Centronuclear myopathies (CNM) are rare congenital disorders characterized by muscle weakness and structural defects including fiber hypotrophy and organelle mispositioning. The main CNM forms are ...caused by mutations in: the
gene encoding the phosphoinositide phosphatase myotubularin (myotubular myopathy), the
gene encoding the mechanoenzyme dynamin 2, the
gene encoding the membrane curvature sensing amphiphysin 2, and the
gene encoding the skeletal muscle calcium release channel/ryanodine receptor. MTM1, BIN1, and DNM2 proteins are involved in membrane remodeling and trafficking, while RyR1 directly regulates excitation-contraction coupling (ECC). Several CNM animal models have been generated or identified, which confirm shared pathological anomalies in T-tubule remodeling, ECC, organelle mispositioning, protein homeostasis, neuromuscular junction, and muscle regeneration. Dynamin 2 plays a crucial role in CNM physiopathology and has been validated as a common therapeutic target for three CNM forms. Indeed, the promising results in preclinical models set up the basis for ongoing clinical trials. Another two clinical trials to treat myotubular myopathy by MTM1 gene therapy or tamoxifen repurposing are also ongoing. Here, we review the contribution of the different CNM models to understanding physiopathology and therapy development with a focus on the commonly dysregulated pathways and current therapeutic targets.
Dynamin 2 mechanoenzyme is a key regulator of membrane remodeling and gain-of-function mutations in its gene cause centronuclear myopathies. Here, we investigate the functions of dynamin 2 isoforms ...and their associated phenotypes and, specifically, the ubiquitous and muscle-specific dynamin 2 isoforms expressed in skeletal muscle. In cell-based assays, we show that a centronuclear myopathy-related mutation in the ubiquitous but not the muscle-specific dynamin 2 isoform causes increased membrane fission. In vivo, overexpressing the ubiquitous dynamin 2 isoform correlates with severe forms of centronuclear myopathy, while overexpressing the muscle-specific isoform leads to hallmarks seen in milder cases of the disease. Previous mouse studies suggested that reduction of the total dynamin 2 pool could be therapeutic for centronuclear myopathies. Here, dynamin 2 splice switching from muscle-specific to ubiquitous dynamin 2 aggravated the phenotype of a severe X-linked form of centronuclear myopathy caused by loss-of-function of the MTM1 phosphatase, supporting the importance of targeting the ubiquitous isoform for efficient therapy in muscle. Our results highlight that the ubiquitous and not the muscle-specific dynamin 2 isoform is the main modifier contributing to centronuclear myopathy pathology.
Human islet amyloid polypeptide (hIAPP), or amylin, has the tendency to aggregate into insoluble amyloid fibrils, a typical feature of islets from type 2 diabetes individuals. Thus, we investigated ...comparatively the impact of hIAPP on key pathways involved in pancreatic beta survival. INS1E-hIAPP cells present a hyperactivation of MTORC1 and an inhibition of autophagy signaling, those cells showing an increase in cell size. Resveratrol, a MTORC1 inhibitor, can reverse TSC2 degradation that occurs in INS1E-hIAPP cells and diminished MTORC1 hyperactivation with concomitant autophagy stimulation. At the same time, a blockade in mitophagy was found in INS1E-hIAPP cells, as compared with control or INS1E-rIAPP cells. Consistently, human amylin overexpression generates a basal induction of nitrotyrosine levels and polyubiquitinated aggregates. Failure of the protein degradation machinery finally results in an accumulation of damaged and fissioned mitochondria, ROS production, and increased susceptibility to endoplasmic reticulum (ER)-stress-induced apoptosis. Overall, hIAPP overexpression in INS1E cells induced MTORC1 activation and mitophagy inhibition, favoring a pro-fission scenario of damaged mitochondria, these cells turn out to be more susceptible to the ER-stress-induced apoptosis and malfunction.
