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HDAC4-myogenin axis as an important marker of HD-related skeletal muscle atrophy.

Mielcarek M, Toczek M, Smeets CJ, Franklin SA, Bondulich MK, Jolinon N, Muller T, Ahmed M, Dick JR, Piotrowska I, Greensmith L, Smolenski RT, Bates GP - PLoS Genet. (2015)

Bottom Line: We found that symptomatic animals developed a progressive impairment of the contractile characteristics of the hind limb muscles tibialis anterior (TA) and extensor digitorum longus (EDL), accompanied by a significant loss of motor units in the EDL.In addition, HD mouse models develop a significant reduction in muscle force, possibly as a result of a deterioration in energy metabolism and decreased oxidation that is accompanied by the re-expression of the HDAC4-DACH2-myogenin axis.These results show that muscle dysfunction is a key pathological feature of HD.

View Article: PubMed Central - PubMed

Affiliation: Department of Medical and Molecular Genetics, King's College London, London, United Kingdom.

ABSTRACT
Skeletal muscle remodelling and contractile dysfunction occur through both acute and chronic disease processes. These include the accumulation of insoluble aggregates of misfolded amyloid proteins that is a pathological feature of Huntington's disease (HD). While HD has been described primarily as a neurological disease, HD patients' exhibit pronounced skeletal muscle atrophy. Given that huntingtin is a ubiquitously expressed protein, skeletal muscle fibres may be at risk of a cell autonomous HD-related dysfunction. However the mechanism leading to skeletal muscle abnormalities in the clinical and pre-clinical HD settings remains unknown. To unravel this mechanism, we employed the R6/2 transgenic and HdhQ150 knock-in mouse models of HD. We found that symptomatic animals developed a progressive impairment of the contractile characteristics of the hind limb muscles tibialis anterior (TA) and extensor digitorum longus (EDL), accompanied by a significant loss of motor units in the EDL. In symptomatic animals, these pronounced functional changes were accompanied by an aberrant deregulation of contractile protein transcripts and their up-stream transcriptional regulators. In addition, HD mouse models develop a significant reduction in muscle force, possibly as a result of a deterioration in energy metabolism and decreased oxidation that is accompanied by the re-expression of the HDAC4-DACH2-myogenin axis. These results show that muscle dysfunction is a key pathological feature of HD.

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Transcriptional deregulation of TEAD family members and their co-activators involved in the skeletal muscle atrophy.(A) Tead-1 (TEA domain family member 1), (B) Tead-2 (TEA domain family member 2), (C) Tead-3 (TEA domain family member 3), (D) Tead-4 (TEA domain family member 4). Tead-2 and Tead-4 transcripts were deregulated in various muscles of the HD models. (E) Vgll-2 (vestigial related factor 2), (F) Vgll-3 (vestigial related factor 3), (G) Vgll-4 (vestigial related factor 4) and (H) Yap-65 (Yes associated protein 65) were significantly up-regulated in skeletal muscles of the HD models. All Taqman qPCR values were normalized to the geometric mean of three housekeeping genes: Atp5b, Yhwaz and Rpl13a. Error bars are SEM (n = 6). Student’s t-test: *p < 0.05, **p < 0.01; ***p < 0.001.
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pgen.1005021.g003: Transcriptional deregulation of TEAD family members and their co-activators involved in the skeletal muscle atrophy.(A) Tead-1 (TEA domain family member 1), (B) Tead-2 (TEA domain family member 2), (C) Tead-3 (TEA domain family member 3), (D) Tead-4 (TEA domain family member 4). Tead-2 and Tead-4 transcripts were deregulated in various muscles of the HD models. (E) Vgll-2 (vestigial related factor 2), (F) Vgll-3 (vestigial related factor 3), (G) Vgll-4 (vestigial related factor 4) and (H) Yap-65 (Yes associated protein 65) were significantly up-regulated in skeletal muscles of the HD models. All Taqman qPCR values were normalized to the geometric mean of three housekeeping genes: Atp5b, Yhwaz and Rpl13a. Error bars are SEM (n = 6). Student’s t-test: *p < 0.05, **p < 0.01; ***p < 0.001.

