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Int J Clin Exp Pathol 2013;6(12):2675-2682

Review Article
The missing puzzle piece: splicing mutations

Marzena A Lewandowska

Molecular Oncology and Genetics Unit, Department of Tumor Pathology and Pathomorphology, The Franciszek Lukaszczyk Oncology Center, Dr
I. Romanowskiej 2, 85-796, Bydgoszcz, Poland; Department of Thoracic Surgery and Tumors, Ludwik Rydygier Collegium Medicum, Bydgoszcz,
Nicolaus, Copernicus University, Torun, Poland

Received October 8, 2013; Accepted October 31, 2013; Epub November 15, 2013; Published December 1, 2013

Abstract: Proper gene splicing is highly dependent on the correct recognition of exons. Among the elements allowing this process are the “cis”
(conserved sequences) and “trans” (snRNP, splicing factors) elements. Splicing mutations are related with a number of genetic disorders and
usually induce exon skipping, form new exon/intron boundaries or activate new cryptic exons as a result of alterations at donor/acceptor sites.
They constitute more than 9% of the currently published mutations, but this value is highly underestimated as many of the potential mutations
are located in the “cis” elements and should be confirmed experimentally. The most commonly detected splicing mutations are located at
donor (5’) and acceptor (3’) sites. Mutations at the branch point are rare (only over a dozen are known to date), and are mostly searched and
detected when no alteration has been detected in the sequenced exons and UTRs. Polypyrimidine tract mutations are equally rare. High
throughput technologies, as well as traditional Sanger sequencing, allow detection of many changes in intronic sequences and intron/exon
boundaries. However, the assessment whether a mutation affects exon recognition and results in a genetic disorder has to be conducted
using molecular biology methods: in vitro transcription of the sequence of interest cloned into a plasmid, with and without alterations, or
mutation analysis via a hybrid minigene system. Even though microarrays and new generation sequencing methods pose difficulties in
detecting novel branch point mutations, these tools seem appropriate to expand the mutation detection panel especially for diagnostic
purposes. (IJCEP1310021).

Keywords: Molecular pathology, mutations, branch point, aberrant splicing

Address correspondence to: Marzena Anna Lewandowska, Molecular Oncology and Genetics Unit, Department of Tumor Pathology and
Pathomorphology, The Franciszek Lukaszczyk Oncology Center, dr I. Romanowskiej 2, 85-796, Bydgoszcz, Poland. E-mail: lewandowskam@co.
bydgoszcz.pl