Laminin in the male germ cells of Drosophila.

To study genes that may be crucial for the male germ cell development of Drosophila we screened a cDNA expression library with a polyclonal antiserum against testis proteins of Drosophila hydei. We identified a cDNA fragment that exhibited a complete sequence similarity with the cDNA of the laminin B2 chain, an important component of the extracellular matrix. Transcripts of laminin B2 were detected in the RNA of male germ cells with the polymerase chain reaction and by in situ hybridization. We studied the reaction of different polyclonal antibodies including those against a Drosophila laminin B2-lac fusion protein, the entire Drosophila laminin complex, or against the mouse laminin complex and against laminin A and B1 chains with specific structures in developing male germ cells of Drosophila. Antigenic sites against laminin B2 were found in the lampbrush loops in primary spermatocyte nuclei, in nuclei of spermatids, and in heads of spermatozoa. The axonemes of elongating spermatids react with antibodies against the Drosophila laminin B1, B2 and laminin A chains. The possible biological functions of the laminin in the male germ cells of Drosophila are discussed.