Evolutionary Origins of Pax6 Control of Crystallin Genes. (16th August 2017)

• Record Type: Journal Article
• Authors: Cvekl, Ales; Zhao, Yilin; McGreal, Rebecca; Xie, Qing; Gu, Xun; Zheng, Deyou
• Is Part Of: Genome biology and evolution. Volume 9:Number 8(2017:Aug.)
• Page Start: 2075
• Page End: 2092
• Publication Date: 2017-08-16
• Subjects: aldehyde dehydrogenase -- crystallin -- eye evolution -- heat shock responsive element -- lens -- Pax6 -- small heat shock protein; Genomics -- Periodicals; Genes -- Periodicals; 572.8605
• DOI: 10.1093/gbe/evx153
• Languages: English
• ISSNs: 1759-6653

Abstract

Abstract: The birth of novel genes, including their cell-specific transcriptional control, is a major source of evolutionary innovation. The lens-preferred proteins, crystallins (vertebrates: α- and β/γ-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 αB-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 αA-crystallin gene in which HSE was converted into another Pax6-binding site. The founding β/γ-crystallin gene arose from the ancestral Hspb1-like gene promoter inserted into a Ca 2+ -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 (Ω-crystallin/Aldh1a9) and both vertebrate lenses (η-crystallin/Aldh1a7 and Aldh3a1) and corneas (Aldh3a1). Collectively, the present data reconstruct the evolution of diverse crystallin gene families.