Native collagen VI delays early muscle stem cell differentiation.

Adult muscle stem cells (MuSCs) are critical for muscle homeostasis and regeneration, and their behavior relies on a finely regulated niche made of specific extracellular matrix (ECM) components and soluble factors. Among ECM proteins, collagen VI (Col6) influences the mechanical properties of the niche and, in turn, MuSC self-renewal capabilities. Here, we investigated whether Col6 can exert a direct function as a biochemical signal for regulating the stemness and differentiation of murine MuSCs and myoblasts. Native Col6, but not its pepsin-resistant fragment, counteracts the early differentiation of myogenic cells by reducing the expression of differentiation marker genes and preserving stemness features, with inhibition of the canonical Wnt pathway. Our data indicate that extracellular Col6 acts as a soluble ligand in delaying early myogenic differentiation by regulating intracellular signals involved in adult myogenesis.

Collagen VI sustains cell stemness and chemotherapy resistance in glioblastoma.

Microenvironmental factors are known fundamental regulators of the phenotype and aggressiveness of glioblastoma (GBM), the most lethal brain tumor, characterized by fast progression and marked resistance to treatments. In this context, the extracellular matrix (ECM) is known to heavily influence the behavior of cancer cells from several origins, contributing to stem cell niches, influencing tumor invasiveness and response to chemotherapy, mediating survival signaling cascades, and modulating inflammatory cell recruitment. Here, we show that collagen VI (COL6), an ECM protein widely expressed in both normal and pathological tissues, has a distinctive distribution within the GBM mass, strongly correlated with the most aggressive and phenotypically immature cells. Our data demonstrate that COL6 sustains the stem-like properties of GBM cells and supports the maintenance of an aggressive transcriptional program promoting cancer cell proliferation and survival. In particular, we identified a specific subset of COL6-transcriptionally co-regulated genes, required for the response of cells to replicative stress and DNA damage, supporting the concept that COL6 is an essential stimulus for the activation of GBM cell response and resistance to chemotherapy, through the ATM/ATR axis. Altogether, these findings indicate that COL6 plays a pivotal role in GBM tumor biology, exerting a pleiotropic action across different GBM hallmarks, including phenotypic identity and gene transcription, as well as response to treatments, thus providing valuable information for the understanding of the complex microenvironmental cues underlying GBM malignancy.

Impact of Gut Microbiota on the Peripheral Nervous System in Physiological, Regenerative and Pathological Conditions.

It has been widely demonstrated that the gut microbiota is responsible for essential functions in human health and that its perturbation is implicated in the development and progression of a growing list of diseases. The number of studies evaluating how the gut microbiota interacts with and influences other organs and systems in the body and vice versa is constantly increasing and several 'gut-organ axes' have already been defined. Recently, the view on the link between the gut microbiota (GM) and the peripheral nervous system (PNS) has become broader by exceeding the fact that the PNS can serve as a systemic carrier of GM-derived metabolites and products to other organs. The PNS as the communication network between the central nervous system and the periphery of the body and internal organs can rather be affected itself by GM perturbation. In this review, we summarize the current knowledge about the impact of gut microbiota on the PNS, with regard to its somatic and autonomic divisions, in physiological, regenerative and pathological conditions.

Collagen VI in the Musculoskeletal System.

Collagen VI exerts several functions in the tissues in which it is expressed, including mechanical roles, cytoprotective functions with the inhibition of apoptosis and oxidative damage, and the promotion of tumor growth and progression by the regulation of cell differentiation and autophagic mechanisms. Mutations in the genes encoding collagen VI main chains, COL6A1, COL6A2 and COL6A3, are responsible for a spectrum of congenital muscular disorders, namely Ullrich congenital muscular dystrophy (UCMD), Bethlem myopathy (BM) and myosclerosis myopathy (MM), which show a variable combination of muscle wasting and weakness, joint contractures, distal laxity, and respiratory compromise. No effective therapeutic strategy is available so far for these diseases; moreover, the effects of collagen VI mutations on other tissues is poorly investigated. The aim of this review is to outline the role of collagen VI in the musculoskeletal system and to give an update about the tissue-specific functions revealed by studies on animal models and from patients' derived samples in order to fill the knowledge gap between scientists and the clinicians who daily manage patients affected by collagen VI-related myopathies.

