Background: The goal of this project was to characterize the molecular and cellular roles of
various gene targets regulated by miRNAs identified in differentiating and stimulating avian macrophages.
Once a monocyte arrives to a site of infection, local signals induce a redistribution of resources
into a macrophage phenotype. This may involve upregulating pathogen pattern recognizing
receptors and increasing the efficiency of lysosomal biogenesis, while simultaneously recycling components
involved in circulatory migration and leukocyte extravasation. a monocyte tooled with
chemokine surface receptors and an internal cytoskeletal structure geared towards mobility may efficiently
sense, react, and migrate toward a site of infection.
Methods: Peripheral blood derived monocytes were purified and cultured from young chickens. RNA
sequencing was performed on both peripheral blood monocytes during differentiation into macrophages
and on mature macrophages following stimulation with interferon gamma. A set of microRNAs
were identified and investigated using bioinformatics methods to ascertain their potential role in
avian macrophage biology.
Results: Among a number of miRNAs that are found to be expressed in avian macrophages, we focused
on eight specific miRNAs (miR-1618, miR-1586, miR-1633, miR-1627, miR-1646, miR-1649,
miR-1610, miR-1647) associated with macrophage differentiation and activation. Expression profiles
of microRNAs were characterized during differentiation and activation. Candidate miRNA targets
were implicated in processes including Wnt signaling, ubiquitination, PPAR mediated macrophage
function, vesicle mediated cytokine trafficking, and WD40 domain protein functions.
Conclusion: A global theme for macrophage function that may be modulated by microRNAs is the
comprehensive redistribution of the cell’s protein repertoire. This redistribution involves two processes:
1) the degradation and recycling of unneeded cytoplasmic and membrane components and 2)
the mobilization of newly synthesized cellular components via vesicular trafficking. Generally, it appears
that macrophages need to closely regulate gene expression for differentiation to be able to activate
successfully in response to a pathogen. This is a process in which miRNAs participate by affecting
several pathways critical for both, differentiation and activation.