SRF overexpression affected the expression of cardiac miRNAs. 4A. The expression of 6 miRNAs in adult wild-type vs SRF-Tg hearts was confirmed by real-time PCR. The data showed that the miRNA levels in SRF-Tg were altered significantly compared to that of wild-type mice (p < 0.05*, n = 3). 4B. Altered expression of microRNAs occurred at as early as 7 days of age, and continued to 6 months of age in SRF Tg mice. miR-21 was increased in the heart of SRF Tg mice, but both miR-1 and miR-133a were decreased in the heart of SRF Tg mice compared to age-matched wild-type mice. The down-regulation of miR-1 correlates closely with that of miR-133a in SRF-Tg at various time points from 7 days to 6 months of age (p < 0.05, n = 3 for all time points, except n = 6 for miR-21 at 6 months).