Cloning, expression of gene SjOST48 from Schistosoma japonicum and evaluation of the immunoprotective efficacy of rSjOST48 in mice / 生物工程学报

To identify SJCHGC01743 gene of Schistosoma japonicum and evaluate the potential of the recombinant protein as a new vaccine candidate for schistosomiasis, polymerase chain reaction (PCR) technique was used to amplify the cDNA of the gene and real-time RT-PCR was used to analyze the transcription profiles of SJCHGC01743 at different development stages. Recombinant plasmid was successfully constructed and transformed into competent Escherichia coli BL21 (DE3). Then the recombinant protein was expressed, purified and emulsified with ISA206 adjuvant to immunize BALB/c mice for three times. The immunogenicity was confirmed by Western blotting and tissue localization was detected by indirect immunofluorescent assay. The specific antibody level was detected by ELISA. The immunoprotection of rSjOST48 was evaluated by the reduction in worm and egg counts in mice. A cDNA with 1 248 nucleotides was isolated from 28-day-old schistosomes cDNAs by PCR. Sequence analysis revealed that SJCHGC01743 was a 48-kDa subunit of the oligosaccharyltransferase complex (OST48) and named as SjOST48. Real-time PCR analysis indicated that this gene was expressed in all investigated stages and had the highest expression level in 28 d worms, the level of gene transcription in female worms was significantly higher than that of male worms. Then recombinant plasmid pET28a(+)-SjOST48 was successfully constructed and expressed in E. coli BL21 (DE3). Western blotting analysis showed that rSjOST48 had good immunogenicity. Indirect immunofluorescent analysis revealed that SjOST48 was mainly distributed on the tegument of the worms. The result of ELISA indicated that the rSjOST48 vaccinated group could induce a significant increase in the level of specific IgG, IgG1 and IgG2a. An immunoprotection experiment showed that the vaccination of rSjOST48 in mice induced 32.62% (P < 0.05) reduction in the numbers of worms and 57.61% (P < 0.01) in eggs in liver, compared with that of the control group. This study provides the foundation for proceeding further research on the biological function of SjOST48 and screening new vaccine candidates for schistosomiasis.

Complete Mitochondrial Genome of Haplorchis taichui and Comparative Analysis with Other Trematodes

Mitochondrial genomes have been extensively studied for phylogenetic purposes and to investigate intra- and interspecific genetic variations. In recent years, numerous groups have undertaken sequencing of platyhelminth mitochondrial genomes. Haplorchis taichui (family Heterophyidae) is a trematode that infects humans and animals mainly in Asia, including the Mekong River basin. We sequenced and determined the organization of the complete mitochondrial genome of H. taichui. The mitochondrial genome is 15,130 bp long, containing 12 protein-coding genes, 2 ribosomal RNAs (rRNAs, a small and a large subunit), and 22 transfer RNAs (tRNAs). Like other trematodes, it does not encode the atp8 gene. All genes are transcribed from the same strand. The ATG initiation codon is used for 9 protein-coding genes, and GTG for the remaining 3 (nad1, nad4, and nad5). The mitochondrial genome of H. taichui has a single long non-coding region between trnE and trnG. H. taichui has evolved as being more closely related to Opisthorchiidae than other trematode groups with maximal support in the phylogenetic analysis. Our results could provide a resource for the comparative mitochondrial genome analysis of trematodes, and may yield genetic markers for molecular epidemiological investigations into intestinal flukes.

A genome-wide RNAi screen identifies genes regulating the formation of P bodies in C. elegans and their functions in NMD and RNAi

Cytoplasmic processing bodies, termed P bodies, are involved in diverse post-transcriptional processes including mRNA decay, nonsense-mediated RNA decay (NMD), RNAi, miRNA-mediated translational repression and storage of translationally silenced mRNAs. Regulation of the formation of P bodies in the context of multicellular organisms is poorly understood. Here we describe a systematic RNAi screen in C. elegans that identified 224 genes with diverse cellular functions whose inactivations result in a dramatic increase in the number of P bodies. 83 of these genes form a complex functional interaction network regulating NMD. We demonstrate that NMD interfaces with many cellular processes including translation, ubiquitin-mediated protein degradation, intracellular trafficking and cytoskeleton structure.We also uncover an extensive link between translation and RNAi, with different steps in protein synthesis appearing to have distinct effects on RNAi efficiency. Moreover, the intracellular vesicular trafficking network plays an important role in the regulation of RNAi. A subset of genes enhancing P body formation also regulate the formation of stress granules in C. elegans. Our study offers insights into the cellular mechanisms that regulate the formation of P bodies and also provides a framework for system-level understanding of NMD and RNAi in the context of the development of multicellular organisms.

