Thesis (M. Med. Sc.)--University of Hong Kong, 2007.

No description available.

No description available.

Thesis advisor: Thomas N. Seyfried / GM1 gangliosidosis is a glycosphingolipid lysosomal storage disease caused by a genetic deficiency of acid b-galactosidase (β-gal), the enzyme that catabolyzes GM1 within lysosomes. Accumulation of GM1 and its asialo form (GA1) occurs primarily in the brain, leading to progressive neurodegeneration and brain dysfunction. Less information is available on the neurochemical pathology in optic nerve and sciatic nerve of GM1- gangliosidosis. Here we analyzed the lipid content and myelin structure in optic and sciatic nerve in 7 and 10 month old normal β-gal (+/?) and GM1-gangliosidosis β-gal (-/-) mice. Optic nerve weight was lower in the β-gal -/- mice than in unaffected β-gal +/? mice, but no difference was seen between the normal and the β-gal -/- mice for sciatic nerve weight. The concentrations of GM1 and GA1 were significantly higher in optic nerve and sciatic nerve in the β-gal -/- mice than in β-gal +/? mice. The content and composition of myelin-enriched cerebrosides, sulfatides, plasmalogen ethanolamines were significantly lower in optic nerve of β-gal -/- mice than in β-gal +/? mice, however cholesteryl esters were enriched in the β-gal -/- mice. No significant abnormalities in these myelin enriched lipids were detected in sciatic nerve of the β-gal -/- mice. The abnormalities in GM1 and myelin lipids in optic nerve of β-gal -/- mice were also associated with abnormalities in the X-ray diffraction pattern including myelin content in fresh nerves [M/(M +B)] and periodicity (d). With the exception of a slight reduction in myelin content, no abnormalities in the X-ray diffraction pattern were observed in sciatic nerve of β-gal -/- mice. The results indicate that neurochemical pathology is greater in optic nerve than in sciatic nerve of β-gal -/- mice. / Thesis (MS) — Boston College, 2014. / Submitted to: Boston College. Graduate School of Arts and Sciences. / Discipline: Biology.

Neuromyelitis optica (NMO) is a central nervous system inflammatory demyelinating disorders (CNS IDD) characterized by acute myelitis (AM) and optic neuritis (ON), especially clinically severe longitudinally extensive transverse myelitis (LETM) and simultaneous bilateral ON. Patients with recurrent AM especially LETM without ON, and patients with recurrent ON without AM may have disorders belonging to the spectrum of NMO, neuromyelitis optica spectrum disorders (NMOSD). NMO is likely autoimmune in nature as a significant proportion of patients are seropositive for aquaporin-4 (AQP4) autoantibodies. I studied the clinical features of local Chinese NMOSD patients and their AQP4 autoantibodies seropositivity rates of by indirect immunofluorescence using tissue slides containing primate cerebellum (tissued-based immunofluorescence assay) in patients with 1) NMO, 2) classical multiple sclerosis (CMS), 3) acute disseminated encephalomyelitis (ADEM), 4) single attack or relapsing AM, 5) single attack or relapsing ON, and 6) other neurological disorders. The results showed that NMOSD are severe CNS IDD affecting patients with a wide range of onset ages. Chinese NMOSD patients predominantly have relapsing NMO and relapsing LETM with severe attack of LETM and/or ON. The six-year mortality rate of patients with NMO or relapsing myelitis with LETM was about 12%. Two-thirds of patients have poor neurological outcome at a mean duration of 6.0 years. The results confirmed that AQP4 autoantibodies are specific for NMOSD, and detection of AQP4 autoantibodies is clinically useful for early diagnosis of NMOSD and distinction from CMS. I proceeded to study a cell-based immunofluorescence assay using transfected human embryonic kidney cells overexpressing human AQP4 on cell membrane and found that cell-based assay has higher sensitivity than tissue-based assay in detection of AQP4 autoantibodies in NMO (78% versus 61%). As our NMOSD patients frequently presented clinically with severe brainstem symptoms and signs and lesions in brainstem and other brain regions on magnetic resonance imaging (MRI), I studied the clinical and neuroradiological characteristics of Chinese NMOSD patients with brain involvement. I found that 59% of NMOSD patients have clinical and/or radiological evidence of brain involvement. Importantly, brainstem is the most frequently affected brain region and 24% of NMOSD patients had clinical manifestation of brainstem encephalitis. I also studied the pathogenicity of AQP4 autoantibodies in the absence of complement activation by passive transfer of IgG isolated from sera of NMOSD patients into mice pretreated with complete Freund’s adjuvant (CFA, containing heat-killed mycobacterium tuberculosis) and pertussis toxin (PTx). I observed that pretreatment with CFA and PTx led to breach of BBB in mouse, and IgG isolated from sera of NMOSD patients seropositive for AQP4 autoantibodies led to asymptomatic loss of AQP4 in gray and white matter in mouse spinal cord without inflammatory cell infiltration, demyelination or astrocytic loss in the absence of complement activation (human IgG cannot activate mouse complements). My findings support that 1) AQP4 autoantibodies binding to astrocytic AQP4 per se can cause downregulation of AQP4 in the absence of complement activation, and 2) complement activation with resultant complement activation products play key roles in the inflammation, demyelination and astrocyte cytotoxicity in NMO. / published_or_final_version / Medicine / Doctoral / Doctor of Philosophy

