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Prenatal muscle development in a mouse model for the secondary dystroglycanopathies.

Kim J, Hopkinson M, Kavishwar M, Fernandez-Fuente M, Brown SC - Skelet Muscle (2016)

Bottom Line: In addition, the total number of Pax7(+) progenitor cells in the FKRP(KD) tibialis anterior at E15.5 was significantly reduced, and myotube cluster/myofibre size showed a significant reduction in size.These data identify an early reduction of laminin α2, reduction of myogenicity and depletion of Pax7(+) progenitor cells which would be expected to compromise subsequent postnatal muscle growth and its ability to regenerate postnatally.These findings are of significance to the development of future therapies in this group of devastating conditions.

View Article: PubMed Central - PubMed

Affiliation: Department of Comparative Biomedical Sciences, Royal Veterinary College, University of London, London, UK.

ABSTRACT

Background: The defective glycosylation of α-dystroglycan is associated with a group of muscular dystrophies that are collectively referred to as the secondary dystroglycanopathies. Mutations in the gene encoding fukutin-related protein (FKRP) are one of the most common causes of secondary dystroglycanopathy in the UK and are associated with a wide spectrum of disease. Whilst central nervous system involvement has a prenatal onset, no studies have addressed prenatal muscle development in any of the mouse models for this group of diseases. In view of the pivotal role of α-dystroglycan in early basement membrane formation, we sought to determine if the muscle formation was altered in a mouse model of FKRP-related dystrophy.

Results: Mice with a knock-down in FKRP (FKRP(KD)) showed a marked reduction in α-dystroglycan glycosylation and reduction in laminin binding by embryonic day 15.5 (E15.5), relative to wild type controls. In addition, the total number of Pax7(+) progenitor cells in the FKRP(KD) tibialis anterior at E15.5 was significantly reduced, and myotube cluster/myofibre size showed a significant reduction in size. Moreover, myoblasts isolated from the limb muscle of these mice at E15.5 showed a marked reduction in their ability to form myotubes in vitro.

Conclusions: These data identify an early reduction of laminin α2, reduction of myogenicity and depletion of Pax7(+) progenitor cells which would be expected to compromise subsequent postnatal muscle growth and its ability to regenerate postnatally. These findings are of significance to the development of future therapies in this group of devastating conditions.

No MeSH data available.


Related in: MedlinePlus

Immunolabelling of laminins α4, α5 γ1 and β1 at E15.5 and P0. Immunolabelling with chain-specific antibodies raised against laminin α4 (A, B, C, D), α5 (E, F, G, H) and γ1 (I, J, K, L), also indicated no clear reduction in FKRPKD relative to wild type at either E15.5 or P0. However, laminin β1 (M, N, O, P) showed a subtle reduction in FKRPKD compared to wild type at E15.5 and P0
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Fig4: Immunolabelling of laminins α4, α5 γ1 and β1 at E15.5 and P0. Immunolabelling with chain-specific antibodies raised against laminin α4 (A, B, C, D), α5 (E, F, G, H) and γ1 (I, J, K, L), also indicated no clear reduction in FKRPKD relative to wild type at either E15.5 or P0. However, laminin β1 (M, N, O, P) showed a subtle reduction in FKRPKD compared to wild type at E15.5 and P0

Mentions: We next examined the impact of reduced α-dystroglycan on laminin expression. Laminin α-chains interact with dystroglycan via their LG domains although each isoform may bind with different affinities. Using chain-specific antibodies, we labelled transverse sections of the tibialis anterior and extensor digitorum longus for laminin α1, α4, α5, β1 and γ1. This showed that laminin α2 was reduced in the FKRPKD relative to wild type at both E15.5 and P0 (Fig. 2b). Laminin α1 immunolabelling was only observed at the dermal–epidermal junction in the skin and myotendinous junction. Whilst no clear differences were seen in the muscle from either FKRPKD or wild type with respect to laminin α1 (data not shown), expression was reduced in the skin of the FKRPKD at E15.5, a feature that was less pronounced by the time of birth (Fig. 2b). These mice however, showed no other noticeable skin defects. A subtle reduction was seen with β1 in the FKRPKD although this would need to be confirmed by Western blot. Immunolabelling for laminin α5, α4 and γ1 was however, equivalent to the wild type (Fig. 4). These observations imply that at these stages of development there is no compensatory increase in either laminin α4 or α5 chains which is sometimes evident in adult muscle. However, given that γ1 levels were similar in FKRPKD and wild type, it remains a possibility that another α-chain at least partially compensates for the reduction in laminin α2.Fig. 4


Prenatal muscle development in a mouse model for the secondary dystroglycanopathies.

