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Antisense-mediated exon skipping: a therapeutic strategy for titin-based dilated cardiomyopathy.

Gramlich M, Pane LS, Zhou Q, Chen Z, Murgia M, Schötterl S, Goedel A, Metzger K, Brade T, Parrotta E, Schaller M, Gerull B, Thierfelder L, Aartsma-Rus A, Labeit S, Atherton JJ, McGaughran J, Harvey RP, Sinnecker D, Mann M, Laugwitz KL, Gawaz MP, Moretti A - EMBO Mol Med (2015)

Bottom Line: Here, we show the beneficial potential of reframing titin transcripts by antisense oligonucleotide (AON)-mediated exon skipping in human and murine models of DCM carrying a previously identified autosomal-dominant frameshift mutation in titin exon 326.Correction of TTN reading frame in patient-specific cardiomyocytes derived from induced pluripotent stem cells rescued defective myofibril assembly and stability and normalized the sarcomeric protein expression.AON treatment in Ttn knock-in mice improved sarcomere formation and contractile performance in homozygous embryos and prevented the development of the DCM phenotype in heterozygous animals.

View Article: PubMed Central - PubMed

Affiliation: Department of Cardiology and Cardiovascular Diseases, Eberhard Karls University, Tübingen, Germany Victor Chang Cardiac Research Institute, Darlinghurst, NSW, Australia michael.gramlich@med.uni-tuebingen.de amoretti@med1.med.tum.de.

No MeSH data available.


