Shimeld, Sebastian M. and Purkiss, Andrew G. and Dirks, R.P.H. and Bateman, Orval A. and Slingsby, Christine and Lubsen, N.H. (2005) Urochordate beta gamma-crystallin and the evolutionary origin of the vertebrate eye lens. Current Biology 15 (18), pp. 1684-1689. ISSN 0960-9822.
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Abstract
A refracting lens is a key component of our image-forming camera eye; however, its evolutionary origin is unknown because precursor structures appear absent in nonvertebrates [1]. The vertebrate beta gamma-crystallin genes encode abundant structural proteins critical for the function of the lens [2]. We show that the urochordate Ciona intestinalis, which split from the vertebrate lineage before the evolution of the lens, has a single gene coding for a single domain monomeric beta gamma-crystallin. The crystal structure of Ciona beta gamma-crystallin is very similar to that of a vertebrate beta gamma-crystallin domain, except for paired, occupied calcium binding sites. The Ciona beta gamma-crystallin is only expressed in the palps and in the otolith, the pigmented sister cell of the light-sensing ocellus. The Ciona beta gamma-crystallin promoter region targeted expression to the visual system, including lens, in transgenic Xenopus tadpoles. We conclude that the vertebrate beta gamma-crystallins evolved from a single domain protein already expressed in the neuroectoderm of the prevertebrate ancestor. The conservation of the regulatory hierarchy controlling beta gamma-crystallin expression between organisms with and without a lens shows that the evolutionary origin of the lens was based on co-option of pre-existing regulatory circuits controlling the expression of a key structural gene in a primitive light-sensing system.
Metadata
| Item Type: | Article |
|---|---|
| Keyword(s) / Subject(s): | sponge geodia-cydonium, ciona-intestinalis, brain, proteins, photoreceptors, superfamily, chordate |
| School: | Birkbeck Faculties and Schools > Faculty of Science > School of Natural Sciences |
| Research Centres and Institutes: | Structural Molecular Biology, Institute of (ISMB) |
| Depositing User: | Sandra Plummer |
| Date Deposited: | 24 Jan 2006 |
| Last Modified: | 02 Aug 2023 16:46 |
| URI: | https://eprints.bbk.ac.uk/id/eprint/302 |
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