Association of variants and expression levels of MYOD1 gene with carcass and muscle characteristic traits in domestic pigeons

This study was to investigate the correlations of myogenic differentiation 1 (MYOD1) gene polymorphisms with carcass traits and its expression with breast muscle development in pigeons. Four SNPs were found in the pigeon MYOD1 gene. Correlation analysis showed that individuals with AA genotype at both SNPs g.2967A > G (p < .01) and g.3044G > A (p < .05) have significantly higher live weight (LW), carcass weight (CW), semi-eviscerated weight (SEW), eviscerated weight (EW) and breast muscle weight (BMW). Moreover, the two SNPs also had the same significant effects on MYOD1 mRNA expression levels in breast muscle of pigeons, ie, the AA genotype showed higher MYOD1 mRNA expression levels. The diameter and cross-section area of muscle fibers continuously increased from 0w to 4w (p < .05), accompanied with the increasing expression of MYOD1 gene, while the density decreased (p < .05) dramatically from 0w to 1w and continuously fell over in the next few weeks (p > .05). What's more, the expression level of MYOD1 gene was positively correlated with a diameter (r = 0.937, p < .05) and cross-sectional area (r = 0.956, p < .01) of myofiber, and negatively correlated with density (r = -0.769, p < .01). The results showed that individuals with AA genotype at both SNPs g.2967A > G and g.3044G > A have showed higher carcass traits (LW, CW, SEW, EW, and BMW) and higher MYOD1 mRNA expression level in breast muscle than AB and BB genotypes. Moreover, the expression level of MYOD1 gene was closely correlated with muscle characteristic traits, indicating variants of MYOD1 gene was closely related to muscle development and could be a potential candidate gene in marker-assisted selection of pigeons.

First Reported Case of Malignant Ectomesenchymoma with p.Leu122Arg Mutation in MYOD1 Gene: Extensive Intra- and Extracranial Tumor in a 15-Year-Old Female

BACKGROUND

Ectomesenchymomas (EMs) are extremely rare neoplasms composed of malignant mesenchymal components and neuroectodermal derivatives. They are described in a wide variety of locations, with the head and neck region being one of the most frequently involved areas. EMs are usually managed as high-risk rhabdomyosarcomas and have similar outcomes.

METHODS

We present the case of a 15-year-old female with an EM that arose in the parapharyngeal space and extended into the intracranial space.

RESULTS

Histologically, the tumor presented an embryonal rhabdomyosarcomatous mesenchymal component and the neuroectodermal component was constituted by isolated ganglion cells. Next-generation sequencing (NGS) revealed a p.Leu122Arg (c.365 T > G) mutation in the MYOD1 gene, a p.Ala34Gly mutation in the CDKN2A gene, and CDK4 gene amplification. The patient was treated with chemotherapy. She died 17 months after the debut of symptoms.

CONCLUSION(S)

To our knowledge, this is the first reported case in English literature of an EM with this MYOD1 mutation. We suggest combining PI3K/ATK pathway inhibitors in these cases. NGS should be performed in EMs cases to detect mutations with potential treatment options.

Clinicopathological and treatment response characteristics of updated rhabdomyosarcoma histomolecular subtypes: An Asian population-based study

AIM

New histomolecular subtypes of rhabdomyosarcoma have recently been defined but their corresponding clinical characteristics are not well described. Also, these clinical phenotypes vary greatly by age and ethnicity but have not been profiled in Asian populations. Thus, we sought to determine the landscape of rhabdomyosarcoma subtypes in a national Asian cohort and compare clinical characteristics among age groups and molecular subtypes.

METHODS

We performed a retrospective population-based study of all rhabdomyosarcoma patients in Singapore public hospitals from 2004 to 2014 (n = 67), and assigned histomolecular subtypes according to the updated 2020 WHO classification of soft tissue tumors following central pathology review and molecular profiling.

RESULTS

Age-specific prevalence followed a tri-modal peak. There were significantly more embryonal and alveolar (p = 0.032) and genitourinary (non-bladder/prostate) tumors (p = 0.033) among children. Older age was associated with complete resection among spindle cell/sclerosing tumors (p = 0.027), with the omission of chemotherapy among embryonal tumors (p = 0.001), and with poorer survival among embryonal and alveolar tumors (p = 0.026, p = 0.022, respectively). Overall survival differed with stage, group, and surgical resection, adjusted for age group (p = 0.004, p = 0.001, p = 0.004, respectively). Spindle-cell/sclerosing tumors showed an indolent phenotype with a significantly lower incidence of nodal metastasis (p = 0.002), but two of 15 patients with MYOD1 mutations had a contrastingly aggressive disease.

CONCLUSION

Disease and treatment response profiles of rhabdomyosarcoma subtypes vary significantly between adults and children, especially surgical resectability. In our Asian population, poorer outcomes were observed in adults with embryonal and alveolar tumors, while activating mutations influence the behavior of otherwise favorable spindle cell/sclerosing tumors.

Bilateral Vocal Fold Paralysis in a Patient With Congenital MYOD1 Myopathy

Congenital bilateral vocal fold paralysis (BVFP) is a rare but significant cause of morbidity in pediatric otolaryngology. The differential diagnosis is expansive, with common etiologies including birth trauma, brainstem neoplasms, and neurologic disorders. There are few known genetic causes of the condition. This report details the first known case of BVFP secondary to a genetic deficiency in MYOD1, a master transcriptional regulator of skeletal muscle cell specification. Genetics consultation and testing may be a useful adjunct in the workup of congenital BVFP and may help guide prognostication, additional workup, counseling, and clinical decision-making.

