From behavior to specific genes, and back again

FERNÁNDEZ-ACOSTA M; BERNABÓ, G; CERIANI MF

Mar del Plata, 27 Septiembre al 1 Octubre 2015.

Congreso; XXX Congreso anual de la SAN; 2015

Sociedad Argentina de Investigaciones en Neurociencias

Through a behavioral screen directed to the circadian neurons in the adult brain, we identi¬fied a gene that we named orsai (osi); while control larvae feed continuously until they reach the critical weight that triggers pupation (a process that runs from 72 to 120 h after egg laying (AEL), osi mutants stop feeding and die around 78 h AEL, as stage 2 (L2) larvae.Although sequence analysis suggested osi could be a component of the mitochondrial respiratory complex I, and as such likely to play a role in cellular metabolism, our data points to another direction.To begin to characterize orsai?s function we measured oxygen consumption and ATP levels in L2 larvae. From those experiments we conclude that osi mutants have an impaired mitochondrial function. Surprisingly, immunohistochemistry analysis showed OSI is differentially localized in specific tissues: while in the gut epithelium and trachea is nuclear, in the fat body (i.e. the liver) is cytoplasmic; however, OSI was never found in mitochondria. osi mutants die around 72 h AEL as L2 larvae; RNAi-mediated downregulation of osi in an ubiquitous pattern (through actinGal4 expression) phenocopies the defect. To define the tissue specificity of OSI´s mediated developmental arrest and death, we expressed osi´s RNAi in different expression domains. The most restrictive patterns that caused lethality were btlGal4 (tracheas and some neurons) and mef2Gal4 (gut and some tracheas). When we downregulated osi in those expression patterns, we observed not only developmental arrest and death but also additional phenotypes: in tracheas, while the main and lateral tracheas develop normally, terminal cells are clearly defective. In the gut, lifespan and larval body size differ according to nutrient availability: a restrictive diet enables larvae to live longer and acquire a larger body size; on the contrary, they die early on in the presence of nutritious food.Taken together our results suggest that despite initial assumptions, OSI is likely not a mitochondrial protein, but instead might play a role in the nucleus, coupling environmental information to cellular (basal) metabolism.