Stem cells from human skin keep to a 24-hour schedule that might protect them from sun damage.

Salvador Aznar Benitah, then of the Centre for Genomic Regulation in Barcelona, Spain, and his colleagues analysed cultures of genetically identical stem cells from human skin at set times. They found that genes related to the 'body clock' are expressed in distinct waves over a 24-hour cycle.

Each wave is associated with peaks in expression for other genes: those that protect against DNA-damaging sunlight are most active during the day, as are those involved in DNA replication and cell growth. Genes that push stem cells to become specialized are most active in the evening and night. Disruptions to the internal clock could lead to premature ageing, the researchers suggest.

Cell Stem Cell (2013)