دانلود رایگان مقاله مطالعه ساختاری فیبرهای عضلانی اسکلتی در سلامت و pseudomyotonia

Summary

Cattle congenital pseudomyotonia (PMT), recognized as naturally occurring animal model of human Brody disease, is an inherited recessive autosomal muscular disorder due to missense mutations in ATP2A1 gene, encoding sarco(endo)plasmic reticulum Ca2+-ATPase protein, isoform 1 (SERCA1). PMT has been described in the Chianina and Romagnola italian cattle breeds and as a single case in Dutch improved Red and White cross-breed. The genetic defect turned out to be heterogeneous in different cattle breeds, even though clinical symptoms were homogeneous. Skeletal muscles of affected animals are characterized by a selective deficiency of SERCA1 in sarcoplasmic reticulum (SR) membranes. Recently, we provided evidence that in Chianina breed, the ubiquitin proteasome system is responsible for SERCA1 mutant premature disposal, even when the mutation does not affect the catalytic properties of the pump. Results presented here show that all SERCA1 mutants described until now, although expressed at low level, are correctly targeted to SR membranes. Ultrastructural studies confirm that in pathological muscle fibres, structure, as well as triads, is well preserved. All together these results suggest that a possible therapeutical approach based on the rescue of the defective protein at SR membranes could be hypothesized. Only fully functionally active missense mutants, whem located at the SR membrane could restore the efficient control of Ca2+ homeostasis and prevent the appearance of the pathological signs. Moreover, these data demonstrate the increasing importance of domestic animals as genetic models of human pathologies.

3. Results and discussion

Cattle congenital PMT associated with ATP2A1 gene mutations has been described in the Chianina, Romagnola breeds (Testoni et al., 2008; Murgiano et al., 2012) and in the Dutch improved Red and White cross-breed (Grünberg et al., 2010). The genetic defect underlying cattle PMT turned out to be heterogeneous, even though clinical signs and symptoms were homogeneous. The effects of different mutations on the level of expression of SERCA1 protein have been extensively investigated by immunoblotting assay onmicrosomal fraction enriched of SRmembranes (Sacchetto et al., 2009; Murgiano et al. 2012; Dorotea et al., 2015) as well as by immunofluorescence analysis of muscle cryosections. Here, we show transverse sections taken