Isolation and characterization of a Drosophila neuropeptide gene

We have purified a 9 amino acid amidated neuropeptide, DPKQDFMRFamide, from whole adult D. melanogaster. This peptide exhibits sequence homology to the molluscan bioactive tetrapeptide FMRFamide and is a novel member of the FMRFamide peptide family. The gene encoding DPKQDFMRFamide has been cloned and characterized. It is present in a single copy per haploid genome, is expressed as a unique 1.7 kb mRNA species, and cytologically maps to 46C on the right arm of chromosome 2. Characterization of a cDNA clone indicates that the precursor protein is 347 amino acids in length and contains 5 copies of DPKQDFMRFamide, as well as 10 additional amidated peptides exhibiting varying degrees of structural relatedness. The Drosophila DPKQDFMRFamide gene and the Aplysia FMRFamide gene are ancestrally related; however, peptides display a higher degree of homology within a species than between species, suggesting intragenic concerted evolution of these neuropeptides.     

Identification of a Drosophila brain-gut peptide related to the neuropeptide Y family.

A neuropeptide F (NPF) was isolated from the fruit fly, Drosophila mellanogaster, based on a radioimmunoassay for a gut peptide from the corn earworm, Helicoverpa zea. A partial sequence was obtained from the fly peptide, and a genomic sequence coding for NPF was cloned after inverse polymerase chain reaction and shown to exist as a single genomic copy. The encoded, putative prepropeptide can be processed into an amidated NPF with 36 residues that is related to invertebrate NPF's and the neuropeptide Y family of vertebrates. In situ hybridization and immunocytochemistry showed that Drosophila NPF was expressed in the brain and midgut of fly larvae and adults.     

Cloning and expression of Ventrhoid, a novel vertebrate homologue of the Drosophila EGF pathway gene rhomboid

In Drosophila melanogaster, the seven-pass transmembrane protein Rhomboid (Rho) is a crucial positive modulator of EGF signaling playing a substantial role in patterning of the ventral neuroectoderm and fate specification of neuroblasts. Here, we describe the cloning and expression pattern of Ventrhoid (Vrho), the novel evolutionarily conserved vertebrate cDNA related to fruit fly rho. Most importantly, like rho in Drosophila, Vrho is also expressed in a spatially restricted manner. Vrho expression is most prominent along the developing ventral neural tube, and is also detectable in the ventral forebrain, prospective diencephalon, otic vesicles, mandibular arches, cranial sensory placodes, last formed pair of somites and hindgut in midgestational mouse embryos.     

Identification and characterization of a GroEL homologue in Rhodobacter sphaeroides

A protein closely related to the Escherichia coli GroEL protein has been isolated from Rhodobacter sphaeroides. Native and SDS-polyacrylamide gel electrophoresis of this protein have shown that it is present in the cell as a multimeric complex of Mr 670,000 which is composed of a monomer of Mr 58,000. Antisera raised against the Mr 58,000 polypeptide have been shown to cross-react with GroEL and the alpha subunit of the pea plastid chaperonin. The N-terminal amino acid sequence of the Mr 58,000 polypeptide is identical to that of GroEL at 15 of 19 residues and is also closely related to the alpha subunit of the pea plastid chaperonin, though less so to the beta subunit.     

Identification of a Drosophila homologue of alpha-catenin and its association with the armadillo protein

The cadherin cell adhesion system plays a central role in cell-cell adhesion in vertebrates, but its homologues are not identified in the invertebrate. alpha-Catenins are a group of proteins associated with cadherins, and this association is crucial for the cadherins' function. Here, we report the cloning of a Drosophila alpha-catenin gene by low stringent hybridization with a mouse alpha E-catenin probe. Isolated cDNAs encoded a 110-kD protein with 60% identity to mouse alpha E- catenin, and this protein was termed D alpha-catenin. The gene of this protein was located at the chromosome band 80B. Immunostaining analysis using a mAb to D alpha-catenin revealed that it was localized to cell- cell contact sites, expressed throughout development and present in a wide variety of tissues. When this protein was immunoprecipitated from detergent extracts of Drosophila embryos or cell lines, several proteins co-precipitated. These included the armadillo product which was known to be a Drosophila homologue of beta-catenin, another cadherin-associated protein in vertebrates, and a 150-kD glycoprotein. These results strongly suggest that Drosophila has a cell adhesion machinery homologous to the vertebrate cadherin-catenin system.     

