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Desmin is essential for the tensile strength and integrity of myofibrils but not for myogenic commitment, differentiation, and fusion of skeletal muscle.

Li Z, Mericskay M, Agbulut O, Butler-Browne G, Carlsson L, Thornell LE, Babinet C, Paulin D - J. Cell Biol. (1997)

Bottom Line: Our results demonstrate that all early stages of muscle differentiation and cell fusion occur normally.However, myofibrillogenesis in regenerating fibers is often abortive, indicating that desmin may be implicated in this repair process.The results presented here show that desmin is essential to maintain the structural integrity of highly solicited skeletal muscle.

View Article: PubMed Central - PubMed

Affiliation: Station Centrale de Microscopie Electronique, Institut Pasteur, Paris, France.

ABSTRACT
A mutation was introduced into the mouse desmin gene by homologous recombination. The desmin knockout mice (Des -/-) develop normally and are fertile. However, defects were observed after birth in skeletal, smooth, and cardiac muscles (Li, Z., E. Colucci-Guyon, M. Pincon-Raymond, M. Mericskay, S. Pournin, D. Paulin, and C. Babinet. 1996. Dev. Biol. 175:362-366; Milner, D.J., G. Weitzer, D. Tran, A. Bradley, and Y. Capetanaki. 1996. J. Cell Biol. 134:1255- 1270). In the present study we have carried out a detailed analysis of somitogenesis, muscle formation, maturation, degeneration, and regeneration in Des -/- mice. Our results demonstrate that all early stages of muscle differentiation and cell fusion occur normally. However, after birth, modifications were observed essentially in weight-bearing muscles such as the soleus or continually used muscles such as the diaphragm and the heart. In the absence of desmin, mice were weaker and fatigued more easily. The lack of desmin renders these fibers more susceptible to damage during contraction. We observed a process of degeneration of myofibers, accompanied by macrophage infiltration, and followed by a process of regeneration. These cycles of degeneration and regeneration resulted in a relative increase in slow myosin heavy chain (MHC) and decrease in fast MHC. Interestingly, this second wave of myofibrillogenesis during regeneration was often aberrant and showed signs of disorganization. Subsarcolemmal accumulation of mitochondria were also observed in these muscles. The lack of desmin was not compensated by an upregulation of vimentin in these mice either during development or regeneration. Absence of desmin filaments within the sarcomere does not interfere with primary muscle formation or regeneration. However, myofibrillogenesis in regenerating fibers is often abortive, indicating that desmin may be implicated in this repair process. The results presented here show that desmin is essential to maintain the structural integrity of highly solicited skeletal muscle.

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Myotome differentiation and migration of myogenic cells from somites into limbs of 11-d.p.c embryos. Sagittal sections at the  somitic level of Des −/− (A), Des +/− (B), and Des +/+ (C) embryos. Myotomes have the same morphology when revealed by the  blue staining. Transversal sections of the limb bud of Des −/− (D), Des +/+ (E) embryos, with the presence in both sections of blue  mononucleated myogenic cells, which have migrated but not yet fused. Analysis of vimentin and desmin expression during embryonic  development in myogenic cells were performed with immunoperoxidase reactions on cryostat sections on 10.5-d.p.c. embryos from Des  +/− heterozygous (G), and Des −/− homozygous (H) mice. The nuclear blue staining was used to characterize the myogenic population. In the control, the desmin-positive, mononucleated cells, which are located in the lateral part of the myotome, have blue nuclei. Immunodetection of desmin stained cytoplasm in brown (F). The adjacent section shows same blue cells negative for vimentin (G). The  mutant, mononucleated cells located in the lateral part of the Des −/− myotome are labeled with a blue nucleus but are negative for  desmin and vimentin (H). The neural tube (nt) is stained with vimentin antibody. Bar, 50 μm.
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Figure 2: Myotome differentiation and migration of myogenic cells from somites into limbs of 11-d.p.c embryos. Sagittal sections at the somitic level of Des −/− (A), Des +/− (B), and Des +/+ (C) embryos. Myotomes have the same morphology when revealed by the blue staining. Transversal sections of the limb bud of Des −/− (D), Des +/+ (E) embryos, with the presence in both sections of blue mononucleated myogenic cells, which have migrated but not yet fused. Analysis of vimentin and desmin expression during embryonic development in myogenic cells were performed with immunoperoxidase reactions on cryostat sections on 10.5-d.p.c. embryos from Des +/− heterozygous (G), and Des −/− homozygous (H) mice. The nuclear blue staining was used to characterize the myogenic population. In the control, the desmin-positive, mononucleated cells, which are located in the lateral part of the myotome, have blue nuclei. Immunodetection of desmin stained cytoplasm in brown (F). The adjacent section shows same blue cells negative for vimentin (G). The mutant, mononucleated cells located in the lateral part of the Des −/− myotome are labeled with a blue nucleus but are negative for desmin and vimentin (H). The neural tube (nt) is stained with vimentin antibody. Bar, 50 μm.

