LAUSR

Immunodeficiency Diagnosis and treatment of inborn errors in immunity remain a challenge. Salzer et al. studied two siblings who were hospitalized for recurrent pediatric infections. Exome sequencing and functional analyses helped to identify homozygous loss-of-function mutations in genes encoding the protein HEM1 in both individuals. HEM1 is a component of actin-remodeling complexes that have a wide range of functions, from cell migration to cell division. By studying immune cells from these individuals and by generating HEM1-deficient mice, the authors established HEM1 as a key regulator of T and B cell functions. They characterized in depth the role of HEM1 in B cells and propose that HEM1 modulates signaling downstream of the B cell receptor. Sci. Immunol. 5 , eabc3979 (2020).