Journal
PLOS ONE
Volume 10, Issue 3, Pages -Publisher
PUBLIC LIBRARY SCIENCE
DOI: 10.1371/journal.pone.0120721
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- Ministry of Science and Technology, Taiwan, R. O. C. [NSC98-2320-B-037-025-MY3, NSC98-2321-B-037-062-, NSC99-2321-B-037-002-, NSC100-2321-B-039-007-]
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Spinal muscular atrophy (SMA) is an inherited neuromuscular disease caused by deletion or mutation of SMN1 gene. All SMA patients carry a nearly identical SMN2 gene, which produces low level of SMN protein due to mRNA exon 7 exclusion. Previously, we found that the testis of SMA mice (smn(-/-) SMN2) expresses high level of SMN2 full-length mRNA, indicating a testis-specific mechanism for SMN2 exon 7 inclusion. To elucidate the underlying mechanism, we established primary cultures of testis cells from SMA mice and analyzed them for SMN2 exon 7 splicing. We found that primary testis cells after a 2-hour culture still expressed high level of SMN2 full-length mRNA, but the level decreased after longer cultures. We then compared the protein levels of relevant splicing factors, and found that the level of Tra2-beta 1 also decreased during testis cell culture, correlated with SMN2 full-length mRNA downregulation. In addition, the testis of SMA mice expressed the highest level of Tra2-beta 1 among the many tissues examined. Furthermore, overexpression of Tra2-beta 1, but not ASF/SF2, increased SMN2 minigene exon 7 inclusion in primary testis cells and spinal cord neurons, whereas knockdown of Tra2-beta 1 decreased SMN2 exon 7 inclusion in primary testis cells of SMA mice. Therefore, our results indicate that high expression level of Tra2-beta 1 is responsible for increased SMN2 exon 7 inclusion in the testis of SMA mice. This study also suggests that the expression level of Tra2-beta 1 may be a modifying factor of SMA disease and a potential target for SMA treatment.
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