This study aimed to better understand the clearance of myelin debris during Wallerian degeneration in the goldfish visual paths. Myelin debris was first examined immunohistochemically in the presence or absence of regenerating axons. From these preliminary experiments it was apparent that the clearance of myelin debris was not affected by regenerating axons and that the debris was removed in a differential pattern along the visual pathway. Specifically, in the distal stump of the nerve as well as in the optic tract, myelin debris had been effectively cleared by one-month postoperative, while in the cranial segment of the nerve debris persisted for at least 6 weeks after injury. The differential pattern of myelin debris in the optic nerve and tract was then analyzed qualitatively and quantitatively using thick and thin plastic sections at various time points during regeneration. The results suggested that highly activated peripheral macrophages were responsible for the effective clearance of myelin in the distal nerve stump. In the optic tract a number of cellular properties, including their unique population of astrocytes may have enhanced the rate of debris clearance. By contrast, in the cranial segment of the nerve persistent debris was found both intracellularly in phagosomes and extracellularly, suggesting that the resident phagocytes were deficient in effecting both phagocytosis and emigration. Deficient phagocytosis may be a result of the production of anti-inflammatory cytokines in this region, while the failure to emigrate is most likely due to the rigid network of astrocytes in the nerve.

Thesis (M.S.)--Texas State University-San Marcos, 2008. / Vita. Appendix: leaves 34-43. Includes bibliographical references (leaves 44-48). Also available on microfilm.

No description available.

Calcium/calmodulin-dependent serine protein kinase (CASK) is a membrane-associated guanylate kinase (MAGUK) family protein, which is encoded by a gene of identical name present on the X chromosome. CASK may participate in presynaptic scaffolding, gene expression regulation, and cell junction formation. CASK is essential for survival in mammals. Heterozygous mutations in the CASK gene (in females) produce X-linked intellectual disability (XLID) and mental retardation and microcephaly with pontine and cerebellar hypoplasia (MICPCH, OMIM# 300749). CASK mutations are also frequently associated with optic nerve hypoplasia (ONH) which is the most common cause of childhood blindness in developed countries. Some patients with mutations in CASK have been also diagnosed with optic nerve atrophy (ONA) and glaucoma. We have used floxed CASK (CASKfloxed), CASK heterozygous knockout (CASK(+/-)), CASK neuronal knockout (CASKNKO) and tamoxifen inducible CASK knockout (CASKiKO) mouse models to investigate the mechanism and pathology of CASK-linked ONH. Our observations indicate that ONH occurs with 100% penetrance in CASK(+/-) mice, which also displayed microcephaly and disproportionate cerebellar hypoplasia. Further, we found that CASK-linked ONH is a complex developmental neuropathology with some degenerative components. Cellular pathologies include loss of retinal ganglion cells (RGC), astrogliosis, axonopathy, and synaptopathy. The onset of ONH is late in development, observed only around the early postnatal stage in mice reaching the plateau phase by three weeks of birth. The developmental nature of the disorder is confirmed by deleting CASK after maturity since CASKiKO mice did not produce any obvious optic nerve pathology. Strikingly the CASKfloxed mice expressing ~49% level of CASK did not manifest ONH despite displaying a slightly smaller brain and cerebellar hypoplasia indicating that ONH may not simply be an extension of microcephaly. We discovered that deleting CASK in neurons produced lethality before the onset of adulthood. The CASKNKO mice exhibited delayed myelination of the optic nerve. Overall this work suggests that CASK is critical for neuronal maturation and CASK-linked ONH is a pervasive developmental disorder of the subcortical visual pathway. Finally, in a side project, I also described a new methodology of targeting neurons using receptor-mediated endocytosis which would help target retinal neurons for therapeutic purposes in the future. / Ph. D. / 7 in 10,000 children suffer from childhood blindness, for whom all the visual information from the outside world is completely blocked. Although classified as a rare disease, optic nerve hypoplasia (ONH), or the underdevelopment of optic nerve, is the leading cause of childhood blindness in developed countries, accounting for 15% of childhood blindness. Only a handful of genes have been shown to associate with ONH. The CASK gene, whose protein product calcium/calmodulin-dependent serine protein kinase (CASK) plays a role in presynaptic scaffolding, is one of them. Mutations in the CASK gene not only produce ONH, but also microcephaly and intellectual disability. Investigating the mechanism of CASK-linked ONH will provide critical data to understand the molecular basis of optic nerve formation and maturation. Here we have used the CASK heterozygous knockout mouse model to replicate the ONH and microcephaly seen in female human patients. We discovered that the onset of CASK-linked ONH corresponded to the late third trimester developmental stage in humans, thus ONH is developmental in nature. ONH pathologies include thinning of optic nerves, axonal atrophy, and synaptopathy. In contrast to the postnatal death of constitutive CASK loss of function in mice, CASK ablation in adult mice did not lead to lethality. CASK deletion also delays neuronal myelination. Overall, our results indicate that CASK is critical for postnatal maturation of the central nervous system and mutations of the CASK gene is sufficient to lead to ONH. Early intervention and proper gene therapy may treat CASK-linked ONH.

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