Cloning and sequence analysis of a new cathepsin L-like cysteine proteinase gene from Ditylenchus destructor / 生物工程学报

The Cathepsin L-like cysteine proteinase genes (cpls) are multifunction genes related to the parasitic abilities of plant parasitic nematodes. A new cathepsin L-like cysteine proteinase gene (Dd-cpl-1) (GenBank Accession GQ 180107) was cloned from Ditylenchus destructor by RT-PCR and RACE. The cDNA sequence consisted of a 1 131 bp open reading frame (ORF) encoding 376 amino acid residues that were franked by a 29 bp 5'-untranslated region (UTR) and a 159 bp 3'-UTR. Genomic sequence analysis showed that Dd-cpl-1 contained 7 introns, obeyed the GT/AG rule in the splice-site junctions. Homology analysis showed that the identity was 77% between Dd-cpl-1 deduced protein Dd-CPL-1 and cathepsin L-like cysteine proteinase of Bursaphelenchus xylophilus. Multi-sequence alignment indicated that there were the catalytic triad (Cys183, His322 and Asn343) and two motifs ERFNIN motif and GNFD motif in deduced protein Dd-CPL-1. Cysteine proteinases phylogenetic analysis showed that Dd-cpl-1 belonged to the sub-clade of cathepsin L-like cysteine proteinases.

Cloning, expression and characterization of a gene encoding alpha2 subunit of the proteasome in Schistosoma japonicum / 生物工程学报

The 26S proteasome is a proteolytic complex responsible for the degradation of the vast majority of eukaryotic proteins. Regulated proteolysis by the proteasome is thought to influence cell cycle progression, transcriptional control, and other critical cellular processes. A novel Schistosoma japonicum gene (GenBank Accession No. AY813725) proteasome alpha2 subunit (SjPSMA2) was cloned. Sequence analysis revealed that the ORF of SjPSMA2 gene contains 708 nucleotides encoding 235 amino acids, and the molecular weight was estimated to be 25.84 kDa. Real-time PCR analysis showed that this gene expressed in 7 d, 13 d, 18 d, 23 d, 32 d and 42 d schistosoma. The mRNA level of SjPSMA2 was lower in 7 d and 23 d schistosomulum than that in other stages. The SjPSMA2 cDNA fragment was subcloned into an expression vector pET28a(+) and transformed into E. coli BL21 (DE3) cells. After induction with IPTCQ the 30 kDa fusion protein was produced as included bodies. Western-blotting revealed that the fusion protein could be recognized by the rabbit serum anti-Schistosoma japonicum adult worm antigen preparation, and the protein in native could be detected. After immunization of BALB/c mice with the fusion protein, the reduction rates of worm counts and liver egg counts were 12.33% and 35.23%. ELISA results revealed that the vaccinated group showed a significant increase in the level of IgG antibody. This study provided an important basis for investigating the regulation mechanism of the proteasome during the development of Schistosoma japonicum.

Aluminium toxicosis causing transferable defects from exposed animals to their progeny in Caenorhabditis elegans / 中华预防医学杂志