Collagen VI is required for the structural and functional integrity of the neuromuscular junction.

The synaptic cleft of the neuromuscular junction (NMJ) consists of a highly specialized extracellular matrix (ECM) involved in synapse maturation, in the juxtaposition of pre- to post-synaptic areas, and in ensuring proper synaptic transmission. Key components of synaptic ECM, such as collagen IV, perlecan and biglycan, are binding partners of one of the most abundant ECM protein of skeletal muscle, collagen VI (ColVI), previously never linked to NMJ. Here, we demonstrate that ColVI is itself a component of this specialized ECM and that it is required for the structural and functional integrity of NMJs. In vivo, ColVI deficiency causes fragmentation of acetylcholine receptor (AChR) clusters, with abnormal expression of NMJ-enriched proteins and re-expression of fetal AChRγ subunit, both in Col6a1 null mice and in patients affected by Ullrich congenital muscular dystrophy (UCMD), the most severe form of ColVI-related myopathies. Ex vivo muscle preparations from ColVI null mice revealed altered neuromuscular transmission, with electrophysiological defects and decreased safety factor (i.e., the excess current generated in response to a nerve impulse over that required to reach the action potential threshold). Moreover, in vitro studies in differentiated C2C12 myotubes showed the ability of ColVI to induce AChR clustering and synaptic gene expression. These findings reveal a novel role for ColVI at the NMJ and point to the involvement of NMJ defects in the etiopathology of ColVI-related myopathies.

Collagen VI at a glance.

Collagen VI represents a remarkable extracellular matrix molecule, and in the past few years, studies of this molecule have revealed its involvement in a wide range of tissues and pathological conditions. In addition to its complex multi-step pathway of biosynthesis and assembly that leads to the formation of a characteristic and distinctive network of beaded microfilaments in the extracellular matrix, collagen VI exerts several key roles in different tissues. These range from unique biomechanical roles to cytoprotective functions in different cells, including myofibers, chondrocytes, neurons, fibroblasts and cardiomyocytes. Indeed, collagen VI has been shown to exert a surprisingly broad range of cytoprotective effects, which include counteracting apoptosis and oxidative damage, favoring tumor growth and progression, regulating autophagy and cell differentiation, and even contributing to the maintenance of stemness. In this Cell Science at a Glance article and the accompanying poster, we present the current knowledge of collagen VI, and in particular, discuss its relevance in stemness and in preserving the mechanical properties of tissues, as well as its links with human disorders.

Collagen VI regulates peripheral nerve regeneration by modulating macrophage recruitment and polarization.

Macrophages contribute to peripheral nerve regeneration and produce collagen VI, an extracellular matrix protein involved in nerve function. Here, we show that collagen VI is critical for macrophage migration and polarization during peripheral nerve regeneration. Nerve injury induces a robust upregulation of collagen VI, whereas lack of collagen VI in Col6a1(-/-) mice delays peripheral nerve regeneration. In vitro studies demonstrated that collagen VI promotes macrophage migration and polarization via AKT and PKA pathways. Col6a1(-/-) macrophages exhibit impaired migration abilities and reduced antiinflammatory (M2) phenotype polarization, but are prone to skewing toward the proinflammatory (M1) phenotype. In vivo, macrophage recruitment and M2 polarization are impaired in Col6a1(-/-) mice after nerve injury. The delayed nerve regeneration of Col6a1(-/-) mice is induced by macrophage deficits and rejuvenated by transplantation of wild-type bone marrow cells. These results identify collagen VI as a novel regulator for peripheral nerve regeneration by modulating macrophage function.

Collagen VI regulates peripheral nerve myelination and function.

