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Ectopic Expression of Retrotransposon-Derived PEG11/RTL1 Contributes to the Callipyge Muscular Hypertrophy.

Xu X, Ectors F, Davis EE, Pirottin D, Cheng H, Farnir F, Hadfield T, Cockett N, Charlier C, Georges M, Takeda H - PLoS ONE (2015)

Bottom Line: The callipyge phenotype is an ovine muscular hypertrophy characterized by polar overdominance: only heterozygous +Mat/CLPGPat animals receiving the CLPG mutation from their father express the phenotype. +Mat/CLPGPat animals are characterized by postnatal, ectopic expression of Delta-like 1 homologue (DLK1) and Paternally expressed gene 11/Retrotransposon-like 1 (PEG11/RTL1) proteins in skeletal muscle.We herein describe newly generated transgenic mice that ectopically express PEG11 in skeletal muscle, and show that they also exhibit a muscular hypertrophy phenotype.Our data suggest that both DLK1 and PEG11 act together in causing the muscular hypertrophy of callipyge sheep.

View Article: PubMed Central - PubMed

Affiliation: Unit of Animal Genomics, GIGA Research Center and Faculty of Veterinary Medicine, University of Liège, 1 Avenue de l'Hôpital, Liège, Belgium.

ABSTRACT
The callipyge phenotype is an ovine muscular hypertrophy characterized by polar overdominance: only heterozygous +Mat/CLPGPat animals receiving the CLPG mutation from their father express the phenotype. +Mat/CLPGPat animals are characterized by postnatal, ectopic expression of Delta-like 1 homologue (DLK1) and Paternally expressed gene 11/Retrotransposon-like 1 (PEG11/RTL1) proteins in skeletal muscle. We showed previously in transgenic mice that ectopic expression of DLK1 alone induces a muscular hypertrophy, hence demonstrating a role for DLK1 in determining the callipyge hypertrophy. We herein describe newly generated transgenic mice that ectopically express PEG11 in skeletal muscle, and show that they also exhibit a muscular hypertrophy phenotype. Our data suggest that both DLK1 and PEG11 act together in causing the muscular hypertrophy of callipyge sheep.

No MeSH data available.


Related in: MedlinePlus

Relative frequency distribution of myofiber cross-sectional size of extensor digitorum longus (A) and soleus (B) muscle sorted by transgene genotype.The minimal Feret’s diameters of on average 1,062 fibers were measured for each animal-muscle type combination so as to cover the entire cross-sectional area of the muscle. Y-axis shows means of relative frequencies among animals with the same genotype. X-axis shows myofiber cross-sectional size ranging from 0 to 75 μm with a bin width 3. Color used for each genotype class, genotype means of myofober diameter (± 1.96 x s.e.m.) and statistical significance of the contrasts between genotypes computed with the Tukey honest significant difference test are shown in the upper right corner of each Fig ***: p < 0.001; n = 3 (+/+), 5 (+/TP) and 2 (TP/TP).
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pone.0140594.g004: Relative frequency distribution of myofiber cross-sectional size of extensor digitorum longus (A) and soleus (B) muscle sorted by transgene genotype.The minimal Feret’s diameters of on average 1,062 fibers were measured for each animal-muscle type combination so as to cover the entire cross-sectional area of the muscle. Y-axis shows means of relative frequencies among animals with the same genotype. X-axis shows myofiber cross-sectional size ranging from 0 to 75 μm with a bin width 3. Color used for each genotype class, genotype means of myofober diameter (± 1.96 x s.e.m.) and statistical significance of the contrasts between genotypes computed with the Tukey honest significant difference test are shown in the upper right corner of each Fig ***: p < 0.001; n = 3 (+/+), 5 (+/TP) and 2 (TP/TP).

