Mature MII oocytes were recovered from females undergoing controlled ovarian stimulations. Oocytes were transferred to a manipulation chamber containing medium with 5 μg ml cytochalasin B and MII spindle-chromosomal complexes were aspirated and isolated using Oosight imaging system (www.cri-inc.com) as described before16 (link). Isolated karyoplasts were briefly exposed to SeV extract (www.cosmobio.co.jp) and placed into perivitelline space on the side opposite to the 1st polar body (Suppl. video). During manipulations, oocyte's zona pellucida was penetrated by laser assisted zona drilling (www.hamiltonthorne.com). After fusion, reconstructed oocytes were fertilized by ISCI and cultured as described before16 (link). Detailed methods are described in Supplementary information at www.nature.com/nature.