Genetic deletion of JAM-C reveals a role in myeloid progenitor generation.

Hematopoietic stem cells (HSCs) have the capacity to self-renew and continuously differentiate into all blood cell lineages throughout life. At each branching point during differentiation, interactions with the environment are key in the generation of daughter cells with distinct fates. Here, we examined the role of the cell adhesion molecule JAM-C, a protein known to mediate cellular polarity during spermatogenesis, in hematopoiesis.

Membrane-anchored human FcRn can oligomerize in the absence of IgG.

FcRn is unique among immunoglobulin G (IgG) Fc receptors in that it is structurally closely related to major histocompatibility complex class I molecules and likewise consists of an alpha-chain and beta2-microglobulin. Crystallographic data show that rat FcRn alpha-chain/beta2m heterodimers can further dimerize via ionic interactions and a carbohydrate handshake. Intriguingly, however, no dimers are found in crystals of human FcRn, probably because the charged amino acids and the carbohydrate implicated in dimerization of rat FcRn are not conserved.

Androgen-dependent expression of FcgammaRIIB2 by thyrocytes from patients with autoimmune Graves' disease: a possible molecular clue for sex dependence of autoimmune disease.

Thyrocyte expression of HLA class I and class II antigens and related accessory molecules would convert these epithelial cells into functional antigen-presenting cells. Here we show that whereas normal thyrocytes express FcRn, Graves' disease thyrocytes also express FcgammaRIIB2. We further find that expression of FcgammaRIIB2, but not FcRn, is repressed by dihydrotestosterone.

beta(2)-Microglobulin is important for cell surface expression and pH-dependent IgG binding of human FcRn.

FcRn is a heterodimer of an alpha-chain and beta(2)-microglobulin (beta(2)m) and differs from other IgG Fc receptors in that it is structurally related to MHC class I molecules. Several functions attributed to FcRn are affected in beta(2)-microglobulin (beta(2)m)-deficient mice, suggesting that the alpha-chain needs to assemble with beta(2)m to form a functional receptor. However, the precise role of beta(2)m in FcRn function is not known.