Neurodegeneration in Drop-Dead Mutant Drosophila melanogaster Is Associated with the Respiratory System but Not with Hypoxia

Abstract

Mutations in the gene drop-dead (drd) cause diverse phenotypes in adult Drosophila melanogaster including early lethality, neurodegeneration, tracheal defects, gut dysfunction, reduced body mass, and female sterility. Despite the identification of the drd gene itself, the causes of early lethality and neurodegeneration in the mutant flies remain unknown. To determine the pattern of drd expression associated with the neurodegenerative phenotype, knockdown of drd with various Gal4 drivers was performed. Early adult lethality and neurodegeneration were observed upon knockdown of drd in the tracheal system with two independent insertions of the breathless-Gal4 driver and upon knockdown in the tracheal system and elsewhere with the DJ717-Gal4 driver. Surprisingly, rescue of drd expression exclusively in the tracheae in otherwise mutant flies rescued the neurodegenerative phenotype but not adult lethality. Gut dysfunction, as measured by defecation rate, was not rescued in these flies, and gut function appeared normal upon tracheal-specific knockdown of drd. Finally, the hypothesis that tracheal dysfunction in drd mutants results in hypoxia was tested. Hypoxia-sensitive reporter transgenes (LDH-Gal4 and LDH-LacZ) were placed on a drd mutant background, but enhanced expression of these reporters was not observed. In addition, manipulation of drd expression in the tracheae did not affect expression of the hypoxia-induced genes LDH, tango, and similar. Overall, these results indicate that there are at least two causes of adult lethality in drd mutants, that gut dysfunction and neurodegeneration are independent phenotypes, and that neurodegeneration is associated with tracheal expression of drd but not with hypoxia.

Hypoxia Activates Calpains in the Nerve Fiber Layer of Monkey Retinal Explants

“…Each explant was cultured with the RGC side facing up on microporous membranes (Millipore, Billerica, MA, USA) in six-well culture plates at 378C under 5% CO 2 in Neurobasal-A medium supplemented with B27 and N2 supplement, and 2 mM L-glutamine (all from Life Technologies), and 100 lg/mL primocine (Invivogen, San Diego, CA, USA). After 3 hours, retinal explants were cultured under hypoxic conditions for 8 or 16 hours in culture medium with 0.5 mM glucose, using a gas-generating pouch system that reportedly maintains oxygen levels at less than 1% (GasPack EZ Anaerobe Pouch System; Becton Dickinson, Franklin Lakes, NJ, USA) [26][27][28] and then reoxygenated for 8 hours in culture medium with 5.5 mM glucose. Low glucose was used in the hypoxia groups as in previous studies 29 because reduced glucose is a contributing factor in many ischemia studies.…”

Different roles of dFOXO and HSF in spatio-temporal dynamics of stress-inducible Hsp70 in lgl-yorkie & lgl-Ras driven epithelial tumours inDrosophila

“…In view of close proximity of tracheae and Hsp70 + cells in tumorous clones, we examined co-localization of hypoxia markers like Sima (fly homolog of HIF-α transcription factor mediating hypoxic response), Lactic dehydrogenase (LDH), or tracheal markers like Gasp and Tango (Sonnenfeld et al, 1997; Tsarouhas et al, 2007) and Hsp70 in wing imaginal discs carrying lgl - yki OE clones at 72hr ACI. The LDH was detected by expressing hypoxia-sensitive reporter transgene LDH-LacZ , which produces β-galactosidase under the LDH promoter (Sansone and Blumenthal, 2013).…”

Loss of glia-neuronal interactions and age-dependent cell death in aDrosophilamodel of adult neurodegeneration

“…This is the first detailed description of cell death and identification of a specific cell death mechanism in the drd mutant fly. drd mutant flies have a shorter median lifespan and show rapid aging [32,33,35,44] along with ND [30,31,35]. Neuronal apoptosis has been linked to nearly all reported neurodegenerative diseases, as well as to axon degeneration, CNS injury, and cellular stress [40,41,[45][46][47][48].…”