Physical mapping of the holoprosencephaly critical region in 18p11.3.

Holoprosencephaly (HPE) is a common developmental defect that results in a spectrum of craniofacial malformations. HPE is genetically heterogeneous, some cases being associated with deletions of the short arm of chromosome 18. In order to map the putative HPE gene located on 18p (HPE4) more precisely, six patients with various cytogenetic 18p deletions and clinical features of HPE have been characterized by using a combination of somatic cell hybrid analysis and FISH. By using a set of 27 chromosome 18p-specific markers, the deletion in each patient was characterized. The HPE minimal critical region on 18p was defined on a molecular level, localizing the HPE4 gene to 18p11.3.