Autophosphorylation of H2AX in a cell-specific frozen dependent way

Effective cryopreservation is a highly desired outcome in many laboratories including clinical and research centers. Cryopreservation-induced cellular damage through necrosis and apoptosis has been well characterized. However, our knowledge of the mechanism of induction of these cell death modalities is limited. H2AX histone phosphorylation to γ-H2AX is a DNA damage response and is an excellent indicator of DNA double stranded break formation. In this study we examined and detected significant phosphorylation of H2AX in response to cryopreservation of HELF and B16 cell lines. The data provide strong evidence of intrinsic alterations in DNA repair pathway members for which the impact is yet to be fully understood. While further investigation will be necessary to characterize this response, our findings show a clear linkage between freezing resulting in phosphorylation and activation of the key DNA repair enzyme H2AX.     

地卷属1中国新记录种——西方地卷(新拟)

通过对采自黑龙江省呼中自然保护区地卷属地衣的形态解剖学和化学研究,结合基因nrDNA ITS序列的系统发育分析,报道了地卷属地衣1中国新记录种——西方地卷(新拟)［Peltigera occidentalis (.E. Dahl) Kristinsson］。该种的识别特征为上表面平滑,中部稍具光泽,无绒毛、裂芽和小裂片;下表面边缘淡棕色,中部棕黑色,脉纹扁平且明显,假根单一至束状。该文对基于中国标本的西方地卷进行了详细描述,并与形态相似的3个种——小瘤地卷、多指地卷和犬地卷分别进行了比较,提供了西方地卷形态相似种的检索表。     

Hydrogen peroxide primes heart regeneration with a derepression mechanism

While the adult human heart has very limited regenerative potential, the adult zebrafish heart can fully regenerate after 20% ventricular resection. Although previous reports suggest that developmental signaling pathways such as FGF and PDGF are reused in adult heart regeneration, the underlying intracellular mechanisms remain largely unknown. Here we show that H₂O₂ acts as a novel epicardial and myocardial signal to prime the heart for regeneration in adult zebrafish. Live imaging of intact hearts revealed highly localized H₂O₂ (∼30 μM) production in the epicardium and adjacent compact myocardium at the resection site. Decreasing H₂O₂ formation with the Duox inhibitors diphenyleneiodonium (DPI) or apocynin, or scavenging H₂O₂ by catalase overexpression markedly impaired cardiac regeneration while exogenous H₂O₂ rescued the inhibitory effects of DPI on cardiac regeneration, indicating that H₂O₂ is an essential and sufficient signal in this process. Mechanistically, elevated H₂O₂ destabilized the redox-sensitive phosphatase Dusp6 and hence increased the phosphorylation of Erk1/2. The Dusp6 inhibitor BCI achieved similar pro-regenerative effects while transgenic overexpression of dusp6 impaired cardiac regeneration. H₂O₂ plays a dual role in recruiting immune cells and promoting heart regeneration through two relatively independent pathways. We conclude that H₂O₂ potentially generated from Duox/Nox2 promotes heart regeneration in zebrafish by unleashing MAP kinase signaling through a derepression mechanism involving Dusp6.