Distribution of acetylcholinesterase activity in the rat embryonic heart with reference to HNK-1 immunoreactivity in the conduction tissue

Abstract

Acetylcholinesterase (AChE) activity was topographically investigated in the presumptive cardiac conduction tissue regions visualized by HNK-1 immunoreactivity in rat embryos, and AChE-positive cells were examined with the electron microscope. On embryonic day (ED) 14.5, when HNK-1 was most intensely visualized, AChE activity could not be detected enzyme-histochemically in the conduction tissue regions, except in the ventricular trabeculae and part of the AV node. On ED 16.5, however, the AChE activity was clearly demonstrated in some parts of the developing conduction tissue. One exception was the AV node region, where an AChE-positive area was in close proximity to an area showing HNK-1 immunoreactivity but did not overlap. Furthermore, AChE activity was demonstrated predominantly in the ventricular trabeculae, including cardiac myocytes, but was rather weak in the atrium. With the electron microscope, AChE reaction products were observed predominantly intracellularly in both developing conduction tissue cells and developing ordinary myocytes, and no reactivity was found in neuronal components. From ED 18.5 until birth, both AChE activity and HNK-1 immunoreactivity faded away in the conduction tissue. Thus, transient AChE activity in the embryonic heart seems to be different from the developing adult form and may be related to a morphogenetic function in embryonic tissues, as proposed by other authors.

Functional characterization of cardiac progenitor cells and their derivatives in the embryonic heart post‐chamber formation

“…þ ANF þ cells were positive for AChE and Cx40, markers frequently found in the developing cardiac conduction cells (Nakamura et al, 1994;Moorman et al, 1998). The CPCs identified in the present study appear to be bipotential in nature similar to those identified by Wu et al in E9.5 mouse hearts (Wu et al, 2006).…”

“…We also found that the majority of Nkx2. (AChE) and Cx40, two markers known to be expressed in cardiac conduction cells (Nakamura et al, 1994;Moorman et al, 1998;Pashmforoush et al, 2004). We showed that Ca 2þ transients could be invoked in Nkx2.5 þ…”

Synergistic Roles of Neuregulin-1 and Insulin-like Growth Factor-I in Activation of the Phosphatidylinositol 3-Kinase Pathway and Cardiac Chamber Morphogenesis

“…As trabeculation of the ventricular wall may depend on NRG-1, expression of acetylcholinesterase (AchE), whose enzymatic activity in the embryonic rat heart is restricted to cardiomyocytes of the trabeculae of the ventricular wall, was selected to follow induced trabecular growth (31,32). Accordingly, we observed AchE mRNA in a restricted expression pattern coincident with the trabeculae and in continuity with the conotruncus at early stages of in utero mouse embryo development, E10 -E13 (data not shown).…”

Notch signaling plays a key role in cardiac cell differentiation

“…1C). HNK-1 antibody recognizes a complex carbohydrate moiety on the cell surface and has been used extensively as a marker for the ventricular conduction system in many species including chick, rat, rabbit and human (Aoyama et al, 1993;Aoyama et al, 1995;Chuck and Watanabe, 1997;Gorza et al, 1988;Ikeda et al, 1990;Luider et al, 1993;Nakagawa et al, 1993;Nakamura et al, 1994;Sakai et al, 1994;Verberne et al, 2000), and overlaps with another conduction system marker, Cx40 ( Supplementary Fig. 1S).…”