtle axonal injury might be contributing to the pathogenesis of disturbed myelination in the NPC mouse.