Publications by authors named "Timothy S Chang"

Background: Alzheimer's disease (AD) is a leading cause of dementia and an escalating public health concern. Although recent research has identified multiple AD risk factors, most studies examine isolated comorbidities rather than complex, sequential progressions. In this study, we sought to identify multi-step trajectories culminating in AD by analysing longitudinal electronic health records (EHRs).

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Coupling genetic profiling with electronic health records from hospital biobanks is a foundational resource for precision medicine. However, lack of ancestral heterogeneity limits discovery and generalizability. We leveraged the UCLA ATLAS Community Health Initiative, a diverse biobank with >35% non-European participants in a single health system, to inform disease prevalence and genetic risk across five continental and 36 fine-scale ancestry groups.

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Background: Progressive supranuclear palsy (PSP) is a rare neurodegenerative disorder characterized by parkinsonism and impairments in balance, language, and cognition. As an atypical parkinsonism, PSP progresses rapidly, lacks effective treatments, and poses significant caregiving burdens. While prior studies have identified risk factors, they often fail to capture the complex temporal dynamics of co-occurring conditions.

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Introduction: Brain network dysfunction, particularly within the default mode network (DMN), is an increasingly apparent contributor to the clinical progression of Alzheimer's disease (AD). Repetitive transcranial magnetic stimulation (rTMS) can target key DMN hubs, maintain signaling function, and delay or improve clinical outcomes in AD. Here, we present the rationale and design of a study using off-the-shelf equipment and the latest clinical evidence to expand on prior rTMS work and reduce participant burden in the process.

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Background: The 17q21.31 region with various structural forms characterized by the H1/H2 haplotypes and three large copy number variations (CNVs) represents the strongest risk locus in progressive supranuclear palsy (PSP).

Objective: To investigate the association between CNVs and structural forms on 17q.

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Genetic risk modeling for dementia offers significant benefits, but studies based on real-world data, particularly for underrepresented populations, are limited. We employ an Elastic Net model for dementia risk prediction using single-nucleotide polymorphisms prioritized by functional genomic data from multiple neurodegenerative disease genome-wide association studies. We compare this model with APOE and polygenic risk score models across genetic ancestry groups (Hispanic Latino American sample: 610 patients with 126 cases; African American sample: 440 patients with 84 cases; East Asian American sample: 673 patients with 75 cases), using electronic health records from UCLA Health for discovery and the All of Us cohort for validation.

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Article Synopsis
  • Progressive supranuclear palsy (PSP) is a rare neurodegenerative disease linked to abnormal tau protein accumulation, and previous studies were limited in exploring rare genetic variants due to the use of genotype arrays.* -
  • In this study, whole genome sequencing (WGS) on a large cohort allowed researchers to confirm known genetic loci related to PSP and discover new associations, particularly highlighting a different role for the APOE ε2 allele compared to Alzheimer's disease.* -
  • The findings expand knowledge of PSP's genetic underpinnings and identify potential targets for future research into the disease's mechanisms and treatments.*
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Importance: The chromosome 17q21.31 region, containing a 900 Kb inversion that defines H1 and H2 haplotypes, represents the strongest genetic risk locus in progressive supranuclear palsy (PSP). In addition to H1 and H2, various structural forms of 17q21.

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Background: Previous studies have established a strong link between late-onset epilepsy (LOE) and Alzheimer's disease (AD). However, their shared genetic risk beyond the gene remains unclear. Our study sought to examine the shared genetic factors of AD and LOE, interpret the biological pathways involved, and evaluate how AD onset may be mediated by LOE and shared genetic risks.

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Background: Genetic risk modeling for dementia offers significant benefits, but studies based on real-world data, particularly for underrepresented populations, are limited.

Methods: We employed an Elastic Net model for dementia risk prediction using single-nucleotide polymorphisms prioritized by functional genomic data from multiple neurodegenerative disease genome-wide association studies. We compared this model with and polygenic risk score models across genetic ancestry groups, using electronic health records from UCLA Health for discovery and All of Us cohort for validation.

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Article Synopsis
  • Progressive supranuclear palsy (PSP) is a rare neurodegenerative disease linked to tau protein accumulation, and previous studies using genotype arrays overlooked important genetic variations like rare variants and structural changes.* -
  • This study utilized whole genome sequencing (WGS) involving 1,718 PSP patients and 2,944 controls, confirming known genetic markers and discovering new associations, including the unique role of the ε2 allele as a risk factor.* -
  • The findings from this research advance the understanding of PSP genetics, highlighting potential new targets for disease mechanisms and treatment strategies.*
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ApoE4 is the primary risk factor for Alzheimer Disease (AD). Early AD pathological events first affect the neuronal endolysosomal system, which in turn causes neuronal protein aggregation and cell death. Despite the crucial influence of lysosomes upon AD pathophysiology, and that apoE4 localizes to lysosomes, the influence of apoE4 on lysosomal function remains unexplored.

