Genetic Basis of Dorso-Ventral Patterning in the Drosophila Eye

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In multi-cellular organisms, axial patterning is required for transition of a mono-layered epithelium of an organ primordium to a three-dimensional organ by delineation of antero-posterior (AP), dorso-ventral (DV), and proximo-distal (PD) axis. We use Drosophila melanogaster (fruit fly) eye model to study the highly conserved fundamental process of (axial) DV patterning and growth. During eye development, DV patterning precedes AP and PD axis patterning, and forms dorsal and ventral compartments. Discerning the mechanism of axes determination (DV) is crucial for our understanding of organogenesis as the problems with DV delineation results in developmental/ birth defects in flies to humans. Our long term goal is to understand the genetic basis of DV patterning which is established by interactions of the dorsal selector genes and the ventral genes. The Drosophila eye begins from a ventral equivalent state on which the dorsal fate is established by onset of expression of GATA-family transcription factor Pannier (Pnr), the secreted morphogen Wingless (Wg), and Iroquois (Iro-C) family proteins. In the dorsal eye, pnr is not the sole regulator of Wg expression. It strongly suggests that there may be other dorsal eye genes that are yet to be identified. We have identified a new dorsal eye selector defective proventriculus (dve), a transcription factor, which acts upstream of wg. To understand the molecular genetic basis of DV patterning, we will analyze the (1) Investigate wg regulation in the dorsal eye. (2) How Wg gradient from dorsal eye is interpreted for eye versus head fate? (3) Test if Hippo signaling co- regulate Wg signaling with DV patterning genes in the eye. Given that the genetic machinery is conserved, we will also test the role of SATB1, a human ortholog of dve in the eye. Our study will have significant bearing on (i) developmental mechanisms of lineage restriction and patterning that follow DV patterning during organogenesis, (ii) role of growth regulatory gene in patterning and (iii) the understanding of etiology of early childhood retinal diseases. (iv) How do independent pathways interact to regulate growth and patterning in the developing eye? The proposed studies will generate insights into (1) how dorsal eye genes interact to determine eye versus head fate by regulating Wg signaling, (2) How two independent pathways like Hippo signaling and DV patterning coregulate Wg signaling to promote growth and patterning in the developing eye? (3) SATB1 is mainly known to regulate growth and our studies in eye will provide insight into growth regulation and patterning function of SATB1. These studies will have significant bearings on understanding the genetic mechanism of early developmental events during organogenesis in higher vertebrates. The knowledge generated from these studies is expected to elucidate fundamental mechanisms in patterning and growth of normal visual function and within the context of retinal disease and birth defects in the eye.