Mentions: In order to corroborate the physiological findings described above, we used Taqman qPCR to quantify contractile transcipt levels that are representtive of the fast or slow type fibers. Given that global transcriptional dysregulation is a pathogenic characteristic of HD, we first performed a systematic study to identify suitable reference genes for use in the expression analysis of different skeletal muscles types from HD mouse models. We used the geNorm™ Housekeeping Gene Selection Mouse Kit and associated software to identify the three most stably expressed genes in specific muscles from R6/2 (S2 Fig.) and HdhQ150 (S3 Fig.) mice. Our relative quantification methods then used the geometric mean of these three selected reference genes for normalization, to accurately determine gene expression levels in WT, R6/2 and HdhQ150 skeletal muscle tissue. We found a significant up-regulation of slow-type contractile proteins such as Tnn1 (Troponin 1, slow) and Myh7 (myosin heavy light chain 7) in TA, EDL and G/P muscles from both HD mouse models (Fig. 2C and E). Consequently, a pronounced down-regulation of the fast-type contractile proteins like Tnn3 (Troponin3, fast) and Myh2 (myosin heavy light chain 2) was also observed in TA, EDL and G/P muscles from both HD mouse models (Fig. 2D and F). These findings indicate that there is a loss of fast-twitch muscle fibres in the EDL and TA of both models. Subsequently, we determined the expression levels of additional genes that are attributed to be altered in fast to slow twitch remodelling. TEA domain (TEAD) transcription factors and their co-activators serve important functional roles during embryonic development as well as in striated muscle gene expression and muscle regeneration [33–36]. It has been shown that striated muscle-restricted TEAD-1 expression induced a transition toward a slow muscle contractile protein phenotype, slower shortening velocity with longer contraction and relaxation times in the adult fast twitch EDL muscles [33]. We found that Tead-2 (TEA domain family member 2) (Fig. 3B) and Tead-4 (TEA domain family member 4) (Fig. 3D) were significantly up-regulated in the all diseased HD muscles in both mouse models, while Tead-1 (TEA domain family member 1) (Fig. 3A) and Tead-3 (TEA domain family member 3) (Fig. 3C) transcripts remained un-changed. The transcriptional activity of TEAD family members is highly dependent on the presence of their co-activators [37–39] and therefore, we used Taqman-qPCR to asses their transcriptional profile in the HD diseased muscles. We established that Vgll-2 (vestigial related factor 2) (Fig. 3E), Vgll-3 (vestigial related factor 3) (Fig. 3F), Vgll-4 (vestigial related factor 4) (Fig. 3G) and Yap-65 (Yes associated protein 65) (Fig. 3H) were significantly up-regulated in the TA, EDL and G/P muscles of R6/2 and HdhQ150 mice.


HDAC4-myogenin axis as an important marker of HD-related skeletal muscle atrophy.

Mielcarek M, Toczek M, Smeets CJ, Franklin SA, Bondulich MK, Jolinon N, Muller T, Ahmed M, Dick JR, Piotrowska I, Greensmith L, Smolenski RT, Bates GP - PLoS Genet. (2015)

Transcriptional deregulation of TEAD family members and their co-activators involved in the skeletal muscle atrophy.(A) Tead-1 (TEA domain family member 1), (B) Tead-2 (TEA domain family member 2), (C) Tead-3 (TEA domain family member 3), (D) Tead-4 (TEA domain family member 4). Tead-2 and Tead-4 transcripts were deregulated in various muscles of the HD models. (E) Vgll-2 (vestigial related factor 2), (F) Vgll-3 (vestigial related factor 3), (G) Vgll-4 (vestigial related factor 4) and (H) Yap-65 (Yes associated protein 65) were significantly up-regulated in skeletal muscles of the HD models. All Taqman qPCR values were normalized to the geometric mean of three housekeeping genes: Atp5b, Yhwaz and Rpl13a. Error bars are SEM (n = 6). Student’s t-test: *p < 0.05, **p < 0.01; ***p < 0.001.
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Related In: Results  -  Collection