Related in: MedlinePlus

Exon skipping-based rescue of SRF target gene expression and Nbr1/p62/SQSTM1/MURF2 subcellular distribution in TTN Ser14450fsX4 iPSC-derived cardiomyocytesqRT–PCR analysis of SRF target genes (MYH6, MYH7 and ACTC1) in CTR and DCM single cardiomyocytes under basal condition (no infection, NI) and after infection with control U7snRNA-ScrAONs-IRES-GFP (Scr-AON) and the U7snRNA-TTNAONs-IRES-GFP (TTN-AON) lentiviruses. Statistical difference was tested using the two-sided Student's t-test (**P = 0.009, CTR Scr-AON versus DCM Scr-AON; *P = 0.04, DCM Scr-AON versus DCM TTN-AON for MYH6; **P = 0.002, CTR Scr-AON versus DCM Scr-AON; **P = 0.002, DCM Scr-AON versus DCM TTN-AON for MYH7; **P = 0.004, CTR Scr-AON versus DCM Scr-AON; *P = 0.02, DCM Scr-AON versus DCM TTN-AON for ACTC1). No significant differences were observed comparing the CTR NI, CTR Scr-AON and CTR TTN-AON groups and comparing the DCM NI and DCM Scr-AON groups. Expression values were relative to CTR Scr-AON, normalized to GAPDH, and presented as mean ± SEM, n = 3.Immunofluorescence images showing normal (a, b, e, f, i, l, o, p) and altered (c, d, g, h, m, n, q, r) intracellular distribution of SRF (a and b, nuclear; c and d, cytoplasmic), MURF2 (e and f, sarcomeric; g and h, nuclear), Nbr1 (i and l, sarcomeric; m and n, diffused), and SQSTM1/p62 (o and p, sarcomeric; q and r, diffused) in representative single cardiomyocytes (left). Sarcomeres are marked by α-actinin. On the right, percentage of CTR and DCM cardiomyocytes showing cytoplasmic expression of SRF, nuclear accumulation of MURF2, and diffused expression of Nbr1 and of SQSTM1/p62 after infection with control U7snRNA-ScrambleAONs-IRES-GFP (Scr-AON) and the U7snRNA-TTNAONs-IRES-GFP (TTN-AON) lentiviruses (right). Data represent mean values ± SEM from two control and two DCM clones. Statistical difference was tested using the two-sided chi-squared test (CTR Scr-AON: n = 874, n = 874, n = 882 and n = 890, CTR TTN-AON: n = 880, n = 990, n = 878 and n = 890, DCM Scr-AON: n = 890, n = 887, n = 884 and n = 886, DCM TTN-AON: n = 900, n = 875, n = 899 and n = 891 for SRF, MURF2, Nbr1 and SQSTM1/p62, respectively; *P = 0.01, CTR Scr-AON versus DCM Scr-AON; *P = 0.04, DCM Scr-AON versus DCM TTN-AON for SRF; *P = 0.02, CTR Scr-AON versus DCM Scr-AON; *P = 0.04, DCM Scr-AON versus DCM TTN-AON for MURF2; *P = 0.03, CTR Scr-AON versus DCM Scr-AON; *P = 0.03, DCM Scr-AON versus DCM TTN-AON for Nbr1; **P = 0.009, CTR Scr-AON versus DCM Scr-AON; *P = 0.01, DCM Scr-AON versus DCM TTN-AON for SQSTM1/p62). No significant differences were observed comparing CTR Scr-AON and CTR TTN-AON groups. Scale bars, 50 μm.
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fig04: Exon skipping-based rescue of SRF target gene expression and Nbr1/p62/SQSTM1/MURF2 subcellular distribution in TTN Ser14450fsX4 iPSC-derived cardiomyocytesqRT–PCR analysis of SRF target genes (MYH6, MYH7 and ACTC1) in CTR and DCM single cardiomyocytes under basal condition (no infection, NI) and after infection with control U7snRNA-ScrAONs-IRES-GFP (Scr-AON) and the U7snRNA-TTNAONs-IRES-GFP (TTN-AON) lentiviruses. Statistical difference was tested using the two-sided Student's t-test (**P = 0.009, CTR Scr-AON versus DCM Scr-AON; *P = 0.04, DCM Scr-AON versus DCM TTN-AON for MYH6; **P = 0.002, CTR Scr-AON versus DCM Scr-AON; **P = 0.002, DCM Scr-AON versus DCM TTN-AON for MYH7; **P = 0.004, CTR Scr-AON versus DCM Scr-AON; *P = 0.02, DCM Scr-AON versus DCM TTN-AON for ACTC1). No significant differences were observed comparing the CTR NI, CTR Scr-AON and CTR TTN-AON groups and comparing the DCM NI and DCM Scr-AON groups. Expression values were relative to CTR Scr-AON, normalized to GAPDH, and presented as mean ± SEM, n = 3.Immunofluorescence images showing normal (a, b, e, f, i, l, o, p) and altered (c, d, g, h, m, n, q, r) intracellular distribution of SRF (a and b, nuclear; c and d, cytoplasmic), MURF2 (e and f, sarcomeric; g and h, nuclear), Nbr1 (i and l, sarcomeric; m and n, diffused), and SQSTM1/p62 (o and p, sarcomeric; q and r, diffused) in representative single cardiomyocytes (left). Sarcomeres are marked by α-actinin. On the right, percentage of CTR and DCM cardiomyocytes showing cytoplasmic expression of SRF, nuclear accumulation of MURF2, and diffused expression of Nbr1 and of SQSTM1/p62 after infection with control U7snRNA-ScrambleAONs-IRES-GFP (Scr-AON) and the U7snRNA-TTNAONs-IRES-GFP (TTN-AON) lentiviruses (right). Data represent mean values ± SEM from two control and two DCM clones. Statistical difference was tested using the two-sided chi-squared test (CTR Scr-AON: n = 874, n = 874, n = 882 and n = 890, CTR TTN-AON: n = 880, n = 990, n = 878 and n = 890, DCM Scr-AON: n = 890, n = 887, n = 884 and n = 886, DCM TTN-AON: n = 900, n = 875, n = 899 and n = 891 for SRF, MURF2, Nbr1 and SQSTM1/p62, respectively; *P = 0.01, CTR Scr-AON versus DCM Scr-AON; *P = 0.04, DCM Scr-AON versus DCM TTN-AON for SRF; *P = 0.02, CTR Scr-AON versus DCM Scr-AON; *P = 0.04, DCM Scr-AON versus DCM TTN-AON for MURF2; *P = 0.03, CTR Scr-AON versus DCM Scr-AON; *P = 0.03, DCM Scr-AON versus DCM TTN-AON for Nbr1; **P = 0.009, CTR Scr-AON versus DCM Scr-AON; *P = 0.01, DCM Scr-AON versus DCM TTN-AON for SQSTM1/p62). No significant differences were observed comparing CTR Scr-AON and CTR TTN-AON groups. Scale bars, 50 μm.