Biological Role and Clinical Implications of MYOD1L122R Mutation in Rhabdomyosarcoma

Major progress in recent decades has furthered our clinical and biological understanding of rhabdomyosarcoma (RMS) with improved stratification for treatment based on risk factors. Clinical risk factors alone were used to stratify patients for treatment in the European Pediatric Soft Tissue Sarcoma Study Group (EpSSG) RMS 2005 protocol. The current EpSSG overarching study for children and adults with frontline and relapsed rhabdomyosarcoma (FaR-RMS NCT04625907) includes FOXO1 fusion gene status in place of histology as a risk factor. Additional molecular features of significance have recently been recognized, including the MYOD1^L122R gene mutation. Here, we review biological information showing that MYOD1^L122R blocks cell differentiation and has a MYC-like activity that enhances tumorigenesis and is linked to an aggressive cellular phenotype. MYOD1^L122R mutations can be found together with mutations in other genes, such as PIK3CA, as potentially cooperating events. Using Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines, ten publications in the clinical literature involving 72 cases were reviewed. MYOD1^L122R mutation in RMS can occur in both adults and children and is frequent in sclerosing/spindle cell histology, although it is also significantly reported in a subset of embryonal RMS. MYOD1^L122R mutated tumors most frequently arise in the head and neck and extremities and are associated with poor outcome, raising the issue of how to use MYOD1^L122R in risk stratification and how to treat these patients most effectively.

Mutation c.-379 C>T in DGAT1 affects intramyocellular lipid content by altering MYOD1 binding affinity

Intramuscular fat (IMF) is one of the most important indexes of pork taste quality. Diacylglycerol acyltransferase 1 (DGAT1), belonging to the acyl-coenzyme A: DGAT enzymes family, is a rate-limiting enzyme responsible for the final step of triglyceride (TG) synthesis. It is involved in TG storage in skeletal muscle; however, the underlying mechanism is not well understood. This study aimed to uncover functional mutations that can influence DGAT1 expression and consequently affect IMF deposition in pork. Two experimental groups containing individuals with high and low IMF content (6.23 ± 0.20 vs. 1.25 ± 0.05, p < 0.01) were formed from 260 Duroc × Large White × Yorkshire (D × L × Y) cross-bred pigs. A novel SNP c.-379 C>T was uncovered in the DGAT1 gene using comparative sequencing with pool DNA of high- and low-IMF groups. The IMF content of CT genotype individuals (3.19 ± 0.11%) was higher than that of CC genotype individuals (2.86 ± 0.11%) when analyzing 260 D × L × Y pigs (p < 0.05). The DGAT1 expression levels revealed a significant positive correlation with IMF content (r = 0.33, p < 0.01). Luciferase assay revealed that the DGAT1 promoter with the c.-379 T allele has a higher transcription activity than that bearing the C allele in C2C12 myoblast cells, but not in 3T3-L1 pre-adipocytes. Online prediction followed by chromatin immunoprecipitation-polymerase chain reaction assay confirmed that myogenic determination factor 1 (MYOD1) binds to the DGAT1 promoter with the c.-379 C allele but not the T allele. In vitro experiments demonstrated that MYOD1 represses DGAT1 transcription and lipogenesis. As a muscle-specific transcription factor, MYOD1 can inhibit the transcription of DGAT1 with the c.-379 C allele in muscle cells. However, in the absence of MYOD1 binding to the mutated DGAT1 promoter with the c.-379 T allele, DGAT1 expresses at a higher level in the muscle cells of the c.-379 T genotype, leading to more intramyocellular lipid accumulation than in the muscle cells of the c.-379 C genotype. The SNP c.-379 C>T in the promoter region of the DGAT1 gene provides a promising molecular marker for improving pork IMF content without affecting other fat depots.

Quantitative Evaluation of Exon Skipping in Urine-Derived Cells for Duchenne Muscular Dystrophy

Antisense oligonucleotide (ASO)-based exon skipping therapy is thought to be promising for Duchenne muscular dystrophy (DMD). For the screening or assessing patient eligibility before administering ASO to patients, in vitro testing using myoblasts derived from each DMD patient is considered crucial. We previously reported state-of-the-art technology to obtain patient primary myoblasts from MYOD1-induced urine-derived cells (UDCs) as a model of DMD. We hypothesize that the myoblasts may potentially reflect specific pathological phenotypes, leading to a path for precision medicine in DMD patients. Here, we describe a detailed protocol for both acquiring MYOD1-induced myoblasts from UDCs and evaluating the correction of DMD mRNA and protein levels after exon-skipping in the cells.

Intestinal Microbiota Regulate Certain Meat Quality Parameters in Chicken

Growing evidence of intestinal microbiota-muscle axis provides a possibility to improve meat quality of broilers through regulating intestinal microbiota. Water-holding capacity is a crucial factor to evaluate the meat quality. High quality of water-holding capacity is usually described as a low drip-losing rate. This study aimed to explore the relationship between intestinal microbiota and water-holding capacity of muscle in broilers. According to our results, two native breeds of broilers (the Arbor Acres broilers and the Beijing-You broilers) exhibited remarkable differences in microbiota composition. However, the regular of gut bacteria compositions gradually became similar when the two breeds of broiler were raised in a same feeding environment. Therefore, this similar regular of intestinal microbiota induced similar water-holding capacity of the muscle from the two breeds. In subsequent fecal microbiota transplantation (FMT) experiments, the intestinal microbiota community of the Arbor Acres broilers was remodeling by oral gavage of bacterial suspension that was derived from the Beijing-You broilers. Then, not only body weight and abdominal fat rate were increased, but also drip loss of muscle was decreased in the Arbor Acres broilers. Additionally, muscle fiber diameter of biceps femoris muscle and expression of MyoD1 were notably enlarged. Muscle fiber diameter and related genes were deemed as important elements for water-holding capacity of muscle. Simultaneously, we screened typical intestinal bacteria in both the two native breeds of broilers by 16S rDNA sequencing. Lachnoclostridium was the only bacteria genus associated with drip-losing rate, meat fiber diameter, body weight, and abdominal fat rate.

