College of Graduate Studieshttp://hdl.handle.net/20.500.12648/11342024-03-29T00:48:56Z2024-03-29T00:48:56ZExploring the roles of the connecting cilium in photoreceptor healthLiu, Yuhttp://hdl.handle.net/20.500.12648/147482024-03-28T06:06:58Z2024-03-26T00:00:00ZExploring the roles of the connecting cilium in photoreceptor health
Liu, Yu
Defects in proteins functioning at the photoreceptor connecting cilium/transition zone (CC/TZ) have been linked to retinal degenerative disorders such as retinitis pigmentosa (RP) and cone-rod dystrophy (CRD). Mutations in eyes shut homolog (EYS, RP25), a secreted ciliary protein with laminin globular (LG) domains, have been linked to RP and CRD. Previously, some LG domains have been shown to interact with O-mannosyl glycans of α-dystroglycan (α-DG). Additionally, mutations in pomgnt1, an enzyme that plays a critical role in the synthesis of these glycans, have also been linked to RP (RP76). At the CC/TZ, the tectonic protein complex functions to maintain the unique biochemical environments of the inner segments (IS) and outer segments (OS) of photoreceptors. Mutations in tectonic complex proteins have been linked to ciliopathies that often include ocular abnormalities. The pathogenic mechanism underlying these mutations are poorly understood; thus, we hypothesized that EYS is an extracellular ciliary protein that interacts with α-DG and the tectonic complex. This project investigated the role of EYS, TMEM216, a member of the tectonic complex, and O-mannosyl glycans of α-DG in photoreceptor health. We determined that the C-terminal LG domains of EYS interacted with the O-mannosyl glycan epitope of α-DG. In pomgnt1 zebrafish mutants, EYS-glycan binding was reduced, and the secretion of EYS to the CC/TZ was significantly disrupted. Furthermore, in the pomgnt1 mutant retina, a substantial accumulation of EYS protein was observed in the soma of photoreceptors. Interestingly, deletion of pomgnt1 resulted in a pattern of photoreceptor degeneration similar to that previously observed in eys zebrafish mutants. By contrast, deletion of TMEM216 did not disrupt localization of EYS or of other tectonic complex proteins, yet photoreceptor degeneration was still observed in these animals. Our study has identified a previously unknown interaction between the LG domain-containing EYS and O-mannosyl glycans. These findings provide novel insight into the functional role of EYS around the CC/TZ and suggest the importance of O-mannosyl glycosylation in the regulation of protein secretion. Furthermore, our results suggest a mechanistic link between the disruption of glycosylation and photoreceptor degeneration, providing a new perspective on the underlying mechanisms behind RP25 and RP76.
2024-03-26T00:00:00ZIPSC-derived neurons as a model for studying the role of RELN in autismMohktari, Ryanhttp://hdl.handle.net/20.500.12648/147372024-03-19T03:28:52Z2024-03-11T00:00:00ZIPSC-derived neurons as a model for studying the role of RELN in autism
Mohktari, Ryan
RELN is strongly associated with Autism Spectrum Disorder (ASD). Homozygous loss of the encoded protein REELIN is associated with severe neurodevelopmental phenotypes characterized by lissencephaly and cerebellar hypoplasia, yet the ASD linked variants are typically heterozygous and appear to require additional genetic risk to cause ASD. To functionally characterize a RELN variant in a patient with ASD, we used induced pluripotent stem cells (iPSCs) from a family of non-autistic parents and their son who had ASD (the proband). The proband has a maternally-inherited missense variant (R2457C) in the RXR motif of the REELIN protein. We differentiated the iPSCs into two types of neurons, inhibitory neurons which model the inhibitory forebrain neurons that secrete REELIN, and excitatory neurons which model the cortical pyramidal neurons that respond to REELIN. Immunoblotting revealed that the proband inhibitory neurons had a lower ratio of extracellular/intracellular REELIN compared to that of the parental neurons, suggesting a decreased REELIN secretion. Sholl analysis on the proband excitatory neurons showed reduced dendritic complexity and reduced total length compared to the parental neurons. REELIN treatment increased the dendritic length and complexity in proband neurons up to the level of parental neurons. CRISPR/Cas9-mediated RELN KO did not change the dendritic phenotype in the excitatory neurons, ruling out a cell autonomous role for REELIN in these neurons. The proband excitatory neurons also had lower mRNA expression of WNT target genes in response to WNT3a, suggesting an underactive WNT signaling, as well as higher total GSK3β protein and lower phosphorylation at the inhibitory S9 site, indicating an overactive GSK3β signaling. Inhibition of GSK3β improved the proband neurons dendritic complexity in the proximal parts of the dendritic arbor. However, inhibition of mTOR signaling, which has shown to regulate REELIN signaling, did not change the dendritic morphology. In conclusion, the pathophysiology of ASD in the proband likely consists of a reduced REELIN secretion from the inhibitory neurons and an additional vulnerability in the REELIN-responding excitatory neurons, the latter likely being an overactive GSK3β and an underactive WNT signaling, all of which result in reduced dendritic complexity.
