Identification of novel growth-regulating genes. H. Stocker¹, S. Oldham^1,3, S. Breuer², A. Sulzer¹, C. Rottig¹, S. Gluderer¹, F. Rintelen¹, B. Schindelholz², P. Daram², M. Vegh², E. Hafen¹. 1) Zoological Institute, University of Zurich, Zurich, Switzerland; 2) The Genetics Company Inc., Wagistrasse 27, CH-8952 Schlieren, Switzerland; 3) The Burnham Institute, Cancer Research Center, La Jolla, USA.

   The regulation and co-ordination of cellular growth represent major tasks for multicellular organisms. Recent studies have highlighted two signaling pathways that modulate growth rates in accordance with environmental conditions, namely the insulin receptor-PI3K-PKB and the TOR-S6K signaling cascades. Selective reduction of the activity of either pathway in the developing eye by means of the ey-Flp/FRT system results in a characteristic size reduction of the adult eye and head capsule (the so-called pinhead phenotype).
   We screened all the major autosome arms for mutations causing a similar size phenotype. Multiple alleles of the insulin receptor, chico, Dp110/PI3K, PKB and TOR were recovered as pinhead mutations. Furthermore, we identified Rheb as a novel component of the TOR signaling branch. Conversely, mutations in the negative regulators PTEN and TSC1/2, respectively, were isolated based on a size increase phenotype.
   We will present our progress in identifying and characterizing novel loci associated with growth phenotypes.