Optix defines a neuroepithelial compartment in the optic lobe of the Drosophila brain

Abstract

BackgroundDuring early brain development, the organisation of neural progenitors into a neuroepithelial sheet maintains tissue integrity during growth. Neuroepithelial cohesion and patterning is essential for orderly proliferation and neural fate specification. Neuroepithelia are regionalised by the expression of transcription factors and signalling molecules, resulting in the formation of distinct developmental, and ultimately functional, domains.ResultsWe have discovered that the Six3/6 family orthologue Optix is an essential regulator of neuroepithelial maintenance and patterning in the Drosophila brain. Six3 and Six6 are required for mammalian eye and forebrain development, and mutations in humans are associated with severe eye and brain malformation. In Drosophila, Optix is expressed in a sharply defined region of the larval optic lobe, and its expression is reciprocal to that of the transcription factor Vsx1. Optix gain- and loss-of-function affects neuroepithelial adhesion, integrity and polarity. We find restricted cell lineage boundaries that correspond to transcription factor expression domains.ConclusionWe propose that the optic lobe is compartmentalised by expression of Optix and Vsx1. Our findings provide insight into the spatial patterning of a complex region of the brain, and suggest an evolutionarily conserved principle of visual system development.

Integration of temporal and spatial patterning generates neural diversity

“…Fig.1b,c): Vsx1 is expressed in the central OPC (cOPC), Rx in the dorsal and ventral posterior arms of the crescent (pOPC), and Optix in the two intervening ‘main arms’ (mOPC) 28 . These three proteins are regionally expressed as early as the embryonic optic anlage and together mark the entire OPC neuroepithelium with sharp, non-overlapping boundaries (Supp.…”

A Unique Class of Neural Progenitors in the Drosophila Optic Lobe Generates Both Migrating Neurons and Glia

“…As medulla NBs divide, they progress through different temporal stages and sequentially express different temporal transcription factors (tTFs) (Li et al, 2013; Suzuki et al, 2013; Bertet et al, 2014). In addition to patterning in the temporal axis, medulla NBs are also patterned spatially: the OPC neuroepithelium is subdivided into several different regions that express specific TFs—visual system homeobox (Vsx), Optix (Gold and Brand, 2014), or retinal homeobox (Rx)—or signaling molecules—Decapentaplegic (Dpp), Wingless (Wg), and Hedgehog (Hh) (Figure S2A). The combinatorial input of temporal and spatial cues specifies progeny fate (Bertet et al, 2014; T.E., unpublished data).…”

Differential control of Yorkie activity by LKB1/AMPK and the Hippo/Warts cascade in the central nervous system

“…Together, these results show that loss of lkb1 function in the larval CNS leads to increased Yki target gene expression, increased cell division rates, and tissue growth. To analyze the effect of LKB1 overexpression on Yki activity in the CB, we used the optix-Gal4 driver line that drives gene expression in a subset of type II NBs and their progeny in the CB, as well as in a subset of OL cells (80,81). LKB1 overexpression alone resulted in cell death; therefore, we coexpressed caspase inhibitor p35 in the compartment.…”