University of Pennsylvania researchers fix a gene tied to lipoprotein production in utero.

CRISPR has previously been used to edit genes in mouse fetuses responsible for liver disease, and now the same team of researchers at the University of Pennsylvania has used CRISPR to correct a gene in mouse fetuses that is associated with lung diseases.

The gene is responsible for the production of a crucial lipoprotein that reduces lung surface tension and enables normal lung function. Babies –– both mouse and human –– with SFTPC mutations typically die within hours of birth.

Using the CRISPR gene-editing technique, the scientists inactivated the mutant gene in 87 mouse fetuses. The gene-editing reagent was injected into the amniotic fluid in order to enable the fetuses to inhale it, allowing delivery to the epithelial cells lining the airways. It was performed four days before birth –– the equivalent of the human trimester. Seven of them survived for more than 24 hours after birth, and five of them continued to appear healthy for seven days.

Gene editing after birth is not helpful for patients with certain types of diseases –– like the lung disease investigated in this study. With gene editing of egg or sperm cells, however, the genetic alterations can be passed to future generations –– a potential problem if editing goes awry. Gene editing in utero avoids this issue but allows treatment of diseases that lead to death within a short time of birth.