An update on rhabdomyosarcoma risk stratification and the rationale for current and future Children's Oncology Group clinical trials

Children and adolescents with rhabdomyosarcoma (RMS) comprise a heterogeneous population with variable overall survival rates ranging between approximately 6% and 100% depending on defined risk factors. Although the risk stratification of patients has been refined across five decades of collaborative group studies, molecular prognostic biomarkers beyond FOXO1 fusion status have yet to be incorporated prospectively in upfront risk-based therapy assignments. This review describes the evolution of risk-based therapy and the current risk stratification, defines a new risk stratification incorporating novel biomarkers, and provides the rationale for the current and upcoming Children's Oncology Group RMS studies.

SIX1 reprograms myogenic transcription factors to maintain the rhabdomyosarcoma undifferentiated state

Rhabdomyosarcoma (RMS) is a pediatric muscle sarcoma characterized by expression of the myogenic lineage transcription factors (TFs) MYOD1 and MYOG. Despite high expression of these TFs, RMS cells fail to terminally differentiate, suggesting the presence of factors that alter their functions. Here, we demonstrate that the developmental TF SIX1 is highly expressed in RMS and critical for maintaining a muscle progenitor-like state. SIX1 loss induces differentiation of RMS cells into myotube-like cells and impedes tumor growth in vivo. We show that SIX1 maintains the RMS undifferentiated state by controlling enhancer activity and MYOD1 occupancy at loci more permissive to tumor growth over muscle differentiation. Finally, we demonstrate that a gene signature derived from SIX1 loss correlates with differentiation status and predicts RMS progression in human disease. Our findings demonstrate a master regulatory role of SIX1 in repression of RMS differentiation via genome-wide alterations in MYOD1 and MYOG-mediated transcription.

Construction of a Porcine Skeletal Muscle-Specific Promoter by Inducing the Seed Region of miR-208a

Transgenic promoter systems are of great interest for their potential use in gene therapy or production due to their high activity, long term, and cell specificity. Here, in order to obtain promoters with high activity and expressed specifically in skeletal muscle, the MYOD1, MYF5, and MCK were selected as the candidate genes. The truncated promoters were amplified and their activity was verified through dual-luciferase reporter gene test. We used genetic engineering techniques to improve promoter activity by tandemly linking enhancers and promoters or two promoters. Furthermore, synthetic promoter was the most active when two eMCK enhancers and pMCK promoter were cascaded. To improve the tissue specificity of the promoter, the seed region of translational repressor miR-208a was inserted into the downstream of the promoter (pGL3-2eMCK-pMCK-T208-mCherry-EGFP). The results showed that the expression level of target genes decreased significantly (P < 0.05) in myocardium rather than in skeletal muscle. The results of in vivo transfection indicated that tandem transcriptional regulatory elements can increase promoter activity in mice. This work laid the foundation for future research on genetically modified pigs.

MYOD1 as a prognostic indicator in rhabdomyosarcoma

BACKGROUND/OBJECTIVES

Rhabdomyosarcoma (RMS) is characterized by the expression of the myogenic regulatory protein MYOD1. Histologic types include alveolar, embryonal (ERMS), and spindle cell sclerosing RMS (SRMS). SRMS harbors MYOD1 mutations in a subset of adult cases in association with poor prognosis.

DESIGN/METHODS

To study the level of MYOD1 protein expression and its clinical significance, we have analyzed variable numbers of pediatric (<18 years of age) and adult (age range ≥18 to 35 years) ERMS and SRMS cases for presence or absence of MYOD1 immunoreactivity in correlation with clinical outcome and MYOD1 L122R mutations.

RESULTS

Lack of MYOD1 immunoreactivity, identified in 23.8% of nonalveolar RMS (non-ARMS) cases, was more prevalent in SRMS (44%) than ERMS (17.2%) and was significantly associated with low overall survival and unfavorable tumor sites (p < .05). Lack of MYOD1 immunoreactivity was not associated with MYOD1 L122R mutations, which were identified in 3/37 (8%) cases including only two of 31 (6.5%) pediatric cases, one of 11 or 9% pediatric SRMS, and one case of infant ERMS.

CONCLUSION

These studies highlight the prognostic role of MYOD1 in non-ARMS. Lack of MYOD1 immunoreactivity is associated with poor prognosis in ERMS and SRMS. MYOD1 gene mutations are generally infrequent in pediatric RMS. Although mutations are predominant in SRMS, they may exceptionally occur in infantile ERMS.

