The role of unzipped axon guidance and targeting in the olfactory system of drosophila melanogaster

Abstract

The olfactory system of Drosophila is a great model to investigate neural wiring complexity. The fly has two sensory appendages named as antenna and maxillary palp. Hair-like structures called as sensilla cover the appendages and house olfactory sensory neurons (OSN) together with supporting cells. Each OSN expresses one specific type of OR out of a total of 62, and project to a single unit of antennal lobe, called a glomerulus. In each glomerulus, specific synapse formation between the dendrites of projection neurons and OSNs occur. Then, the olfactory stimulus is transmitted to higher brain centers such as the mushroom body and lateral horn, in which olfactory information is converted into a behavioral response. Interaction of neurons and glia is essential for establishment of a proper olfactory system. Glial cells are known to act as guidepost cells in the nervous system, navigating neurons both by secreting molecules and mediating cell-to-cell contacts with cell surface molecules. Several cell surface molecules and transcription factors play an essential role in the establishment of this complex network. Additionally, a subtype of glia in the interhemispheric region of the pupal brain forms a ring-like structure called Transient Interhemispheric Fibrous Ring (TIFR), which is crucial for the formation of the midline commisure. Uzip is a cell adhesion molecule, expressed by glia and neurons (Ding et al., 2011). Uzip mutants show midline crossing and mistargeting phenotypes of OSNs (Zülbahar, 2012). In this study, the endogenous expression of Uzip was analyzed using a mCherry-tagged version of Uzip that was generated by BAC engineering and Uzip enhancer trap line. Additionally, the function of Uzip was analyzed in detail using cell-type specific gain-of-function and loss-of-function analyses. These analyses revealed that Unzip function is required in glial cells and especially in TIFR glia for a proper development of the olfactory commissure.