Calsarcin-1 deficient mice develop dilated cardiomyopathy (DCM) phenotype in 
pure C57BL/6 genetic background (Cs1-ko) despite severe contractile dysfunction 
and robust activation of fetal gene program. Here we performed a microRNA 
microarray to identify the molecular causes of this cardiac phenotype that 
revealed the dysregulation of several microRNAs including miR-301a, which was 
highly downregulated in Cs1-ko mice compared to the wild-type littermates. 
Cofilin-2 (Cfl2) was identified as one of the potential targets of miR-301a 
using prediction databases, which we validated by luciferase assay and mutation 
of predicted binding sites. Furthermore, expression of miR-301a contrastingly 
regulated Cfl2 expression levels in neonatal rat ventricular cardiomyocytes 
(NRVCM). Along these lines, Cfl2 was significantly upregulated in Cs1-ko mice, 
indicating the physiological association between miR-301a and Cfl2 in vivo. 
Mechanistically, we found that Cfl2 activated serum response factor response 
element (SRF-RE) driven luciferase activity in neonatal rat cardiomyocytes and 
in C2C12 cells. Similarly, knockdown of miR301a activated, whereas, its 
overexpression inhibited the SRF-RE driven luciferase activity, further 
strengthening physiological interaction between miR-301a and Cfl2. 
Interestingly, the expression of SRF and its target genes was strikingly 
increased in Cs1-ko suggesting a possible in vivo correlation between expression 
levels of Cfl2/miR-301a and SRF activation, which needs to be independently 
validated. In summary, our data demonstrates that miR-301a regulates Cofilin-2 
in vitro in NRVCM, and in vivo in Cs1-ko mice. Our findings provide an 
additional and important layer of Cfl2 regulation, which we believe has an 
extended role in cardiac signal transduction and dilated cardiomyopathy 
presumably due to the reported involvement of Cfl2 in these mechanisms.