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MeCP2 Affects Skeletal Muscle Growth and Morphology through Non Cell-Autonomous Mechanisms.

Conti V, Gandaglia A, Galli F, Tirone M, Bellini E, Campana L, Kilstrup-Nielsen C, Rovere-Querini P, Brunelli S, Landsberger N - PLoS ONE (2015)

Bottom Line: Our results suggest that defects in paracrine/endocrine signaling and, in particular, in the GH/IGF axis appear as the major cause of the observed muscular defects.Remarkably, this is the first study describing the selective deletion of Mecp2 outside the brain.Similar future studies will permit to unambiguously define the direct impact of MeCP2 on tissue dysfunctions.

View Article: PubMed Central - PubMed

Affiliation: Division of Regenerative Medicine, Stem Cells and Gene Therapy, San Raffaele Scientific Institute, Milan, Italy.

ABSTRACT
Rett syndrome (RTT) is an autism spectrum disorder mainly caused by mutations in the X-linked MECP2 gene and affecting roughly 1 out of 10.000 born girls. Symptoms range in severity and include stereotypical movement, lack of spoken language, seizures, ataxia and severe intellectual disability. Notably, muscle tone is generally abnormal in RTT girls and women and the Mecp2- mouse model constitutively reflects this disease feature. We hypothesized that MeCP2 in muscle might physiologically contribute to its development and/or homeostasis, and conversely its defects in RTT might alter the tissue integrity or function. We show here that a disorganized architecture, with hypotrophic fibres and tissue fibrosis, characterizes skeletal muscles retrieved from Mecp2- mice. Alterations of the IGF-1/Akt/mTOR pathway accompany the muscle phenotype. A conditional mouse model selectively depleted of Mecp2 in skeletal muscles is characterized by healthy muscles that are morphologically and molecularly indistinguishable from those of wild-type mice raising the possibility that hypotonia in RTT is mainly, if not exclusively, mediated by non-cell autonomous effects. Our results suggest that defects in paracrine/endocrine signaling and, in particular, in the GH/IGF axis appear as the major cause of the observed muscular defects. Remarkably, this is the first study describing the selective deletion of Mecp2 outside the brain. Similar future studies will permit to unambiguously define the direct impact of MeCP2 on tissue dysfunctions.

No MeSH data available.


Related in: MedlinePlus

Regeneration after acute muscle damage in Mecp2-/y skeletal muscle.(A) Representative gastrocnemius cross-sections of WT and Mecp2-/y mice 5 days (left panels) and 10 days (right panels) after Ctx injury stained with Hematoxylin and Eosin or immunostained for Laminin/DAPI to recognize centrally-nucleated myofibers. Scale bar = 100 μm. (B) Mean CSA ± s.e.m. and distribution of regenerating centronucleated myofibers 5 days (left panel) and 10 days (right panel) after Ctx injury. At least 150 myofibers were counted for each animal; significance is calculated with t test (****: p<0.0001). (C) Quantification of the number of CD68+, CD86+ and CD206+ cells located in the damaged area of WT and Mecp2-/y gastrocnemii 5 days after Ctx injury. Significance is calculated with t test (ns, CD68+: P value 0.8650; CD86+: P value 0.3513; CD206+: P value 0.7421. n≥3). Data are represented as mean ± s.e.m. (D) qPCR evaluation of IL-6, TNF-α, iNOS, IL-10 and IGF-1 mRNA in quadriceps 2, 5, 10 days after Ctx injury of WT and Mecp2-/y mice. All data points were calculated in triplicate, normalized to GAPDH and expressed as relative to not injured WT expression. Each time point is compared to the No Ctx situation of the same genotype and significance is calculated with t test. Data are represented as mean ± s.e.m. (IL-6 P value: ** = 0,0027, * = 0,0277; TNF-α P value: ** = 0,0033, * = 0,0195, ****<0,0001; iNOS P value: * = 0.0215, * = 0,0443, * = 0,0210; IL-10 P value: ** = 0,0089, *** = 0,0009, ****<0,0001; IGF-1 P value: * = 0,0477, * = 0,0191; n = 3).
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pone.0130183.g003: Regeneration after acute muscle damage in Mecp2-/y skeletal muscle.(A) Representative gastrocnemius cross-sections of WT and Mecp2-/y mice 5 days (left panels) and 10 days (right panels) after Ctx injury stained with Hematoxylin and Eosin or immunostained for Laminin/DAPI to recognize centrally-nucleated myofibers. Scale bar = 100 μm. (B) Mean CSA ± s.e.m. and distribution of regenerating centronucleated myofibers 5 days (left panel) and 10 days (right panel) after Ctx injury. At least 150 myofibers were counted for each animal; significance is calculated with t test (****: p<0.0001). (C) Quantification of the number of CD68+, CD86+ and CD206+ cells located in the damaged area of WT and Mecp2-/y gastrocnemii 5 days after Ctx injury. Significance is calculated with t test (ns, CD68+: P value 0.8650; CD86+: P value 0.3513; CD206+: P value 0.7421. n≥3). Data are represented as mean ± s.e.m. (D) qPCR evaluation of IL-6, TNF-α, iNOS, IL-10 and IGF-1 mRNA in quadriceps 2, 5, 10 days after Ctx injury of WT and Mecp2-/y mice. All data points were calculated in triplicate, normalized to GAPDH and expressed as relative to not injured WT expression. Each time point is compared to the No Ctx situation of the same genotype and significance is calculated with t test. Data are represented as mean ± s.e.m. (IL-6 P value: ** = 0,0027, * = 0,0277; TNF-α P value: ** = 0,0033, * = 0,0195, ****<0,0001; iNOS P value: * = 0.0215, * = 0,0443, * = 0,0210; IL-10 P value: ** = 0,0089, *** = 0,0009, ****<0,0001; IGF-1 P value: * = 0,0477, * = 0,0191; n = 3).

