Characterization of
differentially expressed microRNAs during pathogen infection in an
arthropod model
Ticks are important
vectors for a wide variety of microbes and present significant human and
veterinary public health threats to rural, suburban, and even peri-urban
populations in the United States and worldwide. A better understanding of
tick biology may lead to improved strategies for disrupting pathogen
transmission and tick blood feeding on vertebrate hosts. Because ticks can
carry multiple pathogens, a sound strategy for disease protection would
target the tick instead of each individual pathogen they may carry. One of
the most important discoveries of molecular biology in recent years is how
small non coding RNA molecules (called ncRNAs) regulate gene function.
Small regulatory non-coding RNA molecules, known as micro RNAs, are
potential regulators of gene expression at the post-transcriptional
level. MicroRNAs are negative regulators which suppress the gene
functions through translational repression by targeting 3’-UTR in
messenger RNAs (mRNAs) of protein-coding genes, or by inducing instability
of mRNAs. One incredibly important function of these small RNAs in
humans, plants and arthropods is their role in turning genes off.
MicroRNAs are able to recognize the target genes they silence by specific
base-pairing interactions. In Drosophila melanogaster microRNAs control
important developmental processes such as cell division, neural
development, and oogenesis. These small RNAs range in size from about
21-24 nucleotides; these molecules were overlooked for many years due to
their minute size. This project focuses on the functional genomics of
this newly identified class of genes, with the long-term objective of
understanding the roles of non-coding RNA in regulating gene expression.
The central hypothesis is that specific microRNAs selectively turn
expression of target genes off resulting in normal tick feeding and
pathogen transmission to vertebrate hosts. In our studies, we are
exploring the arthropod vector microRNAs as an initial step in
understanding the intricate processes underlying pathogen infection. To
determine the temporal profile of infected arthropod vector microRNAs the
miRCURY array chip was hybridized with a) un-infected, b) Borrelia
burgdorferi and c) Anaplasma phagocytophilum nymphal microRNA probes. The
microRNA profiles found 4 miRNAs to be more than 50% up or down regulated
comparing three samples. In future, we will use qRT-PCR to validate the
arthropod miRNA expression changes in different tissues during pathogen
infection. Studies of microRNAs in diverse arthropod species may provide
important clues to better understand the natural selection of microRNA
genes as well as their impact on biological functions in vector-infection.
