Functional consequences of a germline mutation in the leucine-rich repeat domain of NLRP3 identified in an atypical autoinflammatory disorder.
OBJECTIVE
To gain insight into the pathophysiology of an atypical familial form of an autoinflammatory disorder, characterized by autosomal-dominant sensorineural hearing loss, systemic inflammation, increased secretion of interleukin-1beta (IL-1beta), and the absence of any cutaneous manifestations, and to assess the functional consequences of a missense mutation identified in the leucine-rich repeat (LRR) domain of NLRP3.


METHODS
Microsatellite markers were used to test the familial segregation of the NLRP3 locus with the disease phenotype. All NLRP3 exons were screened for mutations by sequencing. Functional assays were performed in HEK 293T cells to determine the effects of mutated (versus normal) NLRP3 proteins on NF-kappaB activation, caspase 1 signaling, and speck formation.


RESULTS
A heterozygous NLRP3 missense mutation (p.Tyr859Cys) was identified in exon 6, which encodes the LRR domain of the protein. This mutation was found to segregate with the disease phenotype within the family, and had a moderate activating effect on speck formation and procaspase 1 processing and did not alter the inhibitory properties of NLRP3 on NF-kappaB signaling.


CONCLUSIONS
This report is the first to describe a familial form of a cryopyrinopathy associated with a mutation outside of exon 3 of NLRP3. This finding, together with the known efficacy of anti-IL-1 treatments in these disorders, underlines the importance of screening all exons of NLRP3 in patients who present with atypical manifestations. In addition, the gain of function associated with this mutation in terms of activation of caspase 1 signaling was consistent with the observed inflammatory phenotype. Therefore, this study of the functional consequences of an LRR mutation sheds new light on the clinical relevance of in vitro assays.
Jéru
Isabelle
I
INSERM, U933, Université Pierre et Marie Curie-Paris 6, UMR S933, and Assistance Publique Hôpitaux de Paris, Hôpital Armand-Trousseau, 75571 Paris, France.
Marlin
Sandrine
S
Le Borgne
Gaëlle
G
Cochet
Emmanuelle
E
Normand
Sylvain
S
Duquesnoy
Philippe
P
Dastot-Le Moal
Florence
F
Cuisset
Laurence
L
Hentgen
Véronique
V
Fernandes Alnemri
Teresa
T
Lecron
Jean-Claude
JC
Dhote
Robin
R
Grateau
Gilles
G
Alnemri
Emad S
ES
Amselem
Serge
S
D000595:Amino Acid Sequence; D002352:Carrier Proteins / Q000235:genetics*; D002460:Cell Line; D016207:Cytokines / Q000097:blood; D004247:DNA / Q000235:genetics; D017931:DNA Primers; D005260:Female; D014644:Genetic Variation; D018095:Germ-Line Mutation; D056660:Hereditary Autoinflammatory Diseases / Q000235:genetics* / Q000503:physiopathology; D006801:Humans; D053583:Interleukin-1beta / Q000097:blood; D007668:Kidney / Q000196:embryology; D008297:Male; D009000:Monocytes / Q000473:pathology; D009035:Mothers; D020125:Mutation, Missense; D000071199:NLR Family, Pyrin Domain-Containing 3 Protein; D010957:Plasmids; D035781:Siblings
D002352:Carrier Proteins; D016207:Cytokines; D017931:DNA Primers; D053583:Interleukin-1beta; D000071199:NLR Family, Pyrin Domain-Containing 3 Protein; C453881:NLRP3 protein, human; D004247:DNA