Changes in chromatin compaction and nuclear position of <i>Pax6</i> and <i>Fgf8</i> loci during neural differentiation and following manipulation of retinoid and/or FGF signalling.

<p>(A) Schematic summarising changes in local chromatin organisation of <i>Pax6, Irx3</i> and <i>Fgf8</i> loci as neural differentiation commences in the elongating body axis of wildtype and FGFR signalling deficient (+PD173074) and for <i>Pax6</i> and <i>Fgf8</i> in retinoid deficient (<i>Raldh2−/−</i>) mouse embryos and when both these signalling pathways are attenuated. These data indicate that FGF signalling promotes chromatin compaction around <i>Pax6</i> and <i>Irx3</i> loci and regulates nuclear position of <i>Pax6, Irx3</i> and <i>Fgf8</i> gene loci during neural differentiation. Green and red dots represent flanking fosmid pairs and blue circle the nuclear edge, grey cross indicates likely loss of active <i>Fgf8</i>. (B) Summary of chronological steps towards neural differentiation deduced in this study, from the high FGF signalling context in the stem zone to the onset of neural gene expression in the high retinoid signalling environment of the neural tube.