Atrial and Sinoatrial Node Development in the Zebrafish Heart

“…In zebrafish, the SAN is found in a ring-like structure at the venous pole of the heart (the border between the venous sinus and the atrium), embedded within the leaflets of the sinoatrial valve (Arrenberg et al, 2010;Tessadori et al, 2012;Stoyek et al, 2015Stoyek et al, , 2016Abu Nahia et al, 2021). Its development parallels that of the mammalian SAN, occurring from isl1-, tbx-, bmp4-, and hcn4-expressing cells under the control of shox2 and facilitated by the suppression of nkx2.5 through Wnt signalling (Burkhard et al, 2017;Martin and Waxman, 2021;Minhas et al, 2021). The first indication of the currents involved in zebrafish SAN automaticity came from the discovery of a mutation (slow mo) that caused a reduction in HR by affecting a hyperpolarisation-activated inward current with similar properties to I f (Baker et al, 1997;Warren et al, 2001).…”