Co-ordinated expression of innate immune molecules during mouse neurulation

The innate immune system is the first line of defence against pathogens and infection. Recently, it has become apparent that many innate immune factors have roles outside of immunity and there is growing evidence that these factors play important functional roles during the development of a range of model organisms. Several studies have documented developmental expression of individual factors of the toll-like receptor and complement systems, and we recently demonstrated a key role for complement C5a receptor (C5aR1) signalling in neural tube closure in mice. Despite these emerging studies, a comprehensive expression analysis of these molecules in embryonic development is lacking. In the current study, we therefore, examined the expression of key innate immune factors in the early development period of neurulation (7.5-10.5dpc) in mice. We found that complement factor genes were differentially expressed during this period of murine development. Interestingly, the expression patterns we identified preclude activation of the classical and alternative pathways and formation of the membrane attack complex. Additionally, several other classes of innate immune molecules were expressed during the period of neurulation, including toll-like receptors (TLR-2, -3, -4 and -9), receptor for advanced glycation end-products (RAGE), and their signalling adapters (TRAF-4, TRAF-6, TAK-1 and MyD88). Taken together, this study highlights a number of innate immune factors as potential novel players in early embryonic development.