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At least 19 recordsLinked to original sources
PubMed1992

Filarial parasites contain a ras homolog of the TC4/ran/Spil family.

We have isolated and characterized a gene encoding a novel GTP-binding protein of the GTPase superfamily in the filarial parasites Brugia malayi and Onchocerca volvulus. The deduced amino acid sequence of the cloned molecule has approximately 30% overall homology to ras proteins and approximately 90% homology to the 'ras-like' nuclear proteins TC4, ran and Spil. Rabbit antisera to bacterially expressed filarial protein detect a 24-22 kDa doublet in extracts of adult B. malayi and mature microfilariae, which is absent from immature microfilariae. Increased expression of the native parasite protein occurs when worms are cultured in the presence of epidermal growth factor.

Amino Acid Sequence↗
PubMed1992

Reverse genetics of Caenorhabditis elegans.

It is somewhat ironic that animals that are the prime choice for detailed genetic analysis, such as the fruit fly and the nematode, have thus far been largely refractory to reverse genetic analysis. Their detailed genetic map, and small genome size have made them subjects of ambitious genome analysis projects, but there is still no strategy to introduce desired changes into their genomes by homologous recombination. Some alternative approaches have recently become available; this review describes possibilities and unsolved problems for reverse genetics in the nematode Caenorhabditis elegans. The transposon Tc1 could prove to be very useful for the isolation of knock out mutants, and possibly also for introduction of more subtle alterations.

Animals↗
PubMed1992

Schistosoma mansoni: hycanthone/oxamniquine resistance is controlled by a single autosomal recessive gene.

Individual schistosomes of an hycanthone/oxamniquine-sensitive strain were crossed with individual schistosomes of the opposite sex and belonging either to the same sensitive population or to a different strain which exhibited high resistance to the two drugs. Schistosome crosses were performed by transfer of single worm pairs into the mesenteric veins of mice and the drug sensitivity/resistance of individual progeny worms was assessed using an in vitro test. Drug resistance behaved as an autosomal recessive trait, as shown by the results of the F1 and F2 generation and of the backcrosses. Drug-resistant worms appeared to be slightly less viable than their sensitive counterpart at all stages of the life cycle. The results are relevant for an interpretation of drug resistance and drug mechanisms and the approach used in this study may be applicable to different genetic markers in schistosomes.

Animals↗
PubMed1992

Homeoboxes in flatworms.

A search for homeobox-containing genes was done in the genome of a primitive metazoan, the parasitic tapeworm Echinococcus granulosus. Five different homeoboxes were isolated, none of them belonging to the classical Antennapedia-type. Three of the homeodomains are similar to those from the Drosophila melanogaster NK-type genes. The fourth homeodomain shares extensive identity with that of the recently reported homeobox-containing gene goosecoid from Xenopus laevis. The third helix (the recognition helix) of the fifth isolated homeodomain is identical to that of the Xlim-1 gene of X. laevis and the lin11 gene of Caenorharbditis elegans. Using PCR, some Antennapedia-type homeoboxes were cloned from the genome of two other Platyhelminthes, Dugesia tigrina (planaria) and Fasciola hepatica. These data suggest that, contrary to what is found for the majority of the more complex metazoans, Platyhelminthes contain few homeobox genes belonging to the Antennapedia-type.

Amino Acid Sequence↗
PubMed1992

Genetic complementation analysis of two independently isolated hycanthone-resistant strains of Schistosoma mansoni.

The objective of this study is to determine whether various hycanthone resistant strains of schistosomes which have been independently isolated are all affected in the same gene. A strain obtained from a Brazilian patient was compared with a strain of Puerto Rican origin selected in the laboratory. If the mutation conferring resistance involved two different genes, one would expect that progeny of a cross between the two strains would show complementation, i.e. it would be sensitive to the drug. We have performed such a cross and obtained F1 hybrid worms which were essentially all resistant, thus suggesting that the mutation conferring resistance in the two strains involves the same gene.

Animals↗
PubMed1989

Use of chitinase to facilitate detection of protozoan, helminth and single copy genes in squashed whole mosquitoes.

