RESUMO
Proliferation of the self-renewing epithelium of the gastric corpus occurs almost exclusively in the isthmus of the glands, from where cells migrate bidirectionally toward pit and base. The isthmus is therefore generally viewed as the stem cell zone. We find that the stem cell marker Troy is expressed at the gland base by a small subpopulation of fully differentiated chief cells. By lineage tracing with a Troy-eGFP-ires-CreERT2 allele, single marked chief cells are shown to generate entirely labeled gastric units over periods of months. This phenomenon accelerates upon tissue damage. Troy(+) chief cells can be cultured to generate long-lived gastric organoids. Troy marks a specific subset of chief cells that display plasticity in that they are capable of replenishing entire gastric units, essentially serving as quiescent "reserve" stem cells. These observations challenge the notion that stem cell hierarchies represent a "one-way street."
Assuntos
Celulas Principais Gástricas/citologia , Células-Tronco/citologia , Estômago/citologia , Animais , Linhagem da Célula , Celulas Principais Gástricas/química , Mucosa Gástrica/citologia , Camundongos , Organoides/citologia , Receptores do Fator de Necrose Tumoral/análise , Via de Sinalização WntRESUMO
In a screen for genes expressed specifically in gastric mucous neck cells, we identified GKN3, the recently discovered third member of the gastrokine family. We present confirmatory mouse data and novel porcine data showing that mouse GKN3 expression is confined to mucous cells of the corpus neck and antrum base and is prominently expressed in metaplastic lesions. GKN3 was proposed originally to be expressed in some human populations and a pseudogene in others. To investigate that hypothesis, we studied human GKN3 evolution in the context of its paralogous genomic neighbors, GKN1 and GKN2. Haplotype analysis revealed that GKN3 mimics GKN2 in patterns of exonic SNP allocation, whereas GKN1 appeared to be more stringently selected. GKN3 showed signatures of both directional selection and population based selective sweeps in humans. One such selective sweep includes SNP rs10187256, originally identified as an ancestral tryptophan to premature STOP codon mutation. The derived (nonancestral) allele went to fixation in Asia. We show that another SNP, rs75578132, identified 5 bp downstream of rs10187256, exhibits a second selective sweep in almost all Europeans, some Latinos, and some Africans, possibly resulting from a reintroduction of European genes during African colonization. Finally, we identify a mutation that would destroy the splice donor site in the putative exon3-intron3 boundary, which occurs in all human genomes examined to date. Our results highlight a stomach-specific human genetic locus, which has undergone various selective sweeps across European, Asian, and African populations and thus reflects geographic and ethnic patterns in genome evolution.
Assuntos
Proteínas de Transporte/genética , Evolução Molecular , Loci Gênicos/genética , Proteínas de Membrana/genética , Pseudogenes/genética , Grupos Raciais/genética , Seleção Genética/genética , Animais , Proteínas de Transporte/metabolismo , Biologia Computacional , Primers do DNA/genética , Imunofluorescência , Mucosa Gástrica/metabolismo , Genética Populacional , Genótipo , Haplótipos/genética , Humanos , Funções Verossimilhança , Macaca mulatta/genética , Proteínas de Membrana/metabolismo , Camundongos , Camundongos Endogâmicos C57BL/genética , Análise em Microsséries , Microscopia Confocal , Modelos Genéticos , Mutação/genética , Filogenia , Polimorfismo de Nucleotídeo Único/genética , Especificidade da Espécie , Sus scrofa/genéticaRESUMO
Tamoxifen, a selective estrogen receptor modulator, is widely used in research and clinically in patients. We find that treatment of normal mice with a single ≥3 mg/20 g body weight dose of tamoxifen leads to apoptosis of >90% of all gastric parietal cells (PCs) and metaplasia of zymogenic chief cells within 3 days. Remarkably, gastric histology returns to nearly normal by 3 weeks. Tamoxifen toxicity occurs by oral and intraperitoneal administration, in both sexes, in multiple strains, and does not depend on estrogen, though acid secretion inhibition is partially protective. Thus, substantial gastric toxicity is a heretofore unappreciated tamoxifen side effect.