Collagen VI is an extracellular matrix protein with broad distribution in several tissues. Although Col6a1 is expressed by Schwann cells, the role of collagen VI in the peripheral nervous system (PNS) is yet unknown. Here we show that Schwann cells, but not axons, contribute to collagen VI deposition in peripheral nerves. By using Col6a1-null mice, in which collagen VI deposition is compromised, we demonstrate that lack of collagen VI leads to increased myelin thickness (P<0.001) along with 60-130% up-regulation in myelin-associated proteins and disorganized C fibers in the PNS. The hypermyelination of PNS in Col6a1(-/-) mice is supported by alterations of signaling pathways involved in myelination, including increase of P-FAK, P-AKT, P-ERK1, P-ERK2, and P-p38 (4.15, 1.67, 2.47, 3.34, and 2.60-fold, respectively) and reduction of vimentin (0.49-fold), P-JNK (0.74-fold), and P-c-Jun (0.50-fold). Pathologically, Col6a1(-/-) mice display an impairment of nerve conduction velocity and motor coordination (P<0.05), as well as a delayed response to acute pain stimuli (P<0.001), indicating that lack of collagen VI causes functional defects of peripheral nerves. Altogether, these results indicate that collagen VI is a critical component of PNS contributing to the structural integrity and proper function of peripheral nerves.

Gut microbiota depletion delays somatic peripheral nerve development and impairs neuromuscular junction maturation.

Gut microbiota is responsible for essential functions in human health. Several communication axes between gut microbiota and other organs via neural, endocrine, and immune pathways have been described, and perturbation of gut microbiota composition has been implicated in the onset and progression of an emerging number of diseases. Here, we analyzed peripheral nerves, dorsal root ganglia (DRG), and skeletal muscles of neonatal and young adult mice with the following gut microbiota status: a) germ-free (GF), b) gnotobiotic, selectively colonized with 12 specific gut bacterial strains (Oligo-Mouse-Microbiota, OMM12), or c) natural complex gut microbiota (CGM). Stereological and morphometric analyses revealed that the absence of gut microbiota impairs the development of somatic median nerves, resulting in smaller diameter and hypermyelinated axons, as well as in smaller unmyelinated fibers. Accordingly, DRG and sciatic nerve transcriptomic analyses highlighted a panel of differentially expressed developmental and myelination genes. Interestingly, the type III isoform of Neuregulin1 (NRG1), known to be a neuronal signal essential for Schwann cell myelination, was overexpressed in young adult GF mice, with consequent overexpression of the transcription factor Early Growth Response 2 (Egr2), a fundamental gene expressed by Schwann cells at the onset of myelination. Finally, GF status resulted in histologically atrophic skeletal muscles, impaired formation of neuromuscular junctions, and deregulated expression of related genes. In conclusion, we demonstrate for the first time a gut microbiota regulatory impact on proper development of the somatic peripheral nervous system and its functional connection to skeletal muscles, thus suggesting the existence of a novel 'Gut Microbiota-Peripheral Nervous System-axis.'

GBA1 inactivation in oligodendrocytes affects myelination and induces neurodegenerative hallmarks and lipid dyshomeostasis in mice.

