title: Pax7 and superior collicular polarity: insights from Pax6 (Sey) mutant mice.
abstract: Pax genes are important modulators of CNS development. Pax7 and Pax6 polarise the neural tube and regionalise the brain. Pax7 is pivotal in specifying the superior colliculus/tectum, an important centre for integration of visuomotor responses and a target for Pax6+ retinal ganglion cell axons during retinocollicular mapping. Whilst initial Pax7-specification of the mesencephalon is well-established, a role in regulating polarity within the maturing mouse superior colliculus is yet to be defined, although already detailed for the chick tectum. We therefore quantified Pax7 cellular distribution and expression levels at three functionally distinct stages of superior collicular development, and analysed Pax7 expression in response to aberrant axonal input and altered forebrain/midbrain boundary placement in Pax6 mutant mice. Comparative expression profiles of ephrin-A2 and its co-localisation with Pax7 were determined in wildtype and Pax6 mutant mice. Results indicate that graded Pax7 expression in wildtype mice is perturbed in Pax6 mutant mice; changes manifest as a shift in polarity, loss of graded expression and dramatically reduced protein levels during RGC synaptogenesis. Ephrin-A2 expression is similarly altered. These results implicate Pax7 as an important determinant of polarity within the mouse superior colliculus, and suggest a role in retinotopic mapping.
authors.affiliation: School of Exercise, Biomedical and Health Sciences, Edith Cowan University, Joondalup Drive, Joondalup, WA, 6027, Australia.
authors.forename: Jennifer A
authors.initials: JA
authors.lastname: Thompson
authors.forename: Frank J
authors.initials: FJ
authors.lastname: Lovicu
authors.forename: Mel
authors.initials: M
authors.lastname: Ziman
mesh_terms: D000818:Animals; D019521:Body Patterning / Q000235:genetics*; D002450:Cell Communication / Q000235:genetics; D002454:Cell Differentiation / Q000235:genetics; D036383:Ephrin-A2 / Q000235:genetics / Q000378:metabolism; D005136:Eye Proteins / Q000235:genetics; D005260:Female; D018507:Gene Expression Regulation, Developmental / Q000235:genetics; D020439:Growth Cones / Q000378:metabolism / Q000648:ultrastructure; D018398:Homeodomain Proteins / Q000235:genetics; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D008817:Mice, Mutant Strains; D008822:Mice, Transgenic; D009900:Optic Nerve / Q000166:cytology / Q000196:embryology / Q000378:metabolism; D000071841:PAX6 Transcription Factor; D051763:PAX7 Transcription Factor / Q000235:genetics / Q000378:metabolism*; D051761:Paired Box Transcription Factors / Q000235:genetics; D012097:Repressor Proteins / Q000235:genetics; D012160:Retina / Q000166:cytology / Q000196:embryology* / Q000378:metabolism; D012165:Retinal Ganglion Cells / Q000166:cytology / Q000378:metabolism*; D013477:Superior Colliculi / Q000166:cytology / Q000196:embryology* / Q000378:metabolism; D013569:Synapses / Q000378:metabolism / Q000648:ultrastructure; D014795:Visual Pathways / Q000166:cytology / Q000196:embryology* / Q000378:metabolism
chemical_list: D036383:Ephrin-A2; D005136:Eye Proteins; D018398:Homeodomain Proteins; D000071841:PAX6 Transcription Factor; D051763:PAX7 Transcription Factor; D051761:Paired Box Transcription Factors; C000605732:Pax6 protein, mouse; C497322:Pax7 protein, mouse; D012097:Repressor Proteins