Enucleation of feeder cells and egg cells with psoralens.

The cell nucleus must be inactivated or destroyed in order to generate feeder layers for cultured cells or to prepare recipient egg cells for nuclear transfer. Existing enucleation techniques are either cumbersome or employ toxic chemicals. Here we report a new method to enucleate cells by treatment with a psoralen and long-wave ultraviolet light. The technique is >90% efficient and causes little cytoplasmic damage to the treated cell. We have used psoralen treatment to enucleate a wide variety of cells, including eggs, sperm, HeLa cells, and fibroblasts. Colonies of human embryonic stem cells (hESCs) and human keratinocyte precursors grown on psoralen-treated feeders are indistinguishable from those grown on gamma-irradiated or mitomycin C-treated cells. Psoralen enucleation provides a rapid, simple, and non-toxic method to generate feeder cells. The technique is also useful for nuclear transfer studies in species with large eggs whose cleavage divisions are not regulated by cell-cycle checkpoints.