Assuntos
Celulas Principais Gástricas/efeitos dos fármacos , Células Parietais Gástricas/efeitos dos fármacos , Moduladores Seletivos de Receptor Estrogênico/toxicidade , Tamoxifeno/toxicidade , Administração Oral , Animais , Atrofia , Celulas Principais Gástricas/patologia , Feminino , Regulação da Expressão Gênica/efeitos dos fármacos , Injeções Intraperitoneais , Integrases/genética , Óperon Lac , Masculino , Metaplasia , Camundongos , Camundongos Endogâmicos BALB C , Camundongos Endogâmicos C57BL , Camundongos Transgênicos , Células Parietais Gástricas/patologia , Moduladores Seletivos de Receptor Estrogênico/administração & dosagem , Especificidade da Espécie , Tamoxifeno/administração & dosagem , Fatores de TempoRESUMO
BACKGROUND & AIMS: The transition of gastric epithelial mucous neck cells (NCs) to digestive enzyme-secreting zymogenic cells (ZCs) involves an increase in rough endoplasmic reticulum (ER) and formation of many large secretory vesicles. The transcription factor MIST1 is required for granulogenesis of ZCs. The transcription factor XBP1 binds the Mist1 promoter and induces its expression in vitro and expands the ER in other cell types. We investigated whether XBP1 activates Mist1 to regulate ZC differentiation. METHODS: Xbp1 was inducibly deleted in mice using a tamoxifen/Cre-loxP system; effects on ZC size and structure (ER and granule formation) and gastric differentiation were studied and quantified for up to 13 months after deletion using morphologic, immunofluorescence, quantitative reverse-transcriptase polymerase chain reaction, and immunoblot analyses. Interactions between XBP1 and the Mist1 promoter were studied by chromatin immunoprecipitation from mouse stomach and in XBP1-transfected gastric cell lines. RESULTS: Tamoxifen-induced deletion of Xbp1 (Xbp1Δ) did not affect survival of ZCs but prevented formation of their structure. Xbp1Δ ZCs shrank 4-fold, compared with those of wild-type mice, with granulogenesis and cell shape abnormalities and disrupted rough ER. XBP1 was required and sufficient for transcriptional activation of MIST1. ZCs that developed in the absence of XBP1 induced ZC markers (intrinsic factor, pepsinogen C) but showed abnormal retention of progenitor NC markers. CONCLUSIONS: XBP1 controls the transcriptional regulation of ZC structural development; it expands the lamellar rough ER and induces MIST1 expression to regulate formation of large granules. XBP1 is also required for loss of mucous NC markers as ZCs form.
