PLXND1 and Mobius syndrome: Extensive studies have been conducted to explain the HCFP phenotype and to pave the way for genetic studies in MBS, but analysis of genes in the HCFP1 and HCFP2 loci, including the prime candidate gene PLXND1 at chromosome 3q21-q22 (ref. 20), has so far not identified any causative mutations in HCFP and in MBS patients21.