PMC6099424_01
Genetic analysis of the AIRE gene. (A) Electropherograms of representative fragments of exon 3 of the AIRE gene relative to a normal control and the patient. The analysis was performed after informed consent. The wild-type allele for exon 3 is shown for the control (upper panel). The patient (bottom panel) is homozygous revealing two copies of the mutated c.396G>C allele (exon 3). Fifty normal controls tested negative for the novel mutation. (B) The phylogenetic tree relative to the family studies showing the heterozygous state for the novel c.396G>C mutation in both parents and the homozygosity in the patient's DNA.
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F1
Older brother died for unknown reason at the age of 11 years, the four living children, two males and two females, are in apparently good health at the age of 19, 6, 11.5, and 10, respectively (Figure 1). IFN-omega (test carried out at FIRS Laboratories, Cardiff, UK) and IFN-alpha (test carried out at Laboratory of Human Genetics of Infectious Diseases, INSERM, Paris, France) (Figure S1 in Supplementary Material, Table 1) which are typical of APECED patients. CMC-related neutralizing IL-17A, IL-17F, and IL-22 Abs tested negative. Abs to tryptophan hydroxylase (TPH), to acetylcholine receptor, to nuclear (ANA), to mitochondrial (AMA), to smooth muscle (SMA), to liver-kidney microsomal, and to parietal cell (PCA) were tested and showed to be negative (Table 1). Interestingly, the serum of both parents was tested and proved to be positive for IFN-omega Abs at low titer (7.0 IU cutoff <=5 IU) in absence of autoimmune disease manifestations. The novel autoimmune regulator (AIRE) gene c.396G>C (p.Arg132Ser) (exon 3) mutation in homozygosity was detected confirming APECED diagnosis (Figure 1).
Aire protein analysis representation. Schematic representation of Aire protein is shown along with the protein sequence alignment of the region surrounding the site of the p.R132S amino acid replacement among vertebrates. The functional nuclear localization signal (NLS) is highlighted.
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F2
Arg132 resides in the Aire protein region that comprises the functional NLS responsible for the protein correct subcellular localization and thus its activity (Figure 2). As observed in Figure 2 and Figure S2 in Supplementary Material, the central arginine (corresponding to Aire Arg 132) makes a multiplicity of interactions with alpha-importins regardless the KRK cluster is bound to the minor or the major NLS-binding site.