Mentions: Titin is not only required as molecular scaffold during sarcomerogenesis and assists in the process of myofibrillar assembly, but it is also a hot spot for protein–protein interactions and a putative mediator of mechanotransduction. About 20 interaction partners have so far been identified, linking titin to multiple stress signaling pathways that control muscle gene expression and protein turnover (Linke & Kruger, 2010; Linke & Hamdani, 2014). One of the most extensively studied is the Nbr1/p62/SQSTM1/MURF2 signaling complex that associates with titin TK and activates the serum response factor (SRF) upon mechanical stimuli (Lange et al, 2005). TK mutations affecting this interaction result in the dissociation of the Nbr1/p62/SQSTM1/MURF2 complex and translocation of MURF2 into the nucleus, which in turn leads to suppression of SRF-dependent muscle gene transcription (Lange et al, 2005). Therefore, we analyzed expression levels of SRF targets (Miano et al, 2004; Balza & Misra, 2006) in control and patient cardiomyocytes after infection with U7snRNA-ScrAONs-IRES-GFP and U7snRNA-TTNAONs-IRES-GFP viruses. When compared to the control counterpart, a significant down-regulation of α- and β-myosin heavy chain (MYH6 and MYH7) transcripts as well as cardiac α-actin (ACTC1) was measured in the DCM cells untreated or transduced with scrambled AONs (Fig4A). Blocking of exon 326 transcription partially rescued SRF target levels in patient cardiomyocytes, with no effects on control cells (Fig4A). In concordance, immunocytochemistry assessment of SRF localization in iPSC-derived cardiomyocytes at 7 days after dissociation revealed a significant higher percentage of cells with increased extranuclear expression of SRF in the DCM group (Fig4B). Moreover, we observed differences in the subcellular distribution of MURF2, Nbr1, and p62/SQSTM1 in the DCM cardiomyocytes, with an increased number of cells showing a marked nuclear accumulation of MURF2 and a cytosolic, more diffused non-sarcomeric expression of Nbr1 and p62/SQSTM1 (Fig4B). Infection with U7snRNA-TTNAONs-IRES-GFP lentivirus partially normalized the cellular localization of all these proteins in the diseased cells, while no effects were observed in the control cells (Fig4B).


Antisense-mediated exon skipping: a therapeutic strategy for titin-based dilated cardiomyopathy.

Gramlich M, Pane LS, Zhou Q, Chen Z, Murgia M, Schötterl S, Goedel A, Metzger K, Brade T, Parrotta E, Schaller M, Gerull B, Thierfelder L, Aartsma-Rus A, Labeit S, Atherton JJ, McGaughran J, Harvey RP, Sinnecker D, Mann M, Laugwitz KL, Gawaz MP, Moretti A - EMBO Mol Med (2015)

