Yin Yang 1, a vertebrate Polycomb group gene, regulates antero-posterior neural patterning

Polycomb group (PcG) genes are required for the stable repression of the homeotic genes and other developmentally regulated genes. Yin Yang 1 (YY1), a vertebrate homolog of the Drosophila PcG pleiohomeotic (Pho), is a multifunctional protein that can act as a repressor or activator of transcription. Xenopus YY1 (XYY1) protein was localized in the central nervous system (CNS), particularly anterior neural tube of tailbud stage embryos. To elucidate the role of endogenous XYY1, loss-of-function studies were performed using XYY1 antisense morpholino oligonucleotide (XYY1 MO). Inhibition of XYY1 function resulted in embryos with antero-posterior axial patterning defects and reduction of head structures. XYY1 MO also reduced the expression of En2, a midbrain/hindbrain junction marker, which was rescued by co-injection of XYY1 mRNA. However, XYY1 MO-injection did not affect the expression of HoxB9, a spinal cord marker. These results suggest that YY1 controls antero-posterior patterning of the CNS during Xenopus embryonic development.