scholarly journals Phenotype and Genotype Study of Chinese POMT2-Related α-Dystroglycanopathy

2021 ◽  
Vol 12 ◽  
Author(s):  
Xiao-Yu Chen ◽  
Dan-Yu Song ◽  
Li Jiang ◽  
Dan-Dan Tan ◽  
Yi-Dan Liu ◽  
...  
Keyword(s):  
Muscular Dystrophy ◽  
Congenital Muscular Dystrophy ◽  
Genetic Characteristics ◽  
Apparent Lack ◽  
Missense Variants ◽  
Novel Variants ◽  
Bioinformatics Software ◽  
Uncertain Significance ◽  
Genetic Features

ObjectiveAlpha-dystroglycanopathy (α-DGP) is a subtype of muscular dystrophy caused by defects in the posttranslational glycosylation of α-dystroglycan (α-DG). Our study aimed to summarize the clinical and genetic features of POMT2-related α-DGP in a cohort of patients in China.MethodsPedigrees, clinical data, and laboratory tests of patients diagnosed with POMT2-related α-DGP were analyzed retrospectively. The pathogenicity of variants in POMT2 were predicted by bioinformatics software. The variants with uncertain significance were verified by further analysis.ResultsThe 11 patients, comprising eight males and three females, were from nine non-consanguineous families. They exhibited different degrees of muscle weakness, ambulation, and intellectual impairment. Among them, three had a muscle-eye-brain disease (MEB)-like phenotype, five presented congenital muscular dystrophy with intellectual disability (CMD-ID), and three presented limb-girdle muscular dystrophy (LGMD). Overall, nine novel variants of POMT2, including two non-sense, one frameshift and six missense variants, were identified. The pathogenicity of two missense variants, c.1891G > C and c.874G > C, was uncertain based on bioinformatics software prediction. In vitro minigene analysis showed that c.1891G > C affects the splicing of POMT2. Immunofluorescence staining with the IIH6C4 antibody of muscle biopsy from the patient carrying the c.874G > C variant showed an apparent lack of expression.ConclusionThis study summarizes the clinical and genetic characteristics of a cohort of POMT2-related α-DGP patients in China for the first time, expanding the mutational spectrum of the disease. Further study of the pathogenicity of some missense variants based on enzyme activity detection is needed.

scholarly journals Janus-faced EPHB4-associated disorders: novel pathogenic variants and unreported intrafamilial overlapping phenotypes

2021 ◽  
Author(s):  
Silvia Martin-Almedina ◽  
Kazim Ogmen ◽  
Ege Sackey ◽  
Dionysios Grigoriadis ◽  
Christina Karapouliou ◽  
...  
Keyword(s):  
Subcellular Localization ◽  
Fetal Hydrops ◽  
Clinical Phenotypes ◽  
Functional Studies ◽  
Pathogenic Variants ◽  
Disease Mechanisms ◽  
Novel Variants ◽  
Uncertain Significance ◽  
Clinical Phenotyping

Abstract Purpose Several clinical phenotypes including fetal hydrops, central conducting lymphatic anomaly or capillary malformations with arteriovenous malformations 2 (CM-AVM2) have been associated with EPHB4 (Ephrin type B receptor 4) variants, demanding new approaches for deciphering pathogenesis of novel variants of uncertain significance (VUS) identified in EPHB4, and for the identification of differentiated disease mechanisms at the molecular level. Methods Ten index cases with various phenotypes, either fetal hydrops, CM-AVM2, or peripheral lower limb lymphedema, whose distinct clinical phenotypes are described in detail in this study, presented with a variant in EPHB4. In vitro functional studies were performed to confirm pathogenicity. Results Pathogenicity was demonstrated for six of the seven novel EPHB4 VUS investigated. A heterogeneity of molecular disease mechanisms was identified, from loss of protein production or aberrant subcellular localization to total reduction of the phosphorylation capability of the receptor. There was some phenotype–genotype correlation; however, previously unreported intrafamilial overlapping phenotypes such as lymphatic-related fetal hydrops (LRFH) and CM-AVM2 in the same family were observed. Conclusion This study highlights the usefulness of protein expression and subcellular localization studies to predict EPHB4 variant pathogenesis. Our accurate clinical phenotyping expands our interpretation of the Janus-faced spectrum of EPHB4-related disorders, introducing the discovery of cases with overlapping phenotypes.

