GENOTYPE-SPECIFIC EXPRESSION OF UNCLE FESTER SUGGESTS A ROLE IN ALLORECOGNITION EDUCATION IN A BASAL CHORDATE
Anthony De Tomaso, University of California, Santa Barbara
Daryl A. Taketa1, Liviu Cengher1, Delany Rodriguez1, Adam D. Langenbacher1, and Anthony W. De Tomaso1
1. Department of Molecular, Cellular and Developmental Biology University of California, Santa Barbara Santa Barbara, CA 93106
The basal chordate, Botryllus schlosseri, undergoes a natural transplantation reaction controlled by a single, highly polymorphic locus, called the fuhc. Allorecognition occurs at the tips of an extracorporeal vasculature, and two individuals that share one or both fuhc alleles are compatible, and the vessels will fuse, forming a parabiosis between the two individuals. In contrast, individuals with no common fuhc alleles between them will reject, an inflammatory reaction that results in melanin scar formation at the point of contact, blocking anastomosis. Fusibility is determined by sharing of a self-fuhc allele, reminiscent of the ‘missing-self’ mode of recognition utilized by vertebrate Natural Killer (NK) cells. Previous studies have demonstrated that two putative receptors, fester and uncle fester, are involved in this allorecognition response, and that fusion and rejection is due to integration of signals from these two proteins. Uncle fester plays a role in initiating the rejection response:. Here we report the existence of genotype-specific uncle fester expression levels, differing by up to 8-fold at the mRNA-level as confirmed by mRNA-Seq and qPCR. We also found that these changes had functional consequences: in incompatible pairings of genotypes with different expression levels of uncle fester, more points-of-rejection were present on the individual with higher uncle fester expression. These findings support previous conclusions that uncle fester levels modulate the rejection response, and offer an explanation for the variable strength of rejection phenotypes previously observed in Botryllus schlosseri. As fusion or rejection is determined by an integration of inputs from uncle fester, the long term maintenance of genotype specific expression is also evidence of an education process reminiscent of that which occurs in mammalian Natural Killer (NK) cells.