Abstract: A method of producing a reprogrammed cell or reprogrammed cell nucleus, comprising exposing a differentiated cell, or the nucleus of a differentiated cell to a cell or cell extract thereof derived from an oocyte, egg, ovary or early embryo of a cold blooded vertebrate, wherein the cold blooded vertebrate has one or more of the following properties: (i) a primitive vertebrate body plan including laterally projecting ribs and/or spinal projections; (ii) germ cells which do not contain germ plasm; and/or (iii) the oocyte, egg, ovary or early embryo cell or cell from which the cell extract is derived, expresses a highly conserved form of Oct-4 and/or nanog. There is also provided uses of the reprogrammed cells.