BACKGROUND: Mutations in the ß-glucocerebrosidase (GBA1) gene do cause the lysosomal storage Gaucher disease (GD) and are among the most frequent genetic risk factors for Parkinson's disease (PD). So far, studies on both neuronopathic GD and PD primarily focused on neuronal manifestations, besides the evaluation of microglial and astrocyte implication. White matter alterations were described in the central nervous system of paediatric type 1 GD patients and were suggested to sustain or even play a role in the PD process, although the contribution of oligodendrocytes has been so far scarcely investigated. METHODS: We exploited a system to study the induction of central myelination in vitro, consisting of Oli-neu cells treated with dibutyryl-cAMP, in order to evaluate the expression levels and function of ß-glucocerebrosidase during oligodendrocyte differentiation. Conduritol-B-epoxide, a ß-glucocerebrosidase irreversible inhibitor was used to dissect the impact of ß-glucocerebrosidase inactivation in the process of myelination, lysosomal degradation and α-synuclein accumulation in vitro. Moreover, to study the role of ß-glucocerebrosidase in the white matter in vivo, we developed a novel mouse transgenic line in which ß-glucocerebrosidase function is abolished in myelinating glia, by crossing the Cnp1-cre mouse line with a line bearing loxP sequences flanking Gba1 exons 9-11, encoding for ß-glucocerebrosidase catalytic domain. Immunofluorescence, western blot and lipidomic analyses were performed in brain samples from wild-type and knockout animals in order to assess the impact of genetic inactivation of ß-glucocerebrosidase on myelination and on the onset of early neurodegenerative hallmarks, together with differentiation analysis in primary oligodendrocyte cultures. RESULTS: Here we show that ß-glucocerebrosidase inactivation in oligodendrocytes induces lysosomal dysfunction and inhibits myelination in vitro. Moreover, oligodendrocyte-specific ß-glucocerebrosidase loss-of-function was sufficient to induce in vivo demyelination and early neurodegenerative hallmarks, including axonal degeneration, α-synuclein accumulation and astrogliosis, together with brain lipid dyshomeostasis and functional impairment. CONCLUSIONS: Our study sheds light on the contribution of oligodendrocytes in GBA1-related diseases and supports the need for better characterizing oligodendrocytes as actors playing a role in neurodegenerative diseases, also pointing at them as potential novel targets to set a brake to disease progression.

Sustained oral spermidine supplementation rescues functional and structural defects in COL6-deficient myopathic mice.

COL6 (collagen type VI)-related myopathies (COL6-RM) are a distinct group of inherited muscle disorders caused by mutations of COL6 genes and characterized by early-onset muscle weakness, for which no cure is available yet. Key pathophysiological features of COL6-deficient muscles involve impaired macroautophagy/autophagy, mitochondrial dysfunction, neuromuscular junction fragmentation and myofiber apoptosis. Targeting autophagy by dietary means elicited beneficial effects in both col6a1 null (col6a1-/-) mice and COL6-RM patients. We previously demonstrated that one-month per os administration of the nutraceutical spermidine reactivates autophagy and ameliorates myofiber defects in col6a1-/- mice but does not elicit functional improvement. Here we show that a 100-day-long spermidine regimen is able to rescue muscle strength in col6a1-/- mice, with also a beneficial impact on mitochondria and neuromuscular junction integrity, without any noticeable side effects. Altogether, these data provide a rationale for the application of spermidine in prospective clinical trials for COL6-RM.Abbreviations: AChR: acetylcholine receptor; BTX: bungarotoxin; CNF: centrally nucleated fibers; Colch: colchicine; COL6: collagen type VI; COL6-RM: COL6-related myopathies; MAP1LC3/LC3: microtubule-associated protein 1 light chain 3; NMJ: neuromuscular junction; Spd: spermidine; SQSTM1/p62: sequestosome 1; TA: tibialis anterior; TOMM20: translocase of outer mitochondrial membrane 20; TUNEL: terminal deoxynucleotidyl transferase dUTP-mediated nick-end labeling.

Bicalutamide and Trehalose Ameliorate Spinal and Bulbar Muscular Atrophy Pathology in Mice.

