Cell-penetrating peptide-mediated mouse oocyte activation

Abstract

IntroductionThe cell cycle of ovulated oocytes from various animal species, including mice, is arrested in the second meiotic metaphase until fertilization. The meiotic cell cycle must be initiated to initiate embryonic development. Besides natural fertilization, several other methods have been developed to activate unfertilized oocytes without using sperm. These methods are not only utilized for animal production but have also proven effective in studying the molecular mechanisms that regulate the meiotic cell cycle, oocyte activation, and embryonic development. This study aimed to develop a method to activate mouse oocytes using a cell-penetrating peptide based on the knowledge that the C-terminal domain of the meiotic protein Emi2 can resume the arrested meiotic cell cycle. MethodsThis study used female B6D2F1 mice to investigate the effects of a CPP-fused Emi2 peptide on oocyte activation. Second meiotic metaphase oocytes were collected, cultured, and treated with the peptide or strontium chloride. Pronuclear formation, second polar body extrusion, and blastocyst development were assessed, and statistical significance was determined using Fishers exact test. ResultsThe cell-penetrating peptide activated zona-intact oocytes in a manner dependent on specific amino acid residues and peptide concentrations, which are critical components for cell membrane penetration. It has also been confirmed that oocytes activated using this method can develop to the blastocyst stage. DiscussionThe introduction of peptides or functional amino acid sequences using CPP or related methods could be an alternative for easily performing functional analyses of the activity of target proteins in oocytes.