Molecular and clinical analyses of Greig cephalopolysyndactyly and Pallister-Hall syndromes: robust phenotype prediction from the type and position of GLI3 mutations.

National Institutes of Health, National Human Genome Research Institute, Bethesda, MD 20892-4472, USA.
The American Journal of Human Genetics (Impact Factor: 10.99). 05/2005; 76(4):609-22. DOI: 10.1086/429346
Source: PubMed

ABSTRACT Mutations in the GLI3 zinc-finger transcription factor gene cause Greig cephalopolysyndactyly syndrome (GCPS) and Pallister-Hall syndrome (PHS), which are variable but distinct clinical entities. We hypothesized that GLI3 mutations that predict a truncated functional repressor protein cause PHS and that functional haploinsufficiency of GLI3 causes GCPS. To test these hypotheses, we screened patients with PHS and GCPS for GLI3 mutations. The patient group consisted of 135 individuals: 89 patients with GCPS and 46 patients with PHS. We detected 47 pathological mutations (among 60 probands); when these were combined with previously published mutations, two genotype-phenotype correlations were evident. First, GCPS was caused by many types of alterations, including translocations, large deletions, exonic deletions and duplications, small in-frame deletions, and missense, frameshift/nonsense, and splicing mutations. In contrast, PHS was caused only by frameshift/nonsense and splicing mutations. Second, among the frameshift/nonsense mutations, there was a clear genotype-phenotype correlation. Mutations in the first third of the gene (from open reading frame [ORF] nucleotides [nt] 1-1997) caused GCPS, and mutations in the second third of the gene (from ORF nt 1998-3481) caused primarily PHS. Surprisingly, there were 12 mutations in patients with GCPS in the 3' third of the gene (after ORF nt 3481), and no patients with PHS had mutations in this region. These results demonstrate a robust correlation of genotype and phenotype for GLI3 mutations and strongly support the hypothesis that these two allelic disorders have distinct modes of pathogenesis.

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    ABSTRACT: Greig cephalopolysyndactyly (GCPS) syndrome is an autosomal dominant disorder with high penetrance in majority of cases, characterized by a triad of polysyndactyly, macrocephaly and hypertelorism. GCPS is known to be caused by mutations in the transcription factor GLI3 gene (7p13) which results in functional haploinsufficiency of this gene. The present study reports a large multiplex family having 12 members affected with GCPS in 3 generations and several unaffected members showing autosomal dominant pattern of inheritance with complete penetrance. Interestingly an affected member of the family had unusual features including thumb which is although biphalangeal (confirmed with X-ray) but morphologically looks like finger and a unilateral tiny bony outgrown (externally indistinguishable) on the distal phalanx of the first toe of the left foot. This member also presented with mild ichthyosis. Although it is also possible that one or more of these features are coincidentally present in this member and might not be part of GCPS. Resequencing of the GLI3 gene detected a novel frame-shift mutation c.750delC in heterozygous state transmitting in the family and co-segregating with the disorder suggesting it to be the causal for the GCPS phenotype in the family. In silico analysis suggests that this mutation creates a truncated GLI3 protein resulting in its haploinsufficiency leading to GCPS syndrome. Furthermore, genotype-phenotype correlation is supported by the mutation as it lies in the amino terminal domain of the protein.
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