Morpho-Functional Consequences of Swiss Cheese Knockdown in Glia of Drosophila melanogaster

Abstract

Glia are crucial for the normal development and functioning of the nervous system in many animals. Insects are widely used for studies of glia genetics and physiology. Drosophila melanogaster surface glia (perineurial and subperineurial) form a blood–brain barrier in the central nervous system and blood–nerve barrier in the peripheral nervous system. Under the subperineurial glia layer, in the cortical region of the central nervous system, cortex glia encapsulate neuronal cell bodies, whilst in the peripheral nervous system, wrapping glia ensheath axons of peripheral nerves. Here, we show that the expression of the evolutionarily conserved swiss cheese gene is important in several types of glia. swiss cheese knockdown in subperineurial glia leads to morphological abnormalities of these cells. We found that the number of subperineurial glia nuclei is reduced under swiss cheese knockdown, possibly due to apoptosis. In addition, the downregulation of swiss cheese in wrapping glia causes a loss of its integrity. We reveal transcriptome changes under swiss cheese knockdown in subperineurial glia and in cortex + wrapping glia and show that the downregulation of swiss cheese in these types of glia provokes reactive oxygen species acceleration. These results are accompanied by a decline in animal mobility measured by the negative geotaxis performance assay.

Loss of swiss cheese in Neurons Contributes to Neurodegeneration with Mitochondria Abnormalities, Reactive Oxygen Species Acceleration and Accumulation of Lipid Droplets in Drosophila Brain

“…These data suggest that the severe neurodegenerative and longevity phenotypes observed in sws 1 flies predominantly depend on neuronal sws dysfunction. We assume that the sws role in neurons, but not in glia, is more critical for the fly’s organism (for comparison, see our results for panglial sws knockdown [ 32 ], where we show that it does not influence longevity and has a much weaker effect on brain neuropile morphology).…”

“…We found the upregulation of antioxidant defense genes in the organism of flies with the neuronal sws knockdown, suggesting that oxidative stress may be a potential consequence of sws downregulation. Moreover, in our previous study, we found brain ROS acceleration under sws knockdown in glia [ 32 ]. In addition, it is well known that oxidative stress is a hallmark of neurodegeneration, even though the interrelations between cell death rate and reactive oxygen species accumulation remain elusive [ 44 ].…”

“…However, despite promoting the well-characterized glia phenotypes [ 31 ], it did not cause any neurodegeneration when expressed under the elav-GAL4 driver ( Figure S1 ). This could be due to the smaller effect size, which is probably not enough for the neuronal death, while both UAS-sws-RNAi v5469 and UAS-sws-RNAi (BDSC 61338) are enough to induce glia abnormalities [ 31 , 32 ]. Thus, we conclude that the UAS-sws-RNAi v5469 transgene is insufficient to induce sws knockdown in neurons; therefore, we did not use it in other experiments of the current work.…”

“…In addition, we found a lifespan shortage under normal and stressful conditions. In contrast to the neuronal knockdown, glial-specific sws knockdown did not lead to a lifespan reduction [ 32 ], but did result in behavioral defects and brain vacuolization, albeit much less intensive [ 31 , 32 ]. Both neuronal and panglial knockdowns led to accelerated ROS levels in the brains of 5-day-old flies.…”

“…SWS function is shown to be important for both neurons and glia [ 21 ]. Glia-specific sws knockdown induces morphological changes in the fly brain and peripheral nerves, causing locomotion defects [ 31 , 32 ]. At the same time, conditional knockout of NTE/PNPLA6 in peripheral glia of mice reduces axon wrapping by Schwann cells in the peripheral nerves [ 33 ].…”