Mentions: To analyze the role of desmin during somitogenesis we have taken advantage of the replacement of desmin by the LacZ coding sequence via homologous recombination in ES cells. In the resulting desmin knockout (Des −/−) mice, we can follow the specific β-galactosidase expression in myogenic cells by their blue coloration and examine whether there are abnormalities or differences either in the chronology or morphology of the formation of myotomes in the mice lacking desmin. We have compared the blue staining of the Des −/−, the Des +/− mice obtained after crossing heterozygous mice, and the previously described Des +/+ transgenic mice (Li et al., 1993). As shown in Fig. 1, no morphological differences could be detected at this stage (11 d.p.c.) for Des −/− embryos (Fig. 1 B) compared to desmin-expressing embryos Des +/− (Fig. 1 A), and these mice were indistinguishable from the wild-type counterparts. Somites displayed the same morphology as described previously for the Des +/+ transgenic mice (Li et al., 1993). Sections of somites from Des −/−, Des +/−, and Des +/+ are shown in Fig. 2, A–C. We observed a normal ventral extension of the dermomyotome at the thoracic level.


Desmin is essential for the tensile strength and integrity of myofibrils but not for myogenic commitment, differentiation, and fusion of skeletal muscle.

Li Z, Mericskay M, Agbulut O, Butler-Browne G, Carlsson L, Thornell LE, Babinet C, Paulin D - J. Cell Biol. (1997)

Myotome differentiation and migration of myogenic cells from somites into limbs of 11-d.p.c embryos. Sagittal sections at the  somitic level of Des −/− (A), Des +/− (B), and Des +/+ (C) embryos. Myotomes have the same morphology when revealed by the  blue staining. Transversal sections of the limb bud of Des −/− (D), Des +/+ (E) embryos, with the presence in both sections of blue  mononucleated myogenic cells, which have migrated but not yet fused. Analysis of vimentin and desmin expression during embryonic  development in myogenic cells were performed with immunoperoxidase reactions on cryostat sections on 10.5-d.p.c. embryos from Des  +/− heterozygous (G), and Des −/− homozygous (H) mice. The nuclear blue staining was used to characterize the myogenic population. In the control, the desmin-positive, mononucleated cells, which are located in the lateral part of the myotome, have blue nuclei. Immunodetection of desmin stained cytoplasm in brown (F). The adjacent section shows same blue cells negative for vimentin (G). The  mutant, mononucleated cells located in the lateral part of the Des −/− myotome are labeled with a blue nucleus but are negative for  desmin and vimentin (H). The neural tube (nt) is stained with vimentin antibody. Bar, 50 μm.
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Figure 2: Myotome differentiation and migration of myogenic cells from somites into limbs of 11-d.p.c embryos. Sagittal sections at the somitic level of Des −/− (A), Des +/− (B), and Des +/+ (C) embryos. Myotomes have the same morphology when revealed by the blue staining. Transversal sections of the limb bud of Des −/− (D), Des +/+ (E) embryos, with the presence in both sections of blue mononucleated myogenic cells, which have migrated but not yet fused. Analysis of vimentin and desmin expression during embryonic development in myogenic cells were performed with immunoperoxidase reactions on cryostat sections on 10.5-d.p.c. embryos from Des +/− heterozygous (G), and Des −/− homozygous (H) mice. The nuclear blue staining was used to characterize the myogenic population. In the control, the desmin-positive, mononucleated cells, which are located in the lateral part of the myotome, have blue nuclei. Immunodetection of desmin stained cytoplasm in brown (F). The adjacent section shows same blue cells negative for vimentin (G). The mutant, mononucleated cells located in the lateral part of the Des −/− myotome are labeled with a blue nucleus but are negative for desmin and vimentin (H). The neural tube (nt) is stained with vimentin antibody. Bar, 50 μm.
Mentions: To analyze the role of desmin during somitogenesis we have taken advantage of the replacement of desmin by the LacZ coding sequence via homologous recombination in ES cells. In the resulting desmin knockout (Des −/−) mice, we can follow the specific β-galactosidase expression in myogenic cells by their blue coloration and examine whether there are abnormalities or differences either in the chronology or morphology of the formation of myotomes in the mice lacking desmin. We have compared the blue staining of the Des −/−, the Des +/− mice obtained after crossing heterozygous mice, and the previously described Des +/+ transgenic mice (Li et al., 1993). As shown in Fig. 1, no morphological differences could be detected at this stage (11 d.p.c.) for Des −/− embryos (Fig. 1 B) compared to desmin-expressing embryos Des +/− (Fig. 1 A), and these mice were indistinguishable from the wild-type counterparts. Somites displayed the same morphology as described previously for the Des +/+ transgenic mice (Li et al., 1993). Sections of somites from Des −/−, Des +/−, and Des +/+ are shown in Fig. 2, A–C. We observed a normal ventral extension of the dermomyotome at the thoracic level.

