A conserved transcriptional network regulates lamina development in the Drosophila visual system.
The visual system of insects is a multilayered structure composed externally by the compound eye and internally by the three ganglia of the optic lobe: lamina, medulla and the lobula complex. The differentiation of lamina neurons depends heavily on Hedgehog (Hh) signaling, which is delivered by the incoming photoreceptor axons, and occurs in a wave-like fashion. Despite the primary role of lamina neurons in visual perception, it is still unclear how these neurons are specified from neuroepithelial (NE) progenitors. Here we show that a homothorax (hth)-eyes absent (eya)-sine oculis (so)-dachshund (dac) gene regulatory cassette is involved in this specification. Lamina neurons differentiate from NE progenitors that express hth, eya and so. One of the first events in the differentiation of lamina neurons is the upregulation of dac expression in response to Hh signaling. We show that this dac upregulation, which marks the transition from NE progenitors into lamina precursors, also requires Eya/So, the expression of which is locked in by mutual feedback. dac expression is crucial for lamina differentiation because it ensures repression of hth, a negative regulator of single-minded, and thus dac allows further lamina neuron differentiation. Therefore, the specification of lamina neurons is controlled by coupling the cell-autonomous hth-eya-so-dac regulatory cassette to Hh signaling.
['Piñeiro|Cristina|C|', 'Lopes|Carla S|CS|', 'Casares|Fernando|F|']
D000818:Animals D019521:Body Patterning D029721:Drosophila Proteins D004331:Drosophila melanogaster D004742:Enhancer Elements, Genetic D005123:Eye D025461:Feedback, Physiological D018507:Gene Expression Regulation, Developmental D053263:Gene Regulatory Networks D017344:Genes, Insect D046569:Neuroepithelial Cells D009474:Neurons D009899:Optic Lobe, Nonmammalian D012160:Retina D015398:Signal Transduction D013234:Stem Cells D015854:Up-Regulation
Drosophila Homothorax Lamina precursor Dachshund Eyes absent Gene network Sine oculis