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Double-strand breaks (DSB) are one of the most lethal forms of DNA damage that, if left unrepaired, can lead to genomic instability, cellular transformation, and cell death. In this work, we examined how repair of transcription activator-like effector nuclease (TALEN)-induced DNA damage was altered when knocking out, or inhibiting a function of, two DNA repair proteins, XRCC4 and MRE11, respectively. We developed a fluorescent reporter assay that uses TALENs to introduce DSB and detected repair by the presence of GFP fluorescence. We observed repair of TALEN-induced breaks in the XRCC4 knockout cells treated with mirin (a pharmacological inhibitor of MRE11 exonuclease activity), albeit with ~40% reduced efficiency compared to normal cells. Editing in the absence of XRCC4 or MRE11 exonuclease was robust, with little difference between the indel profiles amongst any of the groups. Reviewing the transcriptional profiles of the mirin-treated XRCC4 knockout cells showed 307 uniquely differentially expressed genes, a number far greater than for either of the other cell lines (the HeLa XRCC4 knockout sample had 83 genes, and the mirin-treated HeLa cells had 30 genes uniquely differentially expressed). Pathways unique to the XRCC4 knockout+mirin group included differential expression of p53 downstream pathways, and metabolic pathways indicating cell adaptation for energy regulation and stress response. In conclusion, our study showed that TALEN-induced DSBs are repaired, even when a key DSB repair protein or protein function is not operational, without a change in indel profiles. However, transcriptional profiles indicate the induction of unique cellular responses dependent upon the DNA repair protein(s) hampered.

Background Nontraditional students bring to medicine inherent characteristics and perspectives that enrich the learning environment and contribute to expanding diversity in medicine. However, research has shown that these students, by virtue of their sociodemographic backgrounds, face unique challenges in medical education, which ultimately place them at a disadvantage compared to traditional medical students. The purpose of this study is to explore relationships between sociodemographic factors, stress, and academic performance, in the context of student outcomes that may influence diversity in medicine. Methods Perceived Stress Scale-4 surveys collected at four educational milestones and exam performance data on 358 of 360 students were utilized for the purposes of this retrospective observational cohort study. Using independent samples t-test, mean stress and academic performance were compared between groups based on generational status, underrepresented in medicine (URM) status, socioeconomic status, and age at matriculation. Results were considered significant where (P < .05). Results First-generation college students had significantly higher stress at the end of third year clerkships (mean 7.8 vs. 6.8, P= .03). URM students had significantly lower pre-clinical exam scores (mean 81.37 vs. 83.07, P = .02). Students who were 30 years of age or older at matriculation had significantly lower exam scores on all academic performance measures. Conclusion Expanding the sociodemographic diversity among physicians, and by extension, medical students, has long been recognized as an important avenue to address healthcare inequities for marginalized populations in the US. Results from our study suggest that aspects of medical education undermine the success of URM and older medical students, and thwart well-being in first-generation medical students. Residency program directors continue to use USMLE test scores as a primary metric to screen applicants. Therefore, poor performance on these exams has profound consequences on career trajectory which, in turn, may be impeding progress towards increasing diversity in medicine. Stress, depression, burnout, the learning environment, and academic performance are intimately related. A deeper understanding of the interplay between sociodemographic characteristics and success in medical school, both psychosocially and academically, is prudent to achieve diversity in medicine and, ultimately, health equity.

Double strand breaks are one of the most lethal forms of DNA lesions that, if left unrepaired can lead to genomic instability, cellular transformation, and cell death. However, cells have two main machineries namely error prone Non homologous end joining repair (NHEJ) or an accurate homology dependent repair to repair the double strand breaks. NHEJ is the preferred mechanism for DNA repair and basically consists of two forms: Canonical (C-NHEJ) and Alternative (A-NHEJ) NHEJ. Our study examined the cellular repair outcome when NHEJ is blocked by targeting two key DNA repair proteins: XRCC4 and MRE-11. We developed an extrachromosomal NHEJ fluorescent reporter assay that uses Transcription activator-like effector nucleases (TALEN) to introduce double strand breaks and detect the NHEJ editing by the presence of GFP fluorescence. We demonstrated the presence of NHEJ editing in the XRCC4(-/-) cells treated with Mirin (a pharmacological inhibitor of MRE-11), albeit with a ~52% efficiency of the normal cells. The transcriptional profiles of the Mirin treated HeLa XRCC4(-/-) cells had 307 uniquely differentially expressed genes that was far greater than HeLa XRCC4(-/-) sample (83 genes) and Mirin treated HeLa cells (30 genes). Pathway analysis unique to the XRCC4(-/-) +Mirin group included differential expression of p53 downstream pathways, and metabolic pathways indicating cell adaptation for energy regulation and stress response. In conclusion, our study showed that the double strand DNA repair can be sustained even in absence of key DNA repair proteins XRCC4 and MRE-11.