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pgen.1005021.g003: Transcriptional deregulation of TEAD family members and their co-activators involved in the skeletal muscle atrophy.(A) Tead-1 (TEA domain family member 1), (B) Tead-2 (TEA domain family member 2), (C) Tead-3 (TEA domain family member 3), (D) Tead-4 (TEA domain family member 4). Tead-2 and Tead-4 transcripts were deregulated in various muscles of the HD models. (E) Vgll-2 (vestigial related factor 2), (F) Vgll-3 (vestigial related factor 3), (G) Vgll-4 (vestigial related factor 4) and (H) Yap-65 (Yes associated protein 65) were significantly up-regulated in skeletal muscles of the HD models. All Taqman qPCR values were normalized to the geometric mean of three housekeeping genes: Atp5b, Yhwaz and Rpl13a. Error bars are SEM (n = 6). Student’s t-test: *p < 0.05, **p < 0.01; ***p < 0.001.
Mentions: In order to corroborate the physiological findings described above, we used Taqman qPCR to quantify contractile transcipt levels that are representtive of the fast or slow type fibers. Given that global transcriptional dysregulation is a pathogenic characteristic of HD, we first performed a systematic study to identify suitable reference genes for use in the expression analysis of different skeletal muscles types from HD mouse models. We used the geNorm™ Housekeeping Gene Selection Mouse Kit and associated software to identify the three most stably expressed genes in specific muscles from R6/2 (S2 Fig.) and HdhQ150 (S3 Fig.) mice. Our relative quantification methods then used the geometric mean of these three selected reference genes for normalization, to accurately determine gene expression levels in WT, R6/2 and HdhQ150 skeletal muscle tissue. We found a significant up-regulation of slow-type contractile proteins such as Tnn1 (Troponin 1, slow) and Myh7 (myosin heavy light chain 7) in TA, EDL and G/P muscles from both HD mouse models (Fig. 2C and E). Consequently, a pronounced down-regulation of the fast-type contractile proteins like Tnn3 (Troponin3, fast) and Myh2 (myosin heavy light chain 2) was also observed in TA, EDL and G/P muscles from both HD mouse models (Fig. 2D and F). These findings indicate that there is a loss of fast-twitch muscle fibres in the EDL and TA of both models. Subsequently, we determined the expression levels of additional genes that are attributed to be altered in fast to slow twitch remodelling. TEA domain (TEAD) transcription factors and their co-activators serve important functional roles during embryonic development as well as in striated muscle gene expression and muscle regeneration [33–36]. It has been shown that striated muscle-restricted TEAD-1 expression induced a transition toward a slow muscle contractile protein phenotype, slower shortening velocity with longer contraction and relaxation times in the adult fast twitch EDL muscles [33]. We found that Tead-2 (TEA domain family member 2) (Fig. 3B) and Tead-4 (TEA domain family member 4) (Fig. 3D) were significantly up-regulated in the all diseased HD muscles in both mouse models, while Tead-1 (TEA domain family member 1) (Fig. 3A) and Tead-3 (TEA domain family member 3) (Fig. 3C) transcripts remained un-changed. The transcriptional activity of TEAD family members is highly dependent on the presence of their co-activators [37–39] and therefore, we used Taqman-qPCR to asses their transcriptional profile in the HD diseased muscles. We established that Vgll-2 (vestigial related factor 2) (Fig. 3E), Vgll-3 (vestigial related factor 3) (Fig. 3F), Vgll-4 (vestigial related factor 4) (Fig. 3G) and Yap-65 (Yes associated protein 65) (Fig. 3H) were significantly up-regulated in the TA, EDL and G/P muscles of R6/2 and HdhQ150 mice.

Bottom Line: We found that symptomatic animals developed a progressive impairment of the contractile characteristics of the hind limb muscles tibialis anterior (TA) and extensor digitorum longus (EDL), accompanied by a significant loss of motor units in the EDL.In addition, HD mouse models develop a significant reduction in muscle force, possibly as a result of a deterioration in energy metabolism and decreased oxidation that is accompanied by the re-expression of the HDAC4-DACH2-myogenin axis.These results show that muscle dysfunction is a key pathological feature of HD.

View Article: PubMed Central - PubMed

Affiliation: Department of Medical and Molecular Genetics, King's College London, London, United Kingdom.

ABSTRACT
Skeletal muscle remodelling and contractile dysfunction occur through both acute and chronic disease processes. These include the accumulation of insoluble aggregates of misfolded amyloid proteins that is a pathological feature of Huntington's disease (HD). While HD has been described primarily as a neurological disease, HD patients' exhibit pronounced skeletal muscle atrophy. Given that huntingtin is a ubiquitously expressed protein, skeletal muscle fibres may be at risk of a cell autonomous HD-related dysfunction. However the mechanism leading to skeletal muscle abnormalities in the clinical and pre-clinical HD settings remains unknown. To unravel this mechanism, we employed the R6/2 transgenic and HdhQ150 knock-in mouse models of HD. We found that symptomatic animals developed a progressive impairment of the contractile characteristics of the hind limb muscles tibialis anterior (TA) and extensor digitorum longus (EDL), accompanied by a significant loss of motor units in the EDL. In symptomatic animals, these pronounced functional changes were accompanied by an aberrant deregulation of contractile protein transcripts and their up-stream transcriptional regulators. In addition, HD mouse models develop a significant reduction in muscle force, possibly as a result of a deterioration in energy metabolism and decreased oxidation that is accompanied by the re-expression of the HDAC4-DACH2-myogenin axis. These results show that muscle dysfunction is a key pathological feature of HD.

Show MeSH
Related in: MedlinePlus