Mutations in the perforin gene can be linked to macrophage activation syndrome in patients with systemic onset juvenile idiopathic arthritis.
OBJECTIVE
Macrophage activation syndrome (MAS) in systemic onset juvenile idiopathic arthritis (SoJIA) is considered to be an acquired form of familial haemophagocytic lymphohistiocytosis (fHLH). FHLH is an autosomal recessive disorder, characterized by diminished NK cell function and caused by mutations in the perforin gene (PRF1) in 20-50% of patients. Interestingly, SoJIA patients display decreased levels of perforin in NK cells and diminished NK cell function as well. Here, we analysed PRF1 and its putative promoter in SoJIA patients with or without a history of MAS.


METHODS
DNA of 56 SoJIA patients (41 Italian and 15 Dutch) was isolated. Of these, 15 (27%) had a confirmed history of MAS. We sequenced PRF1 and 1.5 kb of the 5'-upstream region. DNA sequence variations in the promoter region were functionally tested in transfection experiments using a human NK cell line.


RESULTS
We detected a previously undescribed sequence variation (-499 C > T) in the promoter of PRF1 in 18% of the SoJIA patients. However, transfection experiments did not show functional implications of this variation. Secondly, we found that 11 of 56 (20%) SoJIA patients were heterozygous for missense mutations in PRF1. In particular, we found a high prevalence of the Ala91Val mutation, a variant known to result in defective function of perforin. Interestingly, the prevalence of Ala91Val in SoJIA patients with a history of MAS (20%) was increased compared with SoJIA patients without MAS (9.8%). One SoJIA patient, heterozygous for Ala91Val, showed profound decreased perforin levels at the time of MAS.


CONCLUSIONS
These findings suggest that PRF1 mutations play a role in the development of MAS in SoJIA patients.
Vastert
Sebastiaan J
SJ
Department of Paediatric Immunology, Wilhelmina Children's Hospital, University Medical Centre Utrecht, Lundlaan 6, 3584 EA Utrecht, The Netherlands. b.vastert@umcutrecht.nl
van Wijk
Richard
R
D'Urbano
Leila E
LE
de Vooght
Karen M K
KM
de Jager
Wilco
W
Ravelli
Angelo
A
Magni-Manzoni
Silvia
S
Insalaco
Antonella
A
Cortis
Elisabetta
E
van Solinge
Wouter W
WW
Prakken
Berent J
BJ
Wulffraat
Nico M
NM
de Benedetti
Fabrizio
F
Kuis
Wietse
W
D000293:Adolescent; D001171:Arthritis, Juvenile / Q000150:complications* / Q000276:immunology; D002478:Cells, Cultured; D002648:Child; D002675:Child, Preschool; D003602:Cytotoxicity, Immunologic; D020022:Genetic Predisposition to Disease; D005838:Genotype; D006801:Humans; D007223:Infant; D007694:Killer Cells, Natural / Q000276:immunology; D055501:Macrophage Activation Syndrome / Q000209:etiology* / Q000235:genetics / Q000276:immunology; D009154:Mutation; D054353:Perforin; D052899:Pore Forming Cytotoxic Proteins / Q000096:biosynthesis / Q000235:genetics*; D011401:Promoter Regions, Genetic; D014162:Transfection
C510468:PRF1 protein, human; D052899:Pore Forming Cytotoxic Proteins; D054353:Perforin