Engrailed expression in subsets of adult Drosophila sensory neurons: an enhancer-trap study

Abstract

Engrailed (En) has an important role in neuronal development in vertebrates and invertebrates. In adult Drosophila, although En expression persists throughout adulthood, a detailed description of its expression in sensory neurons has not been made. In this study, en-GAL4 was used to drive UAS-CD8::GFP expression and the projections of sensory neurons were examined with confocal microscopy. En protein expression was confirmed using immunocytochemistry. In the antenna, En is present in subsets of Johnston's organ neurons and of olfactory neurons. En-driven GFP is expressed in axons projecting to 18 identifed olfactory glomeruli, originating from basiconic, trichoid and coeloconic sensilla. In most cases both neurons of a sensillum express En. En expression overlaps with that of Acj6, another transcription factor. En-driven GFP is also expressed in a subset of maxillary palp olfactory neurons and in all mechanosensory and gustatory sensilla in the posterior compartment of the labial palps. In the legs and halteres, en-driven GFP is expressed in only a subset of the sensory neurons of different modalities that arise in the posterior compartment. Finally, endriven GFP is expressed in a single multidendritic sensory neuron in each abdominal segment.

Auditory Responses of Engrailed and Invected-Expressing Johnston’s Organ Neurons in Drosophila melanogaster

“…There are approximately 89±6 (N = 5) en-GAL4 -expressing neurons in total. As shown previously [24], and confirmed here, all such neurons contain some immunoreactivity for the Engrailed and Invected proteins, although there is not necessarily a correlation between the intensity of antibody staining and that of CD8::GFP fluorescence. It is therefore reasonable to conclude that the e16E insertion faithfully reports the expression of the engrailed gene.…”

“…The GAL4 enhancer trap line en-GAL4 e16E was used to drive CD8::GFP expression in en -expressing JONs [24]. As shown previously, these neurons lie predominantly in the ventral-most half of the posterior group of receptors (Fig.…”

“…Now it is known that subsets of neurons in the peripheral and central nervous system express the en gene through adulthood [24], and it has recently been shown that En expression, in combination with that of other transcription factors, is necessary for specifying olfactory sensillum identity and odorant receptor ( Or ) gene expression in the third antennal segment [25], [26].…”

“…1 and 2), in a spatially restricted subset of neurons that make up the mechanosensory Johnston’s organ (JO) [24]. The JO is a chordotonal organ containing approximately 200 sensory units called scolopidia, each consisting of 2 or 3 neurons, the eponymous scolopale cell, and ligament and cap cells [27]–[30].…”

Distribution and function of splash, an achaete‐scute homolog in the adult olfactory organ of the Caribbean spiny lobster Panulirus argus

“…Although progenitors of hair cells and support cells express sox2 , knockdown studies showed no effect on hair cell formation but an effect on maintenance of hair cells and support cells (Millimaki et al, 2010). In Drosophila , expression of engrailed (Blagburn, 2008) in mature olfactory sensory neurons suggests additional functions in maintenance rather than in early development. Taken together, transcription factors previously known for functions during early development are now known to have additional roles in later stages, and splash may be another example.…”