Human Embryonic Stem Cells Derived by Somatic Cell Nuclear Transfer

Reprogramming somatic cells into pluripotent em- bryonic stem cells (ESCs) by somatic cell nuclear transfer (SCNT) has been envisioned as an approach for generating patient-matched nuclear transfer (NT)- ESCs for studies of disease mechanisms and for developing specific therapies. Past attempts to pro- duce human NT-ESCs have failed secondary to early embryonic arrest of SCNT embryos. Here, we identified premature exit from meiosis in human oocytes and suboptimal activation as key factors that are responsible for these outcomes. Optimized SCNT approaches designed to circumvent these limita- tions allowed derivation of human NT-ESCs. When applied to premium quality human oocytes, NT- ESC lines were derived from as few as two oocytes. NT-ESCs displayed normal diploid karyotypes and inherited their nuclear genome exclusively from parental somatic cells. Gene expression and differ- entiation profiles in human NT-ESCs were similar to embryo-derived ESCs, suggesting efficient reprog- ramming of somatic cells to a pluripotent state.