Cardiovascular Mettl3 Deficiency Causes Congenital Cardiac Defects and Postnatal Lethality in Mice.

N(6)-methyladenosine (m(6)A) is the most common epigenetic modification of RNA, but whether m(6)A 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 m(6)A 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 m(6)A RNA methylation with CHDs. Using cardiovascular-specific Mettl3 knockout mice (Tagln-Cre; Mettl3(flox/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 m(6)A-specific methylated RNA-immunoprecipitation sequencing identified Sox4, Sox11, and Mef2a, the critical transcription factors involved in the right ventricle and outflow tract development, were the regulatory targets of METTL3-catalyzed m(6)A RNA methylation. Mettl3 deficiency-caused insufficient m(6)A 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 m(6)A-dependent expression of Mef2a, Sox4, and Sox11. METTL3-catalyzed m(6)A RNA methylation may become a potential target for preventing and treating CHDs.