Dedifferentiated liposarcoma with heterologous spindle cell rhabdomyoblastic de-differentiation: An unusual pattern expanding the morphological spectrum

Dedifferentiated liposarcoma (DDLS) is characterized by a wide histopathological spectrum. Spindle cell type of rhabdomyoblastic dedifferentiation has been rarely described in case of DDLS. A 39-year-old male presented with a recurrent retroperitoneal tumor mass, diagnosed as well-differentiated liposarcoma, for which he underwent surgical excisions on two occasions, followed by adjuvant radiation therapy previously. Computed tomogram scan his of abdomen revealed a large-sized, fat-containing recurrent, retroperitoneal mass, measuring 18.1 cm in the largest dimension. Histopathologic examination of the resected tumor revealed distinct areas of well- and dedifferentiated liposarcoma, including areas reminiscent of a myxofibrosarcoma, further progressing into a high-grade spindle cell sarcoma with fascicular and "Herringbone-like" growth patterns (fibrosarcoma-like). Immunohistochemically, high-grade spindle cell sarcomatous (dedifferentiated) component displayed distinct positivity for desmin and MyoD1, along with focal tumor nuclei, showing nuclear positivity for myogenin. Both well-differentiated liposarcomatous and dedifferentiated components displayed diffuse, intense nuclear positivity for MDM2 (overexpression) and p16INK4A. Furthermore, upon testing tumor sections displaying spindly sarcomatous areas for MDM2 amplification, by FISH technique, nearly all tumor cells displayed MDM2 gene amplification. This case constitutes one of the rare cases of DDLS displaying spindle cell rhabdomyoblastic dedifferentiation. Its diagnostic and treatment implications are discussed herewith.

Genomic analysis and preclinical xenograft model development identify potential therapeutic targets for MYOD1-mutant soft-tissue sarcoma of childhood

The myogenic differentiation 1 gene (MYOD1) p.L122R somatic mutation was first discovered in a subset of clinically aggressive embryonal rhabdomyosarcomas and has since been described in both pediatric and adult spindle cell/sclerosing rhabdomyosarcomas. Relatively little is known about the clinical, molecular, and histopathological features of these tumors in children. In order to further characterize the genomic and clinical features of pediatric MYOD1-mutant sarcomas, we evaluated a cohort of soft-tissue sarcoma patients treated at Texas Children's Hospital. Tumor DNA was subjected to next-generation panel sequencing and/or Sanger sequencing of the MYOD1 hotspot mutation. The MYOD1 p.L122R mutation was identified in six tumors, with a variant allele fraction greater than 0.8 in three cases, suggestive of loss of heterozygosity. One sclerosing rhabdomyosarcoma lacking the MYOD1 hotspot mutation was observed to have a MYOD1 copy number gain, also with evidence of loss of heterozygosity. Cancer gene panel sequencing revealed potentially targetable alterations in six of seven (86%) patients with MYOD1 alterations, including four patients with an alteration in the PI3K-AKT pathway: two hotspot PIK3CA mutations and deletions in PTEN and TSC2. On histopathologic review, MYOD1-altered tumors exhibited spindle and/or round cells and varying degrees of hyaline sclerosis. At last follow-up, six patients had died of disease and the seventh progressed early and was subsequently lost to follow-up. Both pre- and post-therapy patient-derived xenograft models were generated from one patient's tumor. These models were confirmed to harbor the MYOD1 and PIK3CA mutations seen in the primary tumor and were shown to be sensitive to PI3K/mTOR inhibition in vitro and in vivo. In conclusion, this study adds to recent reports describing the clinicopathologic and genomic features of MYOD1-altered soft-tissue sarcomas in children, including dismal prognosis and potential molecular targets for therapy. The novel preclinical models developed will facilitate further biological and preclinical study of this rare and aggressive tumor. © 2021 The Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.

Combination of cell signaling molecules can facilitate MYOD1-mediated myogenic transdifferentiation of pig fibroblasts

Background

Myogenic transdifferentiation can be accomplished through ectopic MYOD1 expression, which is facilitated by various signaling pathways associated with myogenesis. In this study, we attempted to transdifferentiate pig embryonic fibroblasts (PEFs) myogenically into skeletal muscle through overexpression of the pig MYOD1 gene and modulation of the FGF, TGF-β, WNT, and cAMP signaling pathways.

Results

The MYOD1 overexpression vector was constructed based on comparative sequence analysis, demonstrating that pig MYOD1 has evolutionarily conserved domains across various species. Although forced MYOD1 expression through these vectors triggered the expression of endogenous muscle markers, transdifferentiated muscle cells from fibroblasts were not observed. Therefore, various signaling molecules, including FGF2, SB431542, CHIR99021, and forskolin, along with MYOD1 overexpression were applied to enhance the myogenic reprogramming. The modified conditions led to the derivation of myotubes and activation of muscle markers in PEFs, as determined by qPCR and immunostaining. Notably, a sarcomere-like structure was observed, indicating that terminally differentiated skeletal muscle could be obtained from transdifferentiated cells.

Conclusions

In summary, we established a protocol for reprogramming MYOD1-overexpressing PEFs into the mature skeletal muscle using signaling molecules. Our myogenic reprogramming can be used as a cell source for muscle disease models in regenerative medicine and the production of cultured meat in cellular agriculture.

MYOD1 inhibits avian adipocyte differentiation via miRNA-206/KLF4 axis

BACKGROUND

A considerable number of muscle development-related genes were differentially expressed in the early stage of avian adipocyte differentiation. However, the functions of them in adipocyte differentiation remain largely known. In this study, the myoblast determination protein 1 (MYOD1) was selected as a representative of muscle development. We investigated its expression, function, and regulation in avian adipocyte differentiation.

