What can sea urchins teach us about immune gene diversification and the evolution of combinatorial immunity?
Speaker: Matan Oren, Ariel university, Israel
Host: Iryna Yakovenko, Department of molecular Biology
Venue: Major Groove, Umeå University Hospital
About the lecture:
The emergence of immune receptor diversity marks a pivotal transition in the evolution of animal immunity. While jawed vertebrates generate adaptive immune diversity through RAG-mediated V(D)J recombination, invertebrates lack classical adaptive immunity yet exhibit unexpectedly sophisticated mechanisms for immune specificity. This seminar draws on evidence from sea urchin models to explore alternative evolutionary and functional pathways to immune diversification.
Sea urchins possess a unique immune effector arm based on the Transformer (Trf) gene family, which generates exceptional molecular diversity and mediates pathogen-specific immune responses. Trf genes encode intrinsically disordered proteins with extensive variation in sequence, structure, and expression, enabling highly tailored immune responses despite the absence of canonical adaptive immunity. Although structurally distinct from vertebrate antibodies, Trf-mediated immunity shares key conceptual parallels with adaptive immune systems, including diversification mechanisms, restricted cellular expression, and functional specificity. Remarkedly, single-cell analyses reveal that individual coelomocytes express a single Trf transcript and undergo somatic gene diversification through deletions, duplications, and point mutations, generating cell-specific immune repertoires within a single organism.
Although the molecular drivers of the Trf combinatorial immune strategy remain unresolved, we have identified recombination activating gene-like (RAGL) homologues in sea urchins that may function as nucleases and potentially contribute to somatic immune gene diversification. Together, these findings position sea urchins as a powerful model for understanding how immune specificity and diversity can emerge independently of vertebrate adaptive immunity.