Kim J, Hopkinson M, Kavishwar M, Fernandez-Fuente M, Brown SC - Skelet Muscle (2016)

Immunolabelling of laminins α4, α5 γ1 and β1 at E15.5 and P0. Immunolabelling with chain-specific antibodies raised against laminin α4 (A, B, C, D), α5 (E, F, G, H) and γ1 (I, J, K, L), also indicated no clear reduction in FKRPKD relative to wild type at either E15.5 or P0. However, laminin β1 (M, N, O, P) showed a subtle reduction in FKRPKD compared to wild type at E15.5 and P0
© Copyright Policy - OpenAccess
Related In: Results  -  Collection

License 1 - License 2
Show All Figures
getmorefigures.php?uid=PMC4759920&req=5

Fig4: Immunolabelling of laminins α4, α5 γ1 and β1 at E15.5 and P0. Immunolabelling with chain-specific antibodies raised against laminin α4 (A, B, C, D), α5 (E, F, G, H) and γ1 (I, J, K, L), also indicated no clear reduction in FKRPKD relative to wild type at either E15.5 or P0. However, laminin β1 (M, N, O, P) showed a subtle reduction in FKRPKD compared to wild type at E15.5 and P0
Mentions: We next examined the impact of reduced α-dystroglycan on laminin expression. Laminin α-chains interact with dystroglycan via their LG domains although each isoform may bind with different affinities. Using chain-specific antibodies, we labelled transverse sections of the tibialis anterior and extensor digitorum longus for laminin α1, α4, α5, β1 and γ1. This showed that laminin α2 was reduced in the FKRPKD relative to wild type at both E15.5 and P0 (Fig. 2b). Laminin α1 immunolabelling was only observed at the dermal–epidermal junction in the skin and myotendinous junction. Whilst no clear differences were seen in the muscle from either FKRPKD or wild type with respect to laminin α1 (data not shown), expression was reduced in the skin of the FKRPKD at E15.5, a feature that was less pronounced by the time of birth (Fig. 2b). These mice however, showed no other noticeable skin defects. A subtle reduction was seen with β1 in the FKRPKD although this would need to be confirmed by Western blot. Immunolabelling for laminin α5, α4 and γ1 was however, equivalent to the wild type (Fig. 4). These observations imply that at these stages of development there is no compensatory increase in either laminin α4 or α5 chains which is sometimes evident in adult muscle. However, given that γ1 levels were similar in FKRPKD and wild type, it remains a possibility that another α-chain at least partially compensates for the reduction in laminin α2.Fig. 4

Bottom Line: In addition, the total number of Pax7(+) progenitor cells in the FKRP(KD) tibialis anterior at E15.5 was significantly reduced, and myotube cluster/myofibre size showed a significant reduction in size.These data identify an early reduction of laminin α2, reduction of myogenicity and depletion of Pax7(+) progenitor cells which would be expected to compromise subsequent postnatal muscle growth and its ability to regenerate postnatally.These findings are of significance to the development of future therapies in this group of devastating conditions.

View Article: PubMed Central - PubMed

Affiliation: Department of Comparative Biomedical Sciences, Royal Veterinary College, University of London, London, UK.

ABSTRACT

Background: The defective glycosylation of α-dystroglycan is associated with a group of muscular dystrophies that are collectively referred to as the secondary dystroglycanopathies. Mutations in the gene encoding fukutin-related protein (FKRP) are one of the most common causes of secondary dystroglycanopathy in the UK and are associated with a wide spectrum of disease. Whilst central nervous system involvement has a prenatal onset, no studies have addressed prenatal muscle development in any of the mouse models for this group of diseases. In view of the pivotal role of α-dystroglycan in early basement membrane formation, we sought to determine if the muscle formation was altered in a mouse model of FKRP-related dystrophy.

Results: Mice with a knock-down in FKRP (FKRP(KD)) showed a marked reduction in α-dystroglycan glycosylation and reduction in laminin binding by embryonic day 15.5 (E15.5), relative to wild type controls. In addition, the total number of Pax7(+) progenitor cells in the FKRP(KD) tibialis anterior at E15.5 was significantly reduced, and myotube cluster/myofibre size showed a significant reduction in size. Moreover, myoblasts isolated from the limb muscle of these mice at E15.5 showed a marked reduction in their ability to form myotubes in vitro.

Conclusions: These data identify an early reduction of laminin α2, reduction of myogenicity and depletion of Pax7(+) progenitor cells which would be expected to compromise subsequent postnatal muscle growth and its ability to regenerate postnatally. These findings are of significance to the development of future therapies in this group of devastating conditions.

No MeSH data available.


Related in: MedlinePlus