The application of DNA probes to detect foreign DNA in whole arthropods has been limited by the inability of the probes to distinguish between small quantities of target DNA and the background signal generated by non-specific hybridization of mosquito material. We report that treatment of nitrocellulose filters upon which mosquitoes have been squashed with chitinase and proteinase K eliminates non-specific hybridization of DNA probes to mosquito components. Using this technique we have been able to detect a single larva of Brugia malayi, sporozoites of Plasmodium falciparum and Plasmodium berghei, and a single-copy gene in directly squashed vector mosquitoes. Use of this simple, rapid technique should facilitate the successful use of DNA probes in field studies.

Aedes↗
PubMed1992

Tegumental proteins of Schistosoma mansoni: complex biomolecules and potent antigens.

The passive transfer of monoclonal antibodies, direct vaccination and in vitro assays have all shown that antigens associated with the tegumental membranes of Schistosoma mansoni are capable of mediating protective immune responses against the parasite in animal models. Furthermore, the principal antigens are highly antigenic during natural infection in man and stimulate strong humoral and cellular responses although, at present, their role in mediating protective immune responses in man remains equivocal. This presentation will review the current state of knowledge of the structure and expression of the major antigenic tegumental proteins of the schistosome and will attempt to relate the relevance of their structural features to possible function both in terms of protective immunity and the parasite's ability to survive within the definitive host. A focus will be the recent advances that have been made in the identification of means of anchoring of the antigenic proteins to the tegumental membrane. In addition, the implications of the structural complexity of the tegumental proteins in terms of their possible utility in vaccination and diagnosis will be considered.

Animals↗
PubMed1990

Developmentally regulated expression and secretion of a polymorphic antigen by Onchocerca infective-stage larvae.

In order to analyse the developmental biology of Onchocerca spp. with a view to identifying molecules with specialised functions, we have devised a novel method for labelling proteins synthesised by larvae during growth in the vectors. Pulse labelling of Onchocerca lienalis by micro-injections of [35S]methionine into blackflies have revealed a major acidic protein of 23 kDa which is developmentally expressed almost exclusively by infective, third-stage larvae. The protein appears to be antigenically conserved between O. lienalis and Onchocerca volvulus, but exhibits size polymorphisms both among species and among individual organisms. It continues to be elaborated after terminal differentiation of the parasite in flies, but not by post-infective larvae entering the phase of development in the vertebrate host. A shift in temperature from 26 degrees C to 37 degrees C triggers secretion of the 23-kDa molecule as a discrete event 24-72 h after transmission. The labelling technique has been successfully employed with filarial species that develop in mosquitoes, and in principle should be widely applicable to the study of endoparasite gene expression within arthropods.

Animals↗
PubMed1992

A cloned antigen for serological diagnosis of Wuchereria bancrofti microfilaremia with daytime blood samples.

By differentially screening an adult Brugia malayi cDNA library with sera from microfilaremic and amicrofilaremic donors infected with Wuchereria bancrofti, we have identified a novel parasite antigen denoted SXP-1. Recombinant SXP-1 filarial antigen is preferentially recognized by sera from microfilaremic persons with bancroftian filariasis and from skin snip-positive patients with onchocerciasis. Antibodies to SXP-1 are restricted to the IgG4 subclass and gradually decline after treatment with diethylcarbamazine. These findings indicate that it may be possible to replace microscopic examination of night blood films with a serological test designed to detect antibodies to a mix of SXP-1 and other suitable antigens for the diagnosis of microfilaremia due to bancroftian filariasis.

Amino Acid Sequence↗
PubMed1989

Evidence for a class of very small introns in the gene for hypoxanthine-guanine phosphoribosyltransferase in Schistosoma mansoni.

The single copy gene for the hypoxanthine-guanine phosphoribosyltransferase (HGPRTase) of the parasitic trematode, Schistosoma mansoni, contains seven introns, the first four of which are only 31, 33, 42, and 32 bases in length. These are the smallest introns ever discovered in a non-viral nuclear gene coding for protein. These very small introns possess the canonical GT...AG splice site sequences but lack the branching sequence, the secondary structure, and the minimum size of approximately 50 bases believed to be required for the splicing of eucaryotic mRNA precursors. Evidently, a somewhat different splicing mechanism for the transcripts of these very small introns is necessary. Their discovery within the genes of helminths raises theoretical considerations for the evolution of introns in eucaryotes.

