The iroquois complex controls the somatotopy of Drosophila notum mechanosensory projectionss

Abstract

Sensory neurons can establish topologically ordered projections in the central nervous system, thereby building an internal representation of the external world. We analyze how this ordering is genetically controlled in Drosophila, using as a model system the neurons that innervate the mechanosensory bristles on the back of the fly (the notum). Sensory neurons innervating the medially located bristles send an axonal branch that crosses the central nervous system midline, defining a ‘medial’ identity, while the ones that innervate the lateral bristles send no such branch, defining a ‘lateral’ identity. We analyze the role of the proneural genes achaete and scute, which are involved in the formation of the medial and lateral bristles, and we show that they have no effect on the ‘medial’ and ‘lateral’ identities of the neurons. We also analyze the role of the prepattern genes araucan and caupolican, two members of the iroquois gene complex which are required for the expression of achaete and scute in the lateral region of the notum, and we show that their expression is responsible for the ‘lateral’ identity of the projection.

Hidden RNA pairings counteract the “first-come, first-served” splicing principle to drive stochastic choice in Dscam1 splice variants

“…Last, MB immunofluorescence staining was imaged with a laser scanning confocal microscope (LSM800, Carl Zeiss). The branching patterns of pSc neurons were visualized by 1,1′-dioctadecyl-3,3,3′,3′-tetramethylindocarbocyanine perchlorate or 1,1’-Dioctadecyl-3,3,3’,3’-Tetramethylindodicarbocyanine,4-Chlorobenzenesulfonate Salt tracing essentially as previously described ( 38 , 39 , 57 ).…”