[The tissue localization of "chitinoprotein", detectable by using specific antibodies, in the development of...

The biosynthesis of cognate glycoproteins with chitinase-sensitive carbohydrate moiety ("chitinoproteins") was detected after incubation of cultured cells of different insect species with 3H-glucosamine (Kramerov et al., Insect Biochem. v. 20; 769-775, 1990). It was also demonstrated that production of the specific chitinoprotein takes place during the development of D. melanogaster as revealed by immunoblotting and autoradiographic analysis of crude tissue extracts. An investigation of the developmental pattern of tissue localization of Drosophila chitinoprotein was performed using antibodies raised in rabbit after immunization with a purified preparation of the chitinoprotein (ChiP) from Drosophila embryonic cultured cells. The paraffin-embedded thin (5 microns) sections of organisms fixed in Bouin fixative were stained immunohistochemically with primary antibodies and peroxidase-conjugated secondary antibodies followed by enhancement of the precipitated DAB product with osmium tetroxide. Preimmune serum and antiserum preadsorbed with the purified ChiP preparation were used as negative controls yielding no specific staining of tissue sections. Negative staining with specific anti-ChiP antibodies was demonstrated for salivary glands, gut, muscles, central and peripheral nerve system and some other tissues. A complex pattern of tissue-specific ChiP localization in a variety of tissues of ectodermal, mesodermal and germ line origin was revealed. The mesodermal derivatives--hemocytes and oenocytes capable of producing the components of cuticle as well as epidermal cells of larvae and imago clearly demonstrated staining of cytoplasmic vesicles, which in the latter case were exocytosed and included into the newly formed endocuticle. Another cell type known to produce cuticle--epithelial cells of imaginal discs (primordia of adult organs)--were also stained with antibodies. One can suppose that ChiP is involved in biogenesis of insect cuticle, probably, as a protein precursor of chitin formation. It was quite surprising to observe a rather strong staining of fat body cells and follicle cells of adult ovaries. The follicular epithelium secreted the stained granules into a growing oocyte that accumulated large amounts of this immunopositive material until transformation into a mature egg. In an early embryo ChiP is localized in blastodermal and pole cells, but not in yolk. This is, probably, the result of segregation of ChiP to the periphery of an egg during the final stage of its maturation and subsequent cellularization in the beginning of embryogenesis. Later ChiP can be found in ectodermal cells and hemocyte-like cells. It should be noted that not all amounts of ChiP detected in embryos are maternally inherited, for an active ChiP biosynthesis takes place in dissociated embryonic cells after incubation with labelled sugar precursor.(ABSTRACT TRUNCATED AT 400 WORDS)