Spinal and bulbar muscular atrophy (SBMA) is characterized by motor neuron (MN) degeneration that leads to slowly progressive muscle weakness. It is considered a neuromuscular disease since muscle has a primary role in disease onset and progression. SBMA is caused by a CAG triplet repeat expansion in the androgen receptor (AR) gene. The translated poly-glutamine (polyQ) tract confers a toxic gain of function to the mutant AR altering its folding, causing its aggregation into intracellular inclusions, and impairing the autophagic flux. In an in vitro SBMA neuronal model, we previously showed that the antiandrogen bicalutamide and trehalose, a natural disaccharide stimulating autophagy, block ARpolyQ activation, reduce its nuclear translocation and toxicity and facilitate the autophagic degradation of cytoplasmic AR aggregates. Here, in a knock-in SBMA mouse model (KI AR113Q), we show that bicalutamide and trehalose ameliorated SBMA pathology. Bicalutamide reversed the formation of the AR insoluble forms in KI AR113Q muscle, preventing autophagic flux blockage. We demonstrated that apoptosis is activated in KI AR113Q muscle, and that both compounds prevented its activation. We detected a decrease of mtDNA and an increase of OXPHOS enzymes, already at early symptomatic stages; these alterations were reverted by trehalose. Overall, bicalutamide and/or trehalose led to a partial recovery of muscle morphology and function, and improved SBMA mouse motor behavior, inducing an extension of their survival. Thus, bicalutamide and trehalose, by counteracting ARpolyQ toxicity in skeletal muscle, are valuable candidates for future clinical trials in SBMA patients.

Collagen VI ablation in zebrafish causes neuromuscular defects during developmental and adult stages.

Collagen VI (COL6) is an extracellular matrix protein exerting multiple functions in different tissues. In humans, mutations of COL6 genes cause rare inherited congenital disorders, primarily affecting skeletal muscles and collectively known as COL6-related myopathies, for which no cure is available yet. In order to get insights into the pathogenic mechanisms underlying COL6-related diseases, diverse animal models were produced. However, the roles exerted by COL6 during embryogenesis remain largely unknown. Here, we generated the first zebrafish COL6 knockout line through CRISPR/Cas9 site-specific mutagenesis of the col6a1 gene. Phenotypic characterization during embryonic and larval development revealed that lack of COL6 leads to neuromuscular defects and motor dysfunctions, together with distinctive alterations in the three-dimensional architecture of craniofacial cartilages. These phenotypic features were maintained in adult col6a1 null fish, which displayed defective muscle organization and impaired swimming capabilities. Moreover, col6a1 null fish showed autophagy defects and organelle abnormalities at both embryonic and adult stages, thus recapitulating the main features of patients affected by COL6-related myopathies. Mechanistically, lack of COL6 led to increased BMP signaling, and direct inhibition of BMP activity ameliorated the locomotor activity of col6a1 null embryos. Finally, treatment with salbutamol, a  ß2-adrenergic receptor agonist, elicited a significant amelioration of the neuromuscular and motility defects of col6a1 null fish embryos. Altogether, these findings indicate that this newly generated zebrafish col6a1 null line is a valuable in vivo tool to model COL6-related myopathies and suitable for drug screenings aimed at addressing the quest for effective therapeutic strategies for these disorders.

Ambra1 deficiency impairs mitophagy in skeletal muscle.

BACKGROUND: Maintaining healthy mitochondria is mandatory for muscle viability and function. An essential surveillance mechanism targeting defective and harmful mitochondria to degradation is the selective form of autophagy called mitophagy. Ambra1 is a multifaceted protein with well-known autophagic and mitophagic functions. However, the study of its role in adult tissues has been extremely limited due to the embryonic lethality caused by full-body Ambra1 deficiency. METHODS: To establish the role of Ambra1 as a positive regulator of mitophagy, we exploited in vivo overexpression of a mitochondria-targeted form of Ambra1 in skeletal muscle. To dissect the consequence of Ambra1 inactivation in skeletal muscle, we generated muscle-specific Ambra1 knockout (Ambra1fl/fl :Mlc1f-Cre) mice. Mitochondria-enriched fractions were obtained from muscles of fed and starved animals to investigate the dynamics of the mitophagic flux. RESULTS: Our data show that Ambra1 has a critical role in the mitophagic flux of adult murine skeletal muscle and that its genetic inactivation leads to mitochondria alterations and myofibre remodelling. Ambra1 overexpression in wild-type muscles is sufficient to enhance mitochondria clearance through the autophagy-lysosome system. Consistently with this, Ambra1-deficient muscles display an abnormal accumulation of the mitochondrial marker TOMM20 by +76% (n = 6-7; P < 0.05), a higher presence of myofibres with swollen mitochondria by +173% (n = 4; P < 0.05), and an alteration in the maintenance of the mitochondrial membrane potential and a 34% reduction in the mitochondrial respiratory complex I activity (n = 4; P < 0.05). Lack of Ambra1 in skeletal muscle leads to impaired mitophagic flux, without affecting the bulk autophagic process. This is due to a significantly decreased recruitment of DRP1 (n = 6-7 mice; P < 0.01) and Parkin (n = 6-7 mice; P < 0.05) to the mitochondrial compartment, when compared with controls. Ambra1-deficient muscles also show a marked dysregulation of the endolysosome compartment, as the incidence of myofibres with lysosomal accumulation is 20 times higher than wild-type muscles (n = 4; P < 0.05). Histologically, Ambra1-deficient muscles of both 3- and 6-month-old animals display a significant decrease of myofibre cross-sectional area and a 52% reduction in oxidative fibres (n = 6-7; P < 0.05), thus highlighting a role for Ambra1 in the proper structure and activity of skeletal muscle. CONCLUSIONS: Our study indicates that Ambra1 is critical for skeletal muscle mitophagy and for the proper maintenance of functional mitochondria.

