Control of mRNA Translation During Spermatogenesis

University Of Massachusetts Boston, Dorchester MA

Investigators

Abstract

The development of sperm cells in mammals is an extraordinary example of translational regulation of gene expression, a phenomenon in which messenger RNAs (mRNAs) are stored in an inactive form in the cytoplasm, sequestered from ribosomes. These mRNAs can be activated subsequently to bind to ribosomes, which then translate the sequence of bases of the mRNA into the sequence of amino acids of a protein. The objective of this research is to identify sequences and proteins that inactivate translation of the mRNA encoding the Sperm Mitochondria-Associated Cysteine-rich Protein (SMCP), a protein that enhances the motility of mammalian sperm. The SMCP mRNA is stored in an inactive state for six days in early haploid developing sperm cells, before it is actively translated in late haploid cells. The experimental approach utilizes the creation of chimeric genes consisting of various parts of the SMCP mRNA and the protein coding region of green fluorescent protein (GFP), the generation of strains of transgenic mice harboring the chimeric SMCP-GFP genes, and microscopic and biochemical analysis of the stages of developing sperm cells that contain GFP-fluorescence and ribosome-bound GFP-SMCP mRNAs. Previous research has demonstrated that the SMCP 5' untranslated region delays translation of SMCP-GFP mRNAs resulting in the total absence of GFP-fluorescence and ribosome-bound GFP-SMCP mRNAs in early haploid cells, whereas the SMCP-3'UTR permits GFP-fluorescence and ribosome-bound GFP-SMCP mRNAs in early haploid cells. The objective of future research is to analyze the function of a promising candidate for a translation control element, a short sequence of bases at the 5' terminus of the SMCP mRNA. Candidate translational repressor proteins will be identified by electrophoretic assays for the formation of slowly migrating RNA-protein complexes. This project is intended to encourage students from underrepresented groups to enter careers in science.