Mentions: To analyze whether MeCP2 expression is required for regeneration of adult muscle, we acutely injured the tissue by injecting gastrocnemius or quadriceps muscles of 6 weeks old Mecp2-/y mice and WT littermates with cardiotoxin (Ctx). Muscles were dissected 2, 5 and 10 days after injury and processed for either histology or mRNA expression analysis. The regeneration process was similar in WT and mutant mice, with transient infiltration of the tissue by inflammatory leukocytes, appearance of regenerating centronucleated myofibers and timely disposal of necrotic debris (Fig 3A, top panels). CSA of regenerating myofibers was significantly lower in injured muscles of Mecp2-/y mice compared to WT littermates both 5 and 10 days after damage (Fig 3A, bottom panels; 3B). These results indicate that also during regeneration fiber growth is affected by MeCP2 deficiency.


MeCP2 Affects Skeletal Muscle Growth and Morphology through Non Cell-Autonomous Mechanisms.

Conti V, Gandaglia A, Galli F, Tirone M, Bellini E, Campana L, Kilstrup-Nielsen C, Rovere-Querini P, Brunelli S, Landsberger N - PLoS ONE (2015)

Regeneration after acute muscle damage in Mecp2-/y skeletal muscle.(A) Representative gastrocnemius cross-sections of WT and Mecp2-/y mice 5 days (left panels) and 10 days (right panels) after Ctx injury stained with Hematoxylin and Eosin or immunostained for Laminin/DAPI to recognize centrally-nucleated myofibers. Scale bar = 100 μm. (B) Mean CSA ± s.e.m. and distribution of regenerating centronucleated myofibers 5 days (left panel) and 10 days (right panel) after Ctx injury. At least 150 myofibers were counted for each animal; significance is calculated with t test (****: p<0.0001). (C) Quantification of the number of CD68+, CD86+ and CD206+ cells located in the damaged area of WT and Mecp2-/y gastrocnemii 5 days after Ctx injury. Significance is calculated with t test (ns, CD68+: P value 0.8650; CD86+: P value 0.3513; CD206+: P value 0.7421. n≥3). Data are represented as mean ± s.e.m. (D) qPCR evaluation of IL-6, TNF-α, iNOS, IL-10 and IGF-1 mRNA in quadriceps 2, 5, 10 days after Ctx injury of WT and Mecp2-/y mice. All data points were calculated in triplicate, normalized to GAPDH and expressed as relative to not injured WT expression. Each time point is compared to the No Ctx situation of the same genotype and significance is calculated with t test. Data are represented as mean ± s.e.m. (IL-6 P value: ** = 0,0027, * = 0,0277; TNF-α P value: ** = 0,0033, * = 0,0195, ****<0,0001; iNOS P value: * = 0.0215, * = 0,0443, * = 0,0210; IL-10 P value: ** = 0,0089, *** = 0,0009, ****<0,0001; IGF-1 P value: * = 0,0477, * = 0,0191; n = 3).
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Related In: Results  -  Collection

