sFRP3 Acts as a Gatekeeper (image) Johns Hopkins Medicine Caption sFRP3 acts as a gatekeeper that links brain activity to new neuron growth. Proliferating progenitor neurons are shown in blue, immature neurons in green, and mature neurons in red. Credit Max Song and Maggie Song Usage Restrictions Credit required Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.