Mentions: We next examined the effect of the oPEG11 transgene on myofiber size distribution. In callipyge sheep, myofiber diameter was increased by 24%, 20% and 7% in longissimus, gluteus medius and supraspinatus muscles, respectively [18]. The ovine DLK1 transgenic mice exhibited increase of the quadriceps myofiber diameter by 7.4%, 8.7% and 10.5% in +/T and T/T (line A), and +/T (line D) genotypes, respectively [9]. We here selected to use extensor digitorum longus (EDL) and soleus (SL) muscles that are known to be rich and poor in type IIB myofibers, respectively (55.7–86.6% for EDL, 0.0–3.1% for SL [19, 20]) where the Mlc 3F/2E regulatory elements are expected to be most active [16]. We dissected the two muscles from ten male mice in two litters at 7 and 10 months of age (n = 3, 5, 2 for +/+, +/TP and TP/TP, respectively) and performed hematoxylin and eosin staining of transverse sections. We measured the minimal Feret’s diameter of myofibers [21] (on average 1,062 myofibers per animal-muscle combination) so as to cover the entire cross-sectional muscle area (Fig 4; S3 Fig). EDL myofiber size was increased by 15.7% and 24.6% in +/TP and TP/TP mice, respectively, compared to +/+ (p < 2.0x10-16). The contrast between +/TP and TP/TP genotypes was also significant (+7.7%, p < 2.0x10-16). On the other hand, none of the corresponding contrasts in SL muscle was significant (p > 5.9x10-2), consistent with the lower contribution of type IIB fibers in SL muscle. Skewness of the myofiber diameter distribution in EDL muscle was changed from right- to left-tailed by increasing the transgene copy number (+/+ = 0.22, +/TP = -0.05, TP/TP = -0.17). This implies that part of the myofibers in EDL muscle (supposedly glycolytic fast twitch fibers) is enlarged by the oPEG11 transgene expression. We did not observe any apparent histological abnormality in these samples (f.i. necrosis, fibrosis, fat deposition, increase of myofibers with centrally located nuclei) (S3 Fig).


Ectopic Expression of Retrotransposon-Derived PEG11/RTL1 Contributes to the Callipyge Muscular Hypertrophy.

Xu X, Ectors F, Davis EE, Pirottin D, Cheng H, Farnir F, Hadfield T, Cockett N, Charlier C, Georges M, Takeda H - PLoS ONE (2015)

Relative frequency distribution of myofiber cross-sectional size of extensor digitorum longus (A) and soleus (B) muscle sorted by transgene genotype.The minimal Feret’s diameters of on average 1,062 fibers were measured for each animal-muscle type combination so as to cover the entire cross-sectional area of the muscle. Y-axis shows means of relative frequencies among animals with the same genotype. X-axis shows myofiber cross-sectional size ranging from 0 to 75 μm with a bin width 3. Color used for each genotype class, genotype means of myofober diameter (± 1.96 x s.e.m.) and statistical significance of the contrasts between genotypes computed with the Tukey honest significant difference test are shown in the upper right corner of each Fig ***: p < 0.001; n = 3 (+/+), 5 (+/TP) and 2 (TP/TP).
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4608697&req=5

