Abstract:

Objective To explore the relationship of the expression of transcriptional factor GATA4 in the heart-forming field and the foregut endoderm with the morphological development of the arterial pole of embryonic mouse heart.Methods Serial sections of mouse embryos on embryonic day(ED)7.5 to ED13, three embryos from each embryonic day, were stained immunohistochemically or immunofluorescently with antibodies against GATA4, Nkx2.5, insulin gene enhancer binding potein (ISL-1), α-smooth muscle actin and myosin heavy chain. The expression of GATA4 and phosphorylated histone H3(pHH3) were measured with Western blotting in the embryonic mouse hearts from ED11 to ED14. Results At ED7.5, positive cells for both transcription factors GATA4 and Nkx2.5 were found in the cardiogenic plate simultaneously. From ED8.5 to ED10, further expression of GATA4 and Nkx2.5 were detected in the splanchnic mesoderm of the dorsal wall of the pericardial cavity that constituted the second heart field(SHF). From ED11 to ED13, GATA4 and Nkx2.5 expressions were found descending from the reflection of dorsal pericardial wall with the distal pole of outflow tract to the base of the ascending aorta and pulmonary trunk. GATA4 expression was also detected in the foregut endoderm of ED11 to ED13 embryos. GATA4 and pHH3 expression in the embryonic mouse hearts reached the highest level between ED11 and ED13. Conclusion Transcription factor GATA4 shows the same expression pattern as that of Nkx2.5 during the early development of the embryonic mouse heart. Higher expression of GATA4 during crucial stages of heart morphogenesis suggests that GATA4 may play an important role in the proliferation of myocardial cells. The GATA4 expression in the foregut endoderm may be involved in the development of the SHF.

Key words: GATA4 , Heart-forming field , Endoderm , Immunohistochemistry , Western blotting , Mouse