BIN1 modulation in vivo rescues dynamin-related myopathy Lionello, Valentina Maria; Kretz, Christine; Edelweiss, Evelina ...
Proceedings of the National Academy of Sciences - PNAS,
03/2022, Letnik:
119, Številka:
9
Journal Article
Recenzirano
Odprti dostop
The mechanoenzyme dynamin 2 (DNM2) is crucial for intracellular organization and trafficking.
is mutated in dominant centronuclear myopathy (DNM2-CNM), a muscle disease characterized by defects in ...organelle positioning in myofibers. It remains unclear how the in vivo functions of DNM2 are regulated in muscle. Moreover, there is no therapy for DNM2-CNM to date. Here, we overexpressed human amphiphysin 2 (BIN1), a membrane remodeling protein mutated in other CNM forms, in
and
mice modeling mild and severe DNM2-CNM, through transgenesis or with adeno-associated virus (AAV). Increasing BIN1 improved muscle atrophy and main histopathological features of
mice and rescued the perinatal lethality and survival of
mice. In vitro experiments showed that BIN1 binds and recruits DNM2 to membrane tubules, and that the BIN1-DNM2 complex regulates tubules fission. Overall, BIN1 is a potential therapeutic target for dominant centronuclear myopathy linked to DNM2 mutations.
Myotubular myopathy, also called X-linked centronuclear myopathy (XL-CNM), is a severe congenital disease targeted for therapeutic trials. To date, biomarkers to monitor disease progression and ...therapy efficacy are lacking. The Mtm1−/y mouse is a faithful model for XL-CNM, due to myotubularin 1 (MTM1) loss-of-function mutations. Using both an unbiased approach (RNA sequencing RNA-seq) and a directed approach (qRT-PCR and protein level), we identified decreased Mstn levels in Mtm1−/y muscle, leading to low levels of myostatin in muscle and plasma. Myostatin (Mstn or growth differentiation factor 8 Gdf8) is a protein released by myocytes and inhibiting muscle growth and differentiation. Decreasing Dnm2 by genetic cross with Dnm2+/− mice or by antisense oligonucleotides blocked or postponed disease progression and resulted in an increase in circulating myostatin. In addition, plasma myostatin levels inversely correlated with disease severity and with Dnm2 mRNA levels in muscles. Altered Mstn levels were associated with a generalized disruption of the myostatin pathway. Importantly, in two different forms of CNMs we identified reduced circulating myostatin levels in plasma from patients. This provides evidence of a blood-based biomarker that may be used to monitor disease state in XL-CNM mice and patients and supports monitoring circulating myostatin during clinical trials for myotubular myopathy.
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X-linked centronuclear myopathy (XL-CNM) is a severe congenital disease targeted for therapeutic trials. The authors identified decreased plasma myostatin levels in XL-CNM patients and mice. Decreasing Dnm2 in mice blocked or postponed disease progression and resulted in an increase in circulating myostatin, supporting monitoring circulating myostatin in XL-CNM clinical trials.
Mutations in the BIN1 (Bridging Interactor 1) gene, encoding the membrane remodeling protein amphiphysin 2, cause centronuclear myopathy (CNM) associated with severe muscle weakness and myofiber ...disorganization and hypotrophy. There is no available therapy, and the validation of therapeutic proof of concept is impaired by the lack of a faithful and easy-to-handle mammalian model. Here, we generated and characterized the Bin1mck−/− mouse through Bin1 knockout in skeletal muscle. Bin1mck−/− mice were viable, unlike the constitutive Bin1 knockout, and displayed decreased muscle force and most histological hallmarks of CNM, including myofiber hypotrophy and intracellular disorganization. Notably, Bin1mck−/− myofibers presented strong defects in mitochondria and T-tubule networks associated with deficient calcium homeostasis and excitation-contraction coupling at the triads, potentially representing the main pathomechanisms. Systemic injection of antisense oligonucleotides (ASOs) targeting Dnm2 (Dynamin 2), which codes for dynamin 2, a BIN1 binding partner regulating membrane fission and mutated in other forms of CNM, improved muscle force and normalized the histological Bin1mck−/− phenotypes within 5 weeks. Overall, we generated a faithful mammalian model for CNM linked to BIN1 defects and validated Dnm2 ASOs as a first translatable approach to efficiently treat BIN1-CNM.
