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Österman, Lennart
Publications (5 of 5) Show all publications
Aripaka, K., Gudey, S. K., Zang, G., Schmidt, A., Åhrling, S. S., Österman, L., . . . Landström, M. (2019). TRAF6 function as a novel co-regulator of Wnt3a target genes in prostate cancer. EBioMedicine, 45, 192-207
Open this publication in new window or tab >>TRAF6 function as a novel co-regulator of Wnt3a target genes in prostate cancer
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2019 (English)In: EBioMedicine, E-ISSN 2352-3964, Vol. 45, p. 192-207Article in journal (Refereed) Published
Abstract [en]

Background: Tumour necrosis factor receptor associated factor 6 (TRAF6) promotes inflammation in response to various cytokines. Aberrant Wnt3a signals promotes cancer progression through accumulation of β-Catenin. Here we investigated a potential role for TRAF6 in Wnt signaling.

Methods: TRAF6 expression was silenced by siRNA in human prostate cancer (PC3U) and human colorectal SW480 cells and by CRISPR/Cas9 in zebrafish. Several biochemical methods and analyses of mutant phenotype in zebrafish were used to analyse the function of TRAF6 in Wnt signaling.

Findings: Wnt3a-treatment promoted binding of TRAF6 to the Wnt co-receptors LRP5/LRP6 in PC3U and LNCaP cells in vitro. TRAF6 positively regulated mRNA expression of β-Catenin and subsequent activation of Wnt target genes in PC3U cells. Wnt3a-induced invasion of PC3U and SW480 cells were significantly reduced when TRAF6 was silenced by siRNA. Database analysis revealed a correlation between TRAF6 mRNA and Wnt target genes in patients with prostate cancer, and high expression of LRP5, TRAF6 and c-Myc correlated with poor prognosis. By using CRISPR/Cas9 to silence TRAF6 in zebrafish, we confirm TRAF6 as a key molecule in Wnt3a signaling for expression of Wnt target genes.

Interpretation: We identify TRAF6 as an important component in Wnt3a signaling to promote activation of Wnt target genes, a finding important for understanding mechanisms driving prostate cancer progression.

Place, publisher, year, edition, pages
Elsevier, 2019
Keywords
beta-Catenin, LRP5, Prostate cancer, TRAF6, Wnt3a, Zebrafish
National Category
Cell and Molecular Biology
Identifiers
urn:nbn:se:umu:diva-161915 (URN)10.1016/j.ebiom.2019.06.046 (DOI)000475860000026 ()31262711 (PubMedID)2-s2.0-85067957867 (Scopus ID)
Available from: 2019-08-06 Created: 2019-08-06 Last updated: 2019-11-04Bibliographically approved
Jonsson, F., Boström, I. M., Österman, L., Sandgren, O., Burstedt, M., Holmberg, M. & Golovleva, I. (2018). ATP-binding cassette subfamily A, member 4 intronic variants c.4773+3A > G and c.5461-10T > C cause Stargardt disease due to defective splicing. Acta Ophthalmologica, 96(7), 737-743
Open this publication in new window or tab >>ATP-binding cassette subfamily A, member 4 intronic variants c.4773+3A > G and c.5461-10T > C cause Stargardt disease due to defective splicing
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2018 (English)In: Acta Ophthalmologica, ISSN 1755-375X, E-ISSN 1755-3768, Vol. 96, no 7, p. 737-743Article in journal (Refereed) Published
Abstract [en]

Purpose

Inherited retinal dystrophies (IRDs) represent a group of progressive conditions affecting the retina. There is a great genetic heterogeneity causing IRDs, and to date, more than 260 genes are associated with IRDs. Stargardt disease, type 1 (STGD1) or macular degeneration with flecks, STGD1 represents a disease with early onset, central visual impairment, frequent appearance of yellowish flecks and mutations in the ATP‐binding cassette subfamily A, member 4 (ABCA4) gene. A large number of intronic sequence variants in ABCA4 have been considered pathogenic although their functional effect was seldom demonstrated. In this study, we aimed to reveal how intronic variants present in patients with Stargardt from the same Swedish family affect splicing.

