Differential Toll-Like Receptor (TLR) mRNA Expression Patterns during Chicken Embryological Development

Abstract

Toll-like receptors (TLRs), important components of innate immune response, play a pivotal role in early recognition of pathogen as well as in the initiation of robust and specific adaptive immune response. In the present study, the expression profile of chicken TLRs (TLR2A, TLR3, TLR4, TLR5, TLR7, TLR15, and TLR21) in various chicken embryonic tissues during embryo development was examined by real-time PCR assay. All the TLR mRNAs were expressed in whole embryonic tissue as early as 3rd embryonic day (ED). Four of the seven TLRs (TLR2, TLR3, TLR4, and TLR7) mRNA expressions were significantly (P < 0.01) higher at 12ED relative to expression at 3 ED, whereas TLR15 mRNA expression was significantly (P < 0.01) higher on 7ED and TLR5 and 21 were highly expressed on 18 ED. Among all the TLRs investigated TLR4 mRNA was the highest expressed and TLR15 mRNA expression was the lowest in all tissues during chicken embryo development. Tissue wise analysis of mRNA expression of TLRs showed that liver expressed significantly (P < 0.01) higher levels of most of the genes (TLR2, TLR4, and TLR21). However no significant difference was found in TLR15 mRNA expression among the tissues during development. Our results suggest the innate preparedness of chicken embryos and also a possible role for TLRs in the regulation of chicken embryo development that needs to be further evaluated.

Lipopolysaccharide stimulation upregulated Toll-like receptor 4 expression in chicken cerebellum

“…Toll-like receptors (TLRs) belong to PRRs subfamily that largely expressed in many of the cells in CNS, especially in microglia. To date, 10 functional TLRs have been identified in humans (Kawai and Akira, 2010;Facci et al, 2014) and chicken (Kannaki et al, 2015) and as many as 13 in mouse (Reuven et al, 2014).…”

“…The expressions of chicken TLRs have been described on immune cells as well as in adult tissues and embryo (Kannaki et al, 2015). TLRs 1-10 have been expressed at detectable levels in human brain (Bsibsi et al, 2002) and TLRs 1-9 in isolated microglia in mouse (Olson et al, 2004).…”

Developmental expression of Toll-like receptors in the guinea pig lung

“…Several lines of evidence have demonstrated the developmental involvement of TLRs in mammalian and non-mammalian species during embryogenesis. For example, Kannaki et al (29) demonstrated differential expression patterns of TLR mRNAs during chicken embryological development, suggesting the potential involvement of TLRs in the regulation of chicken embryo development. This is supported by the initial discovery of Toll in D. melanogaster , the first member of the TLR family, as it was initially characterized as a developmental protein prior to the establishment of its immunological involvement (8,15).…”

The Control of Intestinal Inflammation: A Major Objective in the Research of Probiotic Strains as Alternatives to Antibiotic Growth Promoters in Poultry

“…Avian TLR4 is the main receptor of LPS, which is a major component of the outer membrane of Gram-negative bacteria [73]. After binding to LPS, avian TLR4 triggers a cascade of inflammation responses via the myeloid differentiation factor 88 (MyD88)-dependent signaling pathway, which results in NF-κB activation [67].…”