Further indications that ephrins play a wider role in the developing skull vault come from the identification of heterozygous mutations in EFNA4, encoding ephrin-A4, in patients with nonsyndromic unicoronal craniosynostosis [Merrill et al., 2006], and from partial fusion of the coronal sutures in mice homozygous for an EphA4 null allele [Ting et al., 2009]. The gene discussed is EFNA4; the disease is craniosynostosis.