scholarly journals Collagen-VI supplementation by cell transplantation improves muscle regeneration in Ullrich congenital muscular dystrophy model mice

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Nana Takenaka-Ninagawa ◽  
Jinsol Kim ◽  
Mingming Zhao ◽  
Masae Sato ◽  
Tatsuya Jonouchi ◽  
...  
Keyword(s):  
Skeletal Muscle ◽  
Muscular Dystrophy ◽  
Cell Transplantation ◽  
Muscle Regeneration ◽  
Congenital Muscular Dystrophy ◽  
Induced Pluripotent Stem Cell ◽  
Skeletal Muscle Regeneration ◽  
Ullrich Congenital Muscular Dystrophy

Abstract Background Mesenchymal stromal cells (MSCs) function as supportive cells on skeletal muscle homeostasis through several secretory factors including type 6 collagen (COL6). Several mutations of COL6A1, 2, and 3 genes cause Ullrich congenital muscular dystrophy (UCMD). Skeletal muscle regeneration deficiency has been reported as a characteristic phenotype in muscle biopsy samples of human UCMD patients and UCMD model mice. However, little is known about the COL6-dependent mechanism for the occurrence and progression of the deficiency. The purpose of this study was to clarify the pathological mechanism of UCMD by supplementing COL6 through cell transplantation. Methods To test whether COL6 supplementation has a therapeutic effect for UCMD, in vivo and in vitro experiments were conducted using four types of MSCs: (1) healthy donors derived-primary MSCs (pMSCs), (2) MSCs derived from healthy donor induced pluripotent stem cell (iMSCs), (3) COL6-knockout iMSCs (COL6KO-iMSCs), and (4) UCMD patient-derived iMSCs (UCMD-iMSCs). Results All four MSC types could engraft for at least 12 weeks when transplanted into the tibialis anterior muscles of immunodeficient UCMD model (Col6a1KO) mice. COL6 protein was restored by the MSC transplantation if the MSCs were not COL6-deficient (types 1 and 2). Moreover, muscle regeneration and maturation in Col6a1KO mice were promoted with the transplantation of the COL6-producing MSCs only in the region supplemented with COL6. Skeletal muscle satellite cells derived from UCMD model mice (Col6a1KO-MuSCs) co-cultured with type 1 or 2 MSCs showed improved proliferation, differentiation, and maturation, whereas those co-cultured with type 3 or 4 MSCs did not. Conclusions These findings indicate that COL6 supplementation improves muscle regeneration and maturation in UCMD model mice.

scholarly journals Lamin-related congenital muscular dystrophy alters mechanical signaling and skeletal muscle growth

2020 ◽  
Author(s):  
Daniel J. Owens ◽  
Julien Messéant ◽  
Sophie Moog ◽  
Mark Viggars ◽  
Arnaud Ferry ◽  
...  
Keyword(s):  
Skeletal Muscle ◽  
Muscular Dystrophy ◽  
Disease Severity ◽  
Myogenic Differentiation ◽  
Muscle Growth ◽  
Congenital Muscular Dystrophy ◽  
Skeletal Muscle Growth ◽  
Muscle Biopsies

AbstractBackgroundLaminopathies are a clinically heterogeneous group of disorders caused by mutations in the LMNA gene, which encodes the nuclear envelope proteins lamins A and C. The most frequent diseases associated with LMNA mutations are characterized by skeletal and cardiac involvement, and include autosomal dominant Emery-Dreifuss muscular dystrophy (EDMD), limb-girdle muscular dystrophy type 1B, and LMNA-related congenital muscular dystrophy (LMNA-CMD). Although the exact pathophysiological mechanisms responsible for LMNA-CMD are not yet understood, severe contracture and muscle atrophy suggest that impair skeletal muscle growth may contribute to the disease severity.MethodsWe used human muscle stem cells (MuSCs) carrying 4 different LMNA mutations and two mouse models of muscle laminopathies, representing a spectrum of disease severity, to investigate the ability of skeletal muscle to differentiate and to hypertrophy in response to mechanical challenges. We extended these finding to individuals with LMNA-related muscular dystrophy using muscle biopsies.ResultsIn vitro, we observe impaired myogenic differentiation with disorganized cadherin/β catenin adhesion complexes in MuSCs carrying LMNA-CMD. We show that skeletal muscle from Lmna-CMD mice is unable to hypertrophy in response to functional overload, due to defective accretion of activated MuSCs, defective protein synthesis and defective remodeling of the neuro-muscular junction. Moreover, stretched myotubes and overloaded muscle fibers with LMNA-CMD mutations display aberrant mechanical regulation of the Yes-Associated Protein (YAP), a key sensor and mediator of mechanical cues. We also observe defects in MuSC activation and YAP signaling in muscle biopsies from LMNA-CMD patients. These phenotypes are not recapitulated in closely-related EDMD models.ConclusionsCombining studies in vitro, in vivo and patient samples, we find that LMNA-CMD mutations interfere with mechano-signaling pathways in skeletal muscle, implicating defective skeletal muscle growth as a pathogenic contributor for the severity of LMNA-related muscular dystrophy.