Amino Acid Sequence↗
PubMed1992

Insect muscle actins differ distinctly from invertebrate and vertebrate cytoplasmic actins.

Invertebrate actins resemble vertebrate cytoplasmic actins, and the distinction between muscle and cytoplasmic actins in invertebrates is not well established as for vertebrate actins. However, Bombyx and Drosophila have actin genes specifically expressed in muscles. To investigate if the distinction between muscle and cytoplasmic actins evidenced by gene expression analysis is related to the sequence of corresponding genes, we compare the sequences of actin genes of these two insect species and of other Metazoa. We find that insect muscle actins form a family of related proteins characterized by about 10 muscle-specific amino acids. Insect muscle actins have clearly diverged from cytoplasmic actins and form a monophyletic group emerging from a cluster of closely related proteins including insect and vertebrate cytoplasmic actins and actins of mollusc, cestode, and nematode. We propose that muscle-specific actin genes have appeared independently at least twice during the evolution of animals: insect muscle actin genes have emerged from an ancestral cytoplasmic actin gene within the arthropod phylum, whereas vertebrate muscle actin genes evolved within the chordate lineage as previously described.

Actins↗
PubMed1992

Evolution of EF-hand calcium-modulated proteins. II. Domains of several subfamilies have diverse evolutionary histories.

In the first report in this series we described the relationships and evolution of 152 individual proteins of the EF-hand subfamilies. Here we add 66 additional proteins and define eight (CDC, TPNV, CLNB, LPS, DGK, 1F8, VIS, TCBP) new subfamilies and seven (CAL, SQUD, CDPK, EFH5, TPP, LAV, CRGP) new unique proteins, which we assume represent new subfamilies. The main focus of this study is the classification of individual EF-hand domains. Five subfamilies--calmodulin, troponin C, essential light chain, regulatory light chain, CDC31/caltractin--and three uniques--call, squidulin, and calcium-dependent protein kinase--are congruent in that all evolved from a common four-domain precursor. In contrast calpain and sarcoplasmic calcium-binding protein (SARC) each evolved from its own one-domain precursor. The remaining 19 subfamilies and uniques appear to have evolved by translocation and splicing of genes encoding the EF-hand domains that were precursors to the congruent eight and to calpain and to SARC. The rates of evolution of the EF-hand domains are slower following formation of the subfamilies and establishment of their functions. Subfamilies are not readily classified by patterns of calcium coordination, interdomain linker stability, and glycine and proline distribution. There are many homoplasies indicating that similar variants of the EF-hand evolved by independent pathways.

Amino Acid Sequence↗
PubMed1986

Neither a germ line-specific nor several somatically expressed genes are lost or rearranged during embryonic chromatin diminution in the nematode Ascaris lumbricoides var. suum.

Ascaris lumbricoides var. suum is a parasitic nematode of pigs. Its embryos undergo chromatin diminution between the third and fifth cleavages, resulting in the loss of about 30% of the DNA from all somatic precursor cells while the germ line DNA stays intact. Most of the eliminated DNA has been shown to be satellite sequences. Theodor Boveri [(1910) In "Festschrift fur R. Hertwig, III," Vol. 3, pp. 131-214, Fischer] proposed that functions essential only to the germ line might be lost from the soma. We have examined this proposal by cloning a gene encoding the major sperm protein (MSP) using a cloned MSP gene from Caenorhabditis elegans as a probe. The MSP appears to be expressed only in the testis of Ascaris, as it is in Caenorhabditis. Actin and alpha tubulin were also cloned to serve as somatically expressed gene controls. By probing Southern blots of somatic and germ line DNA with these cloned genes, it was found that none of them was lost or rearranged during chromatin diminution. Thus at least one germ line-specific gene is neither lost nor rearranged during chromatin diminution. We also found that the two nematode species differ widely in their numbers of both MSP and actin genes. Caenorhabditis has greater than 30 MSP genes, but Ascaris has no more than three; whereas Ascaris has many more actin genes than Caenorhabditis.

