FGFR1 and craniosynostosis: Lastly, in order to determine whether aberrant regulation of genes known to be involved in the aetiology of craniosynostosis underpinned any of the defects we observed, we examined the expression of Noggin, FGFR1/pFGFR1, FGFR2, Runx2 and Twist1 by immunohistochemistry (see methods).