The influence of two PAX7 splice variants on WNT signaling activity during embryonic development in the chicken midbrain

Abstract

PAX7 is a well-known transcription factor, that plays an important role in embryonic development and stem cell maintenance in adult organisms. It has been shown to regulate proliferation and differentiation during embryonic development in the dorsal midbrain. In the chicken (Gallus gallus domesticus), a splice variant in the transactivation domain of PAX7 has been found, that is exclusive to birds. In-vitro, this alternative splice variant impacts transcriptional activity. Furthermore, PAX7 has been previously found to interact with canonical Wnt signaling in the dorsal midbrain of chicken embryos. Using an in vivo reporter gene and qPCR, it was possible to show that the protranscriptional activity of PAX7 is required for normal canonical Wnt signaling in the dorsal midbrain at HH stage 17. Expression of PAX7 on an RNA level correlates well with canonical Wnt signaling. Interestingly, PAX7 seems to partially regulate its own expression with differences in regulatory activities between the two transactivation domain splice variants.