How do optogenetics and continuous-wave light stimulation control mouse embryonic cardiogenesis?

Abstract

The mouse embryo is an established model for investigation of regulatory mechanisms controlling cardiac development and congenital heart defects in humans. Previous research has shown that hemodynamics and heartbeat can be manipulated by electrical pacing or pharmacological agents. Recently, a more versatile tool for biophotonic cardiac manipulation has emerged with the use of optical methods for noninvasive cardiodynamic control. Specifically, optogenetics has been shown to control embryonic heartbeat using a variety of stimulation frequencies of pulsed light. This study aims to investigate cardiac contractions using continuous-wave optogenetic light stimulation. Mouse embryos expressing the light-sensitive transmembrane protein Channelrhodopsin-2 (ChR2), were generated to enable optogenetic manipulation of cardiodynamics. Upon activation with blue light (473nm), the channel opens to allow an influx of sodium ions to trigger an action potential. The effect of continuous-wave stimulation was investigated in two genetic mouse crosses. ChR2 expression in embryonic hearts was achieved using the early cardiomyocyte specific Cre line, Nkx2.5-Cre. Global expression of ChR2 was achieved using the ubiquitous Cre line, CMV-Cre. Embryos at embryonic day (E) 8.5 were dissected live and imaged in static culture. In response to continuous-wave stimulation at distinct cardiac regions, different contractile patterns were observed. This study suggests a potential to use continuous wave optogenetic stimulation for quick identification and investigation of developmental origin of cardiac cell populations in addition to previously established noninvasive and reversible manipulation of mouse embryo cardiodynamics.

Speaker

Deirdre Scully
Baylor College of Medicine
United States of America

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