Commissural dentate granule cell projections and their rapid formation in the adult brain.

Dentate granule cells (GCs) have been characterized as unilaterally projecting neurons within each hippocampus. Here, we describe a unique class, the commissural GCs, which atypically project to the contralateral hippocampus in mice. Although commissural GCs are rare in the healthy brain, their number and contralateral axon density rapidly increase in a rodent model of temporal lobe epilepsies.

Pioneer interneurons instruct bilaterality in the Drosophila olfactory sensory map.

Interhemispheric synaptic connections, a prominent feature in animal nervous systems for the rapid exchange and integration of neuronal information, can appear quite suddenly during brain evolution, raising the question about the underlying developmental mechanism. Here, we show in the Drosophila olfactory system that the induction of a bilateral sensory map, an evolutionary novelty in dipteran flies, is mediated by a unique type of commissural pioneer interneurons (cPINs) via the localized activity of the cell adhesion molecule Neuroglian. Differential Neuroglian signaling in cPINs not only prepatterns the olfactory contralateral tracts but also prevents the targeting of ingrowing sensory axons to their ipsilateral synaptic partners.

Inter-axonal recognition organizes Drosophila olfactory map formation.

Olfactory systems across the animal kingdom show astonishing similarities in their morphological and functional organization. In mouse and Drosophila, olfactory sensory neurons are characterized by the selective expression of a single odorant receptor (OR) type and by the OR class-specific connection in the olfactory brain center. Monospecific OR expression in mouse provides each sensory neuron with a unique recognition identity underlying class-specific axon sorting into synaptic glomeruli.

High-resolution ultramicroscopy of the developing and adult nervous system in optically cleared Drosophila melanogaster.

The fruit fly, Drosophila melanogaster, is an important experimental model to address central questions in neuroscience at an organismic level. However, imaging of neural circuits in intact fruit flies is limited due to structural properties of the cuticle. Here we present a novel approach combining tissue clearing, ultramicroscopy, and data analysis that enables the visualisation of neuronal networks with single-cell resolution from the larval stage up to the adult Drosophila.