Scabrous is dimeric glycoprotein that is secreted and found in soluble form in the tissue culture medium. N and Dl are required to repress ato in the vicinity of R8 cells, whereas sca produces effects over several cell diameters. Certain antibodies detect uptake of SCA protein several cells away from its source. The overall growth factor-like structure of SCA protein, its solubility, and its range of effects in vivo are consistent with a diffusible role that complements mechanisms involving direct cell contact. The Sca protein was purified and a cell line expressing 18,000 Notch molecules per cell surface was used to test Sca binding by coimmunoprecipitation, cell adhesion assays, and binding with labeled Sca.
Expression is higher in neuroblasts than in epidermal cells.
Larval During imaginal development, scabrous is expressed in the R8 photoreceptor precursor cells in the eye imaginal disc , and later in R2 and R5 cells. Interactions are described between the Notch locus of Drosophila , and two other loci, scabrous and vestigial , which respectively affect the eyes and wings, were examined. The Notch locus is responsible for mediating decisions of cell fate throughout development in many different tissues. The magnitude of segregating variation for bristle number in Drosophila exceeds that predicted from models of mutation-selection balance. There is considerable GEI for both bristle traits.