Da. Rappolee et al., HEPATOCYTE GROWTH-FACTOR AND ITS RECEPTOR ARE EXPRESSED IN CARDIAC MYOCYTES DURING EARLY CARDIOGENESIS, Circulation research, 78(6), 1996, pp. 1028-1036
In the mouse, the heart primordium arises when mesoderm is set aside d
uring gastrulation, is induced by pharyngeal endoderm, migrates ventra
lly to the midline of the embryo, forms a tube, and begins beating. Li
ttle is known of the molecular mechanisms that mediate the determinati
on, mitosis, differentiation, and migration that lead to the beating h
eart. Transcripts for hepatocyte growth factor/scatter factor (HGF) an
d its receptor are coexpressed transiently and dynamically in the prem
yocardium but not in other heart progenitor cells. Transcripts for HGF
ligand and receptor are first detected before cardiac function and lo
oping and persist through the first looping stage, when heart-morpholo
gy begins to elaborate. HGF ligand and receptor mRNA are detectable af
ter the putative heart transcription factor, Csx/Nkx2-5, and concomita
ntly with the heart structural gene, cardiac actin. HGF receptor mRNA
is detected in the mesoderm of the headfold stage and persists in myoc
ardial precursors of the ventricles and atria (but not in the outflow
tract smooth muscle cells) through the 14-somite stage at approximate
to 8.75 days after fertilization (day E8.75). At the headfold stage, b
etween E7.5 and E8.0, HGF receptor mRNA was detected in myocardial cel
ls before fusion at the ventral midline. HGF ligand and receptor mRNA
transcripts are coexpressed in the embryo, except in the headfold stag
e (when only the HGF receptor can be detected) and in the heart at the
14- to 18-somite stage (when only HGF ligand can be detected). The dy
namic pattern of coexpression suggests an autoregulatory role for HGF
and its receptor in early heart development.