Study On The Mechanism Of Epigenetic Regulator Setdb1b And Atf7ip In Cardiac Development

The heart is the first organ to form and function during embryogenesis.Induced by regulatory signals,cells originating in lateral plate mesoderm were specialized into cardiac precursor cells,and subsequently differentiated into myocardial and endocardial cells.After morphological remodeling and growth,the functional heart with complex structure is formed.Differentiation and proliferation of cardiomyocytes is the key link of heart development.Abnormal heart development often leads to fetal death or congenital heart disease（CHD）and is the leading cause of non-infectious infant death worldwide.In recent years,epigenetics has provided a new perspective for the study of heart development.As a component of epigenetic modification,H3K9me3（histone H3 lysine 9 trimethylation）is required in transcriptional regulation and heterochromatin formation,which plays an important role in cell fate determination and lineage differentiation.At present,the deposition and erasure of H3K9me3 and its crosstalk with different epigenetic modification during heart development is still remain elusive.In this study,zebrafish was used as model organism to study the function and mechanism of histone H3K9 methyltransferase Setdb1b and epigenetic regulatory factor Atf7ip in cardiac development.We firstly constructed the setdb1b mutant lines using CRISPR/Cas9 technique to explore the contribution of Setdb1b in heart development.The results indicated that setdb1b deletion resulted in cardiac malformation and embryonic lethal.By exploring the effects of Setdb1b on cardiomyocyte differentiation and proliferation,we found that setdb1b deletion had no effect on the specification of early cardiac progenitor cells,but could inhibit cardiomyocytes differentiation and heart looping,thus leading to cardiac malformation.Atf7ip is a regulator of Setdb1b,phenotypes observed after the loss of atf7ip are similar to the loss-of-function phenotypes for setdb1b.In addition,overexpression of setdb1b and atf7ip in atf7ip^-/-embryos rescued abnormal cardiac phenotypes.At the molecular level,we verified the interaction between Atf7ip and Setdb1b,and found that knockout of setdb1b or atf7ip in zebrafish resulted in a decrease in Setdb1b-dependent H3K9me3 level.In summary,we identified the role of epigenetic regulator Setdb1b and Atf7ip in cardiac development.By interacting with Atf7ip,histone methyltransferase Setdb1b mediate H3K9me3 level of genes associated with heart development,Thus offering fundamental basis for further analysis of Setdb1b/Atf7ip mediated histone methylation in cardiac development.