Expression and functional characterization of a Drosophila neuropeptide precursor with homology to mammalian preprotachykinin A

Peptides structurally related to mammalian tachykinins have recently been isolated from the brain and intestine of several insect species, where they are believed to function as both neuromodulators and hormones. Further evidence for the signaling role of insect tachykinin-related peptides was provided by the cloning and characterization of cDNAs for two tachykinin receptors from Drosophila melanogaster. However, no endogenous ligand has been isolated for the Drosophila tachykinin receptors to date. Analysis of the Drosophila genome allowed us to identify a putative tachykinin-related peptide prohormone (prepro-DTK) gene. A 1.5-kilobase pair cDNA amplified from a Drosophila head cDNA library contained an 870-base pair open reading frame, which encodes five novel Drosophila tachykinin-related peptides (called DTK peptides) with conserved C-terminal FXGXR-amide motifs common to other insect tachykinin-related peptides. The tachykinin-related peptide prohormone gene (Dtk) is both expressed and post-translationally processed in larval and adult midgut endocrine cells and in the central nervous system, with midgut expression starting at stage 17 of embryogenesis. The predicted Drosophila tachykinin peptides have potent stimulatory effects on the contractions of insect gut. These data provide additional evidence for the conservation of both the structure and function of the tachykinin peptides in the brain and gut during the course of evolution.     

Identification of a mouse germ cell-less homologue with conserved activity in Drosophila

Drosophila Germ cell-less (Gcl) has previously been shown to be important in early events during the formation of pole cells, which are the germ cell precursors in the fly. We have isolated a 524 amino acid mouse gene with 32% identity and 49% similarity to Drosophila gcl, termed mgcl-1. Like Drosophila Gcl, mGcl-1 localizes to the nuclear envelope. Ectopic expression of mgcl-1 in Drosophila rescues the gcl-null phenotype, indicating that mGcl-1 is a functional homologue of Gcl. mgcl-1 maps to chromosome 6 at 47.3 cM, and is expressed at low levels at all embryonic stages examined from 8.5 to 18.5 d.p.c. as well as in many adult tissues. Different from Drosophila gcl, mgcl-1 is not highly expressed at the time the primordial germ cells appear in the mouse, but high mgcl-1 expression is found in selected mouse adult male germ cells. The differences in these expression patterns in light of conserved activity between the two genes is discussed.     

Identification and characterization of the rat homologue of LAIR-1

Leukocyte-associated immunoglobulin-like receptor-1 (LAIR-1) is a cell-surface molecule that functions as an inhibitory receptor on various immune cells in both humans and mice. We have cloned a LAIR-1 homologue from the rat that we have named rat LAIR-1. The LAIR-1 gene maps to rat chromosome 1q12 in a region showing conserved synteny with human chromosome 19q13.4 and mouse chromosome 7, where the leukocyte receptor cluster is located. Rat LAIR-1 shows 40 and 71% protein sequence identity with human LAIR-1 and mouse LAIR-1, respectively, has a single Ig-like domain and contains two immunoreceptor tyrosine-based inhibitory motif-like sequences in its cytoplasmic tail. Soluble rat LAIR-1 fusion proteins bind to the same adherent cell lines as human LAIR-1 and mouse LAIR-1, indicating that a putative ligand for all the LAIR-1 molecules is expressed on these cells. Furthermore, we show that rat and mouse LAIR-1 bind the same molecule expressed on human HT29 cells. Since many autoimmune diseases are studied in rat models, identification of rat LAIR-1 allows for in vivo studies on the function of LAIR molecules in these systems.     

Identification and characterisation of the Drosophila homologue of the yeast Uba2 gene

We have identified the Drosophila uba2 protein (dUba2). Analysis of the amino acid composition reveals similarity with both the mammalian (47% identity) and yeast (31% identity) homologues. dUba2 is present throughout the Drosophila life cycle but is most abundant during stages of proliferation. The protein is nucleoplasmic throughout much of the cell cycle, however it is lost from the nucleus during mitosis. The DUba2 localisation in the nucleoplasm is not uniform but is observed as concentrated patches reminiscent of the staining patterns seen for other proteins from this group. The nature of these sites is not clear, however the failure of dUba2 to localise to the sites of chorion amplification in ovaries suggests that they are not sites of ongoing DNA replication.     

Molecular characterization of KLHL3, a human homologue of the Drosophila kelch gene

The Drosophila kelch protein is a structural component of ring canals and is required for oocyte maturation. Here, we report the cloning and genomic structure of a new human homologue of kelch, KLHL3. At the amino acid level, KLHL3 shares 77% similarity with Drosophila kelch and 89% similarity with Mayven (KLHL2), another human kelch homolog. The approximately 6.5-kb mRNA has a single open reading frame encoding a protein of 587 amino acids with a predicted molecular mass of 650 kDa. Like kelch and KLHL2, the KLHL3 protein contains a poxvirus and zinc finger domain at the N-terminus and six tandem repeats (kelch repeats) at the C-terminus. At least three isoforms, which differ in the length of the N-terminus, are produced and may be the result of alternative promoter usage. We also identified alternative polyadenylation sites and alternative splicing; thus, as many as 12 mRNA variants and six putative protein isoforms could be produced. The KLHL3 gene is mapped to human chromosome 5, band q31, contains 17 exons, and spans approximately 120 kb of genomic DNA. KLHL3 maps within the smallest commonly deleted segment in myeloid leukemias characterized by a deletion of 5q; however, we detected no inactivating mutations of KLHL3 in malignant myeloid disorders with loss of 5q.     

