Nov 19, 2008

A point mutation in the murine Hem1 gene reveals an essential role for Hematopoietic protein 1 in lymphopoiesis and innate immunity

The Journal of Experimental Medicine
Heon ParkBrian M Iritani


Hem1 (Hematopoietic protein 1) is a hematopoietic cell-specific member of the Hem family of cytoplasmic adaptor proteins. Orthologues of Hem1 in Dictyostelium discoideum, Drosophila melanogaster, and Caenorhabditis elegans are essential for cytoskeletal reorganization, embryonic cell migration, and morphogenesis. However, the in vivo functions of mammalian Hem1 are not known. Using a chemical mutagenesis strategy in mice to identify novel genes involved in immune cell functions, we positionally cloned a nonsense mutation in the Hem1 gene. Hem1 deficiency results in defective F-actin polymerization and actin capping in lymphocytes and neutrophils caused by loss of the Rac-controlled actin-regulatory WAVE protein complex. T cell development is disrupted in Hem1-deficient mice at the CD4(-)CD8(-) (double negative) to CD4(+)CD8(+) (double positive) cell stages, whereas T cell activation and adhesion are impaired. Hem1-deficient neutrophils fail to migrate in response to chemotactic agents and are deficient in their ability to phagocytose bacteria. Remarkably, some Rac-dependent functions, such as Th1 differentiation and nuclear factor kappaB (NF-kappaB)-dependent transcription of proinflammatory cytokines proceed normally in Hem1-d...Continue Reading

Mentioned in this Paper

Biochemical Pathway
Hem1 protein, mouse
Neutrophil Band Cells
Cap Formation
Mutation, Nonsense
Colony-Forming Units, Hematopoietic
Cell Motility
Caenorhabditis elegans
Lymphocytes as Percentage of Blood Leukocytes (Lab Test)

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