Src-Yap1 signaling axis controls the trophectoderm and epiblast lineage differentiation in mouse embryonic stem cells

STAT3-mediated up-regulation of DAB2 via SRC-YAP1 signaling axis promotes Helicobacter pylori-driven gastric tumorigenesis

BACKGROUND

Helicobacter pylori (H pylori) infection is the primary cause of gastric cancer (GC). The role of Disabled-2 (DAB2) in GC remains largely unclear. This study aimed to investigate the role of DAB2 in H pylori-mediated gastric tumorigenesis.

METHODS

We screened various datasets of GC to analyze DAB2 expression and cell signaling pathways. DAB2 expression was assessed in human GC tissue microarrays. H pylori infection in vivo and in vitro models were further explored. Immunostaining, immunofluorescence, chromatin immunoprecipitation, co-immunoprecipitation, Western blot, quantitative polymerase chain reaction, and luciferase reporter assays were performed in the current study.

RESULTS

The bioinformatic analysis verified that DAB2 was 1 of the 8 genes contributed to tumorigenesis and associated with poor prognosis in GC. The median overall survival and disease-free survival rates in DAB2high group were significantly less than those in DAB2low group. These findings demonstrated that H pylori transcriptionally activated DAB2 expression via signal transducer and activator of transcription 3 (STAT3)-dependent pathway. By bioinformatics analysis and knockdown or overexpression of DAB2, we found that DAB2 upregulated Yes-associated protein 1 (YAP1) transcriptional activity. Mechanistically, DAB2 served as a scaffold protein for integrin beta 3 (ITGB3) and SRC proto-oncogene non-receptor tyrosine kinase (SRC), facilitated the phosphorylation of SRC, promoted the small GTPase ras homolog family member A (RHOA) activation and phosphorylation of YAP1, and ultimately enhanced the YAP1 transcriptional activity.

CONCLUSIONS

Altogether, these findings indicated that DAB2 is a key mediator in STAT3-regulated translation of YAP1 and plays crucial roles in H pylori-mediated GC development. DAB2 might serve as a novel therapeutic target for GC.

BACE2 variant identified from HSCR patient causes AD-like phenotypes in hPSC-derived brain organoids

β-site APP-cleaving enzyme 2 (BACE2) is a homolog of BACE1, which is considered as the most promising therapeutic target for Alzheimer's disease (AD). However, the expression and functional role of BACE2 in central nervous system (CNS) remain obscured. Previously, we identified several BACE2 rare variants in Hirschsprung disease (HSCR) patients and proved that BACE2-mediated APP cleavage might represent a novel HSCR pathogenesis mechanism in enteric nervous system. Here, we validated that these HSCR-associated BACE2 variants were loss-of-function mutations. Using the human pluripotent stem cell (hPSC)-derived brain organoids (BOs), we further demonstrated that BACE2 was mainly expressed in the ventricular zone and cortical plate of BOs, and its expression level was gradually increased along with the BO maturation. Functionally, we found that the BOs carrying the BACE2 loss-of-function mutation (BACE2G446R) showed greater apoptosis and increased levels of Aβ oligomers compared to the control BOs, resembling with the AD-associated phenotypes. All these phenotypes could be rescued via the removal of APP protein in BACE2G446R BOs. Furthermore, rather than BACE2G446R, BACE2WT overexpression in BOs carrying the APP Swedish/Indiana mutations attenuated the AD-associated phenotypes, including Aβ accumulation and neuronal cell death. Taken together, our results unravel that BACE2 can protect the neuronal cell from apoptosis caused by Aβ accumulation, and the deficiency of BACE2-mediated APP cleavage may represent a common pathological mechanism for both HSCR and AD.

Context-dependent transcriptional regulations of YAP/TAZ in stem cell and differentiation

Hippo pathway is initially identified as a master regulator for cell proliferation and organ size control, and the subsequent researches show this pathway is also involved in development, tissue regeneration and homeostasis, inflammation, immunity and cancer. YAP/TAZ, the downstream effectors of Hippo pathway, usually act as coactivators and are dependent on other transcription factors to mediate their transcriptional outputs. In this review, we will first provide an overview on the core components and regulations of Hippo pathway in mammals, and then systematically summarize the identified transcriptional factors or partners that are responsible for the transcriptional output of YAP/TAZ in stem cell and differentiation. More than that, we will discuss the potential applications and future directions based on these findings.