The discovery and reliable detection of markers for neurodegenerative diseases have been complicated by the inaccessibility of the diseased tissue- such as the inability to biopsy or test tissue from the central nervous system directly. RNAs originating from hard to access tissues, such as neurons within the brain and spinal cord, have the potential to get to the periphery where they can be detected non-invasively. The formation and extracellular release of microvesicles and RNA binding proteins have been found to carry RNA from cells of the central nervous system to the periphery and protect the RNA from degradation. Extracellular miRNAs detectable in peripheral circulation can provide information about cellular changes associated with human health and disease. In order to associate miRNA signals present in cell-free peripheral biofluids with neurodegenerative disease status of patients with Alzheimer's and Parkinson's diseases, we assessed the miRNA content in cerebrospinal fluid and serum from postmortem subjects with full neuropathology evaluations. We profiled the miRNA content from 69 patients with Alzheimer's disease, 67 with Parkinson's disease and 78 neurologically normal controls using next generation small RNA sequencing (NGS). We report the average abundance of each detected miRNA in cerebrospinal fluid and in serum and describe 13 novel miRNAs that were identified. We correlated changes in miRNA expression with aspects of disease severity such as Braak stage, dementia status, plaque and tangle densities, and the presence and severity of Lewy body pathology. Many of the differentially expressed miRNAs detected in peripheral cell-free cerebrospinal fluid and serum were previously reported in the literature to be deregulated in brain tissue from patients with neurodegenerative disease. These data indicate that extracellular miRNAs detectable in the cerebrospinal fluid and serum are reflective of cell-based changes in pathology and can be used to assess disease progression and therapeutic efficacy.

In this study, we assess 34 of the most replicated genetic associations for Alzheimer's disease (AD) using data generated on Affymetrix SNP 6.0 arrays and imputed at over 5.7 million markers from a unique cohort of over 1600 neuropathologically defined AD cases and controls (1019 cases and 591 controls). Testing the top genes from the AlzGene meta-analysis, we confirm the well-known association with APOE single nucleotide polymorphisms (SNPs), the CLU, PICALM and CR1 SNPs recently implicated in unusually large data sets, and previously implicated CST3 and ACE SNPs. In the cases of CLU, PICALM and CR1, as well as in APOE, the odds ratios we find are slightly larger than those previously reported in clinical samples, consistent with what we believe to be more accurate classification of disease in the clinically characterized and neuropathologically confirmed AD cases and controls.

Recent advances in sample preparation and analysis for next generation sequencing have made it possible to profile and discover new miRNAs in a high throughput manner. In the case of neurological disease and injury, these types of experiments have been more limited. Possibly because tissues such as the brain and spinal cord are inaccessible for direct sampling in living patients, and indirect sampling of blood and cerebrospinal fluid are affected by low amounts of RNA. We used a mouse model to examine changes in miRNA expression in response to acute nerve crush. We assayed miRNA from both muscle tissue and blood plasma. We examined how the depth of coverage (the number of mapped reads) changed the number of detectable miRNAs in each sample type. We also found that samples with very low starting amounts of RNA (mouse plasma) made high depth of mature miRNA coverage more difficult to obtain. Each tissue must be assessed independently for the depth of coverage required to adequately power detection of differential expression, weighed against the cost of sequencing that sample to the adequate depth. We explored the changes in total mapped reads and differential expression results generated by three different software packages: miRDeep2, miRNAKey, and miRExpress and two different analysis packages, DESeq and EdgeR. We also examine the accuracy of using miRDeep2 to predict novel miRNAs and subsequently detect them in the samples using qRT-PCR.

Introduction: Safety concerns surrounding the coronavirus 2019 pandemic led to the prohibition of student rotations outside their home institutions. This resulted in emergency medicine (EM)-bound students having less specialty experience and exposure to outside programs and practice environments, and fewer opportunities to gain additional Standardized Letters of Evaluation, a cornerstone of the EM residency application. We filled this void by implementing a virtual clerkship. Methods: We created a two-week virtual, fourth-year visiting clerkship focused on advanced medical knowledge topics, social determinants of health, professional development, and professional identity formation. Students completed asynchronous assignments and participated in small group-facilitated didactic sessions. We evaluated the virtual clerkship with pre- and post-medical knowledge tests and evaluative surveys. Results: We hosted 26 senior medical students over two administrations of the same two-week virtual clerkship. Students had a statistically significant improvement on the medical knowledge post-tests compared to pre-tests (71.7% [21.5/30] to 76.3% [22.9/30]). Students reported being exposed to social determinants of health concepts they had not previously been exposed to. Students appreciated the interactive nature of the sessions; networking with other students, residents, and faculty; introduction to novel content regarding social determinants of health; and exposure to future career opportunities. Screen time, technological issues, and mismatch between volume of content and time allotted were identified as potential challenges and areas for improvement. Conclusion: We demonstrate that a virtual EM visiting clerkship is feasible to implement, supports knowledge acquisition, and is perceived as valuable by participants. The benefits seen and challenges faced in the development and implementation of our clerkship can serve to inform future virtual clerkships, which we feel is a complement to traditional visiting clerkships even though in-person clerkships have been re-established.

In a genome-wide association study (GWAS) of late-onset Alzheimer's disease (AD), we found an association between common haplotypes of the GAB2 gene and AD risk in carriers of the apolipoprotein E (APOE) ε4 allele, the major late-onset AD susceptibility gene. We previously proposed the use of fluorodeoxyglucose positron emission tomography (FDG-PET) measurements as a quantitative presymptomatic endophenotype, more closely related to disease risk than the clinical syndrome itself, to help evaluate putative genetic and non-genetic modifiers of AD risk. In this study, we examined the relationship between the presence or absence of the relatively protective GAB2 haplotype and PET measurements of regional-to-whole brain FDG uptake in several AD-affected brain regions in 158 cognitively normal late-middle-aged APOEε4 homozygotes, heterozygotes, and non-carriers. GAB2 haplotypes were characterized using Affymetrix Genome-Wide Human SNP 6.0 Array data from each of these subjects. As predicted,