Dilp8 requires the neuronal relaxin receptor Lgr3 to couple growth to developmental timing

We thank C. Mirth, C. Ribeiro and A. Jacinto for their comments and suggestions; I. Miguel-Aliaga, A. Jacinto, P. Leopold, P. Domingos, C. Mirth, R. Teodoro, M. Dominguez, M.L. Vasconcelos, J.C. Yin and M. O'Connor, for reagents. Stocks obtained from the Bloomington Drosophila Stock Center (NIH P40OD018537) were used in this study. A.M.G., F.H., A.M., A.R.M.D. and T.K. are supported by the FCT, under the FCT Investigator Programme and FCT fellowships SFRH/BPD/94112/2013, PD/BD/52421/2013, SFRH/BD/94931/2013 and SFRH/BPD/74313/2010, respectively. A.G. is supported by the CONICET and UNS, and Y.A.V. holds a CONICET fellowship. The work in the laboratory of A.M.G. is funded by the CEDOC and the European Commission FP7 (PCIG13-GA-2013-618847). A.G. thanks N.P. Rotstein and L.E. Politi for providing funds and space to develop a part of this project in their lab.How different organs in the body sense growth perturbations in distant tissues to coordinate their size during development is poorly understood. Here we mutate an invertebrate orphan relaxin receptor gene, the Drosophila Leucine-rich repeat-containing G protein-coupled receptor 3 (Lgr3), and find body asymmetries similar to those found in insulin-like peptide 8 (dilp8) mutants, which fail to coordinate growth with developmental timing. Indeed, mutation or RNA intereference (RNAi) against Lgr3 suppresses the delay in pupariation induced by imaginal disc growth perturbation or ectopic Dilp8 expression. By tagging endogenous Lgr3 and performing cell type-specific RNAi, we map this Lgr3 activity to a new subset of CNS neurons, four of which are a pair of bilateral pars intercerebralis Lgr3-positive (PIL) neurons that respond specifically to ectopic Dilp8 by increasing cAMP-dependent signalling. Our work sheds new light on the function and evolution of relaxin receptors and reveals a novel neuroendocrine circuit responsive to growth aberrations.publishersversionpublishe

Correlations Between Pre- and Post-Fasting Growth in Nile Tilapia

We tested the correlation between growth rate before and after a food deprivation phase in twelve single held Nile tilapias, Oreochromis niloticus. The experiment was divided into three phases: before food deprivation (phase 1: 15 d), food deprivation (phase 2: 12 d) and refeeding (phase 3: 15 d). The specific growth rate - SGR, food conversion efficiency - FCE and feed ingestion increased significantly during phase 3. Positive and significant correlations were found either to SGR or to feed ingestion between Phase 1 and 3 but not for FCE. The SGR on phase 3, moreover, were positively correlated to FCE and feed ingestion, while on phase 1 SGR was positively correlated to FCE only. Thus, high pre-fasting SGR or feed ingestion reflects in likewise high post-fasting SGR or feed ingestion values. Moreover, since SGR and FCE are correlated to each other in both phase 1 and 3, but phase 3 SGR is also correlated to feed ingestion; we could suppose that hyperphagic behaviour could be the main compensatory mechanism. Accordingly, we suggest that a fish with an elevated growth performance shall display a proportionally raised post-fasting growth response in order to normalize its predetermined growth trajectory and resume its normal growth rate