A rare genetic defect in a family has helped researchers identify a key signaling component in T cells.

The newly identified protein, Orai1, may be a piece of a long- sought calcium channel in T cells that is critical for lymphocyte function. When two siblings inherited two copies of a mutant form of Orai1, it caused a severe impairment of their immune systems.

Now, more than a decade after their case was reported, Yousang Gwack and Stefan Feske in Anjana Rao’s lab have found the protein responsible for the disease. Their findings appear in the April 2, 2006 Nature.