Identifying alternative hyper-splicing signatures in MG-thymoma by exon arrays.

Abstract

BACKGROUND:

The vast majority of human genes (>70%) are alternatively spliced. Although alternative pre-mRNA processing is modified in multiple tumors, alternative hyper-splicing signatures specific to particular tumor types are still lacking. Here, we report the use of Affymetrix Human Exon Arrays to spot hyper-splicing events characteristic of myasthenia gravis (MG)-thymoma, thymic tumors which develop in patients with MG and discriminate them from colon cancer changes.

METHODOLOGY/PRINCIPAL FINDINGS:

We combined GO term to parent threshold-based and threshold-independent ad-hoc functional statistics with in-depth analysis of key modified transcripts to highlight various exon-specific changes. These denote alternative splicing in MG-thymoma tumors compared to healthy human thymus and to in-house and Affymetrix datasets from colon cancer and healthy tissues. By using both global and specific, term-to-parent Gene Ontology (GO) statistical comparisons, our functional integrative ad-hoc method allowed the detection of disease-relevant splicing events.

CONCLUSIONS/SIGNIFICANCE:

Hyper-spliced transcripts spanned several categories, including the tumorogenic ERBB4 tyrosine kinase receptor and the connective tissue growth factor CTGF, as well as the immune function-related histocompatibility gene HLA-DRB1 and interleukin (IL)19, two muscle-specific collagens and one myosin heavy chain gene; intriguingly, a putative new exon was discovered in the MG-involved acetylcholinesterase ACHE gene. Corresponding changes in spliceosome composition were indicated by co-decreases in the splicing factors ASF/SF(2) and SC35. Parallel tumor-associated changes occurred in colon cancer as well, but the majority of the apparent hyper-splicing events were particular to MG-thymoma and could be validated by Fluorescent In-Situ Hybridization (FISH), Reverse Transcription-Polymerase Chain Reaction (RT-PCR) and mass spectrometry (MS) followed by peptide sequencing. Our findings demonstrate a particular alternative hyper-splicing signature for transcripts over-expressed in MG-thymoma, supporting the hypothesis that alternative hyper-splicing contributes to shaping the biological functions of these and other specialized tumors and opening new venues for the development of diagnosis and treatment approaches.

• Authors: Lilach Soreq, Adi Gilboa-Geffen, Sonia Berrih-Aknin, Paul Lacoste, Ariel Darvasi, Eyal Soreq, Hagai Bergman, Hermona Soreq
• Journal: PloS one (PLoS One) Vol. 3 Issue 6 Pg. e2392 (Jun 11 2008) ISSN: 1932-6203 [Electronic] United States
• PMID: 18545673 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't, Research Support, U.S. Gov't, Non-P.H.S.)

Chemical References

• RNA, Messenger

Topics

• Alternative Splicing
• Colonic Neoplasms (genetics)
• Exons
• Humans
• In Situ Hybridization, Fluorescence
• Proteomics
• RNA, Messenger (genetics)
• Reverse Transcriptase Polymerase Chain Reaction
• Thymus Neoplasms (genetics)