title: Purine-mediated signalling triggers eye development.
abstract: 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.
authors.affiliation: Department of Biological Sciences, Warwick University, Coventry CV4 7AL, UK.
authors.forename: Karine
authors.initials: K
authors.lastname: Massé
authors.forename: Surinder
authors.initials: S
authors.lastname: Bhamra
authors.forename: Robert
authors.initials: R
authors.lastname: Eason
authors.forename: Nicholas
authors.initials: N
authors.lastname: Dale
authors.forename: Elizabeth A
authors.initials: EA
authors.lastname: Jones
mesh_terms: D000244:Adenosine Diphosphate / Q000378:metabolism; D000251:Adenosine Triphosphatases / Q000172:deficiency / Q000235:genetics / Q000378:metabolism; D000255:Adenosine Triphosphate / Q000378:metabolism; D000818:Animals; D002828:Choristoma / Q000235:genetics / Q000378:metabolism; D004625:Embryo, Nonmammalian / Q000196:embryology / Q000378:metabolism; D005123:Eye / Q000196:embryology* / Q000378:metabolism*; D005136:Eye Proteins / Q000235:genetics / Q000378:metabolism; D018507:Gene Expression Regulation, Developmental; D018398:Homeodomain Proteins / Q000235:genetics / Q000378:metabolism; D008969:Molecular Sequence Data; D009419:Nerve Tissue Proteins / Q000235:genetics / Q000378:metabolism; D000071841:PAX6 Transcription Factor; D051761:Paired Box Transcription Factors / Q000235:genetics / Q000378:metabolism; D010641:Phenotype; D011687:Purines / Q000378:metabolism*; D018048:Receptors, Purinergic P2 / Q000172:deficiency / Q000235:genetics / Q000378:metabolism; D058472:Receptors, Purinergic P2Y1; D012097:Repressor Proteins / Q000235:genetics / Q000378:metabolism; D015398:Signal Transduction; D029867:Xenopus Proteins / Q000235:genetics / Q000378:metabolism; D014982:Xenopus laevis / Q000196:embryology* / Q000235:genetics / Q000378:metabolism*; D000097607:Homeobox Protein SIX3
chemical_list: D000244:Adenosine Diphosphate; D000251:Adenosine Triphosphatases; D000255:Adenosine Triphosphate; D005136:Eye Proteins; D018398:Homeodomain Proteins; D009419:Nerve Tissue Proteins; D000071841:PAX6 Transcription Factor; D051761:Paired Box Transcription Factors; D011687:Purines; D018048:Receptors, Purinergic P2; D058472:Receptors, Purinergic P2Y1; D012097:Repressor Proteins; D029867:Xenopus Proteins; D000097607:Homeobox Protein SIX3; C546382:P2RY1 protein, human; C000605730:PAX6 protein, human; C524416:Rax protein, Xenopus; C027201:ectoATPase; C030985:purine