RESUMO
Fibrodysplasia ossificans progressiva (FOP) is a rare genetic disorder characterized by episodic yet cumulative heterotopic ossification (HO) of skeletal muscles, tendons, ligaments, and fascia. FOP arises from missense mutations in Activin Receptor type I (ACVR1), a type I bone morphogenetic protein (BMP) receptor. Although initial findings implicated constitutive activity of FOP-variant ACVR1 (ACVR1FOP) and/or hyperactivation by BMPs, it was later shown that HO in FOP requires activation of ACVR1FOP by Activin A. Inhibition of Activin A completely prevents HO in FOP mice, indicating that Activin A is an obligate driver of HO in FOP, and excluding a key role for BMPs in this process. This discovery led to the clinical development of garetosmab, an investigational antibody that blocks Activin A. In a phase 2 trial, garetosmab inhibited new heterotopic bone lesion formation in FOP patients. In contrast, antibodies to ACVR1 activate ACVR1FOP and promote HO in FOP mice. Beyond their potential clinical relevance, these findings have enhanced our understanding of FOP's pathophysiology, leading to the identification of fibroadipogenic progenitors as the cells that form HO, and the discovery of non-signaling complexes between Activin A and wild type ACVR1 and their role in tempering HO, and are also starting to inform biological processes beyond FOP.
Assuntos
Miosite Ossificante , Humanos , Animais , Camundongos , Miosite Ossificante/tratamento farmacológico , Ativinas , Anticorpos Monoclonais , Receptores de Proteínas Morfogenéticas Ósseas Tipo IRESUMO
Fibrodysplasia ossificans progressiva (FOP) is a rare disease characterized by heterotopic ossification (HO) in connective tissues and painful flare-ups. In the phase 2 LUMINA-1 trial, adult patients with FOP were randomized to garetosmab, an activin A-blocking antibody (n = 20) or placebo (n = 24) in period 1 (28 weeks), followed by an open-label period 2 (28 weeks; n = 43). The primary end points were safety and for period 1, the activity and size of HO lesions. All patients experienced at least one treatment-emergent adverse event during period 1, notably epistaxis, madarosis and skin abscesses. Five deaths (5 of 44; 11.4%) occurred in the open-label period and, while considered unlikely to be related, causality cannot be ruled out. The primary efficacy end point in period 1 (total lesion activity by PET-CT) was not met (P = 0.0741). As the development of new HO lesions was suppressed in period 1, the primary efficacy end point in period 2 was prospectively changed to the number of new HO lesions versus period 1. No placebo patients crossing over to garetosmab developed new HO lesions (0% in period 2 versus 40.9% in period 1; P = 0.0027). Further investigation of garetosmab in FOP is ongoing. ClinicalTrials.gov identifier NCT03188666 .
Assuntos
Miosite Ossificante , Ossificação Heterotópica , Adulto , Humanos , Miosite Ossificante/tratamento farmacológico , Miosite Ossificante/patologia , Tomografia por Emissão de Pósitrons combinada à Tomografia Computadorizada , Ossificação Heterotópica/patologiaRESUMO
Mucopolysaccharidosis VI (MPS VI) is a rare lysosomal disease arising from impaired function of the enzyme arylsulfatase B (ARSB). This impairment causes aberrant accumulation of dermatan sulfate, a glycosaminoglycan (GAG) abundant in cartilage. While clinical severity varies along with age at first symptom manifestation, MPS VI usually presents early and strongly affects the skeleton. Current enzyme replacement therapy (ERT) does not provide effective treatment for the skeletal manifestations of MPS VI. This lack of efficacy may be due to an inability of ERT to reach affected cells or to the irreversibility of the disease. To address the question of reversibility of skeletal phenotypes, we generated a conditional by inversion (COIN) mouse model of MPS VI, ArsbCOIN/COIN, wherein Arsb is initially null and can be restored to WT using Cre. We restored Arsb at different times during postnatal development, using a tamoxifen-dependent global Cre driver. By restoring Arsb at P7, P21, and P56-P70, we determined that skeletal phenotypes can be fully rescued if Arsb restoration occurs at P7, while only achieving partial rescue at P21 and no significant rescue at P56-P70. This work has highlighted the importance of early intervention in patients with MPS VI to maximize therapeutic impact.
