Host microRNA expression may influence various blood traits that, in turn, affect COVID-19 disease severity, a new study appearing in Human Genomics reports. Researchers from New York University Abu Dhabi examined electronic health record data for 259 unvaccinated COVID-19 patients and, for 96 of those patients, they also analyzed genotypic, miRNA, and RNA expression data from samples collected at hospital admission. Nearly quarter of patients were admitted to the intensive care unit at some point in their hospital stay, and the researchers found 97 miRNAs associated with eight blood phenotypes significantly associated with those later ICU admission. For instance, they found that miR-143-3p modulates the expression of its target gene, BCL2, which itself affects neutrophil count. In all, they identified 168 significant cis-miRNA expression quantitative trait loci, about a third of which tie an miRNA to ICU admission or a blood endophenotype. "This study demonstrates that microRNAs are promising biomarkers for disease severity, more broadly, and targets for therapeutic interventions," senior author Youssef Idaghdour from NYU Abu Dhabi says in a statement. "The methods of this study can be applied to other populations to further our understanding of how gene regulation can serve as a core mechanism that impacts COVID-19 and, potentially, severity of other infections."