Pax7 is requisite for maintenance of a subpopulation of superior collicular neurons and shows a diverging expression pattern to Pax3 during superior collicular development.
BACKGROUND
Pax7 encodes a transcription factor well-established as an important determinant of mesencephalic identity and superior collicular development. Pax7 mutant mice, however, present with no obvious morphological impairments to the superior colliculus. This finding is paradoxical and has been attributed to functional redundancy afforded by its paralogue Pax3. Here we utilise Pax7 mutant mice to investigate the precise role of this important developmental regulator during superior collicular development and neuronal specification/differentiation. We also assess its spatiotemporal relationship with Pax3 during embryonic development.


RESULTS
Analysis of the superior colliculus of Pax7 mutant and wildtype mice at a variety of developmental timepoints revealed that whilst correct initial specification is maintained, a subpopulation of dorsal mesencephalic neurons is lost at early postnatal stages. Moreover, a comparative analysis of embryonic Pax3 and Pax7 expression profiles indicate that Pax3 expression overlaps extensively with that of Pax7 initially, but their expression domains increasingly diverge as development progresses, coinciding spatiotemporally with neuronal differentiation and maturation of the tissue. Furthermore, Pax3 expression is perturbed within the CNS of embryonic Pax7 mutant mice.


CONCLUSIONS
In summary, these results demonstrate that during superior collicular development, Pax7 is required to maintain a subpopulation of dorsal, mesencephalic neurons and partially regulates, spatiotemporally, Pax3 expression within the CNS. The differential nature of Pax7 and Pax3 with respect to neuronal differentiation may have implications for future stem cell therapies aimed at exploiting their developmental capabilities.
Thompson
Jennifer A
JA
School of Exercise, Biomedical and Health Science, Edith Cowan University, Joondalup Drive, Joondalup, Western Australia 6027, Australia. jennifer.thompson@ecu.edu.au
Zembrzycki
Andreas
A
Mansouri
Ahmed
A
Ziman
Mel
M
D000818:Animals; D017209:Apoptosis; D049109:Cell Proliferation; D054338:Cell Transdifferentiation; D004622:Embryo, Mammalian; D005455:Fluorescent Antibody Technique; D018507:Gene Expression Regulation, Developmental; D007150:Immunohistochemistry; D051379:Mice; D008817:Mice, Mutant Strains; D009474:Neurons / Q000166:cytology* / Q000378:metabolism; D000072041:PAX3 Transcription Factor; D051763:PAX7 Transcription Factor / Q000096:biosynthesis*; D051761:Paired Box Transcription Factors / Q000096:biosynthesis*; D013477:Superior Colliculi / Q000166:cytology / Q000196:embryology* / Q000378:metabolism
D000072041:PAX3 Transcription Factor; D051763:PAX7 Transcription Factor; D051761:Paired Box Transcription Factors; C497322:Pax7 protein, mouse; C068686:Pax3 protein, mouse