University of Massachusetts Chan Medical School

STING is an evolutionarily conserved key regulator of innate immunity. In the model organism Drosophila melanogaster, STING activates the NF-κB-like transcription factor Relish, initially characterized for its role in the antibacterial IMD pathway. The versatile FADD/Caspase-8 axis is widely used in various immune signaling pathways throughout the animal kingdom, including the IMD pathway. Here, we show that it functions downstream of STING in Drosophila to mediate Relish activation by the Caspase-8 homolog DREDD. We present a detailed structural model illustrating how the adapter protein FADD interacts with two separate STING dimers in the activated oligomerized form of STING, thus providing a molecular explanation for the activation-dependent recruitment of FADD. We further show that FADD interacts with IMD in a structurally distinct but functionally related manner, highlighting how the STING and IMD pathways differentially utilize the adapter protein FADD. Our results illustrate how an ancestral module is incorporated into different innate immune pathways, providing insights into the evolution of host-pathogen interactions.

Mutant phenotypes often vary across genetically distinct individuals. To identify the causes of such genetic background effects, we studied differences in gene essentiality across 18 genetically diverse natural yeast strains. We identified 39 genes that were essential in the laboratory reference strain but not in at least one other genetic background, and we mapped and validated the genetic variants that were responsible for the differences in gene essentiality. These variants typically occurred in single modifier genes that tended to differ between genetic backgrounds. The affected genes often indirectly compensated for the loss of the essential gene and identified naturally occurring evolutionary trajectories. Overall, our results highlight the prevalence of changes in gene essentiality in natural populations, as well as the underlying mechanisms. A thorough understanding of the causes of genetic background effects is crucial for the interpretation of genotype-to-phenotype relationships, including those associated with human disease.

Influenza increases thrombotic risk, and its viral RNA (vRNA) can be sensed by the pattern-recognition receptor, RIG-I, but the function of RIG-I in platelets remains unknown. We sought to determine whether RIG-I can signal in platelets and contribute to thrombotic outcomes. Using RT-qPCR, SDS-, NATIVE-PAGE, and proteomic methods in platelets from non-infected and influenza-infected patients, we show that RIG-I is present and functional. Platelet-RIG-I activation by influenza-derived-vRNA (hpRNA) did not result in α- or δ granule release, or to interferon-pathway activation. Classical RIG-I signaling kinases TBK1 and IkBα were not consistently phosphorylated using hpRNA. Two methods of treatment were evaluated: naked hpRNA and hpRNA in combination with a transfection reagent, lyoVec. Both showed inconsistencies when evaluating phosphorylation of RIG-I downstream kinases in non-infected donors and influenza patients. Interestingly, we found that thrombin (IIa) treatment of platelets resulted in phosphorylation of TBK1. Upon inhibition of this phosphorylation using a small molecule inhibitor, amlexanox (amx), platelet aggregation was reduced in both non-infected donors and influenza patients. This pathway may differ from traditional RIG-I signaling as RIG-I may be degraded as a result of IIa signaling. Naked hpRNA treatments were then used throughout the remainder of the study. Using this method, we found RIG-I signaled through MAVS to increase MLKL-phosphorylation (pMLKL) and Gasdermin E (GSDME) N-fragment cleavage, but not Gasdermin D (GSDMD) N-fragment cleavage. Similarly, RIGI/MAVS signaling increased MLKL and GSDME oligomers and not GSDMD oligomers. MLKL oligomers, but not GSDME oligomers were shown to be MAVS specific. Activation of the RIG-I/MAVS/MLKL axis showed S100A10 (but not S100A8/A9) release and surface presence. Oligomerized pMLKL led to surface punctures, evident by scanning electron microscopy, which were also visible in thrombin-induced platelet clots. Consistent with S100A10 surface localization, RIG-I activation in presence of plasminogen reduced platelet aggregation and led to increased disaggregation in presence of uPA (urokinase-type plasminogen activator). Time-dependent antiviral or prothrombotic changes as a function of RIG-I were determined in platelets isolated every 24 hours for 7 days from influenza (PR8-strain, 50 pfu) infected control and MAVS KO mice. Absence of RIG-I signaling, assessed by using MAVS KO mice, resulted in less favorable FeCl₃-induced carotid artery thrombotic outcomes in vivo during influenza infection. Tail bleed assays showed similar non-favorable thrombotic outcomes in MAVS KO mice on day 3 post-influenza infection. Similar changes in thrombotic impact were observed in the pulmonary veins of infected mice, where thrombus area inversely correlated with leukocyte transmigration early in infection, followed by positive association later on. Our study is the first to demonstrate that platelets have a functionally active vRNA-sensing RIG-I receptor that regulates thrombotic risk and facilitates appropriate leukocyte transmigration during infection.

Equitable access to clinical studies is essential to ensuring that research findings are generalizable, inclusive, and reflective of all populations. When specific demographic or geographic groups are excluded from participation, the external validity of clinical research is undermined and inequities in treatment access are perpetuated. Autoimmune skin disorders are uncommon and often affect patients living far from major research centers, yet no comprehensive analysis of national clinical study accessibility for these conditions has been conducted. We conducted a retrospective, population-level analysis of study accessibility for autoimmune skin disorders in the United States from 2005 to 2024 using ClinicalTrials.gov and U.S. Census data. Population centers were defined as geographic centroids of ZIP codes, and the distance from each population center to the nearest study site was calculated. Trend analyses assessed changes in accessibility over time and differences across racial and urban–rural categories. Although the number of studies has increased over time (approximately six additional studies annually), travel distances to the nearest study site remain substantial. The average distance has decreased modestly by about 3.4 km per year, but 40% of Americans still live more than 200 km from the closest study site, with the greatest distances observed among rural and American Indian populations. Expanding population coverage requires rapidly increasing travel distances. These findings highlight persistent disparities in access to clinical studies. While decentralization and virtual study models may help reduce these gaps, further research is needed to determine whether such strategies effectively improve participation and representation.