Identification and characterization of a protostome homologue of peropsin from a jumping spider

Peropsin, a member of the opsin family, has characteristics of two functionally distinct opsin-groups, that is, amino acid residues conserved among opsins for light-sensing and a retinal-photoisomerase-like molecular property. Although such a bilateral feature of peropsin seems to be important for understanding the diversity of the opsin family, previous studies have been limited to higher deuterostome, vertebrate and amphioxus peropsins. Here, we report a protostome peropsin homologue from a jumping spider. We found a spider opsin that shares amino acid homology and conserved amino acid residues with known peropsins. The spider opsin-based pigment heterologously expressed in cultured cells exhibited photoisomerase-like isomerization characteristics and a bistable nature. Based on the characteristics of both the amino acid homology and its photochemical properties, we concluded that the spider opsin is the first protostome peropsin homologue. These results show that peropsin existed before the deuterostome–protostome split like other members of the opsin family. In addition, the spider peropsin was localized to non-visual cells in the retina, and fluorescence from reduced retinal chromophore was also observed in the region where peropsin was localized. These findings provide the first demonstration that the peropsin can form a photosensitive pigment in vivo and underlie non-visual function.     

Cloning and characterization of an ftsZ homologue from a bacterial symbiont of Drosophila melanogaster

A 1194 by open reading frame that codes for a 398 amino acid peptide was cloned from a λgt11 library of Drosophila melanogaster genomic DNA. The predicted peptide sequence is very similar to three previously characterized protein sequences that are encoded by the ftsZ genes in Escherichia coli, Bacillus subtilis and Rhizobium meliloti. The FtsZ protein has a major role in the initiation of cell division in prokaryotic cells. Using a tetracycline treatment that eradicates bacterial parasites from insects, the ftsZ homologue has been found to be derived from a bacterium that lives within the strain. However, polymerase chain reaction (PCR) amplification of the gene from treated embryos suggests that it is not derived from a gut bacterium. Nevertheless, by amplifying and characterizing part of the 16S rRNA from this bacterium we have been able to demonstrate that it is a member of the genus Wolbachia, a parasitic organism that infects, and disturbs the sexual cycle of various strains of Drosophila simulans. We suggest that this ftsZ homologue is implicated in the cell division of Wolbachia, an organism that fails to grow outside the host organism. Sequence and alignment analysis of this ftsZ homologue show the presence of a potential GTP-binding motif indicating that it may function as a GTPase. The consequences of this function particularly with respect to its role in cell division are discussed.     

Identification and characterization of the Drosophila tau homolog

A pathological hallmark of neurodegenerative tauopathies, including Alzheimer's disease and a group of clinically heterogeneous frontotemporal dementias, is the presence of intracellular neurofibrillary protein lesions (reviewed in Spillantini and Goedert, TINS 10 (1998) 428). The principal component of these structures is the microtubule-associated protein tau. Although tau is normally a highly soluble protein enriched in axons, in these deposits, it is abnormally hyperphosphorylated, insoluble, and redistributed to the somatodendritic compartments of neurons. Through ultrastructual analyses, it has been determined that the tau protein in these lesions is filamentous and organized into paired-helical filaments, straight filaments, or ribbon-like filaments (Goedert et al., The Molecular and Genetic Basis of Neurological Disease (1997) 613). By the dynamic binding of microtubules, tau is thought to promote the structural stability of axons, but whether tau aggregates contribute to neurodegeneration through a direct toxicity on normal cellular functions such as organelle transport or an indirect effect on microtubule stability, is currently unknown. The identification of mutations in the tau locus in patients with familial frontotemporal dementia and Parkinsonism linked to chromosome 17 has demonstrated that mutations in tau are sufficient to cause neurodegenerative disease (Poorkaj et al., Ann. Neurol. 43 (1998) 815; Hutton et al., Nature 393 (1998) 702). To elucidate the mechanisms by which tau dysfunction contributes to neuronal loss, we have sought to model human tauopathies in a genetically tractable organism. Here we describe the isolation of a Drosophila tau cDNA (GenBank accession number AY032977), the production of antibodies that recognize the encoded protein, and their use in determining the expression and subcellular localization of the fly tau protein.