Exon skipping-based rescue of SRF target gene expression and Nbr1/p62/SQSTM1/MURF2 subcellular distribution in TTN Ser14450fsX4 iPSC-derived cardiomyocytesqRT–PCR analysis of SRF target genes (MYH6, MYH7 and ACTC1) in CTR and DCM single cardiomyocytes under basal condition (no infection, NI) and after infection with control U7snRNA-ScrAONs-IRES-GFP (Scr-AON) and the U7snRNA-TTNAONs-IRES-GFP (TTN-AON) lentiviruses. Statistical difference was tested using the two-sided Student's t-test (**P = 0.009, CTR Scr-AON versus DCM Scr-AON; *P = 0.04, DCM Scr-AON versus DCM TTN-AON for MYH6; **P = 0.002, CTR Scr-AON versus DCM Scr-AON; **P = 0.002, DCM Scr-AON versus DCM TTN-AON for MYH7; **P = 0.004, CTR Scr-AON versus DCM Scr-AON; *P = 0.02, DCM Scr-AON versus DCM TTN-AON for ACTC1). No significant differences were observed comparing the CTR NI, CTR Scr-AON and CTR TTN-AON groups and comparing the DCM NI and DCM Scr-AON groups. Expression values were relative to CTR Scr-AON, normalized to GAPDH, and presented as mean ± SEM, n = 3.Immunofluorescence images showing normal (a, b, e, f, i, l, o, p) and altered (c, d, g, h, m, n, q, r) intracellular distribution of SRF (a and b, nuclear; c and d, cytoplasmic), MURF2 (e and f, sarcomeric; g and h, nuclear), Nbr1 (i and l, sarcomeric; m and n, diffused), and SQSTM1/p62 (o and p, sarcomeric; q and r, diffused) in representative single cardiomyocytes (left). Sarcomeres are marked by α-actinin. On the right, percentage of CTR and DCM cardiomyocytes showing cytoplasmic expression of SRF, nuclear accumulation of MURF2, and diffused expression of Nbr1 and of SQSTM1/p62 after infection with control U7snRNA-ScrambleAONs-IRES-GFP (Scr-AON) and the U7snRNA-TTNAONs-IRES-GFP (TTN-AON) lentiviruses (right). Data represent mean values ± SEM from two control and two DCM clones. Statistical difference was tested using the two-sided chi-squared test (CTR Scr-AON: n = 874, n = 874, n = 882 and n = 890, CTR TTN-AON: n = 880, n = 990, n = 878 and n = 890, DCM Scr-AON: n = 890, n = 887, n = 884 and n = 886, DCM TTN-AON: n = 900, n = 875, n = 899 and n = 891 for SRF, MURF2, Nbr1 and SQSTM1/p62, respectively; *P = 0.01, CTR Scr-AON versus DCM Scr-AON; *P = 0.04, DCM Scr-AON versus DCM TTN-AON for SRF; *P = 0.02, CTR Scr-AON versus DCM Scr-AON; *P = 0.04, DCM Scr-AON versus DCM TTN-AON for MURF2; *P = 0.03, CTR Scr-AON versus DCM Scr-AON; *P = 0.03, DCM Scr-AON versus DCM TTN-AON for Nbr1; **P = 0.009, CTR Scr-AON versus DCM Scr-AON; *P = 0.01, DCM Scr-AON versus DCM TTN-AON for SQSTM1/p62). No significant differences were observed comparing CTR Scr-AON and CTR TTN-AON groups. Scale bars, 50 μm.
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fig04: Exon skipping-based rescue of SRF target gene expression and Nbr1/p62/SQSTM1/MURF2 subcellular distribution in TTN Ser14450fsX4 iPSC-derived cardiomyocytesqRT–PCR analysis of SRF target genes (MYH6, MYH7 and ACTC1) in CTR and DCM single cardiomyocytes under basal condition (no infection, NI) and after infection with control U7snRNA-ScrAONs-IRES-GFP (Scr-AON) and the U7snRNA-TTNAONs-IRES-GFP (TTN-AON) lentiviruses. Statistical difference was tested using the two-sided Student's t-test (**P = 0.009, CTR Scr-AON versus DCM Scr-AON; *P = 0.04, DCM Scr-AON versus DCM TTN-AON for MYH6; **P = 0.002, CTR Scr-AON versus DCM Scr-AON; **P = 0.002, DCM Scr-AON versus DCM TTN-AON for MYH7; **P = 0.004, CTR Scr-AON versus DCM Scr-AON; *P = 0.02, DCM Scr-AON versus DCM TTN-AON for ACTC1). No significant differences were observed comparing the CTR NI, CTR Scr-AON and CTR TTN-AON groups and comparing the DCM NI and DCM Scr-AON groups. Expression values were relative to CTR Scr-AON, normalized to GAPDH, and presented as mean ± SEM, n = 3.Immunofluorescence images showing normal (a, b, e, f, i, l, o, p) and altered (c, d, g, h, m, n, q, r) intracellular distribution of SRF (a and b, nuclear; c and d, cytoplasmic), MURF2 (e and f, sarcomeric; g and h, nuclear), Nbr1 (i and l, sarcomeric; m and n, diffused), and SQSTM1/p62 (o and p, sarcomeric; q and r, diffused) in representative single cardiomyocytes (left). Sarcomeres are marked by α-actinin. On the right, percentage of CTR and DCM cardiomyocytes showing cytoplasmic expression of SRF, nuclear accumulation of MURF2, and diffused expression of Nbr1 