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Autism spectrum disorder (ASD) has a complex genetic architecture involving contributions from both de novo and inherited variation. Few studies have been designed to address the role of rare inherited variation or its interaction with common polygenic risk in ASD. Here, we performed whole-genome sequencing of the largest cohort of multiplex families to date, consisting of 4,551 individuals in 1,004 families having two or more autistic children.

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An individual's disease risk is affected by the populations that they belong to, due to shared genetics and environmental factors. The study of fine-scale populations in clinical care is important for identifying and reducing health disparities and for developing personalized interventions. To assess patterns of clinical diagnoses and healthcare utilization by fine-scale populations, we leveraged genetic data and electronic medical records from 35,968 patients as part of the UCLA ATLAS Community Health Initiative.

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Characterizing disease relationships is essential to biomedical research to understand disease etiology and improve clinical decision-making. Measurements of distance between disease pairs enable valuable research tasks, such as subgrouping patients and identifying common time courses of disease onset. Distance metrics developed in prior work focused on smaller, targeted disease sets.

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To capture the full spectrum of genetic risk for autism, we performed a two-stage analysis of rare de novo and inherited coding variants in 42,607 autism cases, including 35,130 new cases recruited online by SPARK. We identified 60 genes with exome-wide significance (P < 2.5 × 10), including five new risk genes (NAV3, ITSN1, MARK2, SCAF1 and HNRNPUL2).

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Alzheimer's disease (AD) is the most common form of dementia and a growing public health burden in the United States. Significant progress has been made in identifying genetic risk for AD, but limited studies have investigated how AD genetic risk may be associated with other disease conditions in an unbiased fashion. In this study, we conducted a phenome-wide association study (PheWAS) by genetic ancestry groups within a large academic health system using the polygenic risk score (PRS) for AD.

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Tau (MAPT) drives neuronal dysfunction in Alzheimer disease (AD) and other tauopathies. To dissect the underlying mechanisms, we combined an engineered ascorbic acid peroxidase (APEX) approach with quantitative affinity purification mass spectrometry (AP-MS) followed by proximity ligation assay (PLA) to characterize Tau interactomes modified by neuronal activity and mutations that cause frontotemporal dementia (FTD) in human induced pluripotent stem cell (iPSC)-derived neurons. We established interactions of Tau with presynaptic vesicle proteins during activity-dependent Tau secretion and mapped the Tau-binding sites to the cytosolic domains of integral synaptic vesicle proteins.

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Coronavirus disease 2019 (COVID-19) has exposed health care disparities in minority groups including Hispanics/Latinxs (HL). Studies of COVID-19 risk factors for HL have relied on county-level data. We investigated COVID-19 risk factors in HL using individual-level, electronic health records in a Los Angeles health system between March 9, 2020, and August 31, 2020.

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Article Synopsis
  • The study investigates how genes and pathways related to the immune system in the brain contribute to neurodegenerative diseases like Alzheimer's, frontotemporal dementia, and progressive supranuclear palsy by analyzing microglial cells and brain tissue from mice and humans.
  • Researchers found that microglial immune responses evolve over time, beginning with a type 1 interferon response linked to tau pathology, then shifting to immune suppression, and finally a type 2 interferon response.
  • The team identified specific gene expression patterns related to genetic risk for each type of dementia and established two major microglial activation states, while also validating these findings with various advanced techniques, suggesting new directions for potential treatments.
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With the continuing coronavirus disease 2019 (COVID-19) pandemic coupled with phased reopening, it is critical to identify risk factors associated with susceptibility and severity of disease in a diverse population to help shape government policies, guide clinical decision making, and prioritize future COVID-19 research. In this retrospective case-control study, we used de-identified electronic health records (EHR) from the University of California Los Angeles (UCLA) Health System between March 9, 2020 and June 14, 2020 to identify risk factors for COVID-19 susceptibility (severe acute respiratory distress syndrome coronavirus 2 (SARS-CoV-2) PCR test positive), inpatient admission, and severe outcomes (treatment in an intensive care unit or intubation). Of the 26,602 individuals tested by PCR for SARS-CoV-2, 992 were COVID-19 positive (3.

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Data-driven analyses are increasingly valued in modern medicine. We integrate quantitative proteomics and transcriptomics from over 1,000 post-mortem brains from six cohorts representing Alzheimer's disease (AD), asymptomatic AD, progressive supranuclear palsy (PSP), and control patients from the Accelerating Medicines Partnership - Alzheimer's Disease consortium. We define robust co-expression trajectories related to disease progression, including early neuronal, microglial, astrocyte, and immune response modules, and later mRNA splicing and mitochondrial modules.

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Article Synopsis
  • The 2013 ACC/AHA guidelines for statin therapy included a complex 10-year risk calculation, leading to low compliance with recommended statin prescriptions among eligible patients.
  • A clinical decision support tool, known as the "statin macro," was developed to streamline guideline recommendations within electronic health records, targeting patients who had not been prescribed statins prior to the study.
  • In a study with 11,877 eligible patients, only 3.2% were documented using the statin macro, resulting in an increase in statin prescriptions for 28% of those patients during the study period.
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