ABSTRACT
Complex patterns of morphogenesis require intricate coordination of multiple, regulatory processes that control cellular identities, shapes, and behaviors, both locally and over vast distances in the developing organism or tissue. Studying Drosophila oogenesis as a model for tissue morphogenesis, we have discovered extraovarian regulation of follicle formation. Clonal analysis and ovary transplantation have demonstrated that long-range control of follicle individualization requires stall gene function in cells outside of the ovary. Although tissue nonautonomous regulation has been shown to govern follicle maturation and survival, this is the first report of an extraovarian pathway involved in normal follicle formation.
Subject(s)
Drosophila melanogaster/genetics , Drosophila melanogaster/physiology , Morphogenesis , Ovarian Follicle/growth & development , Phenotype , Animals , Crosses, Genetic , Drosophila melanogaster/anatomy & histology , Female , Fluorescence , Histological Techniques , Hot Temperature , Indoles , Larva/anatomy & histology , Larva/physiology , Male , Mutation/genetics , Ovarian Follicle/transplantation , Ovary/anatomy & histologyABSTRACT
Expression of the herpes simplex virus type 1 (HSV-1) glycoproteins gB, gD, gH, and gL is necessary and sufficient to cause cell fusion. To identify the requirements for a membrane-spanning domain in HSV-1 glycoprotein-induced cell fusion, we created gB, gD, and gH mutants with transmembrane and cytoplasmic domains replaced by a glycosylphosphatidylinositol (gpi)-addition sequence. The corresponding gBgpi, gDgpi, and gHgpi proteins were expressed with wild-type efficiency at the cell surface and were linked to the plasma membrane via a gpi anchor. The gDgpi mutant promoted cell fusion near wild-type gD levels when co-expressed with gB, gH, and gL in a cell-mixing fusion assay, indicating that the gD transmembrane and cytoplasmic domains were not required for fusion activity. A plasma membrane link was required for fusion because a gD mutant lacking a transmembrane and cytoplasmic domain was nonfunctional for fusion. The gDgpi mutant was also able to cooperate with wild-type gB, gH, and gL to form syncytia, albeit at a size smaller than those formed in the wild-type situation. The gBgpi and gHgpi mutants were unable to promote fusion when expressed with the other wild-type viral glycoproteins, highlighting the requirement of the specific transmembrane and cytoplasmic domains for gB and gH function.