Collagen VI deficiency causes behavioral abnormalities and cortical dopaminergic dysfunction.

Mutations of genes coding for collagen VI (COL6) cause muscle diseases, including Ullrich congenital muscular dystrophy and Bethlem myopathy. Although COL6 genetic variants were recently linked to brain pathologies, the impact of COL6 deficiency in brain function is still largely unknown. Here, a thorough behavioral characterization of COL6-null (Col6a1-/-) mice unexpectedly revealed that COL6 deficiency leads to a significant impairment in sensorimotor gating and memory/attention functions. In keeping with these behavioral abnormalities, Col6a1-/- mice displayed alterations in dopaminergic signaling, primarily in the prefrontal cortex. In vitro co-culture of SH-SY5Y neural cells with primary meningeal fibroblasts from wild-type and Col6a1-/- mice confirmed a direct link between COL6 ablation and defective dopaminergic activity, through a mechanism involving the inability of meningeal cells to sustain dopaminergic differentiation. Finally, patients affected by COL6-related myopathies were evaluated with an ad hoc neuropsychological protocol, revealing distinctive defects in attentional control abilities. Altogether, these findings point towards a previously undescribed role for COL6 in the proper maintenance of dopamine circuitry function and its related neurobehavioral features in both mice and humans. This article has an associated First Person interview with the first author of the paper.

Autophagy in the mesh of collagen VI.

Autophagy is a very versatile process through which the cell degrades damaged long-lived proteins, entire organelles, or pathogens, by engulfing them in characteristic double-membrane vesicles and conveying the cargo to lysosomes. It is a dynamic pathway tunable at multiple levels and responsive to nutrient and stress stimuli, also coming from the extracellular microenvironment and its remodeling. In the extracellular matrix, collagen type VI forms a distinctive set of beaded microfilaments that assemble into an intricate and multimodular meshwork of tightly linked proteins and surface receptors. When missing or defective, collagen VI triggers a series of pathological events in skeletal muscle and other tissues, with a remarkable impact on key cell processes, such as apoptosis and autophagy. In this review, we discuss the current knowledge about collagen VI regulation of autophagy in the different experimental models and human pathologies where it was studied, and provide some hints for future directions aimed at the fine dissection of this intriguing relationship, as well as its prospective translational impact for disease and therapy.

Environmental Impact on Male (In)Fertility via Epigenetic Route.

