Regulatory processes that control haploid expression of salmon sperm mRNAs

Various stages of mRNA processing are necessary for functionally important genes required during late-stage sperm differentiation. Protein-RNA complexes form that edit, stabilize, store, deliver, localize and regulate translation of sperm mRNAs. These regulatory processes are often directed by recognition sequence elements and the particular composition of the proteins associated with the mRNAs. Previous work has shown that the cAMP response element modulator (CREM), estrogen receptor-alpha (ERα) and forkhead box L2A (FOXL2A) proteins are present in late-stage salmon sperm. Here we investigate whether these and other regulatory proteins might control processing of mRNAs not expressed until the haploid stage of development. We also examine regulatory processes that prepare and present mRNAs that generate unique products essential for differentiating sperm (i.e. for flagellar assembly and function).

We provide evidence for potential sperm-specific recognition elements in 5'-untranslated regions (utrs) that may bind CREM, ERα, FOXL2A, Y-box and other proteins. We show that changes within the 5'-utrs and open reading frames of some sperm genes lead to distinct protein termini that may provide specific interfaces necessary for localization and function within the paternal gamete.