Typical Parkinson’s Disease (PD) is a complex disease that arises from a combination of factors including genetics, environment, gene-environment interactions, sex and age. How these factors interact has yet to be elucidated. We have previously published roles for PD-linked genes in response to microbial infections in an effort to model gene-environment interactions in PD. Mutations in the GBA1 gene, encoding a protein that confers glucocerebrosidase (GCase) activity, represent the commonest risk factor for PD development. In the present study, we sought to understand the role of murine Gba1 in microbial infection. GCase activity was found to be sex- and organ-dependent in young adult mice carrying the p.D409V mutation. Mice carrying Gba1 p.D409V knock-in mutations did not show altered immune outcomes in response to Influenza virus H1N1, bacterial Salmonella typhimurium, or serial infections of the two. In response to Vesicular Stomatitis Virus (VSV), p.D409V mice survived at a higher rate overall compared to their wild type littermates, while homozygous males survived at a higher rate compared to wild type males in a sex-dependent manner. Heterozygous females had a lower viral load in the lung after VSV infection. GCase activity was found to be altered in VSV-infected p.D409V mice in a sex-and organ-dependent manner. Taken together, this study identifies a possible role for Gba1 in host response to an acute neurotropic infection and highlights the importance of exploring sex-dependent outcomes in Gba1-focused studies.

京都大学 / 新制・論文博士 / 博士(医学) / 乙第13463号 / 論医博第2250号 / 新制||医||1055(附属図書館) / 京都大学大学院医学研究科医学専攻 / (主査)教授 高橋 淳, 教授 稲垣 暢也, 教授 萩原 正敏 / 学位規則第4条第2項該当 / Doctor of Medical Science / Kyoto University / DFAM

The molecular mechanisms underlying the association between mutations in GBA1 and risk of developing the ‘synucleinopathy’ disorders Parkinson’s disease (PD) and dementia with Lewy bodies (DLB) remain elusive. To better understand the precise molecular cascade that connects GBA1 mutations with α-synuclein dysregulation, a modified lipid extraction and HPTLC protocol was optimized to detect changes in levels of neutral sphingolipids (SLs) from neural cells and tissue expressing wild-type (WT) GBA1, mutant GBA1, or both. We demonstrate that mutant GBA1 does not confer a dominant-negative effect on WT GBA1-mediated activity; however, bona fide loss-of-enzymatic function mutation events led to the accumulation of lipid substrates in neural cells and tissue, and enhance α- synuclein/ubiquitin reactivity in brain tissue of mutant gba1 mice. Our HPLC-MS/MS data are consistent with other studies demonstrating that heterozygous GBA1 mutations do not lead to lipid accumulation, but may alter α-synuclein degradation through a yet-to-be defined novel gain-of-toxic function event.

The molecular mechanisms underlying the association between mutations in GBA1 and risk of developing the ‘synucleinopathy’ disorders Parkinson’s disease (PD) and dementia with Lewy bodies (DLB) remain elusive. To better understand the precise molecular cascade that connects GBA1 mutations with α-synuclein dysregulation, a modified lipid extraction and HPTLC protocol was optimized to detect changes in levels of neutral sphingolipids (SLs) from neural cells and tissue expressing wild-type (WT) GBA1, mutant GBA1, or both. We demonstrate that mutant GBA1 does not confer a dominant-negative effect on WT GBA1-mediated activity; however, bona fide loss-of-enzymatic function mutation events led to the accumulation of lipid substrates in neural cells and tissue, and enhance α- synuclein/ubiquitin reactivity in brain tissue of mutant gba1 mice. Our HPLC-MS/MS data are consistent with other studies demonstrating that heterozygous GBA1 mutations do not lead to lipid accumulation, but may alter α-synuclein degradation through a yet-to-be defined novel gain-of-toxic function event.

Parkinson’s disease is a movement disorder characterized by nigrostriatal dopamine pathway degeneration and neuronal α-synuclein accumulation. Pathogenesis is associated with mutations in α-synuclein and Gba1 encoding alleles. Animal models created to date do not recapitulate the spectrum of clinical disease features. This thesis characterizes the bi-genic Synergy mouse, hypothesized to demonstrate motor behavioural and histological abnormalities downstream of α-synuclein overexpression and mutated Gba1. Synergy and SNCA mice (overexpressed α-synuclein with wild-type Gba1) have early onset deficits in motor coordination, muscle strength and nest building. Both exhibit increased α-synuclein concentration in the brain and cerebellar inclusions positive for two markers of pathological α-synuclein processing. Overall mutant Gba1 expression within Synergy mice does not worsen the behaviour or the histopathological findings associated with overexpression of human α-synuclein in SNCA mice. Future studies will determine whether mutant Gba1 expression alters cognitive behaviour and/or lipid homeostasis in this new bi-genic model of Parkinson’s disease.