microRNAs (miRNAs) are a class of small non-coding RNAs that are 18-25 nucleotides (nt) in length and
negatively regulate gene expression post-transcriptionally. miRNAs are known to mediate myriad processes and pathways.
While many miRNAs are expressed ubiquitously, some are expressed in a tissue specific manner. miR-133 is one of
the most studied and best characterized miRNAs to date. Specifically expressed in muscles, it has been classified as myomiRNAs
and is necessary for proper skeletal and cardiac muscle development and function. Genes encoding miR-133
(miR-133a-1, miR-133a-2 and miR-133b) are transcribed as bicistronic transcripts together with miR-1-2, miR-1-1, and
miR-206, respectively. However, they exhibit opposing impacts on muscle development. miR-133 gets involved in muscle
development by targeting a lot of genes, including SFR, HDAC4, cyclin D2 and so on. Its aberrant expression has been
linked to many diseases in skeletal muscle and cardiac muscle such as cardiac hypertrophy, muscular dystrophy, heart
failure, cardiac arrhythmia. Beyond the study in muscle, miR-133 has been implicated in cancer and identified as a key
factor in cancer development, including bladder cancer, prostate cancer and so on. Much more attention has been drawn to
the versatile molecular functions of miR-133, making it a truly valuable therapeutic gene in miRNA-based gene therapy.
In this review, we identified and summarized the results of studies of miR-133 with emphasis on its function in human
diseases in muscle and cancer, and highlighted its therapeutic value. It might provide researchers a new insight into the
biological significance of miR-133.