Lentiviruses, which belong to the family of retroviruses, are used as vectors to exchange genetic material in cells and can be used to replace a defective gene as defined by gene therapy. Increasing the efficiency of such a treatment poses a major medical challenge: the virus should specifically track the target cells, but the number of virus used should be as low as possible.

In the heart muscle cell above, the arrows show an early sign of replication. In a study that began in a pair of infant siblings with a rare heart defect, Johns Hopkins researchers say they have identified a key molecular switch that regulates heart cell division and normally turns the process off around the time of birth. Their research, they report, could advance efforts to turn the process back on and regenerate heart tissue damaged by heart attacks or disease.