As expected, the array failed to identify very small intronic mutations affecting splicing, for which RNA profiling was necessary.
The negative results in these cases may be explained by whole exon deletions or duplications, intronic mutations affecting splicing, or promoter region mutations in ATP8B1 and ABCB11, as such mutations would not be detected by either strategy.
It is strongly recommended that intronic nucleotide substitutions other than splice-site mutations affecting the −1, −2 or +1, +2 intronic nucleotide positions be examined by cDNA-analysis to determine their splicing outcome.
The mutational-burden hypothesis asserts that noncoding DNA (i.e., intronic and intergenic DNA) is a genetic liability because it is a target for deleterious and potentially lethal mutations, such as mutations affecting sequences involved with intron splicing and gene regulation.
The most common type of mutations are small frameshift insertions or deletions, nonsense mutations, or mutations affecting splice sites resulting in a deletion of complete or partial exons or insertion of intronic sequences.
In a previous survey of 24 TS-EL mutations affecting 13 C. elegans genes, we similarly found that 20 were mis-sense mutations, two were intronic splice site mutations, one was an in-frame deletion, and one caused a premature stop codon (O'Rourke et al. 2011a).
Mutations affecting the DGC cause muscular dystrophies.
The c.427+5G>A mutation affects an intronic nucleotide located close to the donor splicing site of CLDN16 exon 2. The pathogenic character of this mutation needs to be confirmed by expression studies.
Most missense mutations reduce the affinity of tau for microtubules (7), whereas silent or intronic mutations affect E10 splicing and can result in an up to 6-fold excess of tau mRNA containing E10 and in an elevated 4R/3R ratio (4, 6, 8, 9).
Therefore, a conspicuous finding was a deep intronic mutation affecting DPD pre-mRNA splicing in five individuals.