<p><b>OBJECTIVE</b>To study the possibly transferable properties of multi-biological toxicities caused by aluminium exposure from exposed animals to their progeny.</p><p><b>METHODS</b>Multi-biological toxicities in aluminium (2.5 micromol/L, 75 micromol/L, and 200 micromol/L) exposed animals and their progeny were analyzed by using model organism Caenorhabditis elegans. Endpoints of lifespan, development, reproduction, locomotion behavior and behavioral plasticity were selected for the assay of multiple toxicities and their transfer properties. Four groups of experiments were performed for each endpoint assay. Twenty animals were used for assay of lifespan, development, reproduction and locomotion behaviors, and 100 animals were used for assay of behavioral plasticity in each group experiment. The data were performed for statistical analysis using SPSS 13.0 software.</p><p><b>RESULTS</b>Our data suggest that the aluminium exposure could result in multi-biological defects of phenotypes and behaviors. As compared to those average survival days, 24 d, body size, (1.30 +/- 0.05) mm; brood size, (278 +/- 20); generation time (64.0 +/- 1.2) h; body bend, (45.8 +/- 3.0) times, head thrash, (109.33 +/- 7.30) times, behavioral plasticity (3 +/- 4)% in 0 micromol/L aluminum exposed animals, the low-concentration (2.5 micromol/L) aluminium exposure caused severe defects of average survival days (20 d), body size [(1.12 +/- 0.02 ) mm, t = 14.55, P<0.01], brood size [(145 +/- 23), t = 30.62, P< 0.01], body bend [(29.8 +/- 3.0), t = 20.31, P<0.01], and head thrash, (95.8 +/- 6.2), t = 16.43, P < 0.01]. High-concentration aluminium exposure could further result in severe defects of generation time [75 micromol/L, (67.0 +/- 1.7 ) h, t = 8.92, P<0.01; 200 micromol/L, (70.7 +/- 1.5) h, t =15.13, P<0.01] and behavioral plasticity [75 micromol/L, (16.5 +/- 3.0)%, t = 27.11, P<0.05; 200 micromol/L, (23.5 +/- 4.0)%, t = 16.43, P<0.01]. Moreover, most of these toxicities caused by high-concentration aluminium exposure could be transferred from exposed animals to their progeny. In progeny animals, the phenotypic and behavioral defects might be only partially (such as body size, brood size, and locomotion behaviors) or very slightly (such as the lifespan defects induced by high concentrations of aluminium exposure) rescued. Especially, the generation time defects induced by aluminium exposure would become more severe in progeny animals than in their parents.</p><p><b>CONCLUSION</b>The multi-biological defects caused by aluminium exposure might be largely transferred from exposed animals to their progeny in Caenorhabditis elegans.</p>

Screening of T7 phage-display cDNA library from liver of Microtus fortis with extracts of schistosomulum and characterization of the positive clones / 生物工程学报

Microtus fortis is naturally resisitent to Schistosoma japonicum. In order to find schistosome-resistence-related genes of Microtus fortis, a T7 phage-display cDNA library from liver of Microtus fortis was screened with the soluble lysate of schistosomula. The specific phages were enriched 375-fold after 3 rounds of biopanning. Ninety-two positive clones picked at random were sequenced and 19 ESTs including 6 unreported genes were obtained. Compared with the negative phage clone control, five positive clones, No.4 (GenBank Accession No.: EW968294), No.13 (GenBank Accession No.: EW968303), No.14 (GenBank Accession No.: EW968304), No.15 (GenBank Accession No.: EW968305) and No.18 (GenBank Accession No.: EW968308) could induce significantly higher schistosomula mortality rate when co-cultivated with schistosomula. According to the function analysis and the shistosomula-killing effect in vitro, the genes encoding CASP8 and FADD-like apoptosis regulator isoform protein, alpha-2-HS-glycoprotein, M4 protein, R3H domain (binds single-stranded nucleic acids) isoform 2 and 3 previously unreported proteins (No.14, No.15 and No.18) obtained here, were schistosomiasis-resistence-related genes of Microtus fortis.

Molecular cloning and characterization of an acetylcholinesterase gene Dd-ace-2 from sweet potato stem nematode Ditylenchus destructor / 生物工程学报

A cDNA, named Dd-ace-2, encoding an acetylcholinesterase (AChE, EC3.1.1.7), was isolated from sweet-potato-stem nematode, Ditylenchus destructor. The nucleotide and amino acid sequences among different nematode species were compared and analyzed with DNAMAN5.0, MEGA3.0 softwares. The results showed that the complete nucleotide sequence of Dd-ace-2 gene of Ditylenchus destructor contains 2425 base pairs from which deduced 734 amino acids (GenBank accession No. EF583058). The homology rates of amino acid sequences of Dd-ace-2 gene between Ditylenchus destructor and Meloidogyne incognita, Caenorhabditis elegans, Dictyocaulus viviparous were 48.0%, 42.7%, 42.1% respectively. The mature acetylcholinesterase sequences of Ditylenchus destructor may encode by the first 701 residues of deduced 734 amino acids.The conserved motifs involved in the catalytic triad, the choline binding site and 10 aromatic residues lining the catalytic gorge were present in the Dd-ace-2 deduced protein. Phylogenetic analysis based on AChEs of other nematodes and species showed that the deduced AChE formed the same cluster with ACE-2s.

