All coding exons of the ADGRL2 gene by means of the Sanger technique were sequenced in 29 unrelated fœtuses affected with RES alone or with associated mesencephalosynapsis (atresia-forking of the aqueduct of Sylvius and fusion of the colliculi), diencephalosynapsis (atresia of the 3rd ventricle with collapse of the thalami), holoprosencephaly or encephalocele [56]. This evidence concerns the gene ADGRL2 and holoprosencephaly.