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Zebrafish models for nemaline myopathy reveal a spectrum of nemaline bodies contributing to reduced muscle function.

Sztal TE, Zhao M, Williams C, Oorschot V, Parslow AC, Giousoh A, Yuen M, Hall TE, Costin A, Ramm G, Bird PI, Busch-Nentwich EM, Stemple DL, Currie PD, Cooper ST, Laing NG, Nowak KJ, Bryson-Richardson RJ - Acta Neuropathol. (2015)

Bottom Line: Another subtype results from a reduction of actin and forms a more stable cytoplasmic body.In contrast, the final type originates at the Z-disk and is associated with myofibrillar disorganization.In addition, we show that the ACTA1(D286G) mutation causes impaired actin incorporation and localization in the sarcomere.

View Article: PubMed Central - PubMed

Affiliation: School of Biological Sciences, Monash University, Melbourne, VIC, Australia.

ABSTRACT
Nemaline myopathy is characterized by muscle weakness and the presence of rod-like (nemaline) bodies. The genetic etiology of nemaline myopathy is becoming increasingly understood with mutations in ten genes now known to cause the disease. Despite this, the mechanism by which skeletal muscle weakness occurs remains elusive, with previous studies showing no correlation between the frequency of nemaline bodies and disease severity. To investigate the formation of nemaline bodies and their role in pathogenesis, we generated overexpression and loss-of-function zebrafish models for skeletal muscle α-actin (ACTA1) and nebulin (NEB). We identify three distinct types of nemaline bodies and visualize their formation in vivo, demonstrating these nemaline bodies not only exhibit different subcellular origins, but also have distinct pathological consequences within the skeletal muscle. One subtype is highly dynamic and upon breakdown leads to the accumulation of cytoplasmic actin contributing to muscle weakness. Examination of a Neb-deficient model suggests this mechanism may be common in nemaline myopathy. Another subtype results from a reduction of actin and forms a more stable cytoplasmic body. In contrast, the final type originates at the Z-disk and is associated with myofibrillar disorganization. Analysis of zebrafish and muscle biopsies from ACTA1 nemaline myopathy patients demonstrates that nemaline bodies also possess a different protein signature. In addition, we show that the ACTA1(D286G) mutation causes impaired actin incorporation and localization in the sarcomere. Together these data provide a novel examination of nemaline body origins and dynamics in vivo and identifies pathological changes that correlate with muscle weakness.

No MeSH data available.


Related in: MedlinePlus

Maximum projection confocal microscopy images of Actc1b morphants and control zebrafish stained with phalloidin at 2 dpf or with an actinin2 antibody at 2 dpf and 6 dpf. Actinin2 and phalloidin-positive nemaline bodies are observed throughout the muscle fibers (arrows) as well as projecting from the myosepta (arrowheads) in Actc1b morphants compared to controls
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Fig10: Maximum projection confocal microscopy images of Actc1b morphants and control zebrafish stained with phalloidin at 2 dpf or with an actinin2 antibody at 2 dpf and 6 dpf. Actinin2 and phalloidin-positive nemaline bodies are observed throughout the muscle fibers (arrows) as well as projecting from the myosepta (arrowheads) in Actc1b morphants compared to controls

Mentions: We injected two morpholinos (one targeting the exon 2 splice donor site and one targeting the 5′UTR). We observed a reduction in α-actin protein by approximately 43 % (Fig. 9b, c) along with decreased phalloidin staining in Actc1b morphants compared to control zebrafish (Fig. 10). Morphologically, Actc1b morphants (Fig. 11a) display impaired skeletal muscle function, showing a reduction in both maximum acceleration at 2 dpf and in swimming distance at 6 dpf (Fig. 11b, c).Fig. 10


Zebrafish models for nemaline myopathy reveal a spectrum of nemaline bodies contributing to reduced muscle function.

Sztal TE, Zhao M, Williams C, Oorschot V, Parslow AC, Giousoh A, Yuen M, Hall TE, Costin A, Ramm G, Bird PI, Busch-Nentwich EM, Stemple DL, Currie PD, Cooper ST, Laing NG, Nowak KJ, Bryson-Richardson RJ - Acta Neuropathol. (2015)

Maximum projection confocal microscopy images of Actc1b morphants and control zebrafish stained with phalloidin at 2 dpf or with an actinin2 antibody at 2 dpf and 6 dpf. Actinin2 and phalloidin-positive nemaline bodies are observed throughout the muscle fibers (arrows) as well as projecting from the myosepta (arrowheads) in Actc1b morphants compared to controls
© Copyright Policy - OpenAccess
Related In: Results  -  Collection

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getmorefigures.php?uid=PMC4541704&req=5

Fig10: Maximum projection confocal microscopy images of Actc1b morphants and control zebrafish stained with phalloidin at 2 dpf or with an actinin2 antibody at 2 dpf and 6 dpf. Actinin2 and phalloidin-positive nemaline bodies are observed throughout the muscle fibers (arrows) as well as projecting from the myosepta (arrowheads) in Actc1b morphants compared to controls
Mentions: We injected two morpholinos (one targeting the exon 2 splice donor site and one targeting the 5′UTR). We observed a reduction in α-actin protein by approximately 43 % (Fig. 9b, c) along with decreased phalloidin staining in Actc1b morphants compared to control zebrafish (Fig. 10). Morphologically, Actc1b morphants (Fig. 11a) display impaired skeletal muscle function, showing a reduction in both maximum acceleration at 2 dpf and in swimming distance at 6 dpf (Fig. 11b, c).Fig. 10

Bottom Line: Another subtype results from a reduction of actin and forms a more stable cytoplasmic body.In contrast, the final type originates at the Z-disk and is associated with myofibrillar disorganization.In addition, we show that the ACTA1(D286G) mutation causes impaired actin incorporation and localization in the sarcomere.

View Article: PubMed Central - PubMed

Affiliation: School of Biological Sciences, Monash University, Melbourne, VIC, Australia.

ABSTRACT
Nemaline myopathy is characterized by muscle weakness and the presence of rod-like (nemaline) bodies. The genetic etiology of nemaline myopathy is becoming increasingly understood with mutations in ten genes now known to cause the disease. Despite this, the mechanism by which skeletal muscle weakness occurs remains elusive, with previous studies showing no correlation between the frequency of nemaline bodies and disease severity. To investigate the formation of nemaline bodies and their role in pathogenesis, we generated overexpression and loss-of-function zebrafish models for skeletal muscle α-actin (ACTA1) and nebulin (NEB). We identify three distinct types of nemaline bodies and visualize their formation in vivo, demonstrating these nemaline bodies not only exhibit different subcellular origins, but also have distinct pathological consequences within the skeletal muscle. One subtype is highly dynamic and upon breakdown leads to the accumulation of cytoplasmic actin contributing to muscle weakness. Examination of a Neb-deficient model suggests this mechanism may be common in nemaline myopathy. Another subtype results from a reduction of actin and forms a more stable cytoplasmic body. In contrast, the final type originates at the Z-disk and is associated with myofibrillar disorganization. Analysis of zebrafish and muscle biopsies from ACTA1 nemaline myopathy patients demonstrates that nemaline bodies also possess a different protein signature. In addition, we show that the ACTA1(D286G) mutation causes impaired actin incorporation and localization in the sarcomere. Together these data provide a novel examination of nemaline body origins and dynamics in vivo and identifies pathological changes that correlate with muscle weakness.

No MeSH data available.


Related in: MedlinePlus