RESULTS

The expression of MYOD1 decreased significantly in the early stage of avian adipocyte differentiation. CRISPR/Cas9-mediated deletion of MYOD1 induced adipocyte differentiation, whereas over-expression of MYOD1 inhibited adipogenesis. The mRNA-seq data showed that MYOD1 could perturb the lipid biosynthetic process during differentiation. Our results showed that MYOD1 directly up-regulates the miR-206 expression by binding the upstream 1200 bp region of miR-206. Then, over-expression of miR-206 can inhibit the adipogenesis. Furthermore, MYOD1 affected the expression of endogenous miR-206 and its target gene Kruppel-like factor 4 (KLF4), which is an important activator of adipogenesis. Accordingly, the inhibition of miR-206 or over-expression of KLF4 could counteract the inhibitory effect of MYOD1 on adipocyte differentiation.

CONCLUSIONS

Our results establish that MYOD1 inhibits adipocyte differentiation by up-regulating miR-206 to suppress the KLF4 expression. These findings identify a novel function of MYOD1 in adipocyte differentiation, suggesting a potential role in body-fat distribution regulation.

MBNL1 Suppressed Cancer Metastatic of Skin Squamous Cell Carcinoma Via by TIAL1/MYOD1/Caspase-9/3 Signaling Pathways

OBJECTIVE

The incidence of skin squamous cell carcinoma (SSCC) has recently been increasing, with diverse clinical manifestations.SSCC could metastasize to lymph nodes or other organs, posing a great threat to life. The present study was designed to investigate the function and underlying mechanism of muscleblind-like protein 1 (MBNL1) in skin squamous cell carcinoma.

METHODS

SCL-1 cell was used for vitro model and transfected with MBNL1 or siMBNL1 plasmids. MTT Assays, LDH activity ELISA, and Transwell chamber migration experiment were used to confirm the effects of MBNL1 on cell growth of SCL-1 cell. Western blot analysis was used to analyze the mechanism of MBNL1 in SCL-1 cell.

RESULTS

Down-regulation of MBNL1 promoted cell metastasis of SSCC, while up-regulation of MBNL1 reduced cell metastasis of SSCC in vitro. Down-regulation of MBNL1 suppressed the protein expression of T cell intracellular antigen (TIAL1), myogenic determinant 1 (MyoD1) and Caspase-3 in vitro. Consistent with these observations, inhibition of TIAL1 or MYOD1 expression attenuated the effects of MBNL1 in SSCC.

CONCLUSION

The present study revealed that MBNL1 suppressed thecancer metastatic capacity of SSCC via by TIAL1/MYOD1/Caspase-3 signaling pathways.

Highly sensitive screening of antisense sequences for different types of DMD mutations in patients' urine-derived cells

Exon skipping using short antisense oligonucleotides (AONs) is a promising treatment for Duchenne muscular dystrophy (DMD). Several exon-skipping drugs, including viltolarsen (NS-065/NCNP-01), have been approved worldwide. Immortalized human skeletal muscle cell lines, such as rhabdomyosarcoma cells, are frequently used to screen efficient oligonucleotide sequences. However, rhabdomyosarcoma cells do not recapitulate DMD pathophysiology as they express endogenous dystrophin. To overcome this limitation, we recently established a direct human somatic cell reprogramming technology and successfully developed a cellular skeletal muscle DMD model by using myogenic differentiation 1 (MYOD1)-transduced urine-derived cells (MYOD1-UDCs). Here, we compared in vitro drug screening systems in MYOD1-UDCs and rhabdomyosarcoma cells. We collected UDCs from patients with DMD amenable to exon 51 skipping, and obtained MYOD1-UDCs. We then compared the efficiency of exon 51 skipping induced by various morpholino-based AONs, including eteplirsen in differentiated MYOD1-UDCs (UDC-myotubes) and rhabdomyosarcoma cells. Exon skipping was induced more efficiently in UDC-myotubes than in rhabdomyosarcoma cells even at a low AON concentration (1 μM). Furthermore, exon 51 skipping efficiency was higher in UDC-myotubes with a deletion of exons 49-50 than in those with a deletion of exons 48-50, suggesting that the skipping efficiency may vary depending on the DMD mutation pattern. An essential finding of this study is that the sequence of eteplirsen consistently leads to much lower efficiency than other sequences. These findings underscore the importance of AON sequence optimization by our cellular system, which enables highly sensitive screening of exon skipping drugs that target different types of DMD mutations.

Establishment and Characterization of a Sclerosing Spindle Cell Rhabdomyosarcoma Cell Line with a Complex Genomic Profile

Sclerosing spindle cell rhabdomyosarcoma (SSRMS) is a rare rhabdomyosarcomas (RMS) subtype. Especially cases bearing a myogenic differentiation 1 (MYOD1) mutation are characterized by a high recurrence and metastasis rate, often leading to a fatal outcome. SSRMS cell lines are valuable in vitro models for studying disease mechanisms and for the preclinical evaluation of new therapeutic approaches. In this study, a cell line established from a primary SSRMS tumor of a 24-year-old female after multimodal chemotherapeutic pretreatment has been characterized in detail, including immunohistochemistry, growth characteristics, cytogenetic analysis, mutation analysis, evaluation of stem cell marker expression, differentiation potential, and tumorigenicity in mice. The cell line which was designated SRH exhibited a complex genomic profile, including several translocations and deletions. Array-comparative genomic hybridization (CGH) revealed an overall predominating loss of gene loci. The mesenchymal tumor origin was underlined by the expression of mesenchymal markers and potential to undergo adipogenic and osteogenic differentiation. Despite myogenic marker expression, terminal myogenic differentiation was inhibited, which might be elicited by the MYOD1 hotspot mutation. In vivo tumorigenicity could be confirmed after subcutaneous injection into NOD/SCID/γ_c^null mice. Summarized, the SRH cell line is the first adult SSRMS cell line available for preclinical research on this rare RMS subtype.