Assuntos
Mucopolissacaridose VI , N-Acetilgalactosamina-4-Sulfatase , Camundongos , Animais , Humanos , Mucopolissacaridose VI/tratamento farmacológico , Mucopolissacaridose VI/diagnóstico , N-Acetilgalactosamina-4-Sulfatase/genética , N-Acetilgalactosamina-4-Sulfatase/uso terapêutico , Fenótipo , Glicosaminoglicanos , EsqueletoRESUMO
In this study, we leveraged the combined evidence of rare coding variants and common alleles to identify therapeutic targets for osteoporosis. We undertook a large-scale multiancestry exome-wide association study for estimated bone mineral density, which showed that the burden of rare coding alleles in 19 genes was associated with estimated bone mineral density (P < 3.6 × 10-7). These genes were highly enriched for a set of known causal genes for osteoporosis (65-fold; P = 2.5 × 10-5). Exome-wide significant genes had 96-fold increased odds of being the top ranked effector gene at a given GWAS locus (P = 1.8 × 10-10). By integrating proteomics Mendelian randomization evidence, we prioritized CD109 (cluster of differentiation 109) as a gene for which heterozygous loss of function is associated with higher bone density. CRISPR-Cas9 editing of CD109 in SaOS-2 osteoblast-like cell lines showed that partial CD109 knockdown led to increased mineralization. This study demonstrates that the convergence of common and rare variants, proteomics and CRISPR can highlight new bone biology to guide therapeutic development.
Assuntos
Predisposição Genética para Doença , Osteoporose , Humanos , Sequenciamento do Exoma , Osteoporose/genética , Densidade Óssea/genética , Alelos , Fatores de Transcrição/genética , Estudo de Associação Genômica AmplaRESUMO
Body fat distribution is a heritable risk factor for cardiovascular and metabolic disease. In humans, rare Inhibin beta E (INHBE, activin E) loss-of-function variants are associated with a lower waist-to-hip ratio and protection from type 2 diabetes. Hepatic fatty acid sensing promotes INHBE expression during fasting and in obese individuals, yet it is unclear how the hepatokine activin E governs body shape and energy metabolism. Here, we uncover activin E as a regulator of adipose energy storage. By suppressing ß-agonist-induced lipolysis, activin E promotes fat accumulation and adipocyte hypertrophy and contributes to adipose dysfunction in mice. Mechanistically, we demonstrate that activin E elicits its effect on adipose tissue through ACVR1C, activating SMAD2/3 signaling and suppressing PPARG target genes. Conversely, loss of activin E or ACVR1C in mice increases fat utilization, lowers adiposity, and drives PPARG-regulated gene signatures indicative of healthy adipose function. Our studies identify activin E-ACVR1C as a metabolic rheostat promoting liver-adipose cross talk to restrain excessive fat breakdown and preserve fat mass during prolonged fasting, a mechanism that is maladaptive in obese individuals.
Assuntos
Diabetes Mellitus Tipo 2 , Lipólise , Humanos , Camundongos , Animais , Ativinas/metabolismo , Adiposidade/genética , Diabetes Mellitus Tipo 2/metabolismo , PPAR gama/metabolismo , Obesidade/metabolismo , Tecido Adiposo/metabolismo , Receptores de Ativinas Tipo I/genética , Receptores de Ativinas Tipo I/metabolismoRESUMO
Skeletal muscle regeneration requires the coordinated interplay of diverse tissue-resident- and infiltrating cells. Fibro-adipogenic progenitors (FAPs) are an interstitial cell population that provides a beneficial microenvironment for muscle stem cells (MuSCs) during muscle regeneration. Here we show that the transcription factor Osr1 is essential for FAPs to communicate with MuSCs and infiltrating macrophages, thus coordinating muscle regeneration. Conditional inactivation of Osr1 impaired muscle regeneration with reduced myofiber growth and formation of excessive fibrotic tissue with reduced stiffness. Osr1-deficient FAPs acquired a fibrogenic identity with altered matrix secretion and cytokine expression resulting in impaired MuSC viability, expansion and differentiation. Immune cell profiling suggested a novel role for Osr1-FAPs in macrophage polarization. In vitro analysis suggested that increased TGFß signaling and altered matrix deposition by Osr1-deficient FAPs actively suppressed regenerative myogenesis. In conclusion, we show that Osr1 is central to FAP function orchestrating key regenerative events such as inflammation, matrix secretion and myogenesis.
