title: High expression level of Tra2-β1 is responsible for increased SMN2 exon 7 inclusion in the testis of SMA mice.
abstract: 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-β1 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-β1 among the many tissues examined. Furthermore, overexpression of Tra2-β1, but not ASF/SF2, increased SMN2 minigene exon 7 inclusion in primary testis cells and spinal cord neurons, whereas knockdown of Tra2-β1 decreased SMN2 exon 7 inclusion in primary testis cells of SMA mice. Therefore, our results indicate that high expression level of Tra2-β1 is responsible for increased SMN2 exon 7 inclusion in the testis of SMA mice. This study also suggests that the expression level of Tra2-β1 may be a modifying factor of SMA disease and a potential target for SMA treatment.
authors.affiliation: Graduate Institute of Medicine, Kaohsiung Medical University, Kaohsiung, Taiwan.
authors.forename: Yu-Chia
authors.initials: YC
authors.lastname: Chen
authors.affiliation: Epigenome Research Center, China Medical University Hospital, Taichung, Taiwan; Department of Laboratory Medicine, China Medical University Hospital, Taichung, Taiwan; School of Medicine, China Medical University, Taichung, Taiwan.
authors.forename: Jan-Gowth
authors.initials: JG
authors.lastname: Chang
authors.affiliation: Graduate Institute of Medicine, Kaohsiung Medical University, Kaohsiung, Taiwan; Departments of Pediatrics and Clinical Laboratory, Kaohsiung Medical University Hospital, Kaohsiung Medical University, Kaohsiung, Taiwan; Department of Biological Science and Technology, National Chiao Tung University, Hsinchu, Taiwan.
authors.forename: Yuh-Jyh
authors.initials: YJ
authors.lastname: Jong
authors.affiliation: Graduate Institute of Medicine, Kaohsiung Medical University, Kaohsiung, Taiwan.
authors.forename: Ting-Yuan
authors.initials: TY
authors.lastname: Liu
authors.affiliation: Department of Biomedical Science and Environmental Biology, Kaohsiung Medical University, Kaohsiung, Taiwan.
authors.forename: Chung-Yee
authors.initials: CY
authors.lastname: Yuo
mesh_terms: D000818:Animals; D002478:Cells, Cultured; D005091:Exons; D008297:Male; D051379:Mice; D018345:Mice, Knockout; D009134:Muscular Atrophy, Spinal / Q000235:genetics / Q000378:metabolism* / Q000473:pathology; D009687:Nuclear Proteins / Q000235:genetics / Q000378:metabolism*; D012326:RNA Splicing; D016601:RNA-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D000068103:Serine-Arginine Splicing Factors; D055540:Survival of Motor Neuron 2 Protein / Q000096:biosynthesis* / Q000235:genetics; D013737:Testis / Q000378:metabolism*
chemical_list: D009687:Nuclear Proteins; D016601:RNA-Binding Proteins; C000597152:SMN2 protein, mouse; D055540:Survival of Motor Neuron 2 Protein; C100345:Tra2b protein, mouse; D000068103:Serine-Arginine Splicing Factors