Abstract
Intellectual disability (ID) is a heterogeneous disorder with high prevalence and remarkable social and cost burdens. Novel genetic variants of ATF7IP, CAPN9, ITGAV, ITSN1, and UBR4 genes are reported to be associated with the ID among Iranian families. However, in vivo validation is required to confirm the functional role of these variants in ID development. Drosophila melanogaster is a convenient model for such functional investigations as its genome bears ortholog of more than 75% of the disease-causing genes in human and represents numerous approaches to study defects in neuronal function. In this connection, RNAi gene silencing was applied to wde, calpA, if, dap160, and poe genes, the Drosophila ortholog of the selected human genes, and then consequent structural and functional changes in neurons were studied by means of immunohistochemistry and confocal microscopy of mushroom bodies (MBs) and validated behavioural assays including larvae and adult conditioning learning and memories, and ethanol sensitivity. Down-regulation of these genes led to neuronal loss which was evident by decline in total fluorescent signal intensity in micrographs of MBs structure. The gene silencing caused neuronal dysfunction and induction of ID-like symptoms manifested by deficits in larval preference learning, and short-term olfactory memory and courtship suppression learning in adults. Moreover, the RNAi flies showed higher sensitivity to ethanol vapour. Interestingly, the poe knock-down flies exhibited the most severe phenotypes among other genes. Altogether, we believe this study is first-of-its-kind and findings are highly applicable to confirm pathogenecity of the selected ID gene variants in Iranian population.
