IMP-L2 - AN ESSENTIAL SECRETED IMMUNOGLOBULIN FAMILY MEMBER IMPLICATED IN NEURAL AND ECTODERMAL DEVELOPMENT IN DROSOPHILA

The Drosophila IMP-L2 gene was identified as a 20-hydroxyecdysone-indu ced gene encoding a membrane-bound polysomal transcript. IMP-L2 is an apparent secreted member of the immunoglobulin superfamily. We have us ed deficiencies that remove the IMP-L2 gene to demonstrate that IMP-L2 is essential in Drosophila. The viability of IMP-L2 null zygotes is i nfluenced by maternal IMP-L2. IMP-L2 null progeny from IMP-L2+ mothers exhibit a semilethal phenotype. IMP-L2 null progeny from IMP-L2 null mothers are 100% lethal. An IMP-L2 transgene completely suppresses the zygotic lethal phenotype and partially suppresses the lethality of IM P-L2 null progeny from IMP-L2 null mothers. In embryos, IMP-L2 mRNA is first expressed at the cellular blastoderm stage and continues to be expressed through subsequent development. IMP-L2 mRNA is detected in s everal sites including the ventral neuroectoderm, the tracheal pits, t he pharynx and esophagus, and specific neuronal cell bodies. Staining of whole-mount embryos with anti-IMP-L2 antibodies shows that IMP-L2 p rotein is localized to specific neuronal structures late in embryogene sis. Expression of IMP-L2 protein in neuronal cells suggests a role in the normal development of the nervous system but no severe morphologi cal abnormalities have been detected in IMP-L2 null embryos.