Fig. 1
From: FGF receptors are required for proper axonal branch targeting in Drosophila
– The FGFRs Btl and Htl are required for proper synaptic connectivity. a The Drosophila mechanosensory neurons innervate the bristles of the notum. Each bristle is innervated by a single mechanosensory neuron which is uniquely identifiable based on its location. The right pSc neuron and its axonal arbor within the thoracic ganglion are illustrated in magenta. b A cross section of a pSc bristle is shown in brightfield and the corresponding Btl fluorescence in situ hybridization signal in magenta. Btl mRNA (arrowhead) was detected in the neuron underlying the pSc bristle. c A cross section of a pSc bristle is shown with Htl fluorescence in situ hybridization signal in magenta (arrowheads). Htl mRNA was detected in the pSc neuron and its surrounding cells. d The pSc mechanosensory neuron has a unique and stereotyped axonal branching pattern within the central nervous system. The stereotyped connectivity of the pSc neuron can be used to identify axonal targeting errors in mutants. e-g Mis-regulation of Btl expression results in synaptic targeting errors. e Knockdown of Btl using RNAi resulted in a loss of core branches. f Btlnull MARCM mutants also had missing core branches (arrowhead), mostly contralateral to the axonal entry site into the thoracic ganglion. g Increasing Btl expression resulted in misrouting errors as well as ectopic branch formations. h-j Mis-regulation of Htl expression also results in targeting errors. h Knockdown of Htl using RNAi resulted in ectopic branches (arrows) and loss of secondary branches (arrowhead). i Htl Dominant Negative (Htl DN) mutants showed similar axonal targeting errors as Htl RNAi mutants such as ectopic branches towards the midline (arrow). j Overexpression of Htl also resulted in ectopic branches (arrows). Scale bars, 20 μm in (b, c), 50 μm in (d, j). Arrowheads point to absent branches, arrows point to ectopic branches