Gut barrier defect and hyperactivation of innate immune response in a Drosophila model of NGLY1 deficiency
Authors: Ashutosh Pandey 1; Seung Yeop Han 1; William F Mueller 2; Benjamin A Story 2; Antonio Galeone 3; Lars Steinmetz 2, 4; Hamed Jafar-Nejad 1
Affiliations: 1) Department of Molecular & Human Genetics, Baylor College of Medicine, Houston, TX-77030, USA; 2) Genome Biology Unit, European Molecular Biology Laboratory (EMBL), Heidelberg, Germany; 3) Department of Bioscience, University of Milan, Milan, Italy ; 4) Department of Genetics, School of Medicine, Stanford University, Stanford, CA, USA
Keywords: c. innate immunity; p. metabolic disorders
Mutations in human N-glycanase 1 (NGLY1) cause a congenital disorder of de-glycosylation (CDDG) known as NGLY1 deficiency. It is a multisystem disorder with symptoms including global developmental delay, lack of tears, movement disorders, and chronic constipation. However, the biological roles of NGLY1 and pathophysiology of NGLY1 deficiency are not well understood. The Drosophila homolog of human NGLY1 is encoded by Pngl. Loss of Pngl results in semi-lethality. Previous reports from our group have shown developmental and functional defects in Pngl mutant intestine due to impaired BMP signaling and reduced AMPKα level, respectively. However, the lethality in Pngl mutants is only partially explained by these affected pathways (BMP and AMPK). This suggests the potential contribution of other biological pathways to the lethality in Pngl mutants. To investigate this, we performed RNAseq on the midgut tissue of Pngl mutant larvae and observed mis-regulation of a number of gene categories. In agreement with previous studies, proteasomal genes constituted one of the top down-regulated gene categories. Notably, major up-regulated gene categories were related to immune response, leading to the hypothesis that hyperactivation of innate immune response might contribute to the lethality in Pngl mutants. Reducing the innate immune signaling by decreasing Toll and immune deficiency (IMD) pathways rescued the lethality of Pngl mutants by 20-23%. Decreasing the gene dosage of the forkhead box O family transcription factor Foxo (reported to induce immune genes expression in Drosophila midgut upon stress) rescued ~40% of lethality. We observed increased activation of Foxo in the Pngl mutant larval enterocytes. Fluorescently labeled dextran feeding assay showed gut barrier defects in Pngl mutant larvae. Pharmacological disruption of peritrophic matrix (a major component of the gut barrier in flies) by feeding polyoxin D to wild-type larvae showed mild lethality and increased expression of innate immune response genes. Taken together, our data present evidence for gut barrier defects and hyperactivation of innate immune response in a Drosophila model of NGLY1 deficiency.