International policies guiding the selection, analysis, and clinical management of secondary findings from genomic sequencing: A systematic review.

Secondary findings (SFs) from genomic sequencing can have significant impacts on patient health, yet existing practices guiding their clinical investigation are inconsistent. We systematically reviewed existing SFs policies to identify variations and gaps in guidance. We cataloged and appraised international policies from academic databases (n = 5, inception-02/2022) and international human genetic societies (n = 64; inception-05/2022), across the continuum of SFs selection, analysis, and clinical management. We assessed quality using AGREE-II and interpreted results using qualitative description. Of the 63 SFs policies identified, most pertained to clinical management of SFs (98%; n = 62; primarily consent and disclosure), some guided SFs analysis (60%; n = 38), while fewer mentioned SFs selection (48%; n = 30). Overall, policies recommend (1) identifying clinically actionable, pathogenic variants with high positive predictive values for disease (selection), (2) bioinformatically filtering variants using evidence-informed gene lists (analysis), and (3) discussing with affected individuals the SFs identified, their penetrance, expressivity, medical implications, and management (clinical management). Best practices for SFs variant analysis, clinical validation, and follow-up (i.e., surveillance, treatment, etc.) were minimally described. Upon quality assessment, policies were highly rated for scope and clarity (median score, 69) but were limited by their rigor and applicability (median scores, 27 and 25). Our review represents a comprehensive international synthesis of policy guiding SFs across the continuum of selection, analysis, and clinical management. Our synthesis will help providers navigate critical decision points in SFs investigation, although significant work is needed to address gaps in SFs analysis, clinical validation, and follow-up processes and to support evidence-based practice.

Neuron-derived extracellular vesicles enriched from plasma show altered size and miRNA cargo as a function of antidepressant drug response.

Previous work has demonstrated that microRNAs (miRNAs) change as a function of antidepressant treatment (ADT) response. However, it is unclear how representative these peripherally detected miRNA changes are to those occurring in the brain. This study aimed to use peripherally extracted neuron-derived extracellular vesicles (NDEV) to circumvent these limitations and investigate neuronal miRNA changes associated with antidepressant response. Samples were collected at two time points (baseline and after 8 weeks of follow-up) from depressed patients who responded (N = 20) and did not respond (N = 20) to escitalopram treatment, as well as controls (N = 20). Total extracellular vesicles (EVs) were extracted from plasma, and then further enriched for NDEV by immunoprecipitation with L1CAM. EVs and NDEVs were characterized, and NDEV miRNA cargo was extracted and sequenced. Subsequently, studies in cell lines and postmortem tissue were conducted. Characterization of NDEVs revealed that they were smaller than other EVs isolated from plasma (p < 0.0001), had brain-specific neuronal markers, and contained miRNAs enriched for brain functions (p < 0.0001) Furthermore, NDEVs from depressed patients were smaller than controls (p < 0.05), and NDEV size increased with ADT response (p < 0.01). Finally, changes in NDEV cargo, specifically changes in miR-21-5p, miR-30d-5p, and miR-486-5p together (p < 0.01), were associated with ADT response. Targets of these three miRNAs were altered in brain tissue from depressed individuals (p < 0.05). Together, this study indicates that changes in peripherally isolated NDEV can act as both a clinically accessible and informative biomarker of ADT response specifically through size and cargo.

The emerging role of exosomes in mental disorders.

Exosomes are a class of extracellular vesicles of endocytic origin, which are released by cells and are accessible in biofluids, such as saliva, urine, and plasma. These vesicles are enriched with small RNA, and they play a role in many physiological processes. In the brain, they are involved in processes including synaptic plasticity, neuronal stress response, cell-to-cell communication and neurogenesis. While exosomes have been implicated previously in cancer and neurodegenerative diseases, research regarding their role in mental disorders remains scarce. Given their functional significance in the brain, investigation in this field is warranted. Additionally, because exosomes can cross the blood-brain barrier, they may serve as accessible biomarkers of neural dysfunction. Studying exosomes may provide information towards diagnosis and therapeutic intervention, and specifically those derived from the brain may provide a mechanistic view of the disease phenotype. This review will discuss the roles of exosomes in the brain, and relate novel findings to current insights into mental disorders.