Functional characterization of genes encoding ribosomal proteins during preimplantation development of mouse embryos

Abstract

During preimplantation embryonic development, translational control is particularly important, because the embryo is transcriptionally silent at early stages. Recent studies have shown that heterogeneous ribosomes could function in translational control during development. Several ribosomal proteins contribute to ribosome heterogeneity and some of them have been reported to have extra-ribosomal functions. Despite this potential variable nature of ribosomal proteins in function, only a few studies were conducted to investigate ribosomal protein functions during preimplantation embryonic development. Here, I performed a knockdown analysis of six genes encoding various ribosomal proteins (Rpl4, Rps9, Rps11, Rpl13a, Rpl19, and Rpl39). I compared developmental rate, protein synthesis, and proliferation among ribosomal protein gene knockdown embryos. Knockdown of ribosomal protein genes commonly affected morula-to-blastocyst transition. Detailed phenotypes, however, were different. In particular, Rpl13a knockdown embryos showed reduced protein synthesis at an early stage, and knockdown of Rpl39 did not change protein synthesis level. Proliferation was also commonly inhibited. Taken together, the present study demonstrates that ribosomal proteins are largely important for normal blastocyst formation, but not all of them equally contribute to preimplantation embryonic development. The results also show that all cellular conditions, including protein synthesis and proliferation, are required to ensure successful formation of blastocyst.