Two common disease-associated TYK2 variants impact exon splicing and TYK2 dosage.

TYK2 belongs to the JAK protein tyrosine kinase family and mediates signaling of numerous antiviral and immunoregulatory cytokines (type I and type III IFNs, IL-10, IL-12, IL-22, IL-23) in immune and non-immune cells. After many years of genetic association studies, TYK2 is recognized as a susceptibility gene for some inflammatory and autoimmune diseases (AID). Seven TYK2 variants have been associated with AIDs in Europeans, and establishing their causality remains challenging. Previous work showed that a protective variant (P1104A) is hypomorphic and also a risk allele for mycobacterial infection. Here, we have studied two AID-associated common TYK2 variants: rs12720270 located in intron 7 and rs2304256, a non-synonymous variant in exon 8 that causes a valine to phenylalanine substitution (c.1084 G > T, Val362Phe). We found that this amino acid substitution does not alter TYK2 expression, catalytic activity or ability to relay signaling in EBV-B cell lines or in reconstituted TYK2-null cells. Based on in silico predictions that these variants may impact splicing of exon 8, we: i) analyzed TYK2 transcripts in genotyped EBV-B cells and in CRISPR/Cas9-edited cells, ii) measured splicing using minigene assays, and iii) performed eQTL (expression quantitative trait locus) analysis of TYK2 transcripts in primary monocytes and whole blood cells. Our results reveal that the two variants promote the inclusion of exon 8, which, we demonstrate, is essential for TYK2 binding to cognate receptors. In addition and in line with GTEx (Genetic Tissue Expression) data, our eQTL results show that rs2304256 mildly enhances TYK2 expression in whole blood. In all, these findings suggest that these TYK2 variants are not neutral but instead have a potential impact in AID.

Down-regulation of TYK2, CBLB and LMP7 genes expression in relapsing-remitting multiple sclerosis patients treated with interferon-beta.

This study aimed to examine the expression of TYK2, CBLB and LMP7 genes at both mRNA and protein levels in relapsing-remitting MS (RRMS) patients in compare with healthy controls. Seventy-eight RRMS patients treated with IFNß-1a and 79 age- and ethnic-matched healthy subjects were studied. The mRNA expression levels of TYK2, CBLB and LMP7 in PBMCs were quantified by real-time PCR and plasma concentrations of three molecules were measured by ELISA. Results were compared between patients and controls, IFNß-responders and non-responders. Forty-nine of 78 patients were classified as IFNß-responders and 29 cases were non-responders. Significantly down-regulated expression of TYK2, CBLB and LMP7 genes was found in the patients group versus controls (P<0.001). Decreased plasma levels of three molecules were observed in patients compared to controls (P<0.001). IFNß-responders had significantly higher expressions for CBLB (P=0.001) and LMP7 (P=0.02) than non-responders. Also, we observed increased expressions of LMP7 (P=0.39) and CBLB (P=0.02) genes in patients under 30y and increased expression of TYK2 in patients >40years (P=0.002). Our results suggest that expression analysis of TYK2, CBLB and LMP7 genes could be useful for evaluation of T cells immunity and clinical response to IFNß-therapy in RRMS patients.

A patient with tyrosine kinase 2 deficiency without hyper-IgE syndrome.

We describe a Turkish patient with tyrosine kinase 2 deficiency who suffered from disseminated Bacille Calmette-Guerin infection, neurobrucellosis, and cutaneous herpes zoster infection. Tyrosine kinase 2 deficiency should be considered in patients susceptible to herpes viruses and intramacrophage pathogens even in the absence of atopy, high serum IgE, and staphylococcal disease.