Janus kinases (Jaks) play an important role in signal transduction via cytokine receptors. Tyk2 is a Janus kinase, and we developed tyk2-deficient mice to study the requirement for tyk2 in vivo. Tyk2-deficient mice show no overt developmental abnormalities; however, they display a lack of responsiveness to a small amount of IFNalpha, although a high concentration of IFNalpha can fully transduce its signal even in the absence of tyk2. Furthermore, IL-12-induced T cell function is defective in these mice. In contrast, these mice respond normally to IL-6 and IL-10, both of which activate tyk2 in vitro. These observations demonstrate that tyk2 plays only a restricted role in mediating IFNalpha-dependent signaling while being required in mediating IL-12-dependent biological responses.

BackgroundKlotho is a single-pass transmembrane protein, which appears to be implicated in aging. The purpose of the present study was to characterize the relationship between the soluble Klotho level and renal function in patients with various degrees of chronic kidney disease (CKD).MethodsThe levels of soluble Klotho in the serum and urine obtained from one hundred thirty-one CKD patients were determined by a sandwich enzyme-linked immunosorbent assay system.ResultsThe amount of urinary excreted Klotho during the 24 hr period ranged from 1.6 to 5178 ng/day (median 427 ng/day; interquartile range [IR] 56.8-1293.1), and the serum Klotho concentration ranged from 163.9 to 2123.7 pg/ml (median 759.7 pg/ml; IR 579.5-1069.1). The estimated glomerular filtration rate (eGFR) was significantly correlated with the log-transformed values of the amount of 24 hr urinary excreted Klotho (r = 0.407, p < 0.01) and the serum Klotho levels (r = 0.232, p < 0.01). However, a stepwise multiple regression analysis identified eGFR to be a variable independently associated only with the log-transformed value of the amount of 24-hr urinary excreted Klotho but not with the log-transformed serum Klotho concentration. Despite the strong correlation between random urine protein-to-creatinine ratio and the 24 hr urinary protein excretion (r = 0.834, p < 0.01), a moderate linear association was observed between the log-transformed value of the amount of 24 hr urinary excreted Klotho and that of the urinary Klotho-to-creatinine ratio (Klotho/Cr) in random urine specimens (r = 0.726, p < 0.01).ConclusionsThe amount of urinary Klotho, rather than the serum Klotho levels, should be linked to the magnitude of the functioning nephrons in CKD patients. The use of random urine Klotho/Cr as a surrogate for the amount of 24-hr urinary excreted Klotho needs to be evaluated more carefully.

Mice lacking Tyk2, Stat1 or Stat4, which are members of the Jak-Stat signaling cascade, were resistant to LPS-induced endotoxin shock. Interestingly, Tyk2-deficient mice had higher resistance to LPS challenge than mice lacking either Stat1 or Stat4. The activation of MAPK and NF-kappaB by LPS, and the production of TNF-alpha and IL-12 after LPS injection, were not abrogated by the absence of Tyk2, Stat1 or Stat4. In Stat1-deficient mice, the induction of IFN-beta by LPS in macrophages was severely reduced, although the serum level of IFN-gamma was elevated after LPS injection. In contrast, in Stat-4 deficient mice, the induction of IFN-beta by LPS was normal, but the serum level of IFN-gamma remained low after LPS injection. Interestingly, the induction of both IFN-beta and IFN-gamma by LPS was severely reduced in Tyk2-deficient mice. Therefore, Stat1 and Stat4 independently play substantial roles in the susceptibility to LPS. Tyk2 is essential for LPS-induced endotoxin shock, and this signaling pathway is transduced by the activation of Stat1 and Stat4.

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CCCTC binding factor (CTCF) is an important factor in the maintenance of chromatin–chromatin interactions, yet the mechanism regulating its binding to chromatin is unknown. We demonstrate that zinc finger protein 143 (ZNF143) is a key regulator for CTCF-bound promoter–enhancer loops. In the murine genome, a large percentage of CTCF and ZNF143 DNA binding motifs are distributed 37 bp apart in the convergent orientation. Furthermore, deletion of ZNF143 leads to loss of CTCF binding on promoter and enhancer regions associated with gene expression changes. CTCF-bound promoter–enhancer loops are also disrupted after excision of ZNF143. ZNF143-CTCF-bound promoter–enhancer loops regulate gene expression patterns essential for maintenance of murine hematopoietic stem and progenitor cell integrity. Our data suggest a common feature of gene regulation is that ZNF143 is a critical factor for CTCF-bound promoter–enhancer loops.