RESUMO
Vertical sleeve gastrectomy (VSG), the most utilized bariatric procedure in clinical practice, greatly reduces body weight and improves a variety of metabolic disorders. However, one of its long-term complications is bone loss and increased risk of fracture. Elevated circulating sclerostin (SOST) and granulocyte-colony stimulating factor (G-CSF) concentrations have been considered as potential contributors to VSG-associated bone loss. To test these possibilities, we administrated antibodies to SOST or G-CSF receptor and investigated alterations to bone and marrow niche following VSG. Neutralizing either SOST or G-CSF receptor did not alter beneficial effects of VSG on adiposity and hepatic steatosis, and anti-SOST treatment provided a further improvement to glucose tolerance. SOST antibodies partially reduced trabecular and cortical bone loss following VSG by increasing bone formation, whereas G-CSF receptor antibodies had no effects on bone mass. The expansion in myeloid cellularity and reductions in bone marrow adiposity seen with VSG were partially eliminated by treatment with Anti-G-CSF receptor. Taken together, these experiments demonstrate that antibodies to SOST or G-CSF receptor may act through independent mechanisms to partially block effects of VSG on bone loss or marrow niche cells, respectively.
Assuntos
Medula Óssea , Receptores de Fator Estimulador de Colônias de Granulócitos , Humanos , Medula Óssea/metabolismo , Obesidade/metabolismo , Gastrectomia/efeitos adversos , Adipócitos/metabolismoRESUMO
Body fat distribution is a major, heritable risk factor for cardiometabolic disease, independent of overall adiposity. Using exome-sequencing in 618,375 individuals (including 160,058 non-Europeans) from the UK, Sweden and Mexico, we identify 16 genes associated with fat distribution at exome-wide significance. We show 6-fold larger effect for fat-distribution associated rare coding variants compared with fine-mapped common alleles, enrichment for genes expressed in adipose tissue and causal genes for partial lipodystrophies, and evidence of sex-dimorphism. We describe an association with favorable fat distribution (p = 1.8 × 10-09), favorable metabolic profile and protection from type 2 diabetes (~28% lower odds; p = 0.004) for heterozygous protein-truncating mutations in INHBE, which encodes a circulating growth factor of the activin family, highly and specifically expressed in hepatocytes. Our results suggest that inhibin ßE is a liver-expressed negative regulator of adipose storage whose blockade may be beneficial in fat distribution-associated metabolic disease.
Assuntos
Diabetes Mellitus Tipo 2 , Subunidades beta de Inibinas/genética , Tecido Adiposo , Adiposidade/genética , Diabetes Mellitus Tipo 2/genética , Exoma/genética , Humanos , MutaçãoRESUMO
Fibrodysplasia ossificans progressiva (FOP) is a rare genetic disorder whose most debilitating pathology is progressive and cumulative heterotopic ossification (HO) of skeletal muscles, ligaments, tendons, and fascia. FOP is caused by mutations in the type I BMP receptor gene ACVR1, which enable ACVR1 to utilize its natural antagonist, activin A, as an agonistic ligand. The physiological relevance of this property is underscored by the fact that HO in FOP is exquisitely dependent on activation of FOP-mutant ACVR1 by activin A, an effect countered by inhibition of anti-activin A via monoclonal antibody treatment. Hence, we surmised that anti-ACVR1 antibodies that block activation of ACVR1 by ligands should also inhibit HO in FOP and provide an additional therapeutic option for this condition. Therefore, we generated anti-ACVR1 monoclonal antibodies that block ACVR1's activation by its ligands. Surprisingly, in vivo, these anti-ACVR1 antibodies stimulated HO and activated signaling of FOP-mutant ACVR1. This property was restricted to FOP-mutant ACVR1 and resulted from anti-ACVR1 antibody-mediated dimerization of ACVR1. Conversely, wild-type ACVR1 was inhibited by anti-ACVR1 antibodies. These results uncover an additional property of FOP-mutant ACVR1 and indicate that anti-ACVR1 antibodies should not be considered as therapeutics for FOP.
