Expression of polyQ aggregates in Malpighian tubules leads to degeneration in Drosophila melanogaster.

Background: Polyglutamine (polyQ) disorders are caused by expanded CAG (Glutamine) repeats in neurons in the brain. The expanded repeats are also expressed in the non-neuronal cells, however, their contribution to disease pathogenesis is not very well studied. In the present study, we have expressed a stretch of 127 Glutamine repeats in Malpighian tubules (MTs) of Drosophila melanogaster as these tissues do not undergo ecdysone induced histolysis during larval to pupal transition at metamorphosis.

Results: Progressive degeneration, which is the hallmark of neurodegeneration is also observed in MTs. The mutant protein forms inclusion bodies in the nucleus resulting in expansion of the nucleus and affect chromatin organization which appear loose and open, eventually resulting in DNA fragmentation and blebbing. A virtual absence of tubule lumen was observed followed by functional abnormalities. As development progressed, severe abnormalities affecting pupal epithelial morphogenesis processes were observed resulting in complete lethality. Distribution of heterogeneous RNA binding protein (hnRNP), HRB87F, Wnt/wingless and JNK signaling and expression of Relish was also found to be affected. Expression of resistance genes following polyQ expression was up regulated.

Conclusion: The present study gives an insight into the effects of polyQ aggregates in non-neuronal tissues.