Cardiovascular Mettl3 Deficiency Causes Congenital Cardiac Defects and Postnatal Lethality in Mice
N6-methyladenosine (m6A) is the most common epigenetic modification of RNA, but whether m6A RNA methylation modulates cardiovascular development or congenital heart diseases (CHDs) has not been determined. The published high-throughput sequencing data suggested that transcripts of genes related to CHDs were prone to m6A modification, while the expression of methyltransferase-like 3 (METTL3)-involved methyltransferase complex was downregulated in mouse embryonic hearts following prenatal alcohol exposure as a critical CHD risk factor, indicating the association of insufficient m6A RNA methylation with CHDs. Using cardiovascular-specific Mettl3 knockout mice (Tagln-Cre; Mettl3flox/flox), we observed that cardiovascular Mettl3 deficiency resulted in postnatal lethality and profound congenital cardiac defects, including left pulmonary stenosis, ventricular septal defects and right ventricular hypoplasia. The m6A-specific methylated RNA-immunoprecipitation sequencing identified Sox4, Sox11 and Mef2a, the critical transcription factors involved in right ventricle and outflow tract development, were the regulatory targets of METTL3-catalyzed m6A RNA methylation. Mettl3 deficiency-caused insufficient m6A RNA methylation downregulated the expression of SOX4, SOX11 and MEF2A in mouse embryonic hearts. In conclusion, cardiovascular Mettl3 deficiency directly led to congenital cardiac defects by downregulating the m6A-dependent expression of Mef2a, Sox4 and Sox11. METTL3-catalyzed m6A RNA methylation may become a potential target for the prevention and treatment of CHDs. Overall design: MeRIP (m6A immunoprecipitation) for right ventricle and outflow tract tissues of Tagln-Cre; Mettl3flox/flox mice and Mettl3flox/flox mice on embryonic day 10.5 to 11.5