Assuntos
Miosite Ossificante , Ossificação Heterotópica , Receptores de Ativinas Tipo I/genética , Receptores de Ativinas Tipo I/farmacologia , Anticorpos/imunologia , Humanos , Ligantes , Mutação , Miosite Ossificante/genética , Ossificação Heterotópica/genética , Ossificação Heterotópica/patologia , Transdução de Sinais/genéticaRESUMO
Sensorimotor information processing underlies normal cognitive and behavioral traits and has classically been evaluated through prepulse inhibition (PPI) of a startle reflex. PPI is a behavioral dimension deregulated in several neurological and psychiatric disorders, yet the mechanisms underlying the cross-diagnostic nature of PPI deficits across these conditions remain to be understood. To identify circuitry mechanisms for PPI, we performed circuitry recording over the prefrontal cortex and striatum, two brain regions previously implicated in PPI, using wild-type (WT) mice compared to Disc1-locus-impairment (LI) mice, a model representing neuropsychiatric conditions. We demonstrated that the corticostriatal projection regulates neurophysiological responses during the PPI testing in WT, whereas these circuitry responses were disrupted in Disc1-LI mice. Because our biochemical analyses revealed attenuated brain-derived neurotrophic factor (Bdnf) transport along the corticostriatal circuit in Disc1-LI mice, we investigated the potential role of Bdnf in this circuitry for regulation of PPI. Virus-mediated delivery of Bdnf into the striatum rescued PPI deficits in Disc1-LI mice. Pharmacologically augmenting Bdnf transport by chronic lithium administration, partly via phosphorylation of Huntingtin (Htt) serine-421 and its integration into the motor machinery, restored striatal Bdnf levels and rescued PPI deficits in Disc1-LI mice. Furthermore, reducing the cortical Bdnf expression negated this rescuing effect of lithium, confirming the key role of Bdnf in lithium-mediated PPI rescuing. Collectively, the data suggest that striatal Bdnf supply, collaboratively regulated by Htt and Disc1 along the corticostriatal circuit, is involved in sensorimotor gating, highlighting the utility of dimensional approach in investigating pathophysiological mechanisms across neuropsychiatric disorders.
Assuntos
Fator Neurotrófico Derivado do Encéfalo , Corpo Estriado , Proteínas do Tecido Nervoso , Córtex Pré-Frontal , Inibição Pré-Pulso , Animais , Fator Neurotrófico Derivado do Encéfalo/metabolismo , Corpo Estriado/metabolismo , Humanos , Camundongos , Proteínas do Tecido Nervoso/metabolismo , Córtex Pré-Frontal/metabolismo , Inibição Pré-Pulso/fisiologia , Reflexo de Sobressalto/fisiologia , Filtro Sensorial/fisiologiaRESUMO
Increased blood levels of low-density lipoprotein cholesterol (LDL-C) and fibrinogen are independent risk factors for cardiovascular disease. We identified associations between an Amish-enriched missense variant (p.Asn352Ser) in a functional domain of beta-1,4-galactosyltransferase 1 (B4GALT1) and 13.9 milligrams per deciliter lower LDL-C (P = 4.1 × 1019) and 29 milligrams per deciliter lower plasma fibrinogen (P = 1.3 × 105). B4GALT1 genebased analysis in 544,955 subjects showed an association with decreased coronary artery disease (odds ratio = 0.64, P = 0.006). The mutant protein had 50% lower galactosyltransferase activity compared with the wild-type protein. N-linked glycan profiling of human serum found serine 352 allele to be associated with decreased galactosylation and sialylation of apolipoprotein B100, fibrinogen, immunoglobulin G, and transferrin. B4galt1 353Ser knock-in mice showed decreases in LDL-C and fibrinogen. Our findings suggest that targeted modulation of protein galactosylation may represent a therapeutic approach to decreasing cardiovascular disease.
