Project description:The gene expression of bone marrow cells of mice enriched for Gremlin1 vs control was measured (n=3). It is not known if endogenous adult mesenchymal stem cells (MSCs) exist.Following culture,perisinusoidal mesenchymal cells can clonally recapitulate the skeletal microenvironment, but this fails to confirm their endogenous lineage repertoire. Multipotential MSCs in vitro may be fate-restricted in vivo and specific perisinusoidal recombination does not trace bone or cartilage Reconciling in vitro MSCs with their in vivo potential has been challenging and remains untested outside of the bone. We prove that expression of the bone morphogenetic protein (BMP)-antagonist gremlin 1 (Grem1) identifies a population of self-renewing, multipotent bone, cartilage and stromal-primed MSCs in both health and healing that are completely distinct from the established Nes-GFP niche-supporting mesenchymal cells. Grem1 recombination also identifies small intestinal MSCs (siMSCs) that can be transplanted and clonally trace the self-renewing, multilineage periepithelial mesenchymal sheath. Our findings prove the existence of adult MSCs that are regionally and functionally distinct from perisinusoidal Nes-GFP cells. We also established that the mesenchyme undergoes ordered turnover outside of the bone and may help to preserve regional niches. Grem1 MSCs provide a new focus for investigating mesenchymal renewal and repair. a.Adult (6-8 weeks) Grem1;TdTomato mice were induced by oral tamoxifen and their bone marrow harvested by digestion sorted for Non-recombined CD45/CD31/Ter-119 triple negative bone marrow cells (n=3). b.Adult (6-8 weeks) Grem1;TdTomato mice were induced by oral tamoxifen and their bone marrow harvested by digestion sorted for Grem1 (n=3). Same mice as in a so that samples are matched.
Project description:A transcriptome study in mouse hematopoietic stem cells was performed using a sensitive SAGE method, in an attempt to detect medium and low abundant transcripts expressed in these cells. Among a total of 31,380 unique transcript, 17,326 (55%) known genes were detected, 14,054 (45%) low-copy transcripts that have no matches to currently known genes. 3,899 (23%) were alternatively spliced transcripts of the known genes and 3,754 (22%) represent anti-sense transcripts from known genes. Mouse hematopoietic stem cells were purified from bone marrow cells using negative and positive selection with a Magnetic-Activated Cell Sorter (MACS). total RNA and mRNA were purified from the purified cells using Trizol reagent and magnetic oligo dT beads. Double strand cDNAs were synthesized using a cDNA synthesis kit and anchored oligo dT primers. After NlaIII digestion, 3’ cDNAs were isolated and amplified through 16-cycle PCR. SAGE tags were released from the 3’ cDNA after linker ligation. Ditags were formed, concatemerized and cloned into a pZERO vector. Sequencing reactions were performed with the ET sequencing terminator kit. Sequences were collected using a Megabase 1000 sequencer. SAGE tag sequences were extracted using SAGE 2000 software.