Chromatin assembly factor 1B critically controls the early development but not function acquisition of invariant natural killer T cells in mice.

CD4+ CD8+ double-positive thymocytes give rise to both conventional TCRαß+ T cells and invariant natural killer T cells (iNKT cells), but these two kinds of cells display different characteristics. The molecular mechanism underlying iNKT cell lineage development and function acquisition remain to be elucidated. We show that the loss of chromatin assembly factor 1B (CHAF1b) maintains the normal development of conventional TCRαß+ T cells but severely impairs early development of iNKT cells. This dysregulation is accompanied by the impairment in chromatin activation and gene transcription at Vα14-Jα18 locus. Notably, ectopic expression of a Vα14-Jα18 TCR rescues Chaf1b-deficient iNKT cell developmental defects. Moreover, cytokine secretion and antitumor activity are substantially maintained in Vα14-Jα18 TCR transgene-rescued Chaf1b-deficient iNKT cells. Our study identifies CHAF1b as a critical factor that controls the early development but not function acquisition of iNKT cells via lineage- and stage-specific regulation.

Brumimicrobium salinarum sp. nov., isolated from a marine solar saltern.

A Gram-stain-negative, aerobic, rod-shaped and orange-coloured strain, designated LHR20T, was isolated from a marine solar saltern. The novel strain LHR20T was able to grow at 15-40 °C (optimum 33-37 °C), at pH 6.5-9.5 (optimum pH 7.5-8.0) and with 2.0-11.0 % (w/v) NaCl (optimum 4.0-5.0 %). MK-6 was the sole respiratory quinone, and the major fatty acids were iso-C15 : 0 and iso-C17 : 0 3-OH. The predominant polar lipids of strain LHR20T were phosphatidylethanolamine (PE), aminolipid (AL), glycolipid (GL1) and two unidentified lipids (L1, L2). The genomic DNA G+C content was 35.0 mol%. Phylogenetic analysis based on 16S rRNA gene sequences indicated that strain LHR20T was a member of the genus Brumimicrobium and its closest relative was Brumimicrobium mesophilum JCM 14063T (97.5 % sequence similarity). The average nucleotide identity value between strain LHR20T and B. mesophilum JCM 14063T was 73.7 %. This evidence from phenotypic, chemotaxonomic and phylogenetic analyses suggests that strain LHR20T represents a novel species of the genus Brumimicrobium. Therefore, the name Brumimicrobium salinarum sp. nov. is proposed. The type strain is LHR20T (=KCTC 62372T=MCCC 1H00247T).