Actins↗
PubMed1991

cut-1 a Caenorhabditis elegans gene coding for a dauer-specific noncollagenous component of the cuticle.

We have molecularly identified a new gene of Caenorhabditis elegans that codes for a component of the cuticle. The gene has been physically mapped on LGII near the locus sqt-1. The structure and the sequence of the gene have been determined and antisera have been raised against parts of the protein produced as fusions in Escherichia coli. By transcription analysis, and by the use of specific antisera, we have determined that this gene is expressed specifically during dauer larva formation. In extracts of worms completing the dauer transformation the product of this gene migrates in sodium dodecyl sulfate acrylamide gels with an apparent molecular mass of 40 kDa. By immunofluorescence we have determined that it is a component of the cuticles of dauer larvae. It forms a ribbon approximately 2 microns wide running along the lateral lines underneath the alae. Once it is assembled in the cuticle the protein becomes insoluble even in the presence of strong detergents and reducing agents in a manner that is similar to that described for the noncollagenous, insoluble residue of nematode cuticles called cuticlins; therefore, we have named the gene cut-1 for cuticlin 1. cut-1 represents the first gene for a noncollagenous component of C. elegans cuticle that has been characterized molecularly.

Amino Acid Sequence↗
PubMed1992

Schistosoma mansoni: cloning of a complementary DNA encoding a cytosolic Cu/Zn superoxide dismutase and high-yield expression of the enzymatically active gene product in Escherichia coli.

We recently purified a 16-kDa cytosolic Cu/Zn superoxide dismutase (CT Cu/Zn-SOD) from Schistosoma mansoni, a human parasite. Three peptide sequences were obtained, one from the unblocked N-terminal and two from internal peptides which were generated by digestions with trypsin and cyanogen bromide. These sequences were aligned to the corresponding sequences of 19 cytosolic Cu/Zn-SODs from various species. Degenerate oligonucleotides were then designed according to the sequence and the position of each peptide. The oligonucleotides were used to amplify a complete cDNA using the polymerase chain reaction with either adult schistosome total RNA or a cercariae lambda gt11 phage cDNA library as the template. The protein encoded by the cDNA has 153 amino acids with a calculated molecular weight of 15,693. It also has 60-65% homology to 19 cytosolic Cu/Zn-SOD from various species. All of the copper/zinc binding sites and SOD activity sites are conserved. Computer analysis predicts that the Cu/Zn-SOD has a pI value of 6.6, which is very close to the experimental results of IEF analysis (6.0 and 6.3). The entire coding sequence from the cDNA was cloned into a bacterial alkaline phosphatase cytosolic expression vector and a large amount of soluble product was expressed and purified to homogeneity. We compared the bacterially expressed Cu/Zn-SOD with the native enzyme derived from schistosomes and found that they are identical by the following criteria: (1) They focus at the same positions on IEF gels; (2) they form dimers in solution as measured by gel filtration; (3) they have the same unblocked N-terminal sequence; (4) they both are enzymatically active with comparable specific activities. The specific activity of the bacterially derived enzyme was increased somewhat (approximately 10%) by incubation with copper and zinc ions.

Amino Acid Sequence↗
PubMed1992

Eggshell precursor proteins of Fasciola hepatica, I. Structure and expression of vitelline protein B.

Antibody raised against the major eggshell protein of Fasciola hepatica (vitelline protein B, vpB) is employed to isolate cDNAs from an expression library and to localize the protein in whole worms. Two cDNAs corresponding to the protein are homologous through the N-terminal and C-terminal coding regions and widely divergent internally. No repeated regions are apparent and no significant sequence homology is seen with chorion proteins of other genera although the amino acid composition closely reflects that of other chorion proteins. Microheterogeneity observed in the vpB is due to the presence of multiple coding sequences, transcripts and a gradient of post-translational modification. Relative transcription of the vpB mRNA throughout the female reproductive tract is demonstrated.

Amino Acid Sequence↗