Commitment of Autologous Human Multipotent Stem Cells on Biomimetic Poly-L-lactic Acid-Based Scaffolds Is Strongly Influenced by Structure and Concentration of Carbon Nanomaterial

Nanocomposite scaffolds combining carbon nanomaterials (CNMs) with a biocompatible matrix are able to favor the neuronal differentiation and growth of a number of cell types, because they mimic neural-tissue nanotopography and/or conductivity. We performed comparative analysis of biomimetic scaffolds with poly-L-lactic acid (PLLA) matrix and three different p-methoxyphenyl functionalized carbon nanofillers, namely, carbon nanotubes (CNTs), carbon nanohorns (CNHs), and reduced graphene oxide (RGO), dispersed at varying concentrations. qRT-PCR analysis of the modulation of neuronal markers in human circulating multipotent cells cultured on nanocomposite scaffolds showed high variability in their expression patterns depending on the scaffolds’ inhomogeneities. Local stimuli variation could result in a multi- to oligopotency shift and commitment towards multiple cell lineages, which was assessed by the qRT-PCR profiling of markers for neural, adipogenic, and myogenic cell lineages. Less conductive scaffolds, i.e., bare poly-L-lactic acid (PLLA)-, CNH-, and RGO-based nanocomposites, appeared to boost the expression of myogenic-lineage marker genes. Moreover, scaffolds are much more effective on early commitment than in subsequent differentiation. This work suggests that biomimetic PLLA carbon-nanomaterial (PLLA-CNM) scaffolds combined with multipotent autologous cells can represent a powerful tool in the regenerative medicine of multiple tissue types, opening the route to next analyses with specific and standardized scaffold features.

The current landscape of rhabdomyosarcomas: an update

Rhabdomyosarcomas are malignancies associated with a rhabdomyoblastic phenotype which can be demonstrated morphologically or by immunohistochemistry for MYOD1 and myogenin. Rhabdomyosarcomas are currently subdivided into 4 types in the 2013 WHO classification of tumors of soft tissue and bone, including embryonal rhabdomyosarcoma, alveolar rhabdomyosarcoma, spindle cell/sclerosing rhabdomyosarcoma, and pleomorphic rhabdomyosarcoma. Recent studies have significantly impacted this classification with the emergence of three distinct new subtypes of rhabdomyosarcomas, namely rhabdomyosarcoma with MYOD1 mutations, rhabdomyosarcoma with TFCP2 fusions, and rhabdomyosarcoma with VGLL2/NCOA2 fusions. Although all these tumors share the terminology "rhabdomyosarcoma," their morphology, clinical behavior, and underlying molecular alterations are dramatically different. Finally, the presence of a rhabdomyoblastic phenotype within a tumor is by no means a diagnostic of a rhabdomyosarcoma, as this may be seen in many other mesenchymal malignancies, such as mesenchymal chondrosarcomas, malignant peripheral nerve sheaths tumors, and biphenotypic sinonasal sarcomas. In this review, we present the main clinical, morphological, and molecular features of these tumors and discuss the evolution of the current classification.

The expanding morphological and genetic spectrum of MYOD1-mutant spindle cell/sclerosing rhabdomyosarcomas: a clinicopathological and molecular comparison of mutated and non-mutated cases

AIMS

Spindle cell/sclerosing rhabdomyosarcomas (SC/SRMS) feature spindled and/or rounded rhabdomyosarcomatous cells within variably hyalinised stroma. Only 30-67% of SC/SRMSs harbour neomorphic MYOD1 p.L122R mutations, indicating heterogeneity in this RMS type. We compared MYOD1-mutant and non-mutant cases to characterise the histological and genetic spectrum of mutated SC/SRMS.

METHODS AND RESULTS

Seventeen RMSs with spindled, sclerosing or hybrid histology were sequenced to identify MYOD1 and PIK3CA mutations and reappraised to assess histological features and myogenic immunophenotypes. Twelve SC/SRMSs harboured MYOD1 mutations, including homozygous p.L122R (n = 8), heterozygous p.L122R (n = 3) and heterozygous p.E118K (n = 1). MYOD1-mutant tumours affected nine females and three males aged 8-64 years (median = 22.5), had a median size of 4.2 cm (range = 2-22) and involved the head and neck (n = 7), extremities (n = 4) and mediastinum (n = 1). Fascicular/spindle histology was predominant in four cases, including one with heterologous lipoblasts in focally myxoid stroma. Four sclerosing cases mainly comprised rounded cells, including one with multinucleated tumour cells. Four cases were histologically hybrid. The only PIK3CA (p.H1047R) mutation was detected in a predominantly spindled MYOD1-p.L122R-mutated case, but not in its laser-microdissected lipoblast-containing area. All MYOD1-mutant cases exhibited diffuse MYOD1 expression but patchy myogenin reactivity. At final follow-up (median = 13.5 months), recurrences (n = 4), metastases (n = 2) or both (n = 1) occurred in seven MYOD1-mutant cases; one had died of disease. Five non-mutated cases were reclassified as spindle embryonal (n = 3), dense embryonal (n = 1) and unclassifiable (n = 1) RMSs.

