Temporal-spatial Generation of Astrocytes in the Developing Diencephalon / 神经科学通报·英文版

Astrocytes are the largest glial population in the mammalian brain. However, we have a minimal understanding of astrocyte development, especially fate specification in different regions of the brain. Through lineage tracing of the progenitors of the third ventricle (3V) wall via in-utero electroporation in the embryonic mouse brain, we show the fate specification and migration pattern of astrocytes derived from radial glia along the 3V wall. Unexpectedly, radial glia located in different regions along the 3V wall of the diencephalon produce distinct cell types: radial glia in the upper region produce astrocytes and those in the lower region produce neurons in the diencephalon. With genetic fate mapping analysis, we reveal that the first population of astrocytes appears along the zona incerta in the diencephalon. Astrogenesis occurs at an early time point in the dorsal region relative to that in the ventral region of the developing diencephalon. With transcriptomic analysis of the region-specific 3V wall and lateral ventricle (LV) wall, we identified cohorts of differentially-expressed genes in the dorsal 3V wall compared to the ventral 3V wall and LV wall that may regulate astrogenesis in the dorsal diencephalon. Together, these results demonstrate that the generation of astrocytes shows a spatiotemporal pattern in the developing mouse diencephalon.

Resolving the lineage relationship between malignant cells and vascular cells in glioblastomas

Glioblastoma multiforme (GBM), a highly malignant and heterogeneous brain tumor, contains various types of tumor and non-tumor cells. Whether GBM cells can trans-differentiate into non-neural cell types, including mural cells or endothelial cells (ECs), to support tumor growth and invasion remains controversial. Here we generated two genetic GBM models de novo in immunocompetent mouse brains, mimicking essential pathological and molecular features of human GBMs. Lineage-tracing and transplantation studies demonstrated that, although blood vessels in GBM brains underwent drastic remodeling, evidence of trans-differentiation of GBM cells into vascular cells was barely detected. Intriguingly, GBM cells could promiscuously express markers for mural cells during gliomagenesis. Furthermore, single-cell RNA sequencing showed that patterns of copy number variations (CNVs) of mural cells and ECs were distinct from those of GBM cells, indicating discrete origins of GBM cells and vascular components. Importantly, single-cell CNV analysis of human GBM specimens also suggested that GBM cells and vascular cells are likely separate lineages. Rather than expansion owing to trans-differentiation, vascular cell expanded by proliferation during tumorigenesis. Therefore, cross-lineage trans-differentiation of GBM cells is very unlikely to occur during gliomagenesis. Our findings advance understanding of cell lineage dynamics during gliomagenesis, and have implications for targeted treatment of GBMs.

Research progress in lineage tracing to explore hepatic parenchymal cell regeneration and repair mechanisms / 中华肝脏病杂志

Hepatic parenchymal cells are a type of liver cells that performs important functions such as metabolism and detoxification. The contribution of hepatic parenchymal cells, bile duct cells, and hepatic stem/progenitor cells to new hepatic parenchymal cells in the process of liver injury repair has become a controversial issue due to their strong proliferation ability. Lineage tracing technology, which has emerged in the past decade as a new method for exploring the origin of cells, can trace specific type of cells and their daughter cells by labeling cells that express the specific gene and their progeny. The article reviews the current literature on the origin and contribution of hepatic parenchymal cells by this technique. About 98% of new hepatic parenchymal cells originate from the existing hepatic parenchymal cells during liver homeostasis and after acute injury. However, under conditions of severe liver injury, such as inhibition of hepatic parenchymal cell proliferation, bile duct cells (mainly liver stem/progenitor cells) become the predominant source of hepatic parenchymal cells, contributing a steady increased hepatocyte regeneration with the extension of time.

The tankyrase inhibitor G007-LK inhibits small intestine LGR5+ stem cell proliferation without altering tissue morphology

Abstract Background The WNT pathway regulates intestinal stem cells and is frequently disrupted in intestinal adenomas. The pathway contains several potential biotargets for interference, including the poly-ADP ribosyltransferase enzymes tankyrase1 and 2. LGR5 is a known WNT pathway target gene and marker of intestinal stem cells. The LGR5+ stem cells are located in the crypt base and capable of regenerating all intestinal epithelial cell lineages. Results We treated Lgr5-EGFP-Ires-CreERT2;R26R-Confetti mice with the tankyrase inhibitor G007-LK for up to 3 weeks to assess the effect on duodenal stem cell homeostasis and on the integrity of intestinal epithelium. At the administered doses, G007-LK treatment inhibited WNT signalling in LGR5+ stem cells and reduced the number and distribution of cells traced from duodenal LGR5+ stem cells. However, the gross morphology of the duodenum remained unaltered and G007-LK-treated mice showed no signs of weight loss or any other visible morphological changes. The inhibitory effect on LGR5+ stem cell proliferation was reversible. Conclusion We show that the tankyrase inhibitor G007-LK is well tolerated by the mice, although proliferation of the LGR5+ intestinal stem cells was inhibited. Our observations suggest the presence of a tankyrase inhibitor-resistant cell population in the duodenum, able to rescue tissue integrity in the presence of G007-LK-mediated inhibition of the WNT signalling dependent LGR5+ intestinal epithelial stem cells.

Establishment of lineage tracing method of mice small intestinal stem cell and application in radiation injury / 解放军医学杂志

Objective To establish a lineage tracing method with Lgr5-EGFP-CreERT2/ROSA26-stop-EYFP mouse for observing the role of Lgr5+ intestinal stem cells in the renovation of small intestine tissue, and investigate the effects of radiation on the reconstruction of small intestinal stem cell tissue. Methods-Lgr5-EGFP-CreERT2/ROSA26-stop-EYFP mice were identified by genotype analysis. Tamoxifen was used to induce the expression of fluorescent protein in mice. The differentiation of intestinal stem cells induced by Tamoxifen was observed by laser confocal microscopy. Lgr5-EGFP-CreERT2/ROSA26-stop-EYFP mice were irradiated with60Co γ-rays, and the effects of irradiation on the reconstruction of small intestinal stem cell tissue were examined. Results-Double positive mice were obtained by identification of Lgr5 gene (174bp) in DNA extraction from the mice tail with PCR method. In mice treated with single injection of Tamoxifen (100mg/kg), it was observed by laser confocal scanning microscopy that the Lgr5+ intestinal stem cells started dividing at the 5th day after inducement, reached the top of the villi at the 7th day, fluorescence appeared in a few of whole intestinal villi at the 14th day, and spread over more intestinal villi with dense fluorescence at the 45th day. However, in mice exposed to 15Gy irradiation, the intestinal villi fell off seriously without fluorescence in crypts. Conclusion-The lineage tracing model of intestinal stem cell has been successfully established and then used to evaluate the irradiation injuries to intestinal stem cells.