The invention relates to a cell containing a gene encoding a conditional transgenic surface marker that is detectable upon expression on the surface of the cell, wherein the gene encoding a conditional transgenic surface marker comprises: (i) a promoter, operably linked to (ii) a first transcription sequence, and (iii) a second transcription sequence encoding the surface marker, whereby the first transcription sequence prevents the transcription of the second transcription sequence, whereby the first transcription sequence is conditionally removable such that the second transcription sequence is transcribable, and whereby the surface marker renders the cell sortable through the detection of the conditional transgenic surface marker. Furthermore, the invention relates to a construct for generating such a cell, and to a method for separating such a cell from a population of cells.