CDX2 and trisomy 13: This work is highly relevant as regards head dysgenesis diseases in humans because a number of cases, among which the Patau syndrome, are associated with copy number amplification of the chromosome 13 locus overlapping CDX2. Thus, this study highlights that, in addition to single gene mutations in the head ontogenetic program2, the imbalance between head and trunk programs around gastrulation could be a novel basis of head dysgenesis.