2024-03-11T00:00:00ZMonomeric DENV-reactive IgA contributes protective and non-pathologic functions during DENV infectionWegman, Adamhttp://hdl.handle.net/20.500.12648/147302024-03-09T05:33:18Z2024-01-01T00:00:00ZMonomeric DENV-reactive IgA contributes protective and non-pathologic functions during DENV infection
Wegman, Adam
Dengue, caused by the 4 serotypes of dengue viruses (DENVs), is a tropical and subtropical vector-borne febrile illness which causes a significant global disease burden. A particular immunological feature contributing to severe disease is antibody-dependent enhancement (ADE), in which IgG isotype antibodies raised during a primary DENV infection opsonize and enhance the infectivity of DENVs during a secondary heterotypic infection. We and colleagues have described a monomeric serum IgA response during dengue infection. Here, we report on the functional characteristics of monomeric IgA in DENV infection. We show that isotype conversion of IgG to IgA preserves neutralization capacity while abrogating enhancing capacity. We show that DENV-specific IgA competitively antagonizes both IgG-mediated infection and downstream secretion of pro-inflammatory cytokines. This effect is largely attributable to the lower avidity of IgA-DENV immune complexes for permissive cells compared to IgG-DENV complexes. These findings have implications for serodiagnosis, therapeutics, and assessing risk of severe disease.
2024-01-01T00:00:00ZFinding Diamonds in the Rough: Uncovering Genetic Variants, Transcripts, and Biological Processes Associated with Resilience to Alzheimer's DiseaseHou, Jiahuihttp://hdl.handle.net/20.500.12648/140742024-02-01T03:17:43Z2024-01-30T00:00:00ZFinding Diamonds in the Rough: Uncovering Genetic Variants, Transcripts, and Biological Processes Associated with Resilience to Alzheimer's Disease
Hou, Jiahui
Late-onset Alzheimer's disease (LOAD) is a multifactorial disease with a strong genetic component. The growing understanding of the genetic basis and molecular mechanisms underlying LOAD risk presents an opportunity to uncover the factors that counter the risk and protect individuals from developing LOAD. The phenomenon wherein individuals demonstrate adaptability to the burden of disease risk can be referred to as "resilience". In this dissertation, I presented three studies that focused on the resilience to LOAD. Because resilience depends on and interacts with risk, we employed a risk-informed strategy to uncover resilience factors. This approach leveraged the current best-estimated LOAD risk to identify resilient individuals who, despite facing the highest LOAD risk, exhibit no dementia symptoms in old age. In Chapter 1, we demonstrated that a large number of risk-independent common genetic variants could reduce the penetrance of heightened genetic risk burden in LOAD. This study provided insights into the genetic architecture of resilience to LOAD, addressing a significant knowledge gap that requires attention. In addition, this study yielded a polygenic resilience score, enabling the assessment of the relative genetic resilience levels among individuals. In Chapters 2 and 3, we explored resilience to LOAD at the transcriptomic level. The study in Chapter 2 meta-analyzed all publicly available blood and brain transcriptomic studies of AD. This study laid the groundwork for investigating the resilience-conferring genes and pathways by establishing the best-estimated transcriptomic risk features in LOAD. In Chapter 3, we capitalized on the transcriptomic risk defined in Chapter 2 and examined the risk-residual genes that might confer resilience to increased transcriptomic risk of LOAD. This study implicated a couple of interesting pathways in resilience to LOAD and suggested that resilience and risk may operate in the same biological pathways. Taken together, our findings corroborated the idea that resilience in LOAD has a polygenic basis and highlighted the need to gain a deeper understanding of the genetic components, biological mechanisms, and phenotypic characteristics of resilience to LOAD risk. The dissertation contextualized these findings with the existing literature and suggested potential future directions to help further address the gaps in understanding resilience in LOAD.
2024-01-30T00:00:00Z