ClinVar

Slaugenhaupt et al. (2001) found that more than 99.5% of disease alleles causing familial dysautonomia (223900) in Ashkenazi Jewish individuals carried a donor splice site mutation (IVS20+6T-C) which leads to deletion of exon 20 from mRNA. Haplotype analyses were consistent with a common founder. Anderson et al. (2001) identified the same mutation in Ashkenazi Jewish patients with familial dysautonomia.

To determine why the mutation in position 6 of intron 20 causes aberrant splicing only in certain cases, Ibrahim et al. (2007) used an in silico approach to identify potential sequences involved in exon 20 skipping. Computational analyses of the exon 20 5-prime splice site itself predicted that this 9-nucleotide splicing signal, even when it contains the T-C mutation, is not sufficiently weak to explain the familial dysautonomia phenotype. However, the computational analysis predicted that both the upstream 3-prime splice site and exon 20 contain weak splicing signals, indicating that the familial dysautonomia 5-prime splice site, together with the surrounding splicing signals, are not adequate for defining exon 20. These in silico predictions were corroborated by IKBKAP minigenes in a rapid and simple in vitro coupled RNA polymerase II (see 180660) transcription/splicing assay. The weak splicing signals that flank the T-C mutation were validated as the underlying cause of familial dysautonomia in vivo using transient transfection assays. Together, the study demonstrated the general utility of combining in silico data with an in vitro RNA polymerase II transcription/splicing system for rapidly identifying critical sequences that underlie the numerous splicing disorders caused by otherwise silent mutations.