title: No miRNA were found in Plasmodium and the ones identified in erythrocytes could not be correlated with infection.
abstract: BACKGROUND
  The transcriptional regulation of Plasmodium during its complex life cycle requires sequential activation and/or repression of different genetic programmes. MicroRNAs (miRNAs) are a highly conserved class of non-coding RNAs that are important in regulating diverse cellular functions by sequence-specific inhibition of gene expression. What is know about double-stranded RNA-mediated gene silencing (RNAi) and posttranscriptional gene silencing (PTGS) in Plasmodium parasites entice us to speculate whether miRNAs can also function in Plasmodium-infected RBCs.
  
  
  RESULTS
  Of 132 small RNA sequences, no Plasmodium-specific miRNAs have been found. However, a human miRNA, miR-451, was highly expressed, comprising approximately one third of the total identified miRNAs. Further analysis of miR-451 expression and malaria infection showed no association between the accumulation of miR-451 in Plasmodium falciparum-iRBCs, the life cycle stage of P. falciparum in the erythrocyte, or of P. berghei in mice. Moreover, treatment with an antisense oligonucleotide to miR-451 had no significant effect on the growth of the erythrocytic-stage P. falciparum.
  
  
  METHODS
  Short RNAs from a mixed-stage of P. falciparum-iRBC were separated in a denaturing polyacrylamide gel and cloned into T vectors to create a cDNA library. Individual clones were then sequenced and further analysed by bioinformatics prediction to discover probable miRNAs in P. falciparum-iRBC. The association between miR-451 expression and the parasite were analysed by Northern blotting and antisense oligonucleotide (ASO) of miR-451.
  
  
  CONCLUSIONS
  These results contribute to eliminate the probability of miRNAs in P. falciparum. The absence of miRNA in P. falciparum could be correlated with absence of argonaute/dicer genes. In addition, the miR-451 accumulation in Plasmodium-infected RBCs is independent of parasite infection. Its accumulation might be only the residual of erythroid differentiation or a component to maintain the normal function of mature RBCs.
authors.affiliation: Institute for Infectious Diseases and Vaccine Development, Tongji University College of Medicine, 1239 Siping Road, Shanghai 200092, China. wzxxy@yahoo.com.cn
authors.forename: Xiangyang
authors.initials: X
authors.lastname: Xue
authors.forename: Qingfeng
authors.initials: Q
authors.lastname: Zhang
authors.forename: Yufu
authors.initials: Y
authors.lastname: Huang
authors.forename: Le
authors.initials: L
authors.lastname: Feng
authors.forename: Weiqing
authors.initials: W
authors.lastname: Pan
mesh_terms: D000818:Animals; D003001:Cloning, Molecular; D004912:Erythrocytes / Q000469:parasitology*; D005260:Female; D015723:Gene Library; D006801:Humans; D016778:Malaria, Falciparum / Q000469:parasitology; D051379:Mice; D035683:MicroRNAs / Q000145:classification / Q000235:genetics / Q000302:isolation & purification* / Q000378:metabolism; D016376:Oligonucleotides, Antisense / Q000008:administration & dosage; D010962:Plasmodium berghei / Q000235:genetics / Q000254:growth & development; D010963:Plasmodium falciparum / Q000235:genetics* / Q000302:isolation & purification; D016053:RNA, Protozoan / Q000145:classification / Q000235:genetics / Q000302:isolation & purification* / Q000378:metabolism
chemical_list: D035683:MicroRNAs; D016376:Oligonucleotides, Antisense; D016053:RNA, Protozoan