Methods

The splicing of the ABCA4 gene was studied in human embryonic kidney cells, HEK293T, and in human retinal pigment epithelium cells, ARPE‐19, using a minigene system containing variants c.4773+3A>G and c.5461‐10T>C.

Results

We showed that both ABCA4 variants, c.4773+3A>G and c.5461‐10T>C, cause aberrant splicing of the ABCA4 minigene resulting in exon skipping. We also demonstrated that splicing of ABCA4 has different outcomes depending on transfected cell type.

Conclusion

Two intronic variants c.4773+3A>G and c.5461‐10T>C, both predicted to affect splicing, are indeed disease‐causing mutations due to skipping of exons 33, 34, 39 and 40 of ABCA4 gene. The experimental proof that ABCA4 mutations in STGD patients affect protein function is crucial for their inclusion to future clinical trials; therefore, functional testing of all ABCA4 intronic variants associated with Stargardt disease by minigene technology is desirable.

Place, publisher, year, edition, pages
John Wiley & Sons, 2018
Keywords
ABCA4, intronic variants, mutation, splicing, Stargardt disease
National Category
Genetics
Identifiers
urn:nbn:se:umu:diva-154068 (URN)10.1111/aos.13676 (DOI)000451035500011 ()29461686 (PubMedID)
Funder
Västerbotten County Council
Available from: 2018-12-12 Created: 2018-12-12 Last updated: 2018-12-12Bibliographically approved
Rawcliffe, D. F. R., Österman, L., Nordin, A. & Holmberg, M. (2018). PTBP1 acts as a dominant repressor of the aberrant tissue-specific splicing of ISCU in hereditary myopathy with lactic acidosis. Molecular Genetics & Genomic Medicine, 6(6), 887-897
Open this publication in new window or tab >>PTBP1 acts as a dominant repressor of the aberrant tissue-specific splicing of ISCU in hereditary myopathy with lactic acidosis
2018 (English)In: Molecular Genetics & Genomic Medicine, ISSN 2324-9269, Vol. 6, no 6, p. 887-897Article in journal (Refereed) Published
Abstract [en]

Background: Hereditary myopathy with lactic acidosis (HML) is an autosomal recessive disease caused by an intron mutation in the iron-sulfur cluster assembly (ISCU) gene. The mutation results in aberrant splicing, where part of the intron is retained in the final mRNA transcript, giving rise to a truncated nonfunctional ISCU protein. Using an ISCU mini-gene system, we have previously shown that PTBP1 can act as a repressor of the mis-splicing of ISCU, where overexpression of PTBP1 resulted in a decrease of the incorrect splicing. In this study, we wanted to, in more detail, analyze the role of PTBP1 in the regulation of endogenous ISCU mis-splicing.

Methods: Overexpression and knockdown of PTBP1 was performed in myoblasts from two HML patients and a healthy control. Quantification of ISCU mis-splicing was done by qRTPCR. Biotinylated ISCU RNA, representing wildtype and mutant intron sequence, was used in a pull-down assay with nuclear extracts from myoblasts. Levels of PTBP1 in human cell lines and mice tissues were analyzed by qRTPCR and western blot.

Results: PTBP1 overexpression in HML patient myoblasts resulted in a substantial decrease of ISCU mis-splicing while knockdown of PTBP1 resulted in a drastic increase. The effect could be observed in both patient and control myoblasts. We could also show that PTBP1 interacts with both the mutant and wild-type ISCU intron sequence, but with a higher affinity to the mutant sequence. Furthermore, low levels of PTBP1 among examined mouse tissues correlated with high levels of incorrect splicing of ISCU.