scholarly journals Merosin and laminin in myogenesis; specific requirement for merosin in myotube stability and survival.

1996 ◽  
Vol 134 (6) ◽  
pp. 1483-1497 ◽  
Author(s):  
P H Vachon ◽  
F Loechel ◽  
H Xu ◽  
U M Wewer ◽  
E Engvall
Keyword(s):  
Muscular Dystrophy ◽  
Culture Medium ◽  
Molecular Mechanisms ◽  
Congenital Muscular Dystrophy ◽  
In Vitro Models ◽  
Basement Membranes ◽  
In Vitro System ◽  
Multinucleated Myotubes ◽  
Laminin 1

Laminin (laminin-1; alpha 1-beta 1-gamma 1) is known to promote myoblast proliferation, fusion, and myotube formation. Merosin (laminin-2 and -4; alpha 2-beta 1/beta 2-gamma 1) is the predominant laminin variant in skeletal muscle basement membranes; genetic defects affecting its structure or expression are the causes of some types of congenital muscular dystrophy. However, the precise nature of the functions of merosin in muscle remain unknown. We have developed an in vitro system that exploits human RD and mouse C2C12 myoblastic cell lines and their clonal variants to study the roles of merosin and laminin in myogenesis. In the parental cells, which fuse efficiently to multinucleated myotubes, merosin expression is upregulated as a function of differentiation while laminin expression is downregulated. Cells from fusion-deficient clones do not express either protein, but laminin or merosin added to the culture medium induced their fusion. Clonal variants which fuse, but form unstable myotubes, express laminin but not merosin. Exogenous merosin converted these myotubes to a stable phenotype, while laminin had no effect. Myotube instability was corrected most efficiently by transfection of the merosin-deficient cells with the merosin alpha 2 chain cDNA. Finally, merosin appears to promote myotube stability by preventing apoptosis. Hence, these studies identify novel biological functions for merosin in myoblast fusion and muscle cell survival; furthermore, these explain some of the pathogenic events observed in congenital muscular dystrophy caused by merosin deficiency and provide in vitro models to further investigate the molecular mechanisms of this disease.

scholarly journals Clinical and genetic characteristics of congenital muscular dystrophies (Part 1)

2020 ◽  
Vol 10 (1) ◽  
pp. 10-21 ◽  
Author(s):  
P. A. Chausova ◽  
O. P. Ryzhkova ◽  
A. V. Polyakov
Keyword(s):  
Muscular Dystrophy ◽  
Clinical Symptoms ◽  
Muscle Protein ◽  
Molecular Genetic ◽  
Laboratory Data ◽  
Congenital Muscular Dystrophy ◽  
Neuromuscular Diseases ◽  
Muscular Hypotonia ◽  
Genetic Characteristics ◽  
Progressive Muscle Weakness

Congenital muscular dystrophy is an extremely heterogeneous group of hereditary neuromuscular diseases that are clinically characterized by muscular hypotonia, progressive muscle weakness, and dystrophic changes in the muscles. Overlapping clinical symptoms and many genes that have to be analyzed to determine the specific form of the disease in the patient make diagnosis difficult. The molecular genetic stage of diagnosis includes many different methods depending on the clinical hypothesis and their application has not lost its relevance even in the era of massive parallel sequencing. In addition to DNA sequence analysis, the analysis of muscle protein expression can also play a significant role in the diagnosis of congenital muscular dystrophy. In the review, we will consider the most important etiological, pathophysiological, clinical and laboratory data of the main forms of congenital muscular dystrophy known today.

scholarly journals Lamin-Related Congenital Muscular Dystrophy Alters Mechanical Signaling and Skeletal Muscle Growth