Assuntos
LDL-Colesterol/sangue , Fibrinogênio/análise , Galactosiltransferases/genética , Mutação de Sentido Incorreto , Animais , Doença da Artéria Coronariana/genética , Doença da Artéria Coronariana/prevenção & controle , Feminino , Galactose/metabolismo , Galactosiltransferases/metabolismo , Técnicas de Introdução de Genes , Técnicas de Silenciamento de Genes , Glicoproteínas/sangue , Glicosilação , Humanos , Fígado/enzimologia , Masculino , Camundongos , Ácido N-Acetilneuramínico/metabolismo , Polissacarídeos/sangue , Sequenciamento Completo do GenomaRESUMO
Lysosomal diseases are a class of genetic disorders predominantly caused by loss of lysosomal hydrolases, leading to lysosomal and cellular dysfunction. Enzyme replacement therapy (ERT), where recombinant enzyme is given intravenously, internalized by cells, and trafficked to the lysosome, has been applied to treat several lysosomal diseases. However, current ERT regimens do not correct disease phenotypes in all affected organs because the biodistribution of enzyme uptake does not match that of the affected cells that require the enzyme. We present here targeted ERT, an approach that utilizes antibody-enzyme fusion proteins to target the enzyme to specific cell types. The antibody moiety recognizes transmembrane proteins involved in lysosomal trafficking and that are also preferentially expressed in those cells most affected in disease. Using Pompe disease (PD) as an example, we show that targeted ERT is superior to ERT in treating the skeletal muscle phenotypes of PD mice both as a protein replacement therapeutic and as a gene therapy.
Assuntos
Doença de Depósito de Glicogênio Tipo II , Doenças por Armazenamento dos Lisossomos , Animais , Terapia de Reposição de Enzimas , Doença de Depósito de Glicogênio Tipo II/tratamento farmacológico , Doença de Depósito de Glicogênio Tipo II/genética , Hidrolases/metabolismo , Doenças por Armazenamento dos Lisossomos/tratamento farmacológico , Doenças por Armazenamento dos Lisossomos/genética , Lisossomos/metabolismo , Camundongos , Distribuição Tecidual , alfa-Glucosidases/genéticaRESUMO
Large-scale human exome sequencing can identify rare protein-coding variants with a large impact on complex traits such as body adiposity. We sequenced the exomes of 645,626 individuals from the United Kingdom, the United States, and Mexico and estimated associations of rare coding variants with body mass index (BMI). We identified 16 genes with an exome-wide significant association with BMI, including those encoding five brain-expressed G protein-coupled receptors (CALCR, MC4R, GIPR, GPR151, and GPR75). Protein-truncating variants in GPR75 were observed in ~4/10,000 sequenced individuals and were associated with 1.8 kilograms per square meter lower BMI and 54% lower odds of obesity in the heterozygous state. Knock out of Gpr75 in mice resulted in resistance to weight gain and improved glycemic control in a high-fat diet model. Inhibition of GPR75 may provide a therapeutic strategy for obesity.
