Hypoxia-inducible factor 1α is required to establish the larval glycolytic program inDrosophila melanogaster
Authors: Heidarian Yasaman , Fasteen Tess D. , Mungcal Liam , Buddika Kasun , Mahmoudzadeh Nader H. , Nemkov Travis , D’Alessandro Angelo , Tennessen Jason M. 
Published: January 2025

ABSTRACTThe rapid growth that occurs duringDrosophilalarval development requires a dramatic rewiring of central carbon metabolism to support biosynthesis. Larvae achieve this metabolic state, in part, by coordinately up-regulating the expression of genes involved in carbohydrate metabolism. The resulting metabolic program exhibits hallmark characteristics of aerobic glycolysis and establishes a physiological state that supports growth. To date, the only factor known to activate the larval glycolytic program is theDrosophilaEstrogen-Related Receptor (dERR). However, dERR is dynamically regulated during the onset of this metabolic switch, indicating that other factors must be involved. Here we discover that Sima, theDrosophilaortholog of Hif1α, is also essential for establishing the larval glycolytic program. Using a multi-omics approach, we demonstrate thatsimamutants fail to properly activate aerobic glycolysis and die during larval development with metabolic defects that phenocopydERRmutants. Moreover, we demonstrate that dERR and Sima/Hif1α protein accumulation is mutually dependent, as loss of either transcription factor results in decreased abundance of the other protein. Considering that the mammalian homologs of ERR and Hif1α also cooperatively regulate aerobic glycolysis in cancer cells, our findings establish the fly as a powerful genetic model for studying the interaction between these two key metabolic regulators.STRUCTURED ABSTRACTObjectivesThe rapid growth that occurs duringDrosophilalarval development requires a dramatic rewiring of central carbon metabolism to support biosynthesis. Larvae achieve this metabolic state, in part, by coordinately up-regulating the expression of genes involved in carbohydrate metabolism. The resulting metabolic program exhibits hallmark characteristics of aerobic glycolysis and establishes a physiological state that supports growth. To date, the only factor known to activate the larval glycolytic program is theDrosophilaEstrogen-Related Receptor (dERR).However, dERR is dynamically regulated during the onset of this metabolic switch, indicating that other factors must be involved. Here we examine the possibility theDrosophilaortholog of Hypoxia inducible factor 1α (Hif1α) is also required to activate the larval glycolytic program.MethodsCRISPR/Cas9 was used to generate new loss-of-function alleles in theDrosophilagenesimilar(sima), which encodes the sole fly ortholog of Hif1α. The resulting mutant strains were analyzed using a combination of metabolomics and RNAseq for defects in carbohydrate metabolism.ResultsOur studies reveal thatsimamutants fail to activate aerobic glycolysis and die during larval development with metabolic phenotypes that mimic those displayed bydERRmutants. Moreover, we demonstrate that dERR and Sima/Hif1α protein accumulation is mutually dependent, as loss of either transcription factor results in decreased abundance the other protein.ConclusionsThese findings demonstrate that Sima/HIF1α is required during embryogenesis to coordinately up-regulate carbohydrate metabolism in preparation for larval growth. Notably, our study also reveals that the Sima-dependent gene expression profile shares considerable overlap with that observed indERRmutant, suggesting that Sima/HIF1α and dERR cooperatively regulate embryonic and larval glycolytic gene expression.HIGHLIGHTSTheDrosophila melanogastergenesimilar(sima), which encodes the sole fly ortholog of Hif1α, is required to up-regulate glycolysis in preparation for larval growth.simamutant larvae exhibit severe defects in carbohydrate metabolism and die during the second larval instar.simamutant larvae exhibit the same metabolic phenotypes asDrosophila Estrogen Related Receptor(dERR) mutants, suggesting that these two transcription factors coordinately regulate the larval glycolytic program.Sima/Hif1α and dERR accumulation is mutually dependent, as loss of either transcription factor results in decreased abundance of the other.