Functional complementation of a yeast knockout strain by Schistosoma mansoni Rho1 GTPase in the presence of caffeine, an agent that affects mutants defective in the protein kinase C signal transduction pathway

In a previous study, the Schistosoma mansoni Rho1 protein was able to complement Rho1 null mutant Saccharomyces cerevisiae cells at restrictive temperatures and under osmotic stress (low calcium concentration) better than the human homologue (RhoA). It is known that under osmotic stress, the S. cerevisiae Rho1 triggers two distinct pathways: activation of the membrane 1,3-beta-glucan synthase enzymatic complex and activation of the protein kinase C1 signal transduction pathway, promoting the transcription of response genes. In the present work the SmRho1 protein and its mutants smrho1E97P, smrho1L101T, and smrho1E97P, L101T were used to try to clarify the basis for the differential complementation of Rho1 knockout yeast strain by the human and S. mansoni genes. Experiments of functional complementation in the presence of caffeine and in the presence of the osmotic regulator sorbitol were conducted. SmRho1 and its mutants showed a differential complementation of the yeast cells in the presence of caffeine, since smrho1E97P and smrho1E97P, L101T mutants showed a delay in the growth when compared to the yeast complemented with the wild type SmRho1. However, in the presence of sorbitol and caffeine the wild type SmRho1 and mutants showed a similar complementation phenotype, as they allowed yeast growth in all caffeine concentrations tested.

A new record of Paragonimus other than P. westermani in southern Thailand.

Field surveys of Paragonimus in Surat Thani Province, southern Thailand, revealed a new record of a lung fluke species other than P. westermani. The metacercariae were obtained from the crab, Ranguna smalleyi. The cysts of the metacercariae were spherical in shape and the larval body in the cysts contained pinkish granules. Fully mature adult worms were obtained from experimental infections with a rat and a ferret. The adult worms from the two host animals resembled each other, except for size, and had the anatomical characteristics of P. bangkokensis, ie the cuticular spines were arranged mainly in groups, the ovaries were highly branched, while the testes were more simply divided. Chromosomal preparations of the testes showed a haploid number of 11. As no sequence data of P. bangkokensis has been deposited in the GenBank/EMBL/DDBJ nucleotide database, the ITS2 region was sequenced using the metacercariae as starting material. A similarity search of P. bangkokensis ITS2 sequence using the BLAST program revealed that there was only one base difference between this population and P. harinasutai occurring in central Thailand. The result may suggest a close relationship between P. bangkokensis and P. harinasutai. This is the first description of Paragonimus species other than P. westermani occurring in southern Thailand.

Construction and expression of protein self-splicing prokaryotic expression vector pTWIN1- AcAPc2 / 生物医学工程学杂志

To express recombinant Ancylostoma caninum anticoagulant peptide-c2 (AcAPc2), a whole cDNA fragment encoding AcAPc2 was achieved by ligation- PCR and inserted into prokaryotic expression vector pTWIN1 for constructing the specific self-splicing prokaryotic expression vector, pTWIN1-AcAPc2; positive recombinants were transformed into E. coli ER2566 for expression research. The recombinant protein, AcAPc2-intein2-CBD, was soluble and expressed in E. coli ER2566 (about 30.1% fusion protein in total protein). AcAPc2-intein2-CBD was characterized to be 41 KD by SDS-PAGE and identified by Western-blot. The recombinant fusion protein was purified to a efficiently high degree by chitin affinity chromatography. After the process of specific self-splicing induced by beta-Mercaptoethanol, the target protein, AcAPc2, was obtained, characterized to be 21 KD by SDS-PAGE and migrated as a dimmer. Molecular weight of AcAPc2 conformed to native dimmer. Bio-information analysis indicated relationship between secondary construction of AcAPc2 and biologic function. These findings greatly facilitate the purification of AcAPc2 and are very important for the additional studies on its anti-coagulation mechanism and its clinical application as anti-coagulation medicine.

Cloning and characterization of new genes of Schistosoma japonicum / 中南大学学报(医学版)

OBJECTIVE@#To clone and characterize new genes of Schistosoma japonicum, Sj, and to provide efficient vaccine candidates.@*METHODS@#Sj adult cDNA library was screened with rabbit sera raised against male worm soluble antigen. The inserted cDNA fragments from the positively selected clones were amplified with PCR and further sequenced, as well as characterized through internet NCBI GenBank software.@*RESULTS@#Eleven positive clones were obtained and two were verified by GenBank as new, including a novel gene designated as Sj-P8 (GenBank accession No. AF517843) and a new partial cDNA of Sj myosin (GenBank accession No. AY770506). The two new genes encoded a transmembrane protein of 75 amino acids and a myosin protein fragment of 212 amino acids respectively.@*CONCLUSION@#The newly obtained genes may provide useful information for the research on Sj vaccine.