Assuntos
Índice de Massa Corporal , Exoma/genética , Obesidade/genética , Receptores Acoplados a Proteínas G/genética , Animais , Variação Genética , Humanos , Camundongos , Camundongos Knockout , Análise de Sequência de DNA , Aumento de Peso/genéticaRESUMO
Currently, no effective therapies exist for fibrodysplasia ossificans progressiva (FOP), a rare congenital syndrome in which heterotopic bone is formed in soft tissues owing to dysregulated activity of the bone morphogenetic protein (BMP) receptor kinase ALK2 (also known as ACVR1). From a screen of known biologically active compounds, we identified saracatinib as a potent ALK2 kinase inhibitor. In enzymatic and cell-based assays, saracatinib preferentially inhibited ALK2, compared with other receptors of the BMP/TGF-ß signaling pathway, and induced dorsalization in zebrafish embryos consistent with BMP antagonism. We further tested the efficacy of saracatinib using an inducible ACVR1Q207D-transgenic mouse line, which provides a model of heterotopic ossification (HO), as well as an inducible ACVR1R206H-knockin mouse, which serves as a genetically and physiologically faithful FOP model. In both models, saracatinib was well tolerated and potently inhibited the development of HO, even when administered transiently following soft tissue injury. Together, these data suggest that saracatinib is an efficacious clinical candidate for repositioning in FOP treatment, offering an accelerated path to clinical proof-of-efficacy studies and potentially significant benefits to individuals with this devastating condition.
Assuntos
Receptores de Ativinas Tipo I/genética , Benzodioxóis/farmacologia , Proteínas Morfogenéticas Ósseas/efeitos dos fármacos , Músculos/efeitos dos fármacos , Miosite Ossificante/genética , Quinazolinas/farmacologia , Receptores de Ativinas Tipo I/antagonistas & inibidores , Animais , Benzodioxóis/uso terapêutico , Proteínas Morfogenéticas Ósseas/metabolismo , Avaliação Pré-Clínica de Medicamentos , Técnicas de Introdução de Genes , Camundongos , Camundongos Transgênicos , Músculos/metabolismo , Miosite Ossificante/metabolismo , Miosite Ossificante/patologia , Ossificação Heterotópica/genética , Ossificação Heterotópica/metabolismo , Ossificação Heterotópica/patologia , Quinazolinas/uso terapêutico , Peixe-ZebraRESUMO
Noncoding RNAs are exquisitely titrated by the cellular RNA surveillance machinery for regulating diverse biological processes. The RNA exosome, the predominant 3' RNA exoribonuclease in mammalian cells, is composed of nine core and two catalytic subunits. Here, we developed a mouse model with a conditional allele to study the RNA exosome catalytic subunit DIS3. In DIS3-deficient B cells, integrity of the immunoglobulin heavy chain (Igh) locus in its topologically associating domain is affected, with accumulation of DNA-associated RNAs flanking CTCF-binding elements, decreased CTCF binding to CTCF-binding elements and disorganized cohesin localization. DIS3-deficient B cells also accumulate activation-induced cytidine deaminase-mediated asymmetric nicks, altering somatic hypermutation patterns and increasing microhomology-mediated end-joining DNA repair. Altered mutation patterns and Igh architectural defects in DIS3-deficient B cells lead to decreased class-switch recombination but increased chromosomal translocations. Our observations of DIS3-mediated architectural regulation at the Igh locus are reflected genome wide, thus providing evidence that noncoding RNA processing is an important mechanism for controlling genome organization.
Assuntos
Linfócitos B/fisiologia , Complexo Multienzimático de Ribonucleases do Exossomo/genética , RNA não Traduzido/genética , Hipermutação Somática de Imunoglobulina/fisiologia , Animais , Linfócitos B/efeitos dos fármacos , Fator de Ligação a CCCTC/genética , Fator de Ligação a CCCTC/metabolismo , Proteínas de Ciclo Celular/genética , Proteínas de Ciclo Celular/metabolismo , Proteínas Cromossômicas não Histona/metabolismo , Proteínas de Ligação a DNA/genética , Proteínas de Ligação a DNA/metabolismo , Células-Tronco Embrionárias/fisiologia , Complexo Multienzimático de Ribonucleases do Exossomo/metabolismo , Exossomos/genética , Proteínas de Fluorescência Verde/genética , Camundongos Knockout , Camundongos Transgênicos , Mutação , Processamento Pós-Transcricional do RNA , Recombinação Genética , Tamoxifeno/farmacologia , CoesinasRESUMO
Neurodevelopmental disorder with microcephaly, hypotonia and variable brain anomalies (NMIHBA) is an autosomal recessive neurodevelopmental and neurodegenerative disorder characterized by global developmental delay and severe intellectual disability. Microcephaly, progressive cortical atrophy, cerebellar hypoplasia and delayed myelination are neurological hallmarks in affected individuals. NMIHBA is caused by biallelic variants in PRUNE1 encoding prune exopolyphosphatase 1. We provide in-depth clinical description of two affected siblings harboring compound heterozygous variant alleles, c.383G > A (p.Arg128Gln), c.520G > T (p.Gly174*) in PRUNE1. To gain insights into disease biology, we biochemically characterized missense variants within the conserved N-terminal aspartic acid-histidine-histidine (DHH) motif and provide evidence that they result in the destabilization of protein structure and/or loss of exopolyphosphatase activity. Genetic ablation of Prune1 results in midgestational lethality in mice, associated with perturbations to embryonic growth and vascular development. Our findings suggest that NMIHBA results from hypomorphic variant alleles in humans and underscore the potential key role of PRUNE1 exopolyphoshatase activity in neurodevelopment.
