Pluto Bioinformatics

GSE61734: mRNA- and RISC-sequencing of mouse hearts overexpressing miR-378a

Bulk RNA sequencing

Rationale: MicroRNAs play key roles in hypertrophic stress responses. miR-378(-3p) is a highly abundant, cardiomyocyte-enriched microRNA whose downregulation in pressure-overload has been suggested as detrimental to the heart. Previous studies have utilized systemic anti-miR or microRNA-encoding virus administration, and thus questions regarding the cardiomyocyte-autonomous roles of miR-378 remain. Objective: To examine whether persistent overexpression of miR-378 in cardiomyocytes alters the phenotype of the unstressed heart, whether its overexpression is beneficial or deleterious in the setting of pressure-overload, and to comprehensively identify its cardiomyocyte-specific effects on mRNA regulation. Methods and Results: Cardiac function was compared in young (10-12 week-old) mice overexpressing miR-378 in the heart under the control of the Myh6 promoter (alphaMHC-miR-378 mice), in older (40 week-old) mice and their age-matched wild-type controls. Older alphaMHC-miR-378 mice exhibited decreased fractional shortening and modest chamber dilation with an increase in cardiomyocyte length. When subjected to pressure-overload, cardiomyocyte length was increased in young alphaMHC-miR-378 mice, but fractional shortening declined precipitously over two weeks. Transcriptome profiling of wild-type and alphaMHC-miR-378 hearts in unstressed and pressure-overload conditions revealed dysregulation of several upstream metabolic and mitochondrial genes in alphaMHC-miR-378 hearts, compromising the reprogramming that occurs during early adaptation to pressure overload. Ago2 immunoprecipitation with mRNA sequencing revealed novel miR-378 cardiac mRNA targets including Akt1 and Epac2 and demonstrated the contextual nature of previously described miR-378 targeting events. Conclusions: Long-term upregulation of miR-378 levels in the heart is not innocuous and exacerbates contractile dysfunction in pressure-overload hypertrophy through numerous signaling mechanisms. SOURCE: Scot,J,Matkovich (smatkovich@gmail.com) - Washington University School of Medicine