Detection of Schistosomia japonicum 5D gene by polymerase chain reaction and genechip technique / 中华流行病学杂志

<p><b>OBJECTIVE</b>In order to develop the diagnostic genechip for specific detection of Schistosoma japonicum (Chinese mainland strain).</p><p><b>METHODS</b>Probe and primers were designed based on the Schistosoma japonicum 5D gene encoding an immunogenic miracidial antigen. The probe for the conservative and specific gene sequence was spotted onto the specially treated glass slides by pin-based spotting robot Pixsys 5500 and was employed to make genechips. A polymerase chain reaction (PCR) protocol was designed to effectively amplify the 5D gene fragment containing the probe sequence from cercaria, egg, adult worm and infected Oncomelania DNA as well as other flukes DNA, respectively. After 35 cycles by PCR, the products were then labeled with fluorescent Cy3-labeled primer, using dissymmetrical PCR. The labeled PCR products of the target genes were hybridized to the diagnostic genechips for detection of Schistosoma japonicum and a fluorescent scanner (ScanArray 3000) was used to observe and record the hybridization signals.</p><p><b>RESULTS</b>The result obtained from the study showed that a 262 bp DNA fragment was amplified from cercaria, egg and adult worm with the designed primers and enable the genechip be applied to detect a single cercaria, egg and adult worm. When the genechip was used to detect Clonorchis sinensis, Fasciolopsis busk, and Paragonimus westermani DNA, the results showed negative, indicating that the genechip had good specificity.</p><p><b>CONCLUSION</b>The genchip technique for detection of Schistosoma japonicum was established successfully and having the characteristics of high sensitivity and specificity.</p>

Differentiation of Brugia malayi and Brugia pahangi by PCR-RFLP of ITS1 and ITS2.

Lymphatic filariasis has been targeted by the World Health Organization for elimination by the year 2020. Malayan filariasis, caused by Brugia malayi, is endemic in southern Thailand where domestic cats serve as a major reservoir host. However, in nature, domestic cats also carry B. pahangi infection. In addition to chemotherapy and vector control, control in reservoir hosts is necessary to achieve the elimination of the disease. Therefore, differentiation between B. malayi and B. pahangi in the cat reservoir will help the lymphatic control program to monitor and evaluate the real disease situation. It is difficult to differentiate these two Brugia species by microscopic examination. The technique is also time-consuming and requires expertise. We employed the polymerase chain reaction-linked restriction fragment length polymorphism (PCR-RFLP) technique of internal transcribed spacer regions, ITS1 and ITS2, of ribosomal DNA (rDNA) to differentiate B. malayi from B. pahangi species. Among the restriction enzymes tested, only the PCR product of ITS1 digested with Ase I could differentiate B. malayi from B. pahangi. This PCR-RFLP technique will be useful for lymphatic filariasis control programs for monitoring and evaluating animal reservoirs.

Evolution of ascariasis in humans and pigs: a multi-disciplinary approach

The nematode parasite Ascaris lumbricoides infects the digestive tracts of over 1.4 billion people worldwide, and its sister species, Ascaris suum, has infected a countless number of domesticated and feral pigs. It is generally thought that the putative ancestor to these worms infected either humans or pigs, but with the advent of domestication, they had ample opportunity to jump to a new host and subsequently specialize and evolve into a new species. While nuclear DNA markers decisively separate the two populations, mitochondrial sequences reveal that three major haplotypes are found in A. suum and in A. lumbricoides, indicating either occasional hybridization, causing introgression of gene trees, or retention of polymorphism dating back to the original ancestral species. This article provides an illustration of the combined contribution of parasitology, archaeoparasitology, genetics and paleogenetics to the history of ascariasis. We specifically investigate the molecular history of ascariasis in humans by sequencing DNA from the eggs of Ascaris found among ancient archeological remains. The findings of this paleogenetic survey will explain whether the three mitochondrial haplotypes result from recent hybridization and introgression, due to intensive human-pig interaction, or whether their co-occurrence predates pig husbandry, perhaps dating back to the common ancestor. We hope to show how human-pig interaction has shaped the recent evolutionary history of this disease, perhaps revealing the identity of the ancestral host

Phylogenetic relationship of ribosomal ITS2 and mitochondrial COI among diploid and triploid Paragonimus westermani isolates

We compared patterns of intraspecific polymorphism of two markers with contrasting modes of evolution, nuclear ribosomal DNA (rDNA) and mitochondrial DNA (mtDNA), in the lung fluke, diploid and triploid Paragonimus westermani from three geographical regions of Korea. The genetic distances between three populations of Korean diploid and triploid P. westermani showed no significant difference in the nucleotide sequences of the mitochondrial cytochrome c oxidase subunit I (mtCOI) and ribosomaal second internal transcribed spacer (ITS2) genes. A highly resolved strict-consensus tree was obtained that illustrated phylogenetically useful information of the ITS2 and mtCOI sequences from diploid and triploid P. westermani.

