CONICET | Buscador de Institutos y Recursos Humanos

orsai (osi), a novel gene we are characterizing in the lab, is consideredto be part of the LYR domain containing protein family.This family includes proteins involved in the assembly or activity ofthe mitochondrial complex I as a structural component, accessoryprotein, co-factor or part of the assemble machinery of iron-sulfurclusters. The human orthologue of osi, recently characterized, isinvolved in acute encephalopathy, seizures, mild spasticity and neuroradiologicalfeatures when mutated. The main goal of this work isto shed light on osi´s function. As a first step we analyzed its cellularand subcellular localization, as well as the phenotypes triggered byits dysfunction.In Drosophila, while control larvae feed until they reach the criticalweight, osi mutants stop feeding and die early on, as stage 1 larvae.We monitored feeding, locomotion, and olfactory responses inwell characterized behavioral paradigms and performed growth andsurvival curves to examine larval phenotypes in depth; in addition,we performed biochemical experiments to assess mitochondrialfunction; immunostaining to define localization of the protein andelectron microscopy to register morphological phenotypes. Resultswere analyzed using t-test or ANOVA whenever necessary. Behavioralassays suggest that osi mutants respond normally to olfactorycues and are capable of feeding; however, osi depleted larvaebarely grow in size. At the molecular level, this phenotype correlateswith a clear impairment in basal metabolism, characterized by reducedoxygen consumption, decreased mitochondrial ATP alongwith increased ROS levels. As a result, mitochondria are smallerand fragmented. In addition, reduced OSI levels trigger a defectivecell size and shape. Surprisingly, in most tissues OSI was not foundin mitochondria but in the nucleus.From all data we propose that OSI is a nuclear regulator of cellularmetabolism.