Evolutionary origins of Pax6 control of crystallin genes

Ales Cvekl, Yilin Zhao, Rebecca McGreal, Qing Xie, Xun Gu, Deyou Zheng

Research output: Contribution to journalArticlepeer-review

20 Scopus citations


The birth of novel genes, including their cell-specific transcriptional control, is a major source of evolutionary innovation. The lens-preferred proteins, crystallins (vertebrates: a-and b/c-crystallins), provide a gateway to study eye evolution. Diversity of crystallins was thought to originate from convergent evolution through multiple, independent formation of Pax6/PaxB-binding sites within the promoters of genes able to act as crystallins. Here, we propose that aB-crystallin arose from a duplication of small heat shock protein (Hspb1-like) gene accompanied by Pax6-site and heat shock element (HSE) formation, followed by another duplication to generate the aA-crystallin gene in which HSE was converted into another Pax6-binding site. The founding b/c-crystallin gene arose from the ancestral Hspb1-like gene promoter inserted into a Ca2+-binding protein coding region, early in the cephalochordate/tunicate lineage. Likewise, an ancestral aldehyde dehydrogenase (Aldh) gene, through multiple gene duplications, expanded into a multigene family, with specific genes expressed in invertebrate lenses (X-crystallin/Aldh1a9) and both vertebrate lenses (g-crystallin/Aldh1a7 and Aldh3a1) and corneas (Aldh3a1). Collectively, the present data reconstruct the evolution of diverse crystallin gene families.

Original languageEnglish (US)
Pages (from-to)2075-2092
Number of pages18
JournalGenome Biology and Evolution
Issue number8
StatePublished - Aug 1 2017


  • Aldehyde dehydrogenase
  • Crystallin
  • Eye evolution
  • Heat shock responsive element
  • Lens
  • Pax6
  • Small heat shock protein

ASJC Scopus subject areas

  • Ecology, Evolution, Behavior and Systematics
  • Genetics


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