Clustering of Schistosoma mansoni mRNA sequences and analysis of the most transcribed genes: implications in metabolism and biology of different developmental stages

The study of the Schistosoma mansoni genome, one of the etiologic agents of human schistosomiasis, is essential for a better understanding of the biology and development of this parasite. In order to get an overview of all S. mansoni catalogued gene sequences, we performed a clustering analysis of the parasite mRNA sequences available in public databases. This was made using softwares PHRAP and CAP3. The consensus sequences, generated after the alignment of cluster constituent sequences, allowed the identification by database homology searches of the most expressed genes in the worm. We analyzed these genes and looked for a correlation between their high expression and parasite metabolism and biology. We observed that the majority of these genes is related to the maintenance of basic cell functions, encoding genes whose products are related to the cytoskeleton, intracellular transport and energy metabolism. Evidences are presented here that genes for aerobic energy metabolism are expressed in all the developmental stages analyzed. Some of the most expressed genes could not be identified by homology searches and may have some specific functions in the parasite

Cloning and molecular characterization of the Schistosoma mansoni genes RbAp48 and histone H4

The human nuclear protein RbAp48 is a member of the tryptophan/aspartate (WD) repeat family, which binds to the retinoblastoma (Rb) protein. It also corresponds to the smallest subunit of the chromatin assembly factor and is able to bind to the helix 1 of histone H4, taking it to the DNA in replication. A cDNA homologous to the human gene RbAp48 was isolated from a Schistosoma mansoni adult worm library and named SmRbAp48. The full length sequence of SmRbAp48 cDNA is 1036 bp long, encoding a protein of 308 amino acids. The transcript of SmRbAp48 was detected in egg, cercariae and schistosomulum stages. The protein shows 84% similarity with the human RbAp48, possessing four WD repeats on its C-terminus. A hypothetical tridimensional structure for the SmRbAp48 C-terminal domain was constructed by computational molecular modeling using the b-subunit of the G protein as a model. To further verify a possible interaction between SmRbAp48 and S. mansoni histone H4, the histone H4 gene was amplified from adult worm genomic DNA using degenerated primers. The gene fragment of SmH4 is 294 bp long, encoding a protein of 98 amino acids which is 100% identical to histone H4 from Drosophila melanogaster

Cloning and characterization of SmZF1, a gene encoding a Schistosoma mansoni zinc finger protein

The zinc finger motifs (Cys2His2) are found in several proteins playing a role in the regulation of transcripton. SmZF1, a Schistosoma mansoni gene encoding a zinc finger protein was initially isolated from an adult worm cDNA library, as a partial cDNA. The full sequence of the gene was obtained by subcloning and sequencing cDNA and genomic fragments. The collated gene sequence is 2181 nt and the complete cDNA sequence is 705 bp containing the full open reading frame of the gene. Analysis of the genome sequence revealed the presence of three introns interrupting the coding region. The open reading frame theoretically encodes a protein of 164 amino acids, with a calculated molecular mass of 18,667Da. The predicted protein contains three zinc finger motifs, usually present in transcription regulatory proteins. PCR amplification with specific primers for the gene allowed for the detection of the target in egg, cercariae, schistosomulum and adult worm cDNA libraries indicating the expression of the mRNA in these life cycle stages of S. mansoni. This pattern of expression suggests the gene plays a role in vital functions of different life cycle stages of the parasite. Future research will be directed to elucidate the functional role of SmZF1

Ageing, gerontogenes, and hormesis.

Evolutionary theories of ageing and longevity argue against the existence of specific genes that cause ageing. However, genes whose altered activity influences ageing and longevity, may be termed gerontogenes. Several putative gerontogenes have been identified in various ageing systems, including the Drosophila, budding yeast, nematodes and cells in culture. Since ageing is characterized by a progressive failure of maintenance and repair, it is reasoned that genes involved in homeodynamic repair pathways are the most likely candidate gerontogenes. A promising approach for the identification of critical gerontogenic processes is hormesis-like positive effects of stress. Stimulation of various repair pathways by mild stress has significant effects on delaying the onset of various age-associated alterations in cells, tissues and organisms.