EAGER: Paleontological Proteomics Initiative: Developing Theory and Applications in Molecular Paleontology

American Museum Natural History, New York NY

Investigators

Abstract

Molecular paleontology is a new field that uses information derived from biological molecules (biomolecules) to make inferences about evolutionary relationships, in this case for extinct organisms. During life, living things produce many kinds of biomolecules encoded by their DNA, and these may be preserved for varying lengths of time after the organism's death. Proteins, for example, are composed of amino acids, and each amino acid is specified by a precise piece of genetic information that varies slightly from species to species within an evolutionary group. Thus, by working out a protein's amino acid composition, the genetic sequence that originally produced it can be worked out indirectly, even in the absence of the DNA itself. This is significant for paleontological research because structural proteins like collagen, which make up almost all of the organic fraction of a bone, are very hardy and can last a long time after an animal's death; at least 4 million years in favorable circumstances, and possibly much longer. DNA, by contrast, degrades over a few tens to a few hundreds of thousands of years, even in the best preservational contexts. In recent years, instrumentation and lab techniques for acquiring compositional information from ancient biomolecules have greatly improved, enabling the researchers and their interdisciplinary collaborators in geochemistry to undertake a focused range of experiments in molecular paleontology. This research will advance the field of paleo-proteomics by addressing two main goals. The first goal will be to explore the limits of the technique and identify what kinds of fossils and what types of fossil preservation conditions yield the best results for analyses of biomolecules of extinct taxa. The second goal will apply the newly developed technique to specific 'test cases' to highlight the feasibility of the methods and their generality for application to diverse questions in systematics. Molecular methods have already proven vitally important for improving knowledge of the history of life on Earth, and the researchers' work will lead to both theoretical and practical improvements in ancient proteomics. How far back in time can ancient collagen proteomics actually reach and yield high-quality sequence information useful for phylogenetic studies? What are the best targets for preservation and systematic interpretation? Proof-of-concept investigations designed to answer these questions will focus on two areas of interest. (1) To establish fundamental geochemical boundary conditions affecting collagen survival, experiments will be conducted with a physically stabilized protein (collagen in fossil bone) and a proteome with restricted reactants (eggshell proteome). Work will center on assessing thermal age and controlling for mineral diagenesis, with analysis conducted via state-of-the-art mass spectrometry and diagenetic modeling to estimate the kinetics of key decay parameters (racemization, hydrolysis, oxidation, deamidation). (2) To establish the practical value of collagen proteomics for solving systematic problems, taxa from various temporal intervals in North and South America, West Indies, Asia, and Antarctica will be sampled for phylogenetic studies using the same instrumental approach as in (1). In addition to providing phylogenetically useful information, these investigations will further extend assessment of taphonomic conditions that enhance fossil protein preservation. The overall aim is to create a network of collaborative systematic paleontologists and protein geochemists interested in joint research in areas of mutual interest.