Assuntos
Fatores de Transcrição Hélice-Alça-Hélice Básicos/genética , Celulas Principais Gástricas/citologia , Celulas Principais Gástricas/fisiologia , Proteínas de Ligação a DNA/genética , Retículo Endoplasmático Rugoso/fisiologia , Fatores de Transcrição/genética , Animais , Fatores de Transcrição Hélice-Alça-Hélice Básicos/metabolismo , Diferenciação Celular/fisiologia , Linhagem Celular , Celulas Principais Gástricas/ultraestrutura , Proteínas de Ligação a DNA/metabolismo , Integrases/genética , Camundongos , Camundongos Knockout , Microscopia Eletrônica de Transmissão , Regiões Promotoras Genéticas/fisiologia , Fatores de Transcrição de Fator Regulador X , Vesículas Secretórias/fisiologia , Células-Tronco/citologia , Células-Tronco/fisiologia , Fatores de Transcrição/metabolismo , Proteína 1 de Ligação a X-BoxRESUMO
In the mammalian gastrointestinal tract, the cell fate decisions that specify the development of multiple, diverse lineages are governed in large part by interactions of stem and early lineage progenitor cells with their microenvironment, or niche. Here, we show that the gastric parietal cell (PC) is a key cellular component of the previously undescribed niche for the gastric epithelial neck cell, the progenitor of the digestive enzyme secreting zymogenic (chief) cell (ZC). Genetic ablation of PCs led to failed patterning of the entire zymogenic lineage: progenitors showed premature expression of differentiated cell markers, and fully differentiated ZCs failed to develop. We developed a separate mouse model in which PCs localized not only to the progenitor niche, but also ectopically to the gastric unit base, which is normally occupied by terminally differentiated ZCs. Surprisingly, these mislocalized PCs did not maintain adjacent zymogenic lineage cells in the progenitor state, demonstrating that PCs, though necessary, are not sufficient to define the progenitor niche. We induced this PC mislocalization by knocking out the cytoskeleton-regulating gene Cd2ap in Mist1(-/-) mice, which led to aberrant E-cadherin localization in ZCs, irregular ZC-ZC junctions, and disruption of the ZC monolayer by PCs. Thus, the characteristic histology of the gastric unit, with PCs in the middle and ZCs in the base, may depend on establishment of an ordered adherens junction network in ZCs as they migrate into the base.
Assuntos
Diferenciação Celular , Linhagem da Célula , Celulas Principais Gástricas/citologia , Células Epiteliais/citologia , Nicho de Células-Tronco/citologia , Células-Tronco/citologia , Proteínas Adaptadoras de Transdução de Sinal/deficiência , Proteínas Adaptadoras de Transdução de Sinal/metabolismo , Animais , Fatores de Transcrição Hélice-Alça-Hélice Básicos/deficiência , Fatores de Transcrição Hélice-Alça-Hélice Básicos/metabolismo , Caderinas/metabolismo , Polaridade Celular , Proliferação de Células , Celulas Principais Gástricas/metabolismo , Celulas Principais Gástricas/ultraestrutura , Proteínas do Citoesqueleto/deficiência , Proteínas do Citoesqueleto/metabolismo , Células Epiteliais/metabolismo , Células Epiteliais/ultraestrutura , Junções Intercelulares/metabolismo , Junções Intercelulares/ultraestrutura , Camundongos , Modelos Biológicos , Células Parietais Gástricas/citologia , Células Parietais Gástricas/metabolismo , Células Parietais Gástricas/ultraestrutura , Ligação Proteica , Transporte Proteico , Nicho de Células-Tronco/metabolismo , Nicho de Células-Tronco/ultraestrutura , Células-Tronco/metabolismo , Células-Tronco/ultraestruturaRESUMO
The epidermal differentiation complex (EDC) locus comprises a syntenic and linear cluster of genes whose concomitant expression is a hallmark feature of differentiation in the developing skin epidermis. Many of the EDC proteins are cross-linked together to form the cornified envelope, an essential and discrete unit of the mammalian skin barrier. The mechanism underlying coordinate transcriptional activation of the EDC is unknown. Within the human EDC, we identified an epidermal-specific regulatory enhancer, 923, which responded to the developmental and spatiotemporal cues at the onset of epidermal differentiation in the mouse embryo. Comparative chromosomal conformation capture assays in proliferating and differentiated primary mouse keratinocytes revealed multiple physiologically sensitive chromatin interactions between the 923 enhancer and EDC gene promoters, thus depicting the dynamic chromatin topology of the EDC. We elucidate a mechanistic link between c-Jun/AP-1 and 923, whereby AP-1- and 923-mediated EDC chromatin remodeling are required for functional EDC gene activation. Thus, we identify a critical enhancer/transcription factor axis governing the dynamic regulation of the EDC chromatin architecture and gene expression and provide a framework for future studies toward understanding gene regulation in cutaneous diseases.