Nuclear sequestration of delta-sarcoglycan disrupts the nuclear localization of lamin A/C and emerin in cardiomyocytes

Sarcoglycan is a membrane-associated protein complex found at the plasma membrane of cardiomyocytes and skeletal myofibers. Recessive mutations of delta-sarcoglycan that eliminate expression, and therefore function, lead to cardiomyopathy and muscular dystrophy by producing instability of the plasma membrane. A dominant missense mutation in the gene encoding delta-sarcoglycan was previously shown to associate with dilated cardiomyopathy in humans. To investigate the mechanism of dominantly inherited cardiomyopathy, we generated transgenic mice that express the S151A delta-sarcoglycan mutation in the heart using the alpha-myosin heavy-chain gene promoter. Similar to the human delta-sarcoglycan gene mutation, S151A delta-sarcoglycan transgenic mice developed dilated cardiomyopathy at a young age with enhanced lethality. Instead of placement at the plasma membrane, delta-sarcoglycan was found in the nucleus of S151A delta-sarcoglycan cardiomyocytes. Retention of delta-sarcoglycan in the nucleus was accompanied by partial nuclear sequestration of beta- and gamma-sarcoglycan. Additionally, the nuclear-membrane-associated proteins, lamin A/C and emerin, were mislocalized throughout the nucleoplasm. Therefore, the S151A delta-sarcoglycan gene mutation acts in a dominant negative manner to produce trafficking defects that disrupt nuclear localization of lamin A/C and emerin, thus linking together two common mechanisms of inherited cardiomyopathy.     

Nesprins,but not sun proteins,switch isoforms at the nuclear envelope during muscle development

Nesprins are a family of nuclear transmembrane proteins anchored via Sun proteins to the nuclear membrane. Analysis of nesprins during human muscle development revealed an increase in nesprin‐1‐giant during early myogenesis in vitro. During the transition from immature to mature muscle fibres in vivo, nesprin‐2 partly replaced nesprin‐1 at the nuclear envelope and short nesprin isoforms became dominant. Sun1 and Sun2 proteins remained unchanged during this fibre maturation. In emerin‐negative skin fibroblasts, nesprin‐2‐giant was relocated from the nuclear envelope to the cytoplasm, not to the endoplasmic reticulum, while nesprin‐1 remained at the nuclear envelope. In emerin‐negative keratinocytes lacking nesprin‐1, nesprin‐2 remained at the nuclear envelope. HeLa cell nuclear envelopes lacked nesprin‐1, which was the dominant form in myoblasts, while a novel 130‐kD nesprin‐2 isoform dominated Ntera‐2 cells. The results suggest the possibility of isoform‐specific and tissue‐specific roles for nesprins in nuclear positioning. Developmental Dynamics 239:998–1009, 2010. © 2010 Wiley‐Liss, Inc.     

Investigation of the influence of the Mm musculus MyoD1 allele on the efficiency of skeletal muscle regeneration

MyoD1 alleles distinguish between the Mm musculus and Mm domesticus subspecies of Mus musculus . SJL/J mice, which belong to the Mm musculus subspecies, are able to regenerate skeletal muscle more efficiently than BALB/c mice which possess the Mm domesticus MyoD1 allele. Hence the possibility that regeneration responses are due to species-specific genetic differences including MyoD1 was investigated in this study. Quantitative morphometric analysis following muscle crush injury of 2 Mm musculus strains, MBK and MGL, has indicated that regeneration phenotype is not species-specific and may not be directly related to MyoD1 alleles. These results contrast with prior investigations conducted in SJL/J and BALB/c mice, and indicate that other genes may have a direct influence on skeletal muscle regeneration.     

Prostagiandin E1 and F2 α levels during development of shock induced by plague toxin

Laboratory of the Molecular Basis of Pathogenesis of Infectious Diseases, Central Research Institute of Epidemiology, Ministry of Health of the USSR, Moscow. (Presented by Academician of the Academy of Medical Sciences of the USSR V. I. Pokrovskii.) Translated from Byulleten' Éksperimental'noi Biologii i Meditsiny, Vol. 105, No. 3, pp. 313–315, March, 1988.     

Accumulation of Ym1/2 protein in the mouse olfactory epithelium during regeneration and aging

A unique feature of the olfactory system is its efficiency to produce new neurons in the adult. Thus, destruction of the olfactory receptor neurons (ORNs) using chemical (intranasal perfusion with ZnSO4) or surgical (axotomy or bulbectomy) methods, leads to an enhanced rate of proliferation of their progenitors and to complete ORNs regeneration. The aim of our study was to identify new factors implied in this regenerative process. Using an electrophoretic method, we observed the accumulation of a 42 kDa protein after axotomy in the olfactory mucosa, but not in the olfactory bulb. Its expression started after a few days following injury and increased massively during the phase of ORN regeneration. The purification and the sequence characterization revealed that this protein was Ym1/2, recently identified in activated macrophages present in various tissues during inflammation. Western blotting analysis of Ym1/2 confirmed the accumulation of this protein in the regenerating olfactory mucosa consecutively to olfactory axotomy or bulbectomy but also after ZnSO4 irrigation of the nasal cavity. In the olfactory mucosa of control mice, Ym1/2 was hardly detectable in young animals and became more and more abundant with increasing age. In injured and aged mice, Ym1/2 mainly accumulates in the cytoplasm of supporting cells as well as in other cells located throughout the olfactory epithelium. Our results suggest that Ym1/2 is involved in olfactory epithelium remodeling following several kinds of lesions of the adult olfactory mucosa and support the view of a critical role of inflammatory cues in neurodegeneration and aging.     

