CHI-HING CHRISTINA CHENG
My interests are in the broad field of environmental, adaptational and evolutionary physiology of animals. The biological system of my research pertains to freezing avoidance by means of antifreeze (AF) proteins in polar bony fishes, as well as other cold adaptive physiological processes and their responsible protein molecules in these fish. I use approaches that span and integrate past and present environmental thermal histories, organismal physiology, protein structure-function, molecular evolution and genomic scale analyses of environmentally driven evolutionary change in protein genes and function.
More specifically, my laboratory studies the evolution of the diverse antifreeze proteins in marine bony fishes that inhabit frigid Arctic and Antarctic waters. We investigate where these novel protein genes came from (evolutionary ancestry), how they evolved (molecular mechanisms of new gene genesis), and the evolution of the antifreeze gene families. Since the creation of the antifreeze function was directly driven by polar glaciation, we also attempt to determine the time of evolution of the antifreeze genes to infer or corroborate the time of onset of freezing conditions in the polar or subpolar seas. In addition, we examine how the evolution of antifreeze function relates to speciation and organismal diversification, and how variable complexities of different antifreeze gene families relate to the ability to survive in environments of differing severity. The evolutionary dynamics of entire antifreeze gene families (i.e., gain versus loss as related to freezing selection versus absence of selection in closely related taxa) are examined by characterizing large genomic regions housing these genes that we isolate from BAC libraries.
Related interests in cold adaptation encompass other functional proteins and physiological systems. We examine adaptive changes in the retinal visual system (cone and rod opsins) of Antarctic fish associated with their freezing environment, and potential ontogenic changes of expression associated habitat change during development. In addition, we examine the biochemical and structural bases of the protein stability and transparency of the Antarctic fish lens at freezing temperatures (-2oC) where other vertebrate lens would have sustained cold-cataract (at 0oC and above). The molecular diversity and evolution of cold-stable lens crystallin protein isoformers that are integral to whole lens cold stability are being characterized.
For individuals interested in the studies of genomics, evolution, adaptation, protein structure-function, or any aspects related to fish antifreeze proteins I accept graduate students through the Department of Animal Biology and the Program in Ecology and Evolutionary Biology. Application instructions are available through these program's websites.