IDENTIFICATION OF SECRETED AND CYTOSOLIC GELSOLIN IN DROSOPHILA

We have cloned the gene for Drosophila gelsolin. Two mRNAs are produce d from this gene by differential splicing. The protein encoded by the longer mRNA has a signal peptide and its electrophoretic mobility when translated in vitro in the presence of microsomes is higher than when it is translated without microsomes. The protein translated from the shorter mRNA does not show this difference. This indicates that Drosop hila like vertebrates has two forms of gelsolin, one secreted, the oth er cytoplasmic. The mRNA for both is present ubiquitously in the early embryo. Later, the cytoplasmic form is expressed in parts of the gut. The RNA for the secreted form is expressed in the fat body, and the s ecreted protein is abundant in extracellular fluid (hemolymph). The cy toplasmic form of gelsolin co-localizes with F-actin in the cortex of the cells in the embryo and in larval epithelia. However, during cellu larization of the blastoderm it is reduced at the base of the cleavage furrow, a structure similar to the contractile ring in dividing cells .