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A Bin1mck−/− mouse model is generated and recapitulates most of the motor and histology defects observed in patients with autosomal recessive centronuclear myopathy caused by BIN1 mutations. Dnm2 downregulation in this model improves most phenotypes, offering promising perspectives for BIN1-CNM patient treatment.
Abstract In vitro cefditoren antimicrobial activity was tested against 288 Streptococcus pneumoniae and 220 Haemophilus influenzae clinical strains isolated in our hospital from January 2005 to May ...2006 by agar dilution and broth microdilution method, respectively. MICs were also determined for 13 and 10 comparison drugs, respectively. The pneumococci tested comprised 113 (39.2%) penicillin susceptible, 91 (31.6%) penicillin intermediate, and 84 (29.2%) penicillin resistant. Cefditoren was the most active drug on the basis of the MICs (MIC90 = 0.5 μg/mL), followed by ceftriaxone and levofloxacin (MIC90 = 1 μg/mL). Cefditoren MICs ranged from 0.25 to 1 μg/mL for ceftriaxone-resistant isolates, with a modal MIC of 0.5 μg/mL and an MIC90 of 1.0 μg/mL. No S. pneumoniae isolates evaluated in this study showed MICs to cefditoren higher than 1 μg/mL (MIC range, ≤0.015 to 1 μg/mL). Against penicillin-resistant pneumococci, the rank order of intrinsic activity (MIC90 , μg/mL) was cefditoren (0.5) < ceftriaxone (2.0) = cefotaxime (2.0) < amoxicillin/clavulanate (8.0) = amoxicillin (8.0) = cefuroxime (8.0). Among the 220 strains of H. influenzae , 42 (19.09%) produced a β-lactamase (Hi β+) and 3 (1.1%) were β-lactamase (Hi β-) negative but have reduced susceptibility to ampicillin (BLNAR). The most active drugs on the basis of MICs were cefditoren and levofloxacin, showing MIC50 and MIC90 values of 0.015/0.06 μg/mL. Cefditoren at concentration of 0.06 μg/mL inhibited all 3 BLNAR (ampicillin MICs >4 μg/mL). Against H. influenzae (Hi β+), the rank order of intrinsic activity (MIC90 , μg/mL) was cefditoren (0.03) < cefixime (0.06) < ceftriaxone (0.12) = cefotaxime (0.12) < cefuroxime (1.0) < amoxicillin/clavulanate (2.0) < ampicillin (>8.0).
We report herein results of a study performed in the Balearic Islands which had the following goals: 1) Determine the proportion of pregnant or non-pregnant women planning pregnancy, who would choose ...to undergo a screening test for Fragile X Syndrome (FXS), if it is accompanied by the appropriate information; 2) Assess satisfaction and any increase in stress among women who participate in screening; 3) Collect epidemiological information about the incidence of the disease in our population; and 4) Collect demographic and health history data and assess participants’ awareness of the disease. Screening was performed on 3,731 pregnant and non-pregnant women of childbearing age and the results indicate: a very high voluntary rate of participation; a high level of self-reported satisfaction and low levels of stress because of the test; a very high incidence of premutation (1/106) in our population; and a low level of awareness about the existence of FXS (25 %). Additional findings indicate no significant correlation between self-reported health history and premutation detection, and the high premutation incidence does not seem to be specific to the indigenous Balearic population. Based on these results, we discuss the pros and cons of an implementation of preconception and pregnant women screening for FXS within a public health screening program.
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