2020 ◽  
Vol 22 (1) ◽  
pp. 306
Author(s):  
Daniel J. Owens ◽  
Julien Messéant ◽  
Sophie Moog ◽  
Mark Viggars ◽  
Arnaud Ferry ◽  
...  
Keyword(s):  
Skeletal Muscle ◽  
Muscular Dystrophy ◽  
Muscle Growth ◽  
Congenital Muscular Dystrophy ◽  
Muscle Stem Cells ◽  
Skeletal Muscle Growth ◽  
Mechanical Signaling ◽  
Muscle Biopsies

Laminopathies are a clinically heterogeneous group of disorders caused by mutations in the LMNA gene, which encodes the nuclear envelope proteins lamins A and C. The most frequent diseases associated with LMNA mutations are characterized by skeletal and cardiac involvement, and include autosomal dominant Emery–Dreifuss muscular dystrophy (EDMD), limb-girdle muscular dystrophy type 1B, and LMNA-related congenital muscular dystrophy (LMNA-CMD). Although the exact pathophysiological mechanisms responsible for LMNA-CMD are not yet understood, severe contracture and muscle atrophy suggest that mutations may impair skeletal muscle growth. Using human muscle stem cells (MuSCs) carrying LMNA-CMD mutations, we observe impaired myogenic fusion with disorganized cadherin/β catenin adhesion complexes. We show that skeletal muscle from Lmna-CMD mice is unable to hypertrophy in response to functional overload, due to defective fusion of activated MuSCs, defective protein synthesis and defective remodeling of the neuromuscular junction. Moreover, stretched myotubes and overloaded muscle fibers with LMNA-CMD mutations display aberrant mechanical regulation of the yes-associated protein (YAP). We also observe defects in MuSC activation and YAP signaling in muscle biopsies from LMNA-CMD patients. These phenotypes are not recapitulated in closely related but less severe EDMD models. In conclusion, combining studies in vitro, in vivo, and patient samples, we find that LMNA-CMD mutations interfere with mechanosignaling pathways in skeletal muscle, implicating A-type lamins in the regulation of skeletal muscle growth.

scholarly journals Detailed genetic characteristics of an international large cohort of patients with Stargardt disease: ProgStar study report 8

2018 ◽  
Vol 103 (3) ◽  
pp. 390-397 ◽  
Author(s):  
Kaoru Fujinami ◽  
Rupert W Strauss ◽  
John (Pei-Wen) Chiang ◽  
Isabelle S Audo ◽  
Paul S Bernstein ◽  
...  
Keyword(s):  
Allele Frequency ◽  
Stargardt Disease ◽  
Genetic Characteristics ◽  
Mild Phenotype ◽  
Missense Variants ◽  
Pathogenic Variants ◽  
Significant Difference ◽  
Novel Variants ◽  
The Usa ◽  
Subsequent Comparison

Background/aimsTo describe the genetic characteristics of the cohort enrolled in the international multicentre progression of Stargardt disease 1 (STGD1) studies (ProgStar) and to determine geographic differences based on the allele frequency.Methods345 participants with a clinical diagnosis of STGD1 and harbouring at least one disease-causing ABCA4 variant were enrolled from 9 centres in the USA and Europe. All variants were reviewed and in silico analysis was performed including allele frequency in public databases and pathogenicity predictions. Participants with multiple likely pathogenic variants were classified into four national subgroups (USA, UK, France, Germany), with subsequent comparison analysis of the allele frequency for each prevalent allele.Results211 likely pathogenic variants were identified in the total cohort, including missense (63%), splice site alteration (18%), stop (9%) and others. 50 variants were novel. Exclusively missense variants were detected in 139 (50%) of 279 patients with multiple pathogenic variants. The three most prevalent variants of these patients with multiple pathogenic variants were p.G1961E (15%), p.G863A (7%) and c.5461-10 T>C (5%). Subgroup analysis revealed a statistically significant difference between the four recruiting nations in the allele frequency of nine variants.ConclusionsThere is a large spectrum of ABCA4 sequence variants, including 50 novel variants, in a well-characterised cohort thereby further adding to the unique allelic heterogeneity in STGD1. Approximately half of the cohort harbours missense variants only, indicating a relatively mild phenotype of the ProgStar cohort. There are significant differences in allele frequencies between nations, although the three most prevalent variants are shared as frequent variants.

