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Mitochondrial DNA mutations are established in human colonic stem cells, and mutated clones expand by crypt fission.

ABSTRACT: The understanding of the fixation of mutations within human tissues and their subsequent clonal expansion is a considerable problem, of which little is known. We have previously shown that nononcogenic mutations in the mitochondrial genome occur in one of a number of morphologically normal colonic crypt stem cells, the progeny of which later occupy the whole crypt. We propose that these wholly mutated crypts then clonally expand by crypt fission, where each crypt divides into two mutated daughter crypts. Here we show that (i) mutated crypts in the process of fission share the same mutated mitochondrial genotype not present in neighboring cytochrome c oxidase-positive crypts (the odds of this being a random event are >or=2.48 x 10(9):1); (ii) neighboring mutated crypts have the same genotype, which is different from adjacent cytochrome c oxidase-positive crypts; (iii) mutated crypts are clustered together throughout the colon; and (iv) patches of cytochrome c oxidase-deficient crypts increase in size with age. We thus demonstrate definitively that crypt fission is the mechanism by which mutations spread in the normal human colon. This has important implications for the biology of the normal adult human colon and possibly for the growth and spread of colorectal neoplasms.

SUBMITTER: Greaves LC

PROVIDER: S-EPMC1325106 | biostudies-literature |

REPOSITORIES: biostudies-literature

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Project description:BACKGROUND & AIMS:Paneth cells contribute to the small intestinal niche of Lgr5(+) stem cells. Although the colon also contains Lgr5(+) stem cells, it does not contain Paneth cells. We investigated the existence of colonic Paneth-like cells that have a distinct transcriptional signature and support Lgr5(+) stem cells. METHODS:We used multicolor fluorescence-activated cell sorting to isolate different subregions of colon crypts, based on known markers, from dissociated colonic epithelium of mice. We performed multiplexed single-cell gene expression analysis with quantitative reverse transcriptase polymerase chain reaction followed by hierarchical clustering analysis to characterize distinct cell types. We used immunostaining and fluorescence-activated cell sorting analyses with in vivo administration of a Notch inhibitor and in vitro organoid cultures to characterize different cell types. RESULTS:Multicolor fluorescence-activated cell sorting could isolate distinct regions of colonic crypts. Four major epithelial subtypes or transcriptional states were revealed by gene expression analysis of selected populations of single cells. One of these, the goblet cells, contained a distinct cKit/CD117(+) crypt base subpopulation that expressed Dll1, Dll4, and epidermal growth factor, similar to Paneth cells, which were also marked by cKit. In the colon, cKit(+) goblet cells were interdigitated with Lgr5(+) stem cells. In vivo, this colonic cKit(+) population was regulated by Notch signaling; administration of a ?-secretase inhibitor to mice increased the number of cKit(+) cells. When isolated from mouse colon, cKit(+) cells promoted formation of organoids from Lgr5(+) stem cells, which expressed Kitl/stem cell factor, the ligand for cKit. When organoids were depleted of cKit(+) cells using a toxin-conjugated antibody, organoid formation decreased. CONCLUSIONS:cKit marks small intestinal Paneth cells and a subset of colonic goblet cells that are regulated by Notch signaling and support Lgr5(+) stem cells.

Project description:IntroductionParoxysmal nocturnal hemoglobinuria (PNH) is a rare hematological disease characterized by intravascular hemolysis, thrombosis, and bone marrow (BM) failure. Although PNH is caused by excessive proliferation of hematopoietic stem cell (HSC) clones with loss of function mutations in phosphatidylinositol N-acetylglucosaminyltransferase subunit A (PIGA) genes, what drives PNH clones to expand remains elusive.Case descriptionWe present a case of a 26-year-old female who presented with hemolytic anemia, thrombocytopenia, and leukopenia. Flow cytometry analysis of peripheral blood showed that 71.9% and 15.3% of the granulocytes and erythrocytes were glycosylphosphatidylinositol-anchored protein deficient (GPI[-]) cells. The patient was diagnosed with PNH with non-severe aplastic anemia. Deep-targeted sequencing covering 390 different genes of sorted GPI(-) granulocytes revealed three different PIGA mutations (p.I69fs, variant allele frequency (VAF) 24.2%; p.T192P, VAF 5.8%; p.V300fs, VAF 5.1%) and no other mutations. She received six cycles of eculizumab and oral cyclosporine. Although the patient's serum lactate dehydrogenase level decreased, she remained dependent on red blood cell transfusion. Six months after diagnosis, she received a syngeneic bone marrow transplant (BMT) from a genetically identical healthy twin, following an immune ablative conditioning regimen consisting of cyclophosphamide 200 mg/kg and rabbit anti-thymocyte globulin 10 mg/kg. After four years, the patient's blood count remained normal without any signs of hemolysis. However, the peripheral blood still contained 0.2% GPI (-) granulocytes, and the three PIGA mutations that had been detected before BMT persisted at similar proportions to those before transplantation (p.I69fs, VAF 36.1%; p.T192P, VAF 3.7%; p.V300fs, VAF 8.6%) in the small PNH clones that persisted after transplantation.ConclusionsThe PNH clones that had increased excessively before BMT decreased, but persisted at low percentages for more than four years after the immunoablative conditioning regimen followed by syngeneic BMT. These findings indicate that as opposed to conventional theory, immune pressure on HSCs, which caused BM failure before BMT, was sufficient for PIGA-mutated HSCs to clonally expand to develop PNH.

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Mitochondrial DNA mutations are established in human colonic stem cells, and mutated clones expand by crypt fission.

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