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Craniofrontonasal Syndrome and EFNB1 Mutations 

Craniofrontonasal Syndrome and EFNB1 Mutations
Chapter:
Craniofrontonasal Syndrome and EFNB1 Mutations
Author(s):

Peter Wieacker

and Judit Horvath

DOI:
10.1093/med/9780199934522.003.0087
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date: 07 March 2021

Craniofrontonasal syndrome (CFNS) is mainly characterized by hypertelorism, asymmetry, midline defects, and skeletal abnormalities. This X-linked syndrome shows an unexpected pattern of manifestation because females are typically affected, whilst males mostly exhibit a milder phenotype. Using a combination of linkage analysis and candidate gene approach EFNB1 encoding the ligand ephrinB1 was identified as the causative gene for CFNS. So far, about 100 different mutations have been detected in familial and sporadic cases of CFNS. EphrinB1 is a member of the ephrin/ephrin receptor (Eph) system which is involved in cell communication and cell sorting during embryogenesis. The interaction between ephrin expressing cells and Eph expressing cells leads by repulsion and other mechanisms to the definition of tissue boundaries. EFNB1 is subjected to random X inactivation resulting in two cell populations (ephrinB1-positive and ephrinB1-negative cell populations) in heterozygotes. The more severe phenotype in females has been explained by a model named cellular interference leading to aberrant sorting of ephrinB1 positive and ephrinB1 negative cells in their interaction with Eph expressing cells and resulting in ectopic tissue boundaries. The typically milder phenotype in males may be caused by the redundancy in the ephrin/Eph system.

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