scholarly journals Clinical and genetic characteristics of 14 patients from 13 Japanese families with RPGR-associated retinal disorder: report of eight novel variants

2019 ◽  
Vol 6 (1) ◽  
Author(s):  
Go Mawatari ◽  
◽  
Kaoru Fujinami ◽  
Xiao Liu ◽  
Lizhu Yang ◽  
...  
Keyword(s):  
Retinitis Pigmentosa ◽  
Japanese Population ◽  
Age Of Onset ◽  
Genetic Characteristics ◽  
Therapeutic Trials ◽  
Novel Variants ◽  
Genetic Features ◽  
The Mean ◽  
The Right ◽  
Retinal Disorder

AbstractVariants in the retinitis pigmentosa GTPase regulator (RPGR) gene are a major cause of X-linked inherited retinal disorder (IRD). We herein describe the clinical and genetic features of 14 patients from 13 Japanese families harboring RPGR variants in a nationwide cohort. Comprehensive ophthalmological examinations were performed to classify the patients into one of the phenotype subgroups: retinitis pigmentosa (RP) and cone rod dystrophy (CORD). The mean age of onset/at examination was 13.8/38.1 years (range, 0–50/11–72), respectively. The mean visual acuity in the right/left eye was 0.43/0.43 (range, 0.1–1.7/−0.08–1.52) LogMAR unit. Eight patients had RP, and six had CORD. Whole-exome sequencing with target analyses identified 13 RPGR variants in 730 families with IRD, including 8 novel variants. An association between the phenotype subgroup and the position of variants (cutoff of amino acid 950) was revealed. To conclude, the clinical and genetic spectrum of RPGR-associated retinal disorder was first illustrated in a Japanese population, with a high proportion of novel variants. These results suggest the distinct genetic background of RPGR in the Japanese population, in which the genotype–phenotype association was affirmed. This evidence should be helpful monitoring and counseling patients and in selecting patients for future therapeutic trials.

scholarly journals Structural and Functional Impact of Seven Missense Variants of Phenylalanine Hydroxylase

Genes ◽  
2019 ◽  
Vol 10 (6) ◽  
pp. 459 ◽  
Author(s):  
Martina Pecimonova ◽  
Daniela Kluckova ◽  
Frantisek Csicsay ◽  
Kamila Reblova ◽  
Jan Krahulec ◽  
...  
Keyword(s):  
Protein Level ◽  
Hepg2 Cells ◽  
Phenylalanine Hydroxylase ◽  
Functional Characterization ◽  
Missense Variants ◽  
Protein Levels ◽  
Novel Variants ◽  
And Function ◽  
Pah Gene

The molecular genetics of well-characterized inherited diseases, such as phenylketonuria (PKU) and hyperphenylalaninemia (HPA) predominantly caused by mutations in the phenylalanine hydroxylase (PAH) gene, is often complicated by the identification of many novel variants, often with no obvious impact on the associated disorder. To date, more than 1100 PAH variants have been identified of which a substantial portion have unknown clinical significance. In this work, we study the functionality of seven yet uncharacterized PAH missense variants p.Asn167Tyr, p.Thr200Asn, p.Asp229Gly, p.Gly239Ala, p.Phe263Ser, p.Ala342Pro, and p.Ile406Met first identified in the Czech PKU/HPA patients. From all tested variants, three of them, namely p.Asn167Tyr, p.Thr200Asn, and p.Ile406Met, exerted residual enzymatic activity in vitro similar to wild type (WT) PAH, however, when expressed in HepG2 cells, their protein level reached a maximum of 72.1% ± 4.9%, 11.2% ± 4.2%, and 36.6% ± 7.3% compared to WT PAH, respectively. Remaining variants were null with no enzyme activity and decreased protein levels in HepG2 cells. The chaperone-like effect of applied BH4 precursor increased protein level significantly for p.Asn167Tyr, p.Asp229Gly, p.Ala342Pro, and p.Ile406Met. Taken together, our results of functional characterization in combination with in silico prediction suggest that while p.Asn167Tyr, p.Thr200Asn, and p.Ile406Met PAH variants have a mild impact on the protein, p.Asp229Gly, p.Gly239Ala, p.Phe263Ser, and p.Ala342Pro severely affect protein structure and function.

Sign in / Sign up

Export Citation Format

Share Document