Search bioRxivSearch

Biology subjects

Zhang, X.-S.

Publications and source records attributed to Zhang, X.-S..

2 recordsLinked to original sources

Positively interacting strains that circulate in a network structured population induce cycling epidemics of Mycoplasma Pneumoniae

In many countries Mycoplasma pneumoniae (MP) epidemics last approximately one to two years and occur every three to seven years. Poor understanding of the drivers of recurrent MP epidemics limits the predictability of and dynamic responses to the outbreak. Taking into account network structured contacts among people and co-circulating strains of MP, we propose a multi-strain SIRS network model of epidemics of MP where different strains interact during re-infection and within secondary infection. Simulations show that although strain interactions and network-mediated spatial correlations are two separate mechanisms for MP epidemics cycling, each requires very restricted model parameter values such as strong strain interactions and strong network contacts, respectively. When both mechanisms work collectively, MP recurrent epidemics become feasible within the plausible ranges of model parameters. This indicates that positively interacting strains that co-circulate within network contacts induce periodicity and dominant strain shift in observed MP incidence.

epidemiology

Acidic microenvironment shaped by lactate accumulation promotes pluripotency through multiple mechanisms

Enhanced glycolysis is a distinct feature associated with numerous stem cells and cancer cells. However, little is known about its regulatory roles in gene expression and cell fate determination. Here we show that acidic environment shaped by lactate accumulation promotes the self-renewal and pluripotency of both mouse and human embryonic stem cells (ESCs). Mechanistically, acidic pH reduces the tri-methylation of H3K27 globally at transcriptional start sites to partially prevent ESC differentiation. In addition, acidic pH stabilizes a large number of mRNAs including pluripotency genes. Furthermore, we found that AGO1 protein is downregulated at acidic conditions, leading to the de-repression of a subset of microRNA targets in low-pH treated ESCs. Altogether, our study provides insights into mechanisms whereby acidic microenvironment produced by enhanced glycolysis regulates gene expression to determine cell fate and has broad implications in the fields of regenerative medicine and cancer biology.

developmental biology