The ryanodine receptor modulates the spontaneous beating rate of cardiomyocytes during development.
In adult myocardium, the heartbeat originates from the sequential activation of ionic currents in pacemaker cells of the sinoatrial node. Ca(2+) release via the ryanodine receptor (RyR) modulates the rate at which these cells beat. In contrast, the mechanisms that regulate heart rate during early cardiac development are poorly understood. Embryonic stem (ES) cells can differentiate into spontaneously contracting myocytes whose beating rate increases with differentiation time. These cells thus offer an opportunity to determine the mechanisms that regulate heart rate during development. Here we show that the increase in heart rate with differentiation is markedly depressed in ES cell-derived cardiomyocytes with a functional knockout (KO) of the cardiac ryanodine receptor (RyR2). KO myocytes show a slowing of the rate of spontaneous diastolic depolarization and an absence of calcium sparks. The depressed rate of pacemaker potential can be mimicked in wild-type myocytes by ryanodine, and rescued in KO myocytes with herpes simplex virus (HSV)-1 amplicons containing full-length RyR2. We conclude that a functional RyR2 is crucial to the progressive increase in heart rate during differentiation of ES cell-derived cardiomyocytes, consistent with a mechanism that couples Ca(2+) release via RyR before an action potential with activation of an inward current that accelerates membrane depolarization.
Yang
Huang-Tian
HT
National Institute on Aging, Laboratory of Cardiovascular Science, National Institutes of Health, Baltimore, MD 21224, USA.
Tweedie
David
D
Wang
Su
S
Guia
Antonio
A
Vinogradova
Tatiana
T
Bogdanov
Konstantin
K
Allen
Paul D
PD
Stern
Michael D
MD
Lakatta
Edward G
EG
Boheler
Kenneth R
KR
D000200:Action Potentials; D000818:Animals; D020013:Calcium Signaling / Q000502:physiology; D002454:Cell Differentiation; D002478:Cells, Cultured; D005318:Fetal Heart / Q000166:cytology / Q000196:embryology / Q000502:physiology*; D005822:Genetic Vectors; D006339:Heart Rate / Q000502:physiology*; D018259:Herpesvirus 1, Human / Q000235:genetics; D051379:Mice; D018345:Mice, Knockout; D019837:Ryanodine Receptor Calcium Release Channel / Q000172:deficiency / Q000235:genetics / Q000502:physiology*; D013234:Stem Cells / Q000166:cytology / Q000502:physiology
D019837:Ryanodine Receptor Calcium Release Channel