Xenopus pax6 mutants affect eye development and other organ systems, and have phenotypic similarities to human aniridia patients.
Mutations in the Pax6 gene cause ocular defects in both vertebrate and invertebrate animal species, and the disease aniridia in humans. Despite extensive experimentation on this gene in multiple species, including humans, we still do not understand the earliest effects on development mediated by this gene. This prompted us to develop pax6 mutant lines in Xenopus tropicalis taking advantage of the utility of the Xenopus system for examining early development and in addition to establish a model for studying the human disease aniridia in an accessible lower vertebrate. We have generated mutants in pax6 by using Transcription Activator-Like Effector Nuclease (TALEN) constructs for gene editing in X. tropicalis. Embryos with putative null mutations show severe eye abnormalities and changes in brain development, as assessed by changes in morphology and gene expression. One gene that we found is downregulated very early in development in these pax6 mutants is myc, a gene involved in pluripotency and progenitor cell maintenance and likely a mediator of some key pax6 functions in the embryo. Changes in gene expression in the developing brain and pancreas reflect other important functions of pax6 during development. In mutations with partial loss of pax6 function eye development is initially relatively normal but froglets show an underdeveloped iris, similar to the classic phenotype (aniridia) seen in human patients with PAX6 mutations. Other eye abnormalities observed in these froglets, including cataracts and corneal defects, are also common in human aniridia. The frog model thus allows us to examine the earliest deficits in eye formation as a result of pax6 lesions, and provides a useful model for understanding the developmental basis for the aniridia phenotype seen in humans.
Department of Biology, University of Virginia, Charlottesville, VA 22904, USA.
Takuya
T
Nakayama
Department of Biology, University of Virginia, Charlottesville, VA 22904, USA.
Marilyn
M
Fisher
Division of Embryology and Genetics, Institute for Amphibian Biology, Hiroshima University, Higashihiroshima 739-8526, Japan.
Keisuke
K
Nakajima
Department of Biology, University of Virginia, Charlottesville, VA 22904, USA.
Akinleye O
AO
Odeleye
Department of Biology, University of Virginia, Charlottesville, VA 22904, USA.
Keith B
KB
Zimmerman
Department of Biology, University of Virginia, Charlottesville, VA 22904, USA.
Margaret B
MB
Fish
Division of Embryology and Genetics, Institute for Amphibian Biology, Hiroshima University, Higashihiroshima 739-8526, Japan.
Yoshio
Y
Yaoita
Department of Cellular Biology, University of Georgia, Athens, GA, 30602, USA.
Jena L
JL
Chojnowski
Department of Cellular Biology, University of Georgia, Athens, GA, 30602, USA.
James D
JD
Lauderdale
Department of Ophthalmology, University of Virginia School of Medicine, Charlottesville, VA 22908, USA.
Peter A
PA
Netland
Department of Biology, University of Virginia, Charlottesville, VA 22904, USA; Department of Ophthalmology, University of Virginia School of Medicine, Charlottesville, VA 22908, USA. Electronic address: rmg9p@virginia.edu.
Robert M
RM
Grainger
D000818:Animals; D015783:Aniridia / Q000196:embryology* / Q000235:genetics* / Q000473:pathology; D001483:Base Sequence; D018389:Codon, Nonsense; D004247:DNA / Q000235:genetics; D004195:Disease Models, Animal; D005091:Exons; D005123:Eye / Q000196:embryology / Q000254:growth & development; D005136:Eye Proteins / Q000235:genetics* / Q000502:physiology*; D018390:Gene Targeting; D018398:Homeodomain Proteins / Q000235:genetics* / Q000502:physiology*; D006801:Humans; D008969:Molecular Sequence Data; D016296:Mutagenesis; D009154:Mutation; D000071841:PAX6 Transcription Factor; D051761:Paired Box Transcription Factors / Q000172:deficiency / Q000235:genetics* / Q000502:physiology*; D010641:Phenotype; D012097:Repressor Proteins / Q000172:deficiency / Q000235:genetics* / Q000502:physiology*; D013045:Species Specificity; D014981:Xenopus / Q000196:embryology* / Q000235:genetics*
D018389:Codon, Nonsense; D005136:Eye Proteins; D018398:Homeodomain Proteins; D000071841:PAX6 Transcription Factor; C000605730:PAX6 protein, human; D051761:Paired Box Transcription Factors; D012097:Repressor Proteins; D004247:DNA
Lens; Neural patterning; Retina; Transcription Activator-Like Effector Nuclease (TALEN); Xenopus tropicalis