Allorecognition reactions, wherein a colony detects and reacts to a conspecific on the basis of cell-cell contact, are near ubiquitous amongst the clonal marine benthos. These phenomena interest cell biologists as recognition systems, population geneticists by virtue of the substantial allotypic diversity they display, evolutionists in the role such interactions play in mediating the units of selection, immunologists in their similarity to tissue transplantation and pregnancy, and ecologists in the coupling of allorecognition to the mechanisms and outcomes of intraspecific competition.
My lab has developed the study of allorecognition in the colonial hydroid Hydractinia into one of the two available invertebrate models for the study of these phenomena. In recent years we have generated inbred and congenic lines, used them to identify and map a chromosomal interval controlling allorecognition, identified by positional cloning two allodeterminants and discovered a large family IgSF genes that control the response. Our current funding work is directed to understanding the extraordinary variation displayed by this gene family, to elucidating the cell biology of the transient fusion response and to mapping the signal transduction pathway from allodeterminants to effector mechanisms.
Colony circulatory design
The colonial animal circulatory system is a microfluidic design that reliably generates an ontogeny. Colonial animals are typically comprised of repeated units (polyps, zooids, and so on) connected to one another by a system of vascular canals. These circulatory systems differ in three major respects from the vertebrate circulatory systems. In particular, the vascular canals of colonial animal circulatory systems anastomose rather than dichotomously branch, they often have multiple pumps driving the flow, as opposed to a single heart, and flow is often alternately bidirectional.
We investigate the manner in which colony ontogeny is coupled to circulatory dynamics in the colonial hydroid Podocoryna. Understanding of the system is derived from continuous interplay between a modeling effort and high-resolution time series observations of circulation patterns in living animals.
The Phylum Placozoa has been known for over a century, but aside from a decade long research program in the 1970's by the German protozoologist Karl Grell and his collaborators, the group has received relatively little attention. This is odd in that placozoans are the simplest free-living invertebrate known, comprised of only four cell types.
Along with collaborators at Yale, we initiated (and completed) the Trichoplax genome project. Recent work has established that placozoans have sex, that the phylum is speciose, and that the animals employ anti-predatory defense molecules. Our current efforts are focused on the kinematics and cell biology of asexual reproduction in Trichoplax.