Expression of the differentiation antigen F7D6 in tumorous tissues of Drosophila

Abstract

The 63-kDa antigen recognized by the monoclonal antibody F7D6 is present in all Drosophila embryonic cells and disappears from most tissues as each one reaches its final, differentiated state. Larval tissues lose the antigen around the time of hatching, imaginal tissues lose it during metamorphosis, and germ cells lose it during gametogenesis (Bedian et al: Devel Biol 115:105-118, 1986). The nervous system and spontaneously contracting musculature of the gut and gonads are exceptions and remain antigen positive at all stages. The F7D6 antigen appears to be associated with dividing, undifferentiated cells and electrogenic cells. This prompted us to test tumors for antigen presence. We tested four different recessive mutants that give rise to four different types of tumorous transformation: the embryonic tumor Notch, several larval melanotic tumors, the imaginal disc tumor 1(2)gl, and three alleles of the ovarian tumor otu. In all cases, tumorous tissues in homozygotes contained the F7D6 antigen. The electrophoretic mobility of the antigen appeared to be unaltered in tumorous tissues compared to normal cells, but the antigen is expressed at higher levels. The antigen is found on the cytoplasmic surface of plasma membranes and appears to be a marker of undifferentiated normal and tumorous cells. Similarities and differences between the F7D6 antigen and Drosophila c-src protein are discussed.

Apical junctions and cell signalling in epithelia

“…The adherens junction is a thick density that forms a con tinuous belt around the apical end of each epithelial cell (Kramer et al, 1991;Cagan and Ready, 1989b) sevenless (Banerjee et al, 1987; crumbs Phosphotyrosine (J.-W. Wu, D. F. Woods and P. J. Bryant, unpublished) boss (Krämer et al, 1991;Cagan et al, 1992) sevenless (Banerjee et al, 1987; Notch (Artavanis-Tsakonas et al, 1991;Fehon et al, 1991) dig (Woods and Bryant, 1991) Fasciclin III (Snow et al, 1989) DA.1B6 antigen (Brower et al, 1980) Band 4.1 (R. Fehon, personal communication) PS2 antigen (Brower et al, 1985) (enriched basally) F7D6 (Bedian and Jungklaus, 1987) (enriched basally) armadillo (Peifer and Wieschaus, 1990) wingless (González et al, 1991) Actin Neuroglian (Bieber et al, 1989) Dabl (Bennett and Hoffmann, 1992) a-Spectrin (Dubreuil et al, 1987) Neuroglian (Bieber et al, 1989) and is associated with actin microfilaments (Poodry and Schneiderman, 1970;Rodriguez-Boulan and Nelson, 1989). One of the main functions of adherens junctions appears to be in cell adhesion (Geiger et al, 1987) and at least one group of cell adhesion molecules, the cadherins, and their associated anchoring molecules, the catenins, have been localized at adherens junctions (Geiger and Ayalon, 1992).…”