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Explosive expansion of betagamma-crystallin genes in the ancestral vertebrate.

ABSTRACT: In jawed vertebrates, betagamma-crystallins are restricted to the eye lens and thus excellent markers of lens evolution. These betagamma-crystallins are four Greek key motifs/two domain proteins, whereas the urochordate betagamma-crystallin has a single domain. To trace the origin of the vertebrate betagamma-crystallin genes, we searched for homologues in the genomes of a jawless vertebrate (lamprey) and of a cephalochordate (lancelet). The lamprey genome contains orthologs of the gnathostome betaB1-, betaA2- and gammaN-crystallin genes and a single domain gammaN-crystallin-like gene. It contains at least two gamma-crystallin genes, but lacks the gnathostome gammaS-crystallin gene. The genome also encodes a non-lenticular protein containing betagamma-crystallin motifs, AIM1, also found in gnathostomes but not detectable in the uro- or cephalochordate genome. The four cephalochordate betagamma-crystallin genes found encode two-domain proteins. Unlike the vertebrate betagamma-crystallins but like the urochordate betagamma-crystallin, three of the predicted proteins contain calcium-binding sites. In the cephalochordate betagamma-crystallin genes, the introns are located within motif-encoding region, while in the urochordate and in the vertebrate betagamma-crystallin genes the introns are between motif- and/or domain encoding regions. Coincident with the evolution of the vertebrate lens an ancestral urochordate type betagamma-crystallin gene rapidly expanded and diverged in the ancestral vertebrate before the cyclostomes/gnathostomes split. The beta- and gammaN-crystallin genes were maintained in subsequent evolution, and, given the selection pressure imposed by accurate vision, must be essential for lens function. The gamma-crystallin genes show lineage specific expansion and contraction, presumably in adaptation to the demands on vision resulting from (changes in) lifestyle.

SUBMITTER: Kappe G

PROVIDER: S-EPMC2929430 | biostudies-literature | 2010 Sep

REPOSITORIES: biostudies-literature

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Explosive expansion of betagamma-crystallin genes in the ancestral vertebrate.

Kappé Guido G Purkiss Andrew G AG van Genesen Siebe T ST Slingsby Christine C Lubsen Nicolette H NH

Journal of molecular evolution 20100820 3

In jawed vertebrates, betagamma-crystallins are restricted to the eye lens and thus excellent markers of lens evolution. These betagamma-crystallins are four Greek key motifs/two domain proteins, whereas the urochordate betagamma-crystallin has a single domain. To trace the origin of the vertebrate betagamma-crystallin genes, we searched for homologues in the genomes of a jawless vertebrate (lamprey) and of a cephalochordate (lancelet). The lamprey genome contains orthologs of the gnathostome be ...[more]

PMID: 20725717

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Project description:In vertebrates, non-lens betagamma-crystallins are widely expressed in various tissues, but their functions are unknown. The molecular mechanisms of trefoil factors, initiators of mucosal healing and being greatly involved in tumorigenesis, have remained elusive.A naturally existing 72-kDa complex of non-lens betagamma-crystallin (alpha-subunit) and trefoil factor (beta-subunit), named betagamma-CAT, was identified from frog Bombina maxima skin secretions. Its alpha-subunit and beta-subunit (containing three trefoil factor domains), with a non-covalently linked form of alphabeta(2), show significant sequence homology to ep37 proteins, a group of non-lens betagamma-crystallins identified in newt Cynops pyrrhogaster and mammalian trefoil factors, respectively. betagamma-CAT showed potent hemolytic activity on mammalian erythrocytes. The specific antiserum against each subunit was able to neutralize its hemolytic activity, indicating that the two subunits are functionally associated. betagamma-CAT formed membrane pores with a functional diameter about 2.0 nm, leading to K(+) efflux and colloid-osmotic hemolysis. High molecular weight SDS-stable oligomers (>240-kDa) were detected by antibodies against the alpha-subunit with Western blotting. Furthermore, betagamma-CAT showed multiple cellular effects on human umbilical vein endothelial cells. Low dosages of betagamma-CAT (25-50 pM) were able to stimulate cell migration and wound healing. At high concentrations, it induced cell detachment (EC(50) 10 nM) and apoptosis. betagamma-CAT was rapidly endocytosed via intracellular vacuole formation. Under confocal microscope, some of the vacuoles were translocated to nucleus and partially fused with nuclear membrane. Bafilomycin A1 (a specific inhibitor of the vacuolar-type ATPase) and nocodazole (an agent of microtuble depolymerizing), while inhibited betagamma-CAT induced vacuole formation, significantly inhibited betagamma-CAT induced cell detachment, suggesting that betagamma-CAT endocytosis is important for its activities.These findings illustrate novel cellular functions of non-lens betagamma-cyrstallins and action mechanism via association with trefoil factors, serving as clues for investigating the possible occurrence of similar molecules and action mechanisms in mammals.

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Explosive expansion of betagamma-crystallin genes in the ancestral vertebrate.

Publications

Explosive expansion of betagamma-crystallin genes in the ancestral vertebrate.

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