Cell type-specific role of lamin-B1 and its inflammation-driven reduction in organ building and aging

Abstract

Cellular architectural proteins often participate in organ development and maintenance.Although functional decay of some of these proteins during aging is known, the cell-type specific developmental role and the cause and consequence of their subsequent decay remain to be established especially in mammals. By studying lamins, the nuclear structural proteins, we demonstrate that lamin-B1 functions specifically in the thymic epithelial cells (TECs) for proper thymus organogenesis. An upregulation of proinflammatory cytokines in the intra-thymic myeloid immune cells during aging accompanies a gradual reduction of adult TEC lamins-B1.These cytokines cause adult TEC senescence and lamin-B1 reduction. We identify 17 adult TEC subsets and show that TEC lamin-B1 maintains the composition of these TECs. Lamin-B1 supports the expression of TEC genes needed for maintaining adult thymic architecture and function. Thus, structural proteins involved in organ building and maintenance can undergo inflammation-driven decay which can in turn contribute to age-associated organ degeneration. mTECs. We mixed an adherent keratin-negative cell line (RAW264.7 from ATCC #TIB-71) applying FACS to isolate macrophages in thymuses dissected from 2, 6, 12, 16, and 20-mon-old 0 Chromium and then single-cell RNA-seq libraries were generated using the Chromium Single Cell 3' Reagent Kit (10X Genomics) by the core facility at the Embryology Department of Carnegie Institute for Science. Briefly, TEC single-cell suspension (~1,000 cells per 1 µl PBS) was mixed thoroughly with Single Cell 3' gel beads and partitioning oil into a Single Cell 3' Chip (10X genomics) following the recommended protocol for the Chromium Single Cell 3' Reagent Kit (v2 Chemistry). RNA transcripts of single cells were uniquely barcoded and reversetranscribed within the individual droplets. cDNA molecules were then pre-amplified and pooled together followed by the final library construction. Libraries were sequenced by paired-end 150bp reads on Illumina NextSeq500. Post-processing and quality control were performed by the same genomics core facility using the 10X Cell Ranger package (V2.