A directed approach for the identification of transcripts harbouring the spliced leader sequence and the effect of trans-splicing knockdown in Schistosoma mansoni

Schistosomiasis is a major neglected tropical disease caused by trematodes from the genus Schistosoma. Because schistosomes exhibit a complex life cycle and numerous mechanisms for regulating gene expression, it is believed that spliced leader (SL) trans-splicing could play an important role in the biology of these parasites. The purpose of this study was to investigate the function of trans-splicing in Schistosoma mansoni through analysis of genes that may be regulated by this mechanism and via silencing SL-containing transcripts through RNA interference. Here, we report our analysis of SL transcript-enriched cDNA libraries from different S. mansoni life stages. Our results show that the trans-splicing mechanism is apparently not associated with specific genes, subcellular localisations or life stages. In cross-species comparisons, even though the sets of genes that are subject to SL trans-splicing regulation appear to differ between organisms, several commonly shared orthologues were observed. Knockdown of trans-spliced transcripts in sporocysts resulted in a systemic reduction of the expression levels of all tested trans-spliced transcripts; however, the only phenotypic effect observed was diminished larval size. Further studies involving the findings from this work will provide new insights into the role of trans-splicing in the biology of S. mansoni and other organisms. All Expressed Sequence Tags generated in this study were submitted to dbEST as five different libraries. The accessions for each library and for the individual sequences are as follows: (i) adult worms of mixed sexes (LIBEST_027999: JZ139310 - JZ139779), (ii) female adult worms (LIBEST_028000: JZ139780 - JZ140379), (iii) male adult worms (LIBEST_028001: JZ140380 - JZ141002), (iv) eggs (LIBEST_028002: JZ141003 - JZ141497) and (v) schistosomula (LIBEST_028003: JZ141498 - JZ141974).

Footprints of a trypanosomatid RNA world: pre-small subunit rRNA processing by spliced leader addition trans-splicing

The addition of a capped mini-exon [spliced leader (SL)] through trans-splicing is essential for the maturation of RNA polymerase (pol) II-transcribed polycistronic pre-mRNAs in all members of the Trypanosomatidae family. This process is an inter-molecular splicing reaction that follows the same basic rules of cis-splicing reactions. In this study, we demonstrated that mini-exons were added to precursor ribosomal RNA (pre-rRNA) are transcribed by RNA pol I, including the 5' external transcribed spacer (ETS) region. Additionally, we detected the SL-5'ETS molecule using three distinct methods and located the acceptor site between two known 5'ETS rRNA processing sites (A' and A1) in four different trypanosomatids. Moreover, we detected a polyadenylated 5'ETS upstream of the trans-splicing acceptor site, which also occurs in pre-mRNA trans-splicing. After treatment with an indirect trans-splicing inhibitor (sinefungin), we observed SL-5'ETS decay. However, treatment with 5-fluorouracil (a precursor of RNA synthesis that inhibits the degradation of pre-rRNA) led to the accumulation of SL-5'ETS, suggesting that the molecule may play a role in rRNA degradation. The detection of trans-splicing in these molecules may indicate broad RNA-joining properties, regardless of the polymerase used for transcription.

Morphological and molecular description of Blastocrithidia cyrtomeni sp. nov. (Kinetoplastea: Trypanosomatidae) associated with Cyrtomenus bergi Froeschner (Hemiptera: Cydnidae) from Colombia

A new trypanosomatid species, Blastocrithidia cyrtomeni, is herein described using morphological and molecular data. It was found parasitising the alimentary tract of the insect host Cyrtomenus bergi, a polyphagous pest. The morphology of B. cyrtomeni was investigated using light and transmission microscopy and molecular phylogeny was inferred from the sequences of spliced leader RNA (SL rRNA) - 5S rRNA gene repeats and the 18S small subunit (SSU) rRNA gene. Epimastigotes of variable size with straphanger cysts adhering to the middle of the flagellum were observed in the intestinal tract, hemolymph and Malpighian tubules. Kinetoplasts were always observed anterior to the nucleus. The ultrastructure of longitudinal sections of epimastigotes showed the flagellum arising laterally from a relatively shallow flagellar pocket near the kinetoplast. SL RNA and 5S rRNA gene repeats were positive in all cases, producing a 0.8-kb band. The amplicons were 797-803 bp long with > 98.5 percent identity, indicating that they originated from the same organism. According to the sequence analysis of the SL-5S rRNA gene repeats and the 18S SSU rRNA gene, B. cyrtomeni is different from all other known species or isolates of Trypanosomatidae. Both analyses indicate that among known species, it is most closely related to Blastocrithidia triatomae.

Diagnóstico molecular de Enterobius vermicularis (Lannaeus, 1758) em populações pré-históricas: análise da região intergênica do gene ribossomal 5S RNA e do gene SL 1 RNA / Molecular diagnosis of Enterobius vermicularis (Lannaeus, 1758) in prehistoric populations: analysis of the intergenic region of the ribossomal gene 5S RNA and gene SL 1 RNA

As análises de DNA antigo (aDNA) recuperado de espécimes arqueológicos têm revolucionado áreas das Ciências especialmente na evolução humana e na origem das doenças humanas. Estudos paleoparasitológicos têm mostrado a presença do parasito Enterobius vermicularis em coprólitos de populações antigas das Américas. Até agora o diagnóstico de E. vermiculares em restos arqueológicos depende do exame microscópico. O propósito deste trabalho foi desenvolver uma abordagem metodológica para a recuperação de aDNA e o diagnóstico molecular de E. vermicularis a partir de coprólitos humanos. Propomos o diagnóstico molecular usando como alvo a região intergênica do gene ribossomal 5S RNA de E. vermicularis. Esta estratégia foi analisada quanto a sua especificidade e sensibilidade em parasitos recuperados de amostras fecais e em coprólitos experimentais...Cinqüenta e uma amostras fecais coletadas de pacientes de distintas regiões geográficas do Brasil, e positivas microscopicamente para diversos enteroparasitos incluindo 24 para E. vermicularis fizeram parte deste estudo. O diagnóstico molecular, considerando 420pb da região intergênica do gene 5S rRNA de E. vermicularis identificou 20 das 24 amostras positivas microscopicamente para o parasito, e quando a região de 198pb foi considerada, 100 por cento das amostras analisadas positivas pela análise microscópica, inclusive amostras co-infetadas, foram positivas. A PCR da de 198pb foi sensível para diagnosticar E. vermicularis em amostras fecais com apenas um único ovo do parasito. Os métodos de polimerização reconstrutora e de Nested PCR previamente aplicados em coprólitos experimentais mostraram se úteis na recuperação de aDNA de E. vermicularis em 9 amostras de coprólitos do total de 27 amos5S rRNA de 9 amostras fecais de distintas regiões do Brasil e 7 de coprólitos da América do Norte e da América do Sul, revelou um alto grau de conservação nesta região e a presença do gene SL1 RNA. Nós sugerimos a estrutura secundária do gene SL1 de E. vermicularis, a qual é similar à estrutura modelo de três hastes-alças, e com as mesmas peculiaridades que, em outros organismos são essenciais para a reação de trans-splincing. Pela primeira vez é demonstrada a recuperação de seqüências de aDNA de E. vermicularis provenientes de restos arqueológicos. O diagnóstico molecular específico e sensível para o parasito e a identificação da seqüência e estrutura secundária do gene SL1 RNA de E. vermicularis, também são resultados inéditos.