Bottom Line: Our results demonstrate that all early stages of muscle differentiation and cell fusion occur normally.However, myofibrillogenesis in regenerating fibers is often abortive, indicating that desmin may be implicated in this repair process.The results presented here show that desmin is essential to maintain the structural integrity of highly solicited skeletal muscle.

View Article: PubMed Central - PubMed

Affiliation: Station Centrale de Microscopie Electronique, Institut Pasteur, Paris, France.

ABSTRACT
A mutation was introduced into the mouse desmin gene by homologous recombination. The desmin knockout mice (Des -/-) develop normally and are fertile. However, defects were observed after birth in skeletal, smooth, and cardiac muscles (Li, Z., E. Colucci-Guyon, M. Pincon-Raymond, M. Mericskay, S. Pournin, D. Paulin, and C. Babinet. 1996. Dev. Biol. 175:362-366; Milner, D.J., G. Weitzer, D. Tran, A. Bradley, and Y. Capetanaki. 1996. J. Cell Biol. 134:1255- 1270). In the present study we have carried out a detailed analysis of somitogenesis, muscle formation, maturation, degeneration, and regeneration in Des -/- mice. Our results demonstrate that all early stages of muscle differentiation and cell fusion occur normally. However, after birth, modifications were observed essentially in weight-bearing muscles such as the soleus or continually used muscles such as the diaphragm and the heart. In the absence of desmin, mice were weaker and fatigued more easily. The lack of desmin renders these fibers more susceptible to damage during contraction. We observed a process of degeneration of myofibers, accompanied by macrophage infiltration, and followed by a process of regeneration. These cycles of degeneration and regeneration resulted in a relative increase in slow myosin heavy chain (MHC) and decrease in fast MHC. Interestingly, this second wave of myofibrillogenesis during regeneration was often aberrant and showed signs of disorganization. Subsarcolemmal accumulation of mitochondria were also observed in these muscles. The lack of desmin was not compensated by an upregulation of vimentin in these mice either during development or regeneration. Absence of desmin filaments within the sarcomere does not interfere with primary muscle formation or regeneration. However, myofibrillogenesis in regenerating fibers is often abortive, indicating that desmin may be implicated in this repair process. The results presented here show that desmin is essential to maintain the structural integrity of highly solicited skeletal muscle.

Show MeSH
Related in: MedlinePlus