Purine-mediated signalling triggers eye development

• Published in: Nature (London) 2007-10, Vol.449 (7165), p.1058-1062
• Main Authors: Bhamra, Surinder, Jones, Elizabeth A, Dale, Nicholas, Massé, Karine, Eason, Robert
• Format: Article
• Language: English
• Subjects: Adenosine diphosphate; Adenosine Diphosphate - metabolism; Adenosine triphosphatase; Adenosine Triphosphatases - deficiency; Adenosine Triphosphatases - genetics; Adenosine Triphosphatases - metabolism; Adenosine Triphosphate - metabolism; Animals; ATP; Biological and medical sciences; Choristoma - genetics; Choristoma - metabolism; Chromosomes; Embryo, Nonmammalian - embryology; Embryo, Nonmammalian - metabolism; Eye; Eye - embryology; Eye - metabolism; Eye and associated structures. Visual pathways and centers. Vision; Eye Proteins - genetics; Eye Proteins - metabolism; Eyes & eyesight; Fundamental and applied biological sciences. Psychology; Gene expression; Gene Expression Regulation, Developmental; Genetic aspects; Health aspects; Homeobox Protein SIX3; Homeodomain Proteins - genetics; Homeodomain Proteins - metabolism; Humanities and Social Sciences; Invertebrates; letter; Medical examination; Molecular Sequence Data; multidisciplinary; Nerve Tissue Proteins - genetics; Nerve Tissue Proteins - metabolism; Paired Box Transcription Factors - genetics; Paired Box Transcription Factors - metabolism; PAX6 Transcription Factor; Phenotype; Purines; Purines - metabolism; Receptors, Purinergic P2 - deficiency; Receptors, Purinergic P2 - genetics; Receptors, Purinergic P2 - metabolism; Receptors, Purinergic P2Y1; Repressor Proteins - genetics; Repressor Proteins - metabolism; Science; Science (multidisciplinary); Signal Transduction; Vertebrates; Vertebrates: nervous system and sense organs; Xenopus laevis - embryology; Xenopus laevis - genetics; Xenopus laevis - metabolism; Xenopus Proteins - genetics; Xenopus Proteins - metabolism
• ISSN: 0028-0836; 1476-4687
• DOI: 10.1038/nature06189

A conserved network of eye field transcription factors (EFTFs) underlies the development of the eye in vertebrates and invertebrates. To direct eye development, Pax6, a key gene in this network, interacts with genes encoding other EFTFs such as Rx1 and Six3 (refs 4-6). However, the mechanisms that control expression of the EFTFs remain unclear. Here we show that purine-mediated signalling triggers both EFTF expression and eye development in Xenopus laevis. Overexpression of ectonucleoside triphosphate diphosphohydrolase 2 (E-NTPDase2), an ectoenzyme that converts ATP to ADP, caused ectopic eye-like structures, with occasional complete duplication of the eye, and increased expression of Pax6, Rx1 and Six3. In contrast, downregulation of endogenous E-NTPDase2 decreased Rx1 and Pax6 expression. E-NTPDase2 therefore acts upstream of these EFTFs. To test whether ADP (the product of E-NTPDase2) might act to trigger eye development through P2Y1 receptors, selective in Xenopus for ADP, we simultaneously knocked down expression of the genes encoding E-NTPDase2 and the P2Y1 receptor. This could prevent the expression of Rx1 and Pax6 and eye formation completely. We next measured ATP release in the presumptive eye field, demonstrating a transient release of ATP at a time that could plausibly trigger (once converted to ADP) expression of the EFTFs. This surprising role for transient purine-mediated signalling in eye development may be widely conserved, because alterations to the locus of E-NTPDase2 on human chromosome 9 cause severe head and eye defects, including microphthalmia. Our results suggest a new mechanism for the initiation of eye development.