Assuntos
Hidrolases Anidrido Ácido/deficiência , Deficiência Intelectual/patologia , Microcefalia/patologia , Hipotonia Muscular/patologia , Mutação , Transtornos do Neurodesenvolvimento/patologia , Monoéster Fosfórico Hidrolases/genética , Alelos , Animais , Pré-Escolar , Feminino , Humanos , Lactente , Deficiência Intelectual/etiologia , Deficiência Intelectual/metabolismo , Masculino , Camundongos , Microcefalia/etiologia , Microcefalia/metabolismo , Hipotonia Muscular/etiologia , Hipotonia Muscular/metabolismo , Transtornos do Neurodesenvolvimento/etiologia , Transtornos do Neurodesenvolvimento/metabolismo , Linhagem , FenótipoRESUMO
Heterotopic ossification (HO), the formation of ectopic bone in soft tissues, has been extensively studied in its two primary forms: post-traumatic HO (tHO) typically found in patients who have experienced musculoskeletal or neurogenic injury and in fibrodysplasia ossificans progressiva (FOP), where it is genetically driven. Given that in both diseases HO arises via endochondral ossification, the molecular mechanisms behind both diseases have been postulated to be manifestations of similar pathways including those activated by BMP/TGFß superfamily ligands. A significant step towards understanding the molecular mechanism by which HO arises in FOP was the discovery that FOP causing ACVR1 variants trigger HO in response to activin A, a ligand that does not activate signaling from wild type ACVR1, and that is not inherently osteogenic in wild type settings. The physiological significance of this finding was demonstrated by showing that activin A neutralizing antibodies stop HO in two different genetically accurate mouse models of FOP. In order to explore the role of activin A in tHO, we performed single cell RNA sequencing and compared the expression of activin A as well as other BMP pathway genes in tHO and FOP HO. We show that activin A is expressed in response to injury in both settings, but by different types of cells. Given that wild type ACVR1 does not transduce signal when engaged by activin A, we hypothesized that inhibition of activin A will not block tHO. Nonetheless, as activin A was expressed in tHO lesions, we tested its inhibition and compared it with inhibition of BMPs. We show here that anti-activin A does not block tHO, whereas agents such as antibodies that neutralize ACVR1 or ALK3-Fc (which blocks osteogenic BMPs) are beneficial, though not completely curative. These results demonstrate that inhibition of activin A should not be considered as a therapeutic strategy for ameliorating tHO.
Assuntos
Miosite Ossificante , Ossificação Heterotópica , Receptores de Ativinas Tipo I/genética , Ativinas , Animais , Humanos , Camundongos , Miosite Ossificante/genéticaRESUMO
Activin A functions in BMP signaling in two ways: it either engages ACVR1B to activate Smad2/3 signaling or binds ACVR1 to form a non-signaling complex (NSC). Although the former property has been studied extensively, the roles of the NSC remain unexplored. The genetic disorder fibrodysplasia ossificans progressiva (FOP) provides a unique window into ACVR1/Activin A signaling because in that disease Activin can either signal through FOP-mutant ACVR1 or form NSCs with wild-type ACVR1. To explore the role of the NSC, we generated 'agonist-only' Activin A muteins that activate ACVR1B but cannot form the NSC with ACVR1. Using one of these muteins, we demonstrate that failure to form the NSC in FOP results in more severe disease pathology. These results provide the first evidence for a biological role for the NSC in vivo and pave the way for further exploration of the NSC's physiological role in corresponding knock-in mice.