CONCLUSION

MYOD1-mutant RMSs are uncommonly mutated with PIK3CA and behave aggressively with an expanded morphological and genetic spectrum, including lipoblastic differentiation, multinucleated cells and the alternative p.E118K mutation.

Update on Myogenic Sarcomas

Myogenic sarcomas include soft tissue sarcomas that show skeletal muscle differentiation (rhabdomyosarcoma) and those with smooth muscle differentiation (leiomyosarcoma). Rhabdomyosarcomas are more common in the pediatric age group and leiomyosarcomas occur more often in the adult population. Based on the clinico-pathologic features and genetic abnormalities identified, the rhabdomyosarcomas are classified into embryonal, alveolar, spindle cell/sclerosing, and pleomorphic subtypes. Each subtype shows distinctive morphology and has characteristic genetic abnormalities. In this update on myogenic sarcomas, each entity is discussed with special emphasis on recent updates in genetic findings and the diagnostic approach to these tumors.

Clinicopathologic features and molecular spectrum of spindle cell and sclerosing rhabdomyosarcomas in the head and neck region

Recently, spindle cell/sclerosing rhabdomyosarcoma (SRMS/ScRMS) has been recognized as a stand-alone entity in the latest edition of WHO Classification of Tumors of Soft Tissue and Bone. As SRMS/ScRMS have a predilection for the head and neck, we evaluated the clinicopathologic and molecular features of 20 cases of SRMS/ScRMS (13 SRMS and 7 ScRMS) arising in the head and neck region. 10 patients were men, and 10 were women, and their ages ranged from 2 months to 57 years. Tumor size ranged from 1.5 to 20 cm. By immunohistochemistry, all tumors showed diffuse desmin expression, and MYOD1 immunostaining was diffuse to multifocally positive: 16 cases showed myogenin positive immunostaining. 2 patients had local recurrences, and 5 patients developed distant metastases. So far, 10 patients have died of the disease. 7 of 13 SRMS and 4 of 7 ScRMS showed PIK3CA mutations, while 8 of 13 SRMS and all 7 ScRMS showed MYOD1 mutations. A novel p.R524K hotspot mutation in 8 of 11 cases showed PIK3CA mutations. SRMS/ScRMS shares similar clinicopathological and molecular features. Diagnostic pitfalls from other spindle or sclerosing sarcomas should be avoided with the use of appropriate immunohistochemical stains and relevant clinical information. Co-occurrence of PIK3CA and MYOD1 mutations are associated with unfavorable clinical outcomes.

MeCP2 Promotes Gastric Cancer Progression Through Regulating FOXF1/Wnt5a/β-Catenin and MYOD1/Caspase-3 Signaling Pathways

Methyl-CpG binding protein 2 (MeCP2) has recently been characterized as an oncogene frequently amplified in several types of cancer. However, its precise role in gastric cancer (GC) and the molecular mechanism of MeCP2 regulation are still largely unknown. Here we report that MeCP2 is highly expressed in primary GC tissues and the expression level is correlated with the clinicopathologic features of GC. In our experiments, knockdown of MeCP2 inhibited tumor growth. Molecular mechanism of MeCP2 regulation was investigated using an integrated approach with combination of microarray analysis and chromatin immunoprecipitation sequencing (ChIP-Seq). The results suggest that MeCP2 binds to the methylated CpG islands of FOXF1 and MYOD1 promoters and inhibits their expression at the transcription level. Furthermore, we show that MeCP2 promotes GC cell proliferation via FOXF1-mediated Wnt5a/β-Catenin signaling pathway and suppresses apoptosis through MYOD1-mediated Caspase-3 signaling pathway. Due to its high expression level in GC and its critical function in driving GC progression, MeCP2 represents a promising therapeutic target for GC treatment.

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MeCP2 inhibits FOXF1 and MYOD1 transcription by binding to their promoter regions.

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MeCP2 promotes GC cell proliferation via FOXF1-mediated Wnt/β-Catenin signaling pathway.

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MeCP2 suppresses GC cell apoptosis through MYOD1-mediated Caspase-3 signaling pathway.

Gastric cancer is the fourth most common malignant cancer and the third most frequent cause of cancer-related deaths worldwide. The molecular mechanism underlying gastric carcinogenesis and progression is still unknown. Methyl-CpG binding protein 2 (MeCP2) has recently been characterized as an oncogene frequently amplified in several types of cancer. However, its precise role and the molecular mechanism of MeCP2 regulation in gastric cancer are largely unknown. Our results show that MeCP2 promotes gastric cancer cell proliferation via FOXF1-mediated Wnt5a/β-Catenin signaling pathway and suppresses cell apoptosis through MYOD1-mediated Caspase-3 signaling pathway. MeCP2 represents a promising therapeutic target for gastric cancer treatment.

Molecular diagnostics in the management of rhabdomyosarcoma

INTRODUCTION

A classification of rhabdomyosarcoma (RMS) with prognostic relevance has primarily relied on clinical features and histologic classification as either embryonal or alveolar RMS. The PAX3-FOXO1 and PAX7-FOXO1 gene fusions occur in 80% of cases with the alveolar subtype and are more predictive of outcome than histologic classification. Identifying additional molecular hallmarks that further subclassify RMS is an active area of research. Areas Covered: The authors review the current state of the PAX3-FOXO1 and PAX7-FOXO1 fusions as prognostic biomarkers. Emerging biomarkers, including mRNA expression profiling, MYOD1 mutations, RAS pathway mutations and gene fusions involving NCOA2 or VGLL2 are also reviewed. Expert commentary: Strategies for modifying RMS risk stratification based on molecular biomarkers are emerging with the potential to transform the clinical management of RMS, ultimately improving patient outcomes by tailoring therapy to predicted patient risk and identifying targets for novel therapies.

