Two important microRNAs, gga-let-7b and gga-let-7i were examined for the relative expression in liver and bone marrow tissues from specific pathogen free chickens that were challenged either with GD1109 or NX0101 strain of subgroup J avian leukosis virus (ALV-J). The GD1109 strain of ALV-J reportedly causes hemangioma (HE) and NX0101 reportedly causes myeloma (ML) in susceptible chickens. Temporal changes of both gga-let-7b and gga-let-7i expression in ALV-J infected chickens were observed in contrast to its counterpart of a non-infected negative control group of chickens (P < 0.05 or P < 0.01) during the first 120 days post infection. Use of the web-based computational DIANA-mirPath software (available at http://microrna.gr/mirpath ), it was predicted that both gga-let-7b and gga-let-7i were involved in multiple pathways including signaling pathways, such as MAPK, TGF-beta, Notch, Wnt, mTOR, Cell cycle, P53 and Jak-STAT. Combining our experimental data with reports on the microRNAs, we suggest that both gga-let-7i and gga-let-7b may also act as tumor suppressors in chicken, especially play a critical role in tumorigenesis induced by ALV-J.
Keywords: ALV-J; Gga-let-7b/7i; Temporal expression; Tumorigenesis; microRNA.