Alzheimer’s disease (AD) is a progressive neurological disorder associated with protein deposits in the brain, and causes a decline in memory, cognition, and social skills. There is no cure for AD, and as the disease advances, complications lead to incapacitation and death. Insulin-like growth factor 1 receptor (IGF1r) is a transmembrane receptor that responds to the hormone insulin-like growth factor 1, and is associated with healthy aging. An IGF1r variant in exon 6 (Arg-407-His) was found to be enriched in centenarians compared to shorter-lived relatives. Characterizing the role of this IGF1r variant in the development and progression of AD would provide information into a novel therapeutic target. Older-aged C57BL6 mice expressing a CRISPr-generated human Arg-407-His variant of the IGF1r gene were intravenously injected with a neurogenic AAV vector, consisting of the pathogenic components Aβ42 and p301L tau, or SHAM. After 3 months, mice with the IGF1r variant found escape holes more quickly than mice without the variant, using a spatial navigation learning task. Following humane euthanasia, brains were collected and fixed in formalin for immunohistochemistry (IHC). Brain sections were stained with biomarkers for Aêžµ42, ptau, and inflammatory microglia, and digitally imaged for quantitative analysis. Brains from IGF1r variant mice showed a decrease in expression of Aêžµ42 and ptau in line with improved cognition, and an increase in inflammatory glial cells. These preliminary observations help establish IGF1r Arg-407-His variant mice as a model to better understand the role of IGF1r in AD neuropathology, and provide insight into new potential therapeutic approaches for older human patients with AD.

Cognitive decline with increasing age is an aspect of growing old. Age-related cognitive impairment (ARCI) entails the early stages of decline and is extremely common, affecting millions of older people. However, little is known about why some people have ARCI and some are cognitively normal at older ages. A recently characterized mouse model of naturally occurring ARCI, showing a distribution of affected and non-affected animals similar to older humans, was used to interrogate brain samples for transcriptomic profiles generated by RNA sequencing (RNA-seq). Hippocampal brain samples were collected from 22-month-old male and female C57BL/6 mice with and without ARCI (as determined by a spatial navigation learning task). RNA-seq was done by the NovoGene UC Davis sequencing Center. Preliminary data show a stronger presence of pathways of neurodegeneration and oxidative phosphorylation in the hippocampus of mice with ARCI compared to mice without ARCI. Detailed computational analysis will be done to investigate gene-expression quantifications using sequencing pipelines aligning Differential Gene Expression, KEGG orthology pathways, and Star RNA-seq read mapper in order to more accurately identify unique transcriptomic profiles in the brains of mice with and without ARCI. These findings will help identify genetic pathways that could be therapeutically targeted to ameliorate and possibly reverse the effects of ARCI, and provide insight into internal brain factors responsible for an increased risk in developing more severe conditions of neurodegeneration and dementia such as Alzheimer’s disease.

Joubert syndrome (JS) is a neurodevelopmental condition diagnosed by the appearance of the “molar tooth sign” on axial brain magnetic imaging (MRI). Patients display hypotonia, abnormal eye movements, and ataxia. Substantial progress has been made on identifying the genetic causes of JS, which typically displays recessive inheritance. Nonetheless, the cause cannot be identified in ~25% of our cohort of JS-affected families. The contribution of variants that impact RNA splicing remains unknown. Our goal is to evaluate the role of noncanonical splice variants in the pathogenesis of JS. Canonical splice variants impact RNA splicing by disrupting the splice site directly, whereas noncanonical splice variants may affect it through alternative mechanisms, which need to be validated by RNA analysis. We previously identified genetic causes in 520 of 679 families with JS. To identify additional causes, we used SpliceAI (SpliceAI score >0.5) to identify candidate variants that impact splicing. We extracted RNA from patient cell lines and converted it into complementary DNA (cDNA). Then we used polymerase chain reaction (PCR) to amplify the affected exons with two sets of primers flanking the relevant splice junction. We evaluated PCR product size and sequence using gel electrophoresis and Sanger sequencing. We found 74 families with ≥1 canonical splice variant. An additional 34 families have ≥1 candidate noncanonical splice variant. We confirmed the pathogenicity of two of the candidate noncanonical splice variants by demonstrating an abnormal splicing event in AHI1 and MKS1 in two patient samples. By extrapolation from our data in JS, noncanonical splice variants may contribute as much as 10% to the genetic causes of recessive conditions. A precise genetic diagnosis informs prognosis, avoids unnecessary work-up, guides monitoring for associated complications, and opens the door to gene-specific treatments.

Merkel cell carcinoma (MCC) is an aggressive skin cancer with high risk of metastasis. Recent developments of PD-1/PD-L1 immunotherapy significantly improved treatment outcomes of metastatic MCC. While approximately half of patients respond to immunotherapy, the other half of the patients do not benefit. Thus, it has become increasingly important to identify factors that potentially impact immunotherapy response. Multiple studies in melanoma have demonstrated that patients who are older or have a higher body mass index (BMI) show better immunotherapy response. The purpose of this study is to explore the effects of age and/or BMI in MCC patients to immunotherapy response. I helped create a cohort of 183 patients who had undergone immunotherapy initially identified in a longitudinal single center registry. I then helped collect information about age and BMI at the start of immunotherapy along with other clinical features. Treatment response, disease-specific and overall survival were analyzed in 183 patients using cox regression and natural cubic spline models. During this process, I assisted in distinguishing the number of splines we would like to use for our analysis, as well as choosing the best model to accurately represent data for different variables. After adjusting for age, sex, and stage, BMI did not have significant impact on overall survival (p=1.0), objective response (p=0.5), or disease progression (p=0.8) while on immunotherapy. A nonlinear relationship between age and immunotherapy response was observed and showed potentially worse response to treatment in older patients. However, this was not statistically significant (p<0.1). Unlike prior studies in melanoma, we found that BMI does not have a significant impact on immunotherapy in MCC. Older age may have a negative impact on the response. This warrants additional research into the difference between melanoma and MCC to further elucidate mechanism of actions.