Synthetically modified mRNA for efficient and fast human iPS cell generation and direct transdifferentiation to myoblasts

Synthetic mRNA transfection enables efficient and controlled gene expression in human cells, without genome integrations. Further, modifications to the mRNA and transfection protocol now allow for repeated transfection and long-term gene expression of an otherwise short-lived mRNA expression. This is mainly achieved through introducing modified nucleosides and interferon suppression. In this study we provide an overview and details of the advanced synthesis and modifications of mRNA originally developed for reprogramming. This mRNA allows for very efficient transfection of fibroblasts enabling the generation of high quality human iPS cells with a six-factor mRNA cocktail in 9 days. Furthermore, we synthesised and transfected modified MYOD1 mRNA to transdifferentiate human fibroblasts into myoblast-like cells without a transgene footprint. This efficient and integration-free mRNA technology opens the door for safe and controlled gene expression to reverse or redirect cell fate.

Epigenetic Alteration by DNA Methylation of ESR1, MYOD1 and hTERT Gene Promoters is Useful for Prediction of Response in Patients of Locally Advanced Invasive Cervical Carcinoma Treated by Chemoradiation

AIMS

Locally advanced invasive cervical cancer [International Federation of Gynecology and Obstetrics (FIGO) IIB/III] is treated by chemoradiation. The response to treatment is variable within a given FIGO stage. Therefore, the aim of the present study was to evaluate the gene promoter methylation profile and corresponding transcript expression of a panel of six genes to identify genes which could predict the response of patients treated by chemoradiation.

MATERIALS AND METHODS

In total, 100 patients with invasive cervical cancer in FIGO stage IIB/III who underwent chemoradiation treatment were evaluated. Ten patients developed systemic metastases during therapy and were excluded. On the basis of patient follow-up, 69 patients were chemoradiation-sensitive, whereas 21 were chemoradiation-resistant. Gene promoter methylation and gene expression was determined by TaqMan assay and quantitative real-time PCR, respectively, in tissue samples.

RESULTS

The methylation frequency of ESR1, BRCA1, RASSF1A, MLH1, MYOD1 and hTERT genes ranged from 40 to 70%. Univariate and hierarchical cluster analysis revealed that gene promoter methylation of MYOD1, ESR1 and hTERT could predict for chemoradiation response. A pattern of unmethylated MYOD1, unmethylated ESR1 and methylated hTERT promoter as well as lower ESR1 transcript levels predicted for chemoradiation resistance.

CONCLUSION

Methylation profiling of a panel of three genes that includes MYOD1, ESR1 and hTERT may be useful to predict the response of invasive cervical carcinoma patients treated with standard chemoradiation therapy.

Insulin acutely triggers transcription of Slc2a4 gene: participation of the AT-rich, E-box and NFKB-binding sites

AIMS

The insulin-sensitive glucose transporter protein GLUT4 (solute carrier family 2 member 4 (Slc2a4) gene) plays a key role in glycemic homeostasis. Decreased GLUT4 expression is a current feature in insulin resistant conditions such as diabetes, and the restoration of GLUT4 content improves glycemic control. This study investigated the effect of insulin upon Slc2a4/GLUT4 expression, focusing on the AT-rich element, E-box and nuclear factor NF-kappa-B (NFKB) site.

MAIN METHODS

Rat soleus muscles were incubated during 180 min with insulin, added or not with wortmannin (phosphatidylinositol-4,5-bisphosphate 3-kinase catalytic subunit gamma isoform (PI3K)-inhibitor), ML9 (serine/threonine protein kinase (AKT) inhibitor) and tumor necrosis factor (TNF, GLUT4 repressor), and processed for analysis of GLUT4 protein (Western blotting); Slc2a4, myocyte enhancer factor 2a/d (Mef2a/d), hypoxia inducible factor 1a (Hif1a), myogenic differentiation 1 (Myod1) and nuclear factor of kappa light polypeptide gene enhancer in B-cells 1 (Nfkb1) messenger ribonucleic acids (mRNAs) (polymerase chain reaction (PCR)); and AT-rich- (myocyte-specific enhancer factor 2 (MEF2)-binding site), E-box- (hypoxia inducible factor 1 alpha (HIF1A)- and myoblast determination protein 1 (MYOD1)-binding site), and NFKB-binding activity (electrophoretic mobility assay).

KEY FINDINGS

Insulin increased Slc2a4 mRNA expression (140%) and nuclear proteins binding to AT-rich and E-box elements (~90%), all effects were prevented by wortmannin and ML9. Insulin also increased Mef2a/d and Myod1 mRNA expression, suggesting the participation of these transcriptional factors in the Slc2a4 enhancing effect. Conversely, insulin decreased Nfkb1 mRNA expression and protein binding to the NFKB-site (~50%). Furthermore, TNF-induced inhibition of GLUT4 expression (~40%) was prevented by insulin in an NFKB-binding repressing mechanism. GLUT4 protein paralleled the Slc2a4 mRNA regulations.

SIGNIFICANCE

Insulin enhances the Slc2a4/GLUT4 expression in the skeletal muscle by activating AT-rich and E-box elements, in a PI3K/AKT-dependent mechanism, and repressing NFKB-site activity as well. These results unravel how post-prandial increase of insulin may guarantee GLUT4 expression, and how the insulin signaling impairment can participate in insulin resistance-induced repression of GLUT4.