In mammals, a new life begins with the sperm successfully meeting the oocyte. Parthenogenetic activation (PA), also known as Parthenogenesis, is an asexual reproduction that activates an oocyte to escape the metaphase II arrest so that it can develop to the next stage. This is a way of generating offspring solely from unfertilized oocytes using chemical agents mimicking the calcium oscillation induced by sperm; thus is a relatively simple way to assess the developmental competence of an embryo in vitro.
Haploid (n) parthenogenesis uses Strontium Chloride (SrCl2) to induce the oocyte to extrude the 2nd polar body (PB), resulting in a cell with one set of chromosomes. Meanwhile, Diploid (2n) parthenogenesis combines Strontium Chloride (SrCl2) with a cytokinesis inhibitor, namely Cytochalasin B (CB), to prevent the extrusion of 2nd polar body, keeping it in the cytoplasm so that it shows a 2-pronuclear-look. The use of calcium-free media is necessary, as external calcium in culture media has been reported to interfere with the function of Strontium [1].
Parthenogenesis is limited because of problems arising from genomic imprinting [2]; mouse parthenogenetic embryos die by day 10 of gestation [3]. However, some advancements have been made that make parthenogenesis-derived embryos able to develop into viable offspring [2, 3].
Here, I used ICR female and male mice to perform parthenogenesis.
Photos are personal documentation.
References:
[1] Kishigami & Wakayama. 2007. Efficient Strontium-Induced Activation of Mouse Oocytes in Standard Culture Media by Chelating Calcium. Journal of Reproduction and Development
[2] Wei, Yang, & Zhao. 2022. Viable offspring derived from single unfertilized mammalian oocytes. PNAS
[3] Kono, Obata, Wu. et al. 2004. Birth of parthenogenetic mice that can develop to adulthood. Nature 428
