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Most members of the Toll-like receptor (TLR) and interleukin-1 receptor (IL-1R) families transduce signals via a canonical pathway involving the MyD88 adapter and the interleukin-1 receptor-associated kinase (IRAK) complex. This complex contains four molecules, including at least two (IRAK-1 and IRAK-4) active kinases. In mice and humans, deficiencies of IRAK-4 or MyD88 abolish most TLR (except for TLR3 and some TLR4) and IL-1R signaling in both leukocytes and fibroblasts. TLR and IL-1R responses are weak but not abolished in mice lacking IRAK-1, whereas the role of IRAK-1 in humans remains unclear. We describe here a boy with X-linked MECP2 deficiency-related syndrome due to a large de novo Xq28 chromosomal deletion encompassing both MECP2 and IRAK1. Like many boys with MECP2 null mutations, this child died very early, at the age of 7 mo. Unlike most IRAK-4- or MyD88-deficient patients, he did not suffer from invasive bacterial diseases during his short life. The IRAK-1 protein was completely absent from the patient's fibroblasts, which responded very poorly to all TLR2/6 (PAM2CSK4, LTA, FSL-1), TLR1/2 (PAM3CSK4), and TLR4 (LPS, MPLA) agonists tested but had almost unimpaired responses to IL-β. By contrast, the patient's peripheral blood mononuclear cells responded normally to all TLR1/2, TLR2/6, TLR4, TLR7, and TLR8 (R848) agonists tested, and to IL-1β. The death of this child precluded long-term evaluations of the clinical consequences of inherited IRAK-1 deficiency. However, these findings suggest that human IRAK-1 is essential downstream from TLRs but not IL-1Rs in fibroblasts, whereas it plays a redundant role downstream from both TLRs and IL-1Rs in leukocytes. [ABSTRACT FROM AUTHOR]

Glomerulopathy with fibronectin (FN) deposits (GFND) is an autosomal dominant disease with age-related penetrance, characterized by proteinuria, microscopic hematuria, hypertension, and massive glomerular deposits of FN that lead to end-stage renal failure. The genetic abnormality underlying GFND was still unknown. We hypothesized that mutations in FN1, which encodes FN, were the cause of GFND. In a large Italian pedigree with eight affected subjects, we found linkage with GFND at the FN1 locus at 2q32. We sequenced the FN1 in 15 unrelated pedigrees and found three heterozygous missense mutations, the W1925R, L1974R, and Y973C, that cosegregated with the disease in six pedigrees. The mutations affected two domains of FN (Hep-II domain for the W1925R and the L1974R, and Hep-Ill domain for the Y973C) that play key roles in FN-cell interaction and in FN fibrillogenesis. Mutant recombinant Hep-II fragments were expressed, and functional studies revealed a lower binding to heparin and to endothelial cells and podocytes compared with wild-type Hep-II and an impaired capability to induce endothelial cell spreading and cytoskeletal reorganization. Overall dominant mutations in FN1 accounted for 40% of cases of GFND in our study group. These findings may help understanding the pathogenesis of proteinuria and glomerular FN deposits in GFND and possibly in more common renal diseases such as diabetic nephropathy. IgA nephropathy, and lupus nephritis. To our knowledge no FN1 mutation causing a human disease was previously reported. [ABSTRACT FROM AUTHOR]