A mutation in Orai1 causes immune deficiency by abrogating CRAC channel function

Area of Science:

• Immunology
• Molecular Biology
• Genetics

Background:

• Immune cell activation involves calcium (Ca2+) influx via CRAC channels, crucial for pathogen response.
• Severe combined immune deficiency (SCID) patients exhibit defects in store-operated Ca2+ entry and CRAC channel function.
• Previous research linked these defects to hereditary SCID syndromes.

Purpose of the Study:

• To identify the genetic cause of a specific form of hereditary severe combined immune deficiency (SCID).
• To elucidate the molecular basis of store-operated calcium (Ca2+) entry and CRAC channel function in immune cells.

Main Methods:

• Utilized two unbiased genome-wide approaches: SNP array-based linkage analysis and a Drosophila RNA interference screen.
• Screening focused on identifying regulators of store-operated Ca2+ entry and NFAT nuclear import.
• Genetic analysis of SCID patients and functional studies involving gene expression.

Main Results:

• Identified a novel protein, Orai1, containing four transmembrane segments, as the causative gene defect.
• SCID patients were homozygous for a missense mutation in the ORAI1 gene.
• Restored wild-type Orai1 expression in SCID T cells normalized store-operated Ca2+ influx and CRAC current (ICRAC).

Conclusions:

• Orai1 is identified as the gene responsible for a form of severe combined immune deficiency (SCID).
• Orai1 is proposed to be a critical component or regulator of the calcium release-activated calcium (CRAC) channel complex.
• This finding advances the understanding of immune cell signaling and the molecular basis of SCID.