MicroRNAs (miRNAs) are small, non-coding RNA molecules that play a vital role in regulating gene expression. They are found in all eukaryotes, including animals, plants, and fungi, and are involved in a wide range of biological processes, including development, differentiation, and cell growth.

MiRNAs are short, single-stranded RNA molecules that are about 22 nucleotides in length. They are transcribed from DNA but are not translated into protein. Instead, they function by binding to specific target mRNA molecules and inhibiting their translation into protein or promoting their degradation.

MiRNAs play a critical role in gene regulation and are involved in many different cellular processes. They are involved in the regulation of a wide range of genes, including those involved in development, differentiation, cell growth, and apoptosis.


The discovery of miRNAs has revolutionized our understanding of gene regulation and has led to numerous scientific advances and practical applications. MiRNAs have been linked to a wide range of diseases, including cancer, cardiovascular disease, and neurodegenerative diseases, and are being studied as potential therapeutic targets.

Overall, miRNAs are a very important group of small RNA molecules that play a key role in controlling genes and have major effects on human health and disease.

What are microRNAs?

MicroRNA is a class of post-transcriptional regulators. They are short ~22 nucleotide RNA sequences that bind to complementary sequences in the 3’ UTR of multiple target mRNAs, usually resulting in their silencing. MicroRNAs target ~60% of all genes, are abundantly present in all human cells, and are able to repress hundreds of targets each.

History of MicroRNA

The discovery of microRNA (miRNA) can be traced back to the early 1990s, when researchers first identified small RNA molecules that were involved in the regulation of gene expression. In 1993, Andrew Fire and Craig Mello published a seminal paper describing the discovery of small RNA molecules that were able to interfere with the expression of specific genes in the nematode worm Caenorhabditis elegans. This discovery started the field of RNA interference (RNAi), and the small RNA molecules found in this study were later called small interfering RNAs (siRNAs).

In the years that followed, researchers began to uncover the role of small RNA molecules in other organisms, including plants and mammals. In 2000, a group of researchers led by Victor Ambros and Gary Ruvkun identified a class of small RNA molecules in C. elegans that was distinct from siRNAs and was involved in the regulation of gene expression at the post-transcriptional level. These molecules, which they named miRNA, were later found to be present in a variety of organisms, including humans.

Since their discovery, miRNAs have become an important area of study in the field of molecular biology and have been linked to a variety of biological processes and diseases. MiRNA has also been studied as a potential therapeutic target for the treatment of various diseases, and several miRNA-based therapies are currently in clinical trials.

Features of microRNA

These features, coupled with their conservation in organisms ranging from the unicellular algae Chlamydomonas reinhardtii to mitochondria, suggest they are a vital part of genetic regulation with ancient origins.

MicroRNAs were first discovered in 1993 by Victor Ambros, Rosalind Lee, and Rhonda Feinbaum during a study into development in the nematode Caenorhabditis elegans (C. elegans) regarding the gene lin-14.

What is microRNA? Special class Post-Transcriptional Regulators
  • MicroRNA (miRNA) is a small, non-coding RNA molecule that is involved in the regulation of gene expression.

  • MiRNA is typically 20–22 nucleotides in length and is synthesised from a hairpin-shaped precursor molecule known as a pri-miRNA.

  • MiRNA is found in animals, plants, and some viruses and plays a role in a variety of biological processes, including development, cell differentiation, and cell death.

  • MiRNA can inhibit the expression of specific genes by binding to complementary sequences in the mRNA of those genes and preventing their translation into proteins.

  • MiRNA can target multiple genes, and a single miRNA can have multiple targets, making it a powerful regulatory molecule.

  • miRNA expression can be controlled by many things, like environmental signals, signalling pathways, transcriptional and post-transcriptional mechanisms, and so on.

  • Dysregulation of miRNA expression has been linked to a number of diseases, such as cancer, heart disease, and diseases that damage nerve cells.

  • MiRNA has been looked at as a possible way to treat a number of diseases, and a number of therapies based on miRNA are currently in clinical trials. 

    Unfortunately, the rate of validation of microRNA targets is substantially more time consuming than that of predicting sequences and targets.

    • Due to their abundant presence and far-reaching potential, microRNAs have all sorts of functions in physiology, from cell differentiation, proliferation, apoptosis to the endocrine system, hematopoiesis, fat metabolism, limb morphogenesis.
    • They display different expression profiles from tissue to tissue, reflecting the diversity of cellular phenotypes and as such suggest a role in tissue differentiation and maintenance.

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