Variation in protein coding genes identifies information flow as a contributor to animal complexity

Across the metazoans there is a trend towards greater organismal complexity. How complexity is generated, however, is uncertain. Since and humans have approximately the same number of genes, the explanation will depend on how genes are used, rather than their absolute number. Functional diversity is a measure that quantifies the isoforms, domains and paralogues of a gene. In this paper we determine functional diversity for each protein-coding gene in the human genome and its orthologues across eight commonly used model organisms. From this we derive the Compx list of genes that correlate positively with their increase in cell-type number. We then select genes common to the Compx list and the ExAC list, whose genes show minimal variation across many human genomes, and identify genes with common functions, notably in chromatin structure, RNA splicing, vesicular transport and ubiquitin-mediated protein degradation. Together these functions reveal that information flow within the cell relates to cell-type number, used as a measure of organismal complexity.