In the last 40 years, male reproductive health-which is very sensitive to both environmental exposure and metabolic status-has deteriorated and the poor sperm quality observed has been suggested to affect offspring development and its health in adult life. In this scenario, evidence now suggests that epigenetics shapes endocrine functions, linking genetics and environment. During fertilization, spermatozoa share with the oocyte their epigenome, along with their haploid genome, in order to orchestrate embryo development. The epigenetic signature of spermatozoa is the result of a dynamic modulation of the epigenetic marks occurring, firstly, in the testis-during germ cell progression-then, along the epididymis, where spermatozoa still receive molecules, conveyed by epididymosomes. Paternal lifestyle, including nutrition and exposure to hazardous substances, alters the phenotype of the next generations, through the remodeling of a sperm epigenetic blueprint that dynamically reacts to a wide range of environmental and lifestyle stressors. With that in mind, this review will summarize and discuss insights into germline epigenetic plasticity caused by environmental stimuli and diet and how spermatozoa may be carriers of induced epimutations across generations through a mechanism known as paternal transgenerational epigenetic inheritance.

Role of adiponectin in the metabolism of skeletal muscles in collagen VI-related myopathies.

The role of adiponectin has been particularly deepened in diabetic muscles while the study of adiponectin in hereditary myopathies has been marginally investigated. Here, we report the study about adiponectin effects in Col6a1-/- (collagen VI-null) mice. Col6a1-/- mice show myophatic phenotype closer to that of patients with Bethlem myopathy, thus representing an excellent animal model for the study of this hereditary disease. Our findings demonstrate that Col6a1-/- mice have decreased plasma adiponectin content and diseased myoblasts have an impaired autocrine secretion of the hormone. Moreover, Col6a1-/- myoblasts show decreased glucose uptake and mitochondria with depolarized membrane potential and impaired functionality, as supported by decreased oxygen consumption. Exogenous addition of globular adiponectin modifies the features of Col6a1-/- myoblasts, becoming closer to that of the healthy myoblasts. Indeed, globular adiponectin enhances glucose uptake in Col6a1-/- myoblasts, modifies mitochondrial membrane potential, and restores oxygen consumption, turning closer to those of wild-type myoblasts. Finally, increase of plasma adiponectin level in Col6a1-/- mice is induced by fasting, a condition that has been previously shown to lead to the amelioration of the dystrophic phenotype. Collectively, our results demonstrate that exogenous replenishment of adiponectin reverses metabolic abnormalities observed in Col6a1-/- myoblasts. KEY MESSAGES: Col6a1-/- mice have decreased level of plasma adiponectin. Myoblasts from Col6a1-/- muscles have impaired local adiponectin secretion. Col6a1-/- myoblasts reveal altered metabolic features. Addition of exogenous adiponectin ameliorates Col6a1-/- metabolic features.

Autosomal recessive Bethlem myopathy: A clinical, genetic and functional study.

Bethlem myopathy represents the milder form of the spectrum of Collagen VI-related dystrophies, which are characterized by a clinical continuum between the two extremities, the Bethlem myopathy and the Ullrich congenital muscular dystrophy, and include less defined intermediate phenotypes. Bethlem myopathy is mainly an autosomal dominant disorder and the causing mutations occur in the COL6A genes encoding for the α1 (COL6A1), α2 (COL6A2) and α3 (COL6A3) chains. However, few cases of recessive inheritance have been also reported. We here describe clinical, genetic and functional findings in a recessive Bethlem myopathy family harbouring two novel pathogenic mutations in the COL6A2 gene. Two adult siblings presented with muscle weakness and wasting, elbows and Achilles tendon retractions, lumbar hyperlordosis, waddling gait and positive Gowers' sign. Muscle biopsy showed a dystrophic pattern. Molecular analysis of the COL6A2 gene revealed the novel paternally-inherited nonsense p.Gln889* mutation and the maternally-inherited p.Pro260_Lys261insProPro small insertion. Fibroblast studies in both affected patients showed the concomitant reduction in the amount of normal Collagen VI (p.Gln889*) and impairment of Collagen VI secretion and assembly (p.Pro260_Lys261insProPro). Each of the two variants behave as a recessive mutation as shown by the asymptomatic heterozygous parents, while their concomitant effects determined a relatively mild Bethlem myopathy phenotype. This study confirms the occurrence of recessive inherited Bethlem myopathy and expands the genetic heterogeneity of this group of muscle diseases.