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pone.0130183.g003: Regeneration after acute muscle damage in Mecp2-/y skeletal muscle.(A) Representative gastrocnemius cross-sections of WT and Mecp2-/y mice 5 days (left panels) and 10 days (right panels) after Ctx injury stained with Hematoxylin and Eosin or immunostained for Laminin/DAPI to recognize centrally-nucleated myofibers. Scale bar = 100 μm. (B) Mean CSA ± s.e.m. and distribution of regenerating centronucleated myofibers 5 days (left panel) and 10 days (right panel) after Ctx injury. At least 150 myofibers were counted for each animal; significance is calculated with t test (****: p<0.0001). (C) Quantification of the number of CD68+, CD86+ and CD206+ cells located in the damaged area of WT and Mecp2-/y gastrocnemii 5 days after Ctx injury. Significance is calculated with t test (ns, CD68+: P value 0.8650; CD86+: P value 0.3513; CD206+: P value 0.7421. n≥3). Data are represented as mean ± s.e.m. (D) qPCR evaluation of IL-6, TNF-α, iNOS, IL-10 and IGF-1 mRNA in quadriceps 2, 5, 10 days after Ctx injury of WT and Mecp2-/y mice. All data points were calculated in triplicate, normalized to GAPDH and expressed as relative to not injured WT expression. Each time point is compared to the No Ctx situation of the same genotype and significance is calculated with t test. Data are represented as mean ± s.e.m. (IL-6 P value: ** = 0,0027, * = 0,0277; TNF-α P value: ** = 0,0033, * = 0,0195, ****<0,0001; iNOS P value: * = 0.0215, * = 0,0443, * = 0,0210; IL-10 P value: ** = 0,0089, *** = 0,0009, ****<0,0001; IGF-1 P value: * = 0,0477, * = 0,0191; n = 3).
Mentions: To analyze whether MeCP2 expression is required for regeneration of adult muscle, we acutely injured the tissue by injecting gastrocnemius or quadriceps muscles of 6 weeks old Mecp2-/y mice and WT littermates with cardiotoxin (Ctx). Muscles were dissected 2, 5 and 10 days after injury and processed for either histology or mRNA expression analysis. The regeneration process was similar in WT and mutant mice, with transient infiltration of the tissue by inflammatory leukocytes, appearance of regenerating centronucleated myofibers and timely disposal of necrotic debris (Fig 3A, top panels). CSA of regenerating myofibers was significantly lower in injured muscles of Mecp2-/y mice compared to WT littermates both 5 and 10 days after damage (Fig 3A, bottom panels; 3B). These results indicate that also during regeneration fiber growth is affected by MeCP2 deficiency.

Bottom Line: Our results suggest that defects in paracrine/endocrine signaling and, in particular, in the GH/IGF axis appear as the major cause of the observed muscular defects.Remarkably, this is the first study describing the selective deletion of Mecp2 outside the brain.Similar future studies will permit to unambiguously define the direct impact of MeCP2 on tissue dysfunctions.

View Article: PubMed Central - PubMed

Affiliation: Division of Regenerative Medicine, Stem Cells and Gene Therapy, San Raffaele Scientific Institute, Milan, Italy.

ABSTRACT
Rett syndrome (RTT) is an autism spectrum disorder mainly caused by mutations in the X-linked MECP2 gene and affecting roughly 1 out of 10.000 born girls. Symptoms range in severity and include stereotypical movement, lack of spoken language, seizures, ataxia and severe intellectual disability. Notably, muscle tone is generally abnormal in RTT girls and women and the Mecp2- mouse model constitutively reflects this disease feature. We hypothesized that MeCP2 in muscle might physiologically contribute to its development and/or homeostasis, and conversely its defects in RTT might alter the tissue integrity or function. We show here that a disorganized architecture, with hypotrophic fibres and tissue fibrosis, characterizes skeletal muscles retrieved from Mecp2- mice. Alterations of the IGF-1/Akt/mTOR pathway accompany the muscle phenotype. A conditional mouse model selectively depleted of Mecp2 in skeletal muscles is characterized by healthy muscles that are morphologically and molecularly indistinguishable from those of wild-type mice raising the possibility that hypotonia in RTT is mainly, if not exclusively, mediated by non-cell autonomous effects. Our results suggest that defects in paracrine/endocrine signaling and, in particular, in the GH/IGF axis appear as the major cause of the observed muscular defects. Remarkably, this is the first study describing the selective deletion of Mecp2 outside the brain. Similar future studies will permit to unambiguously define the direct impact of MeCP2 on tissue dysfunctions.

No MeSH data available.


Related in: MedlinePlus