Biomedical subjects

Marion Bonnet

Publications and source records attributed to Marion Bonnet.

3 recordsLinked to original sources

PubMed2006

The NEMO mutation creating the most-upstream premature stop codon is hypomorphic because of a reinitiation of translation.

Amorphic mutations in the NF- kappa B essential modulator (NEMO) cause X-dominant incontinentia pigmenti, which is lethal in males in utero, whereas hypomorphic mutations cause X-recessive anhidrotic ectodermal dysplasia with immunodeficiency, a complex developmental disorder and life-threatening primary immunodeficiency. We characterized the NEMO mutation 110_111insC, which creates the most-upstream premature translation termination codon (at codon position 49) of any known NEMO mutation. Surprisingly, this mutation is associated with a pure immunodeficiency. We solve this paradox by showing that a Kozakian methionine codon located immediately downstream from the insertion allows the reinitiation of translation. The residual production of an NH(2)-truncated NEMO protein was sufficient for normal fetal development and for the subsequent normal development of skin appendages but was insufficient for the development of protective immune responses.

Amino Acid Sequence↗

PubMed2003

Pyogenic bacterial infections in humans with IRAK-4 deficiency.

Members of the Toll-like receptor (TLR) and interleukin-1 receptor (IL-1R) superfamily share an intracytoplasmic Toll-IL-1 receptor (TIR) domain, which mediates recruitment of the interleukin-1 receptor-associated kinase (IRAK) complex via TIR-containing adapter molecules. We describe three unrelated children with inherited IRAK-4 deficiency. Their blood and fibroblast cells did not activate nuclear factor kappaB and mitogen-activated protein kinase (MAPK) and failed to induce downstream cytokines in response to any of the known ligands of TIR-bearing receptors. The otherwise healthy children developed infections caused by pyogenic bacteria. These findings suggest that, in humans, the TIR-IRAK signaling pathway is crucial for protective immunity against specific bacteria but is redundant against most other microorganisms.

Alleles↗

PubMed2003

A hypermorphic IkappaBalpha mutation is associated with autosomal dominant anhidrotic ectodermal dysplasia and T cell immunodeficiency.

X-linked anhidrotic ectodermal dysplasia with immunodeficiency (XL-EDA-ID) is caused by hypomorphic mutations in the gene encoding NEMO/IKKgamma, the regulatory subunit of the IkappaB kinase (IKK) complex. IKK normally phosphorylates the IkappaB-inhibitors of NF-kappaB at specific serine residues, thereby promoting their ubiquitination and degradation by the proteasome. This allows NF-kappaB complexes to translocate into the nucleus where they activate their target genes. Here, we describe an autosomal-dominant (AD) form of EDA-ID associated with a heterozygous missense mutation at serine 32 of IkappaBalpha. This mutation is gain-of-function, as it enhances the inhibitory capacity of IkappaBalpha by preventing its phosphorylation and degradation, and results in impaired NF-kappaB activation. The developmental, immunologic, and infectious phenotypes associated with hypomorphic NEMO and hypermorphic IKBA mutations largely overlap and include EDA, impaired cellular responses to ligands of TIR (TLR-ligands, IL-1beta, and IL-18), and TNFR (TNF-alpha, LTalpha1/beta2, and CD154) superfamily members and severe bacterial diseases. However, AD-EDA-ID but not XL-EDA-ID is associated with a severe and unique T cell immunodeficiency. Despite a marked blood lymphocytosis, there are no detectable memory T cells in vivo, and naive T cells do not respond to CD3-TCR activation in vitro. Our report highlights both the diversity of genotypes associated with EDA-ID and the diversity of immunologic phenotypes associated with mutations in different components of the NF-kappaB signaling pathway.

Child↗