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Human microRNAs originated from two periods at accelerated rates in mammalian evolution

Hisakazu Iwama1, Kiyohito Kato, Hitomi Imachi

  • 1Life Science Research Center, Kagawa University, Kita-gun, Kagawa, Japan. iwama@med.kagawa-u.ac.jp

Molecular Biology and Evolution
|November 23, 2012
PubMed

Insights

Human microRNA (miRNA) gene evolution shows two major origin peaks, with most originating during the hominoid lineage. Newer miRNA genes generally have lower expression levels.

Area of Science:

  • Evolutionary biology
  • Genomics
  • Molecular biology

Background:

  • MicroRNAs (miRNAs) are crucial noncoding RNAs regulating gene expression post-transcriptionally.
  • Evolutionary dynamics of miRNA gene repertoires are not fully understood.
  • Identifying origins of human miRNA genes provides insights into mammalian evolution.

Purpose of the Study:

  • To systematically determine the evolutionary periods of origin for human microRNA genes.
  • To investigate the rates of miRNA gene origination across mammalian evolution.
  • To correlate miRNA gene age with expression levels.

Main Methods:

  • Analysis of 1,433 human miRNA genes using genome alignments of 38 species.
  • Phylogenetic analysis to estimate evolutionary periods of miRNA gene origin.
  • Correlation analysis between miRNA gene age and expression levels.

Main Results:

  • Two significant accelerated periods of human miRNA gene origination were identified.
  • The most accelerated rate occurred during the early hominoid lineage (28% of human miRNAs).
  • A general trend of decreasing miRNA expression with younger gene age was observed, with a notable exception during the hominoid lineage.

Conclusions:

  • The majority of human miRNA genes originated relatively recently in mammalian evolution, particularly within the hominoid lineage.
  • Recent miRNA gene acquisition is associated with lower expression, but the hominoid period shows increased functional acquisition.
  • Understanding miRNA gene evolution offers insights into species-specific genetic innovations.

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