pone.0140594.g004: Relative frequency distribution of myofiber cross-sectional size of extensor digitorum longus (A) and soleus (B) muscle sorted by transgene genotype.The minimal Feret’s diameters of on average 1,062 fibers were measured for each animal-muscle type combination so as to cover the entire cross-sectional area of the muscle. Y-axis shows means of relative frequencies among animals with the same genotype. X-axis shows myofiber cross-sectional size ranging from 0 to 75 μm with a bin width 3. Color used for each genotype class, genotype means of myofober diameter (± 1.96 x s.e.m.) and statistical significance of the contrasts between genotypes computed with the Tukey honest significant difference test are shown in the upper right corner of each Fig ***: p < 0.001; n = 3 (+/+), 5 (+/TP) and 2 (TP/TP).
Mentions: We next examined the effect of the oPEG11 transgene on myofiber size distribution. In callipyge sheep, myofiber diameter was increased by 24%, 20% and 7% in longissimus, gluteus medius and supraspinatus muscles, respectively [18]. The ovine DLK1 transgenic mice exhibited increase of the quadriceps myofiber diameter by 7.4%, 8.7% and 10.5% in +/T and T/T (line A), and +/T (line D) genotypes, respectively [9]. We here selected to use extensor digitorum longus (EDL) and soleus (SL) muscles that are known to be rich and poor in type IIB myofibers, respectively (55.7–86.6% for EDL, 0.0–3.1% for SL [19, 20]) where the Mlc 3F/2E regulatory elements are expected to be most active [16]. We dissected the two muscles from ten male mice in two litters at 7 and 10 months of age (n = 3, 5, 2 for +/+, +/TP and TP/TP, respectively) and performed hematoxylin and eosin staining of transverse sections. We measured the minimal Feret’s diameter of myofibers [21] (on average 1,062 myofibers per animal-muscle combination) so as to cover the entire cross-sectional muscle area (Fig 4; S3 Fig). EDL myofiber size was increased by 15.7% and 24.6% in +/TP and TP/TP mice, respectively, compared to +/+ (p < 2.0x10-16). The contrast between +/TP and TP/TP genotypes was also significant (+7.7%, p < 2.0x10-16). On the other hand, none of the corresponding contrasts in SL muscle was significant (p > 5.9x10-2), consistent with the lower contribution of type IIB fibers in SL muscle. Skewness of the myofiber diameter distribution in EDL muscle was changed from right- to left-tailed by increasing the transgene copy number (+/+ = 0.22, +/TP = -0.05, TP/TP = -0.17). This implies that part of the myofibers in EDL muscle (supposedly glycolytic fast twitch fibers) is enlarged by the oPEG11 transgene expression. We did not observe any apparent histological abnormality in these samples (f.i. necrosis, fibrosis, fat deposition, increase of myofibers with centrally located nuclei) (S3 Fig).

Bottom Line: The callipyge phenotype is an ovine muscular hypertrophy characterized by polar overdominance: only heterozygous +Mat/CLPGPat animals receiving the CLPG mutation from their father express the phenotype. +Mat/CLPGPat animals are characterized by postnatal, ectopic expression of Delta-like 1 homologue (DLK1) and Paternally expressed gene 11/Retrotransposon-like 1 (PEG11/RTL1) proteins in skeletal muscle.We herein describe newly generated transgenic mice that ectopically express PEG11 in skeletal muscle, and show that they also exhibit a muscular hypertrophy phenotype.Our data suggest that both DLK1 and PEG11 act together in causing the muscular hypertrophy of callipyge sheep.

View Article: PubMed Central - PubMed

Affiliation: Unit of Animal Genomics, GIGA Research Center and Faculty of Veterinary Medicine, University of Liège, 1 Avenue de l'Hôpital, Liège, Belgium.

ABSTRACT
The callipyge phenotype is an ovine muscular hypertrophy characterized by polar overdominance: only heterozygous +Mat/CLPGPat animals receiving the CLPG mutation from their father express the phenotype. +Mat/CLPGPat animals are characterized by postnatal, ectopic expression of Delta-like 1 homologue (DLK1) and Paternally expressed gene 11/Retrotransposon-like 1 (PEG11/RTL1) proteins in skeletal muscle. We showed previously in transgenic mice that ectopic expression of DLK1 alone induces a muscular hypertrophy, hence demonstrating a role for DLK1 in determining the callipyge hypertrophy. We herein describe newly generated transgenic mice that ectopically express PEG11 in skeletal muscle, and show that they also exhibit a muscular hypertrophy phenotype. Our data suggest that both DLK1 and PEG11 act together in causing the muscular hypertrophy of callipyge sheep.

No MeSH data available.


Related in: MedlinePlus