The kinetic properties of transcriptional bursting were comprehensively analyzed in mouse embryonic stem cells.

γδT cells produce inflammatory cytokines and have been implicated in the pathogenesis of cancer, infectious diseases, and autoimmunity. The T cell receptor (TCR) signal transduction that specifically regulates the development of IL-17–producing γδT (γδT17) cells largely remains unclear. Here, we showed that the receptor proximal tyrosine kinase Syk is essential for γδTCR signal transduction and development of γδT17 in the mouse thymus. Zap70, another tyrosine kinase essential for the development of αβT cells, failed to functionally substitute for Syk in the development of γδT17. Syk induced the activation of the PI3K/Akt pathway upon γδTCR stimulation. Mice deficient in PI3K signaling exhibited a complete loss of γδT17, without impaired development of IFN-γ–producing γδT cells. Moreover, γδT17-dependent skin inflammation was ameliorated in mice deficient in RhoH, an adaptor known to recruit Syk. Thus, we deciphered lineage-specific TCR signaling and identified the Syk/PI3K pathway as a critical determinant of proinflammatory γδT cell differentiation.

Macrophages play essential roles in immune defense and tissue homeostasis, but the mechanisms underlying their colonization in the gut mucosa remain incompletely understood. Here, we identify CSF1, primarily derived from fibroblasts, as the dominant factor maintaining mucosal macrophage colonization, whereas IL-34 deficiency alone has a minimal impact. We reveal that CSF1R ligands originate from distinct cellular sources: macrophages at the upper villus region depend on fibroblast-derived CSF1 and IL-34, while macrophages in the lower villus and the submucosal (lower villus + SM) region are regulated by CSF1 from both fibroblasts and endothelial cells. Additionally, within the lower villus + SM region, CSF1-producing CD81⁺ LepR⁺ fibroblasts directly interact with CD163⁺ macrophages, forming a localized niche. The loss of Csf1 in fibroblasts results in accelerated systemic dissemination of Salmonella Typhimurium, highlighting fibroblast-derived CSF1 as a key regulator of gut macrophage function in host defense. Collectively, our findings uncover a previously unrecognized fibroblast-macrophage crosstalk that governs gut macrophage homeostasis and immunity.

To identify factors involved in the earliest phase of the differentiation of human embryonic stem cells (hESCs) into brown adipocytes (BAs), we performed multi-time point microarray analyses. We found that growth/differentiation factor 15 (GDF15) expressions were specifically upregulated within three days of differentiation, when expressions of immature hESC markers were sustained. Although GDF15 expressions continued to increase in the subsequent differentiation phases, GDF15-deficient hESCs differentiated into mature BAs (Day 10) without apparent abnormalities. In addition, GDF15-deficient mice had normal brown adipose tissue (BAT) and were metabolically healthy. Unexpectedly, we found that interleukin-6 (IL6) expression was significantly lowered in the BAT of GDF15^-/- mice. In addition, GDF15^-/- hESCs showed abortive IL6 expressions in the later phase (>Day 6) of the differentiation. Interestingly, GDF15 expression was markedly repressed throughout the whole course of the differentiation of IL6^-/- hESCs into BAs, indicating IL6 is essential for the induction of GDF15 in the differentiation of hESCs. Finally, intraperitoneally transplanted BAT grafts of GDF15^-/- donor mice, but not those of wild-type (WT) mice, failed in the long-term survival (12 weeks) in GDF15^-/- recipient mice. Collectively, GDF15 is required for long-term survival of BAT grafts by creating a mutual gene induction loop with IL6.