Biochemists illuminate mechanisms of organism complexity at the genetic level

By Mohamad Hamze

Researchers from the University of Portsmouth have published their findings regarding what they believe to be the reasons that certain organisms are more “complex” than others. It was previously well-documented that most multicellular organism genomes were similar in total number of genes, so Dr. Colin Sharpe and his team set out to discover other factors of organism complexity.

Genome studies of nine different animals revealed the varying presence of proteins that serve to interact with chromatin in the nucleus. These proteins were not found to regulate gene expression through direct interaction with the DNA, but rather through their ability “’to regulate the dynamic organization of chromatin in the nucleus as a component of animal complexity,”’ as Sharpe describes.

The NCOR gene – for the nuclear receptor co-repressor family of proteins – was compared in humans and in sea urchins and found to exhibit three factors that varied in complexity between the two organisms. First, the gene in humans is subjected to greater levels of gene duplication resulting in daughter genes that can take on multiple functions. Second, processing of the mRNA of the NCOR gene is less complex in sea urchins than in humans, where the mRNA is subjected to splicing that generates over 30 different RNA transcripts to the sea urchins’ one. Finally, the resultant proteins in humans exhibit more domains than those in sea urchins, which increase their potential for interaction with nuclear receptors.

This new understanding of the factors of complexity in different organisms could become a consideration for biochemists when choosing appropriate animal models in which to study cellular mechanisms of human disease.


University of Portsmouth. "Genes that separate humans from fruit flies found." ScienceDaily. ScienceDaily, 29 September 2017. 

Lopes Cardoso D, Sharpe C (2017) Relating protein functional diversity to cell type number identifies genes that determine dynamic aspects of chromatin organisation as potential contributors to organismal complexity. PLOS ONE 12(9): e0185409.