Haematopoietic stem cells (HSCs) must achieve a balance between quiescence and activation that fulfils immediate demands for haematopoiesis without compromising long-term stem cell maintenance, yet little is known about the molecular events governing this balance. Phosphatase and tensin homologue (PTEN) functions as a negative regulator of the phosphatidylinositol-3-OH kinase (PI(3)K)-Akt pathway, which has crucial roles in cell proliferation, survival, differentiation and migration. Here we show that inactivation of PTEN in bone marrow HSCs causes their short-term expansion, but long-term decline, primarily owing to an enhanced level of HSC activation. PTEN-deficient HSCs engraft normally in recipient mice, but have an impaired ability to sustain haematopoietic reconstitution, reflecting the dysregulation of their cell cycle and decreased retention in the bone marrow niche. Mice with PTEN-mutant bone marrow also have an increased representation of myeloid and T-lymphoid lineages and develop myeloproliferative disorder (MPD). Notably, the cell populations that expand in PTEN mutants match those that become dominant in the acute myeloid/lymphoid leukaemia that develops in the later stages of MPD. Thus, PTEN has essential roles in restricting the activation of HSCs, in lineage fate determination, and in the prevention of leukaemogenesis. 相似文献
In this study, an ASD spectrometer made in USA is used to derive the hyperspectral data of cotton leaves in canopy in north Xinjiang. The integral area variables of red edge are used to estimate the total nitrogen (TN) content in cotton leaves in canopy. The first order differential of reflective spectra is carried out. The analysis methods based on the spectral position variables are derived from the first order differential spectral data. The analysis on the correlation between the integral area of red edge (SDr, regarded as the independent variable) and the TN content (regarded as the function) is carried out, and the correlation mathematical model between the integral area of red edge and the TN content in canopy leaves of cotton varieties named as Xinluzao No.6 is developed. The analysis on the correlation between the chlorophyll content and the TN content in single cotton leaves in canopy growing under the irrigation with different water volumes is carried out. The results show that there is a significant positive correlation between the chlorophyll content and the TN content (R = 0.8723, n = 39), and the data of chlorophyll content can be used to estimate the TN content in single cotton leaves; the correlation between the integral area variable of red edge and the TN content in cotton leaves in canopy is significant, their correlation coefficient is 0.7394 (n = 40), the TN contents in canopy leaves of cotton varieties named as Xinluzao No. 6 and No. 8 can be accurately estimated by using the developed model, and their RMSE values are 0.3859 and 0.4272 respectively. After researching, it is considered that there is an applying potential to use the integral area variables of red edge for estimating the TN content in cotton leaves in canopy, and the mathematical model developed with the third-side area variables has a high applying value in deriving the TN content in crop canopy. It is also considered that it is feasible to recognize the moisture stress suffered by cotton plants by researching the shift and change extent of red edge, and the key is to develop the corresponding rational recognition index system.
