The Genomic Analysis of Erythrocyte microRNA Expression in Sickle Cell Diseases

BACKGROUND: Since mature erythrocytes are terminally differentiated cells without nuclei and organelles, it is commonly thought that they do not contain nucleic acids. In this study, we have re-examined this issue by analyzing the transcriptome of a purified population of human mature erythrocytes from individuals with normal hemoglobin (HbAA) and homozygous sickle cell disease (HbSS). METHODS AND FINDINGS: Using a combination of microarray analysis, real-time RT-PCR and Northern blots, we found that mature erythrocytes, while lacking ribosomal and large-sized RNAs, contain abundant and diverse microRNAs. MicroRNA expression of erythrocytes was different from that of reticulocytes and leukocytes, and contributed the majority of the microRNA expression in whole blood. When we used microRNA microarrays to analyze erythrocytes from HbAA and HbSS individuals, we noted a dramatic difference in their microRNA expression pattern. We found that miR-320 played an important role for the down-regulation of its target gene, CD71 during reticulocyte terminal differentiation. Further investigation revealed that poor expression of miR-320 in HbSS cells was associated with their defective downregulation CD71 during terminal differentiation. CONCLUSIONS: In summary, we have discovered significant microRNA expression in human mature erythrocytes, which is dramatically altered in HbSS erythrocytes and their defect in terminal differentiation. Thus, the global analysis of microRNA expression in circulating erythrocytes can provide mechanistic insights into the disease phenotypes of erythrocyte diseases

The long and winding road: virulence effector proteins of plant pathogenic bacteria

Plant pathogenic bacteria inject about 30 virulence effector proteins into the host cell using a specialized secretion apparatus. Bacteria which are unable to do this elicit host immunity and cannot grow inside living plant tissue. Thus, the primary function of the effectors is to suppress host immunity. The identity of individual effectors within each complement varies even between closely related bacterial strains, and effectors themselves act redundantly and are apparently interchangeable. Many effectors are known to target components of plant defense pathways, but it is difficult to study their role in molecular terms. For some of them, there is controversy about their mode of action. We propose that effectors act promiscuously by targeting host molecules with low specificity and affinity