Assuntos
Receptores de Ativinas Tipo I/metabolismo , Ativinas/metabolismo , Proteínas Morfogenéticas Ósseas/metabolismo , Miosite Ossificante/genética , Transdução de Sinais/genética , Receptores de Ativinas Tipo I/genética , Ativinas/genética , Animais , Receptores de Proteínas Morfogenéticas Ósseas Tipo II/genética , Receptores de Proteínas Morfogenéticas Ósseas Tipo II/metabolismo , Proteínas Morfogenéticas Ósseas/genética , Técnicas de Introdução de Genes , Camundongos , Camundongos Transgênicos , Mutação , Miosite Ossificante/patologiaRESUMO
Previously we reported the identification of a homozygous COL27A1 (c.2089G>C; p.Gly697Arg) missense variant and proposed it as a founder allele in Puerto Rico segregating with Steel syndrome (STLS, MIM #615155); a rare osteochondrodysplasia characterized by short stature, congenital bilateral hip dysplasia, carpal coalitions, and scoliosis. We now report segregation of this variant in five probands from the initial clinical report defining the syndrome and an additional family of Puerto Rican descent with multiple affected adult individuals. We modeled the orthologous variant in murine Col27a1 and found it recapitulates some of the major Steel syndrome associated skeletal features including reduced body length, scoliosis, and a more rounded skull shape. Characterization of the in vivo murine model shows abnormal collagen deposition in the extracellular matrix and disorganization of the proliferative zone of the growth plate. We report additional COL27A1 pathogenic variant alleles identified in unrelated consanguineous Turkish kindreds suggesting Clan Genomics and identity-by-descent homozygosity contributing to disease in this population. The hypothesis that carrier states for this autosomal recessive osteochondrodysplasia may contribute to common complex traits is further explored in a large clinical population cohort. Our findings augment our understanding of COL27A1 biology and its role in skeletal development; and expand the functional allelic architecture in this gene underlying both rare and common disease phenotypes.
Assuntos
Anormalidades Múltiplas/genética , Colágenos Fibrilares/genética , Efeito Fundador , Luxação do Quadril/genética , Escoliose/genética , Anormalidades Múltiplas/patologia , Adolescente , Animais , Desenvolvimento Ósseo , Criança , Pré-Escolar , Consanguinidade , Matriz Extracelular/metabolismo , Matriz Extracelular/patologia , Feminino , Colágenos Fibrilares/metabolismo , Frequência do Gene , Luxação do Quadril/patologia , Homozigoto , Humanos , Masculino , Camundongos , Camundongos Endogâmicos C57BL , Mutação , Linhagem , Escoliose/patologia , SíndromeRESUMO
Group 2 innate lymphoid cells (ILC2s) are type 2 cytokine-producing cells that have important roles in helminth infection and allergic inflammation. ILC2s are tissue-resident cells, and their phenotypes and roles are regulated by tissue-specific environmental factors. While the role of ILC2s in the lung, intestine and bone marrow has been elucidated in many studies, their role in adipose tissues is still unclear. Here, we report on the role of ILC2-derived bone morphogenetic protein 7 (BMP7) in adipocyte differentiation and lipid accumulation. Co-culture of fat-derived ILC2s with pluripotent mesenchymal C3H10T1/2 cells and committed white preadipocyte 3T3-L1 cells resulted in their differentiation to adipocytes and induced lipid accumulation. Co-culture experiments using BMP7-deficient ILC2s revealed that BMP7, produced by ILC2s, induces differentiation into brown adipocytes. Our results demonstrate that BMP7, produced by ILC2s, affects adipocyte differentiation, particularly in brown adipocytes.