and of SQSTM1/p62 after infection with control U7snRNA-ScrambleAONs-IRES-GFP (Scr-AON) and the U7snRNA-TTNAONs-IRES-GFP (TTN-AON) lentiviruses (right). Data represent mean values ± SEM from two control and two DCM clones. Statistical difference was tested using the two-sided chi-squared test (CTR Scr-AON: n = 874, n = 874, n = 882 and n = 890, CTR TTN-AON: n = 880, n = 990, n = 878 and n = 890, DCM Scr-AON: n = 890, n = 887, n = 884 and n = 886, DCM TTN-AON: n = 900, n = 875, n = 899 and n = 891 for SRF, MURF2, Nbr1 and SQSTM1/p62, respectively; *P = 0.01, CTR Scr-AON versus DCM Scr-AON; *P = 0.04, DCM Scr-AON versus DCM TTN-AON for SRF; *P = 0.02, CTR Scr-AON versus DCM Scr-AON; *P = 0.04, DCM Scr-AON versus DCM TTN-AON for MURF2; *P = 0.03, CTR Scr-AON versus DCM Scr-AON; *P = 0.03, DCM Scr-AON versus DCM TTN-AON for Nbr1; **P = 0.009, CTR Scr-AON versus DCM Scr-AON; *P = 0.01, DCM Scr-AON versus DCM TTN-AON for SQSTM1/p62). No significant differences were observed comparing CTR Scr-AON and CTR TTN-AON groups. Scale bars, 50 μm.
Mentions: Titin is not only required as molecular scaffold during sarcomerogenesis and assists in the process of myofibrillar assembly, but it is also a hot spot for protein–protein interactions and a putative mediator of mechanotransduction. About 20 interaction partners have so far been identified, linking titin to multiple stress signaling pathways that control muscle gene expression and protein turnover (Linke & Kruger, 2010; Linke & Hamdani, 2014). One of the most extensively studied is the Nbr1/p62/SQSTM1/MURF2 signaling complex that associates with titin TK and activates the serum response factor (SRF) upon mechanical stimuli (Lange et al, 2005). TK mutations affecting this interaction result in the dissociation of the Nbr1/p62/SQSTM1/MURF2 complex and translocation of MURF2 into the nucleus, which in turn leads to suppression of SRF-dependent muscle gene transcription (Lange et al, 2005). Therefore, we analyzed expression levels of SRF targets (Miano et al, 2004; Balza & Misra, 2006) in control and patient cardiomyocytes after infection with U7snRNA-ScrAONs-IRES-GFP and U7snRNA-TTNAONs-IRES-GFP viruses. When compared to the control counterpart, a significant down-regulation of α- and β-myosin heavy chain (MYH6 and MYH7) transcripts as well as cardiac α-actin (ACTC1) was measured in the DCM cells untreated or transduced with scrambled AONs (Fig4A). Blocking of exon 326 transcription partially rescued SRF target levels in patient cardiomyocytes, with no effects on control cells (Fig4A). In concordance, immunocytochemistry assessment of SRF localization in iPSC-derived cardiomyocytes at 7 days after dissociation revealed a significant higher percentage of cells with increased extranuclear expression of SRF in the DCM group (Fig4B). Moreover, we observed differences in the subcellular distribution of MURF2, Nbr1, and p62/SQSTM1 in the DCM cardiomyocytes, with an increased number of cells showing a marked nuclear accumulation of MURF2 and a cytosolic, more diffused non-sarcomeric expression of Nbr1 and p62/SQSTM1 (Fig4B). Infection with U7snRNA-TTNAONs-IRES-GFP lentivirus partially normalized the cellular localization of all these proteins in the diseased cells, while no effects were observed in the control cells (Fig4B).

Bottom Line: Here, we show the beneficial potential of reframing titin transcripts by antisense oligonucleotide (AON)-mediated exon skipping in human and murine models of DCM carrying a previously identified autosomal-dominant frameshift mutation in titin exon 326.Correction of TTN reading frame in patient-specific cardiomyocytes derived from induced pluripotent stem cells rescued defective myofibril assembly and stability and normalized the sarcomeric protein expression.AON treatment in Ttn knock-in mice improved sarcomere formation and contractile performance in homozygous embryos and prevented the development of the DCM phenotype in heterozygous animals.

View Article: PubMed Central - PubMed

Affiliation: Department of Cardiology and Cardiovascular Diseases, Eberhard Karls University, Tübingen, Germany Victor Chang Cardiac Research Institute, Darlinghurst, NSW, Australia michael.gramlich@med.uni-tuebingen.de amoretti@med1.med.tum.de.

No MeSH data available.


Related in: MedlinePlus