Optimization study of a closed-cycle low-temperature evaporation system based on mathematical model and CFD.

Treating high salt and high organic matter wastewater (HHW) generated during rapid socio-economic development is a significant challenge. This study aims to optimize a closed-cycle low-temperature evaporation (CCLE) system using mathematical modelling to be adapted to industrial applications. By using mathematical modelling and computational fluid dynamics (CFD), this study investigated the operating mechanism of the system under different operating conditions. Parametric analysis shows that increasing the compressor evaporation temperature and decreasing the condensation temperature is conducive to improving the performance of the heat pump unit, thereby increasing the wastewater treatment efficiency of the system and that a smaller heat transfer coil windward area is conducive to heat and mass transfer within the humidifier. The unique characteristics of the CCLE system are identified, and the wastewater treatment process under various operating conditions is explained. These findings may provide supporting information for the treatment of HHW by the CCLE system.

A functional crosstalk between the H3K9 methylation writers and their reader HP1 in safeguarding embryonic stem cell identity.

Histone H3 lysine 9 (H3K9) methylation, as a hallmark of heterochromatin, has a central role in cell lineage and fate determination. Although evidence of a cooperation between H3K9 methylation writers and their readers has started to emerge, their actual interplay remains elusive. Here, we show that loss of H3K9 methylation readers, the Hp1 family, causes reduced expression of H3K9 methyltransferases, and that this subsequently leads to the exit of embryonic stem cells (ESCs) from pluripotency and a reciprocal gain of lineage-specific characteristics. Importantly, the phenotypes of Hp1-null ESCs can be rescued by ectopic expression of Setdb1, Nanog, and Oct4. Furthermore, Setdb1 ablation results in loss of ESC identity, which is accompanied by a reduction in the expression of Hp1 genes. Together, our data support a model in which the safeguarding of ESC identity involves the cooperation between the H3K9 methylation writers and their readers.

Functional redundancy among Polycomb complexes in maintaining the pluripotent state of embryonic stem cells.

Polycomb group proteins assemble into multi-protein complexes, known as Polycomb repressive complexes 1 and 2 (PRC1 and PRC2), that guide cell fate decisions during embryonic development. PRC1 forms an array of biochemically distinct canonical PRC1 (cPRC1) or non-canonical PRC1 (ncPRC1) complexes characterized by the mutually exclusive presence of PCGF (PCGF1-PCGF6) paralog subunit; however, whether each one of these subcomplexes fulfills a distinct role remains largely controversial. Here, by performing a CRISPR-based loss-of-function screen in embryonic stem cells (ESCs), we uncovered a previously unappreciated functional redundancy among PRC1 subcomplexes. Disruption of ncPRC1, but not cPRC1, displayed severe defects in ESC pluripotency. Remarkably, coablation of non-canonical and canonical PRC1 in ESCs resulted in exacerbation of the phenotype observed in the non-canonical PRC1-null ESCs, highlighting the importance of functional redundancy among PRC1 subcomplexes. Together, our studies demonstrate that PRC1 subcomplexes act redundantly to silence lineage-specific genes and ensure robust maintenance of ESC identity.

The MuvB complex safeguards embryonic stem cell identity through regulation of the cell cycle machinery.

Increasing evidences indicate that unlimited capacity for self-renewal and pluripotency, two unique properties of embryonic stem cells (ESCs), are intrinsically linked to cell cycle control. However, the precise mechanisms coordinating cell fate decisions and cell cycle regulation remain to be fully explored. Here, using CRISPR/Cas9-mediated genome editing, we show that in ESCs, deficiency of components of the cell cycle regulatory MuvB complex Lin54 or Lin52, but not Lin9 or Lin37, triggers G2/M arrest, loss of pluripotency, and spontaneous differentiation. Further dissection of these phenotypes demonstrated that this cell cycle arrest is accompanied by the gradual activation of mesoendodermal lineage-specifying genes. Strikingly, the abnormalities observed in Lin54-null ESCs were partially but significantly rescued by ectopic coexpression of genes encoding G2/M proteins Cyclin B1 and Cdk1. Thus, our study provides new insights into the mechanisms by which the MuvB complex determines cell fate through regulation of the cell cycle machinery.