Conclusion: Our results show that PTBP1 acts as a dominant repressor of ISCU mis-splicing. We also show an inverse correlation between the levels of PTBP1 and ISCU mis-splicing, suggesting that the high level of mis-splicing in the skeletal muscle is primarily due to the low levels of PTBP1.

Place, publisher, year, edition, pages
John Wiley & Sons, 2018
Keywords
alternative splicing, hereditary myopathy, ISCU, PTBP1
National Category
Medical Genetics
Identifiers
urn:nbn:se:umu:diva-153102 (URN)10.1002/mgg3.413 (DOI)000454205500003 ()30209894 (PubMedID)2-s2.0-85053400372 (Scopus ID)
Available from: 2018-11-07 Created: 2018-11-07 Last updated: 2019-01-14Bibliographically approved
Rawcliffe, D. F. R., Österman, L., Lindsten, H. & Holmberg, M. (2016). The High Level of Aberrant Splicing of ISCU in Slow-Twitch Muscle May Involve the Splicing Factor SRSF3. PLoS ONE, 11(10), Article ID e0165453.
Open this publication in new window or tab >>The High Level of Aberrant Splicing of ISCU in Slow-Twitch Muscle May Involve the Splicing Factor SRSF3
2016 (English)In: PLoS ONE, ISSN 1932-6203, E-ISSN 1932-6203, Vol. 11, no 10, article id e0165453Article in journal (Refereed) Published
Abstract [en]

Hereditary myopathy with lactic acidosis (HML) is an autosomal recessive disease caused by an intronic one-base mutation in the iron-sulfur cluster assembly (ISCU) gene, resulting in aberrant splicing. The incorrectly spliced transcripts contain a 100 or 86 bp intron sequence encoding a non-functional ISCU protein, which leads to defects in several Fe-S containing proteins in the respiratory chain and the TCA cycle. The symptoms in HML are restricted to skeletal muscle, and it has been proposed that this effect is due to higher levels of incorrectly spliced ISCU in skeletal muscle compared with other energy-demanding tissues. In this study, we confirm that skeletal muscle contains the highest levels of incorrect ISCU splice variants compared with heart, brain, liver and kidney using a transgenic mouse model expressing human HML mutated ISCU. We also show that incorrect splicing occurs to a significantly higher extent in the slow-twitch soleus muscle compared with the gastrocnemius and quadriceps. The splicing factor serine/arginine-rich splicing factor 3 (SRSF3) was identified as a potential candidate for the slow fiber specific regulation of ISCU splicing since this factor was expressed at higher levels in the soleus compared to the gastrocnemius and quadriceps. We identified an interaction between SRSF3 and the ISCU transcript, and by overexpressing SRSF3 in human myoblasts we observed increased levels of incorrectly spliced ISCU, while knockdown of SRSF3 resulted in decreased levels. We therefore suggest that SRSF3 may participate in the regulation of the incorrect splicing of mutant ISCU and may, at least partially, explain the muscle-specific symptoms of HML.

Place, publisher, year, edition, pages
Public library science, 2016
National Category
Medical Genetics
Identifiers
urn:nbn:se:umu:diva-129745 (URN)10.1371/journal.pone.0165453 (DOI)000389602800075 ()27783661 (PubMedID)
Available from: 2017-01-09 Created: 2017-01-09 Last updated: 2018-11-08Bibliographically approved
Rawcliffe, D. F. R., Johansson, M., Österman, L. & Holmberg, M.MBNL1 and RBM39 can activate the incorrect splicing of ISCU and the aberrant transcript is a target for nonsense-mediated decay.
Open this publication in new window or tab >>MBNL1 and RBM39 can activate the incorrect splicing of ISCU and the aberrant transcript is a target for nonsense-mediated decay
(English)Manuscript (preprint) (Other academic)
National Category
Medical Genetics
Identifiers
urn:nbn:se:umu:diva-153148 (URN)
Available from: 2018-11-08 Created: 2018-11-08 Last updated: 2018-11-09
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