Dr. Richter proposes to examine the regulation of maternal mRNA expression during the early development of Xenopus laevis. Oocytes of all animals contain a supply of mRNA which far exceeds the cells' immediate protein synthesis requirements. This maternal mRNA is synthesized and stored during the protracted period of oogenesis and, in Xenopus, is translated during oocyte maturation and early embryogenesis. Dr. Richter has obtained cDNA clones for mRNAs that are translated at only certain stages of early development. He has also determined that these mRNAs bind different proteins in oocytes. He will first assess the nucleotide sequences of the mRNAs that are important for their translational regulation, and then will determine the proteins that are bound to those sequences. These experiments will be performed by making deletion and chimeric mutants in SP6-derived mRNAs. These mutants will then be injected into various staged oocytes and their translational potential will be assessed by sucrose gradient centrifugation. The proteins that bind various regions of these mRNAs will be assessed by UV-induced crosslinking. %%% The early development of an organism is driven by the differential expression of various proteins. These early processes are studied in the toad, Xenopus laevis because the eggs are large and easy to work with. In this organism the very early embryonic development is programmed not by the activation of specific genes, but rather by differential expression of messenger RNAs stored within the egg prior to fertilization. Dr. Richter will investigate how the expression of various proteins is regulated in early embryogenesis.
