Dissecting the molecular mechanisms in craniofrontonasal syndrome: differential mRNA expression of mutant EFNB1 and the cellular mosaic

Eur J Hum Genet. 2008 Feb;16(2):184-91. doi: 10.1038/sj.ejhg.5201968. Epub 2007 Nov 28.


Craniofrontonasal syndrome (CFNS) is an X-linked malformation syndrome with variable phenotype that is caused by mutations in the ephrin-B1 gene (EFNB1). Over 50% of EFNB1 mutations result in premature termination codons that may elicit mRNA degradation by the nonsense-mediated decay pathway. To assess the effects of various mutations at the transcript level, expression of EFNB1 mRNA was studied by RT-PCR in fibroblast cultures established from CFNS female patients. Compared to the wild-type and two missense mutation alleles, severe depletion of transcripts was observed for mutant alleles harbouring either splice site mutation c.407-2A>T at the exon 2/3 boundary or frameshift mutation c.377_384delTCAAGAAG in exon 2. In contrast, escape from mRNA decay was observed for mutation c.614_615delCT, which generates a premature termination codon close to the 3'-end of the penultimate exon 4 disobeying the '50-55 bp' rule. These results suggest differential degradation of mutant EFNB1 transcripts by the nonsense-mediated mRNA decay pathway. Although the clinical phenotypes of the patients were not highly suggestive of a phenotype-genotype correlation, the two female patients were diagnosed with diaphragmatic hernia harbouring putative ephrin-B1 truncating mutations. Previously, disease manifestation in heterozygous females had been attributed mainly to cellular interference of divergent cell populations expressing wild-type or mutant EFNB1, depending on the pattern of X-inactivation. Upon clonal expansion of patient cells with either the wild-type or mutant EFNB1 on the active X-chromosome, we were able to separate mutant and wild-type EFNB1-expressing cells in vitro, further supporting the concept of cellular interference in CFNS.

Publication types

  • Comparative Study
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adult
  • Amino Acid Sequence
  • Base Sequence
  • Cells, Cultured
  • Child
  • Codon, Nonsense / genetics
  • Craniofacial Abnormalities / genetics*
  • Craniofacial Abnormalities / pathology
  • Ephrin-B1 / biosynthesis
  • Ephrin-B1 / genetics*
  • Female
  • Frameshift Mutation* / physiology
  • Heterozygote
  • Humans
  • Infant
  • Male
  • Molecular Sequence Data
  • Mutation, Missense* / physiology
  • RNA Splice Sites* / physiology
  • RNA, Messenger / biosynthesis*
  • RNA, Messenger / genetics
  • Random Allocation
  • Syndrome


  • Codon, Nonsense
  • EFNB1 protein, human
  • Ephrin-B1
  • RNA Splice Sites
  • RNA, Messenger