High impact information on sca

• Here we present in vivo and biochemical evidence that the secreted protein Scabrous associates with Notch, and can stabilize Notch protein at the surface [1].
• Based on its loss-of-function phenotype, expression pattern, and the predicted structure of its product, a secreted peptide with homology to the fibrinogen gene family, we propose that sca encodes a signal involved in lateral inhibition within individual domains of the developing nervous system [2].
• During imaginal development, sca is mainly expressed in the R8 photoreceptor precursor cells in the eye imaginal disc and in sensory organ precursor cells in other discs [2].
• The sca transcription unit is 12 kb and consists of four exons that are joined in a 3.2-kb mRNA [2].
• During embryogenesis, sca is expressed in a dynamic pattern associated with neural development [2].

Biological context of sca

• Similar phenotypes showed that sca and gp150 genes act in a common pathway [3].
• We detail here the dynamic pattern of sca transcript accumulation during embryogenesis and show that mutation of Ubx results in the ectopic transcription of sca in the first abdominal segment [4].
• This pattern is established during disc development, when clusters rotate through 90 degrees, a process dependent on planar cell polarity and rotation-specific factors such as Nemo and Scabrous [5].
• In an enhancer trap screen we have isolated several P[lacZ] insertions close to the sca transcription start site [2].
• Three sites in regulatory regions were associated with female-specific variation in abdominal bristle number, one of which was an SSCP site in the region of the gene associated with regulation of sca in embryonic abdominal segments [6].

Anatomical context of sca

• scabrous modifies epithelial cell adhesion and extends the range of lateral signalling during development of the spaced bristle pattern in Drosophila [7].
• Gp150 concentrated Sca protein in late endosomes [3].
• In scabrous (sca) mutants, the pattern of R8 photoreceptor differentiation is altered [8].
• Mutations at the scabrous (sca) locus alter the locations where precursor cells form in the peripheral nervous system [12,13] [9].

Associations of sca with chemical compounds

• Using expression in Drosophila Schneider cells, we showed that sca encoded a dimeric glycoprotein which was secreted and found in soluble form in the tissue culture medium [8].
• The sca protein contained both N- and O-linked carbohydrates and interacted with heparin [8].

Other interactions of sca

• We show that Dl, a membrane-bound ligand for Notch, can inhibit adjacent cells, in direct contact with the precursor, in the absence of Sca [7].
• Mosaic analysis found that the gp150 and sca genes were required in different cells from one another [3].
• We propose that a direct interaction of Ubx with cis-acting elements in sca negatively regulates the gene [4].
• N and Dl were required to repress ato in the vicinity of R8 cells, whereas sca had effects over several cell diameters [8].
• The identity of the secreted inhibitor remains elusive but, contrary to previous suggestions, we show that it is not Argos. This Egfr-dependent inhibition acts in parallel to the inhibition of atonal by the secreted protein Scabrous [10].

References