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 identi- fied 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.