Stuck in the past

Molecular remnants may limit potential of reprogrammed stem cells

Barbra Streisand probably wasn’t thinking about reprogrammed stem cells when she crooned “The Way We Were,” but it turns out that the cells also retain misty watercolor memories of their former selves.

By most standards, a cocktail of four proteins can reprogram skin or blood into stem cells nearly indistinguishable from those isolated from embryos (SN: 11/24/07, p.