Allorecognition in Ciona intestinalis: molecular basis for self-sterility in a hermaphroditic urochordate
Final Report Abstract
Every organism must be able to unambiguously distinguish “self” cells from any imaginable “non-self”. Adaptive immune system of vertebrates seems to be the ultimate solution for this “self” / “non-self” discrimination challenge. However, invertebrate animals which lack adaptive immunity are also evolutionary successful and are able to withstand continuous attacks of permanently evolving pathogens. How do they manage to achieve that? What kind of molecular machinery do they use to comprehend “self” and “non-self”. All “self” / “non-self” discrimination systems known to date are based on highly variable molecules which vary among conspecific individuals. Well known examples are the S-locus proteins in plants which take part in the prevention of self pollination, G-protein coupled receptors in the mating locus of fungi and the MHC antigens in vertebrates. In our project we analysed the function of highly polymorphic gene vCRL1 which is expressed in follicle and blood cells of Ciona intestinalis pointing to possible recognition roles either during fertilization or in immune reactions. By using segregation analysis we demonstrated that vCRL1 locus is not involved in the control of self-sterility. Interestingly, genetic knockdown of vCRL1 in all tissues or specifically in hemocytes results in a drastic developmental arrest during metamorphosis exactly when blood system formation in Ciona normally occurs. Our data demonstrate that vCRL1 gene might be essential for the establishment of a functional blood system in Ciona. Presumably, presence of the vCRL1 receptor on the surface of blood cells renders them as “self” while any cell lacking it is referred to as “non-self” and will be consequently destroyed. We propose that individualspecific receptor vCRL1 might be utilized to facilitate somatic self / non-self discrimination. Functional analysis of vCRL1 indicates that receptors with SCR/CCP domains might have an evolutionary ancient function not only in regulation of innate immunity (that is their major responsibility in vertebrates) but also in self / non-self recognition.
Publications
- (2012) Blood system formation in the urochordate Ciona intestinalis requires the variable receptor vCRL1. Mol Biol Evol. May 3
Sommer F, Awazu S, Anton-Erxleben F, Jiang D, Klimovich AV, Klimovich BV, Samoilovich MP, Satou Y, Krüss M, Gelhaus C, Kürn U, Bosch TC, Khalturin K
(See online at https://doi.org/10.1093/molbev/mss120)
