It is shown that coassociative cones in R7 that are r-oriented and ruled by 2-planes are equivalent to CR-holomorphic curves in the oriented Grassmanian of 2-planes in R7. The geometry of these CR-holomorphic curves is studied and related to holomorphic curves in S6. This leads to an equivalence between associative cones on one side and the coassociative cones whose second fundamental form has ...

We have examined the roles played by the Drosophila neural RNA-binding protein Musashi (MSI) in eye development. MSI expression was observed in the nuclei of all photoreceptor cells (R1-R8). Although a msi loss-of-function mutation resulted in only weak abnormalities in photoreceptor differentiation, we found that the msi eye phenotype was significantly enhanced in a seven in absentia (sina) ba...

Differentiation of the R7 photoreceptor cell is dependent on the Sevenless receptor tyrosine kinase, which activates the RAS1/mitogen-activated protein kinase signaling cascade. Kinase suppressor of Ras (KSR) functions genetically downstream of RAS1 in this signal transduction cascade. Expression of dominant-negative KSR (KDN) in the developing eye blocks RAS pathway signaling, prevents R7 cell...

The Drosophila eye has contributed much to our knowledge of cell differentiation. This understanding has primarily come from the study of the R7 photoreceptor; much less is known about the development of the other classes of photoreceptor or the nonneuronal cone or pigment cells. I have used a dominant-negative form of the Drosophila epidermal growth factor receptor (DER) to show that this rece...

Different Drosophila photoreceptors (R cells) connect to neurons in different optic lobe layers. R1-R6 axons project to the lamina; R7 and R8 axons project to separate layers of the medulla. We show a receptor tyrosine phosphatase, PTP69D, is required for lamina target specificity. In Ptp69D mutants, R1-R6 project through the lamina, terminating in the medulla. Genetic mosaics, transgene rescue...

How neurons form appropriately sized dendritic fields to encounter their presynaptic partners is poorly understood. The Drosophila medulla is organized in layers and columns and innervated by medulla neuron dendrites and photoreceptor axons. Here, we show that three types of medulla projection (Tm) neurons extend their dendrites in stereotyped directions and to distinct layers within a single c...