Correlations between MyoD, myogenin, SERCA1, SERCA2 and phospholamban transcripts during transformation of type-II to type-I skeletal muscle fibers

 Canine latissimus dorsi, composed predominantly of fast-twitch muscle fibers, were subjected to chronic 1 Hz neuromuscular stimulation for periods up to 42 days to induce changes in gene expression. This produced down regulation of SERCA1 (fast-twitch isoform of sarco(endo)plasmic reticulum Ca²⁺-ATPase), a gene product of fast-twitch muscle, and up regulation of SERCA2 (slow-twitch isoform of sarco(endo)plasmic reticulum Ca²⁺-ATPase) and phospholamban, products of genes expressed by slow-twitch muscles. To assess the involvement of MyoD and myogenin in the regulation of the expression of these genes their levels were measured during the stimulation period. The prompt, at 7 days, fall in SERCA1 mRNA preceded the fall in MyoD by about 7 days, suggesting that the decline in MyoD was not causally related to the decline in SERCA1. The prompt rise in SERCA2 mRNA at 7 days preceded the rise in myogenin by 14 days. The rise in myogenin at 21 days did correlate with the similar rise in phospholamban mRNA. Received: 13 January 1997 / Accepted: 24 March 1997     

Loss of heterozygosity at 1p36 predicts poor prognosis in gastrointestinal stromal/smooth muscle tumors

Gastrointestinal stromal/smooth muscle tumors are uncommon neoplasms for which current criteria for diagnosing malignancy (size and mitotic index) sometimes fail to predict outcome. Cytogenetic studies reveal frequent chromosome 1 abnormalities in these tumors, but significant underlying molecular changes have not been elucidated, and their significance is unknown. DNA was obtained from the formalin-fixed, paraffin-embedded tissue of 80 gastrointestinal stromal/smooth muscle tumors. Tumors were topographically microdissected from surrounding normal tissue; microsatellite markers from tumor and normal tissue were amplified by PCR in the regions of chromosome 1p36 (D1S199, D1S228, D1S450, D1S214, D1S243), 1p12 (D1S418),1p13 (D1S252, D1S514), and 1q32(D1S103). The presence or absence of heterozygosity for each case was mapped at each informative marker. Relationships among loss of heterozygosity (LOH), tumor size, mitotic index, and survival were investigated using correlation analysis, Kaplan-Meier plots, and the Cox model. LOH at 1p36 was found in 24 of 80 cases, suggesting the possibility of a tumor suppressor gene at 1 p36 near the site of a suspected neuroblastoma tumor suppressor gene. Patients whose tumors demonstrated LOH at 1 p36 had significantly shorter survival (p = 0.017) than those whose tumors did not. LOH at 1 p36 retained independent prognostic significance in a multivariate model that included KIT mutation status and tumor size; the mitotic index, however, did not retain independent significance in such a model. LOH was observed at 1 p12-1p13 (most frequently at 1p13.3) in 19 of 80 cases, but loss of heterozygosity at this site did not influence survival. No LOH was observed near 1q32. These findings provide strong evidence for a prognostically significant tumor suppressor gene in the region of chromosome 1p36.3.     

Expression and evaluation of Chikungunya virus E1 and E2 envelope proteins for serodiagnosis of Chikungunya virus infection

Purpose

Chikungunya virus (CHIKV) causes endemic or epidemic outbreaks of CHIKV fever, which is a mosquitoe-transmitted viral disease in Africa, India, South-East Asia, and recently Southern Europe. Currently, serological diagnostic tests such as hemagglutination inhibition test (HI test), in-house IgM capture enzyme-linked immunosorbent assays (ELISA), and indirect immunofluorescence test were used for diagnosis of chikungunya fever, which are based on whole virus antigens.

Materials and Methods

CHIKV E1, and E2 envelope proteins for the CHIKV-specific serodiagnostic reagents for chikungunya fever were expressed in baculovirus expression system. The seroreactivity of recombinant CHIKV E1 and E2 envelope proteins were evaluated using sera panels of patients from Laboratoire Marcel Merieux by indirect IgM capture ELISA.

Results

The recombinant CHIKV E1 and E2 envelope protein showed sensitivity of 77.5% and 90%, respectively. The specificities of both CHIKV E1 and E2 envelope proteins were 100%.

Conclusion

The recombinant CHIKV E1 and E2 envelope proteins could be a useful diagnostic reagent for CHIKV infection.