Implications of the Wnt5a/CaMKII pathway in retinoic acid-induced myogenic tongue abnormalities of developing mice

Proteomic analysis illustrates the potential involvement of motor proteins in cleft palate development

Cleft palate (CP) is a congenital condition characterized by a complex etiology and limited diagnostic and therapeutic options. In this study, we delved into the molecular mechanisms associated with retinoic acid (RA)-induced CP in Kun Ming mice. Proteomic analysis of control and RA-induced CP samples at embryonic day 15.5 revealed 25 upregulated and 19 downregulated proteins. Further analysis identified these differentially expressed proteins (DEPs) as being involved in extracellular matrix organization, actin cytoskeleton, and myosin complex. Moreover, these DEPs were found to be enriched in pathways related to motor protein activity and extracellular matrix-receptor interaction. Protein-protein interaction network analysis identified 10 hub proteins, including motor proteins and ECM-related proteins, which exhibited higher expression levels in CP compared to control tissues. These findings provide insights into the molecular mechanisms underlying CP and highlight potential targets for diagnostic and therapeutic purposes.

Lysine Distinctively Manipulates Myogenic Regulatory Factors and Wnt/Ca2+ Pathway in Slow and Fast Muscles, and Their Satellite Cells of Postnatal Piglets

Muscle regeneration, representing an essential homeostatic process, relies mainly on the myogenic progress of resident satellite cells, and it is modulated by multiple physical and nutritional factors. Here, we investigated how myogenic differentiation-related factors and pathways respond to the first limiting amino acid lysine (Lys) in the fast and slow muscles, and their satellite cells (SCs), of swine. Thirty 28-day-old weaned piglets with similar body weights were subjected to three diet regimens: control group (d 0-28: 1.31% Lys, n = 12), Lys-deficient group (d 0-28: 0.83% Lys, n = 12), and Lys rescue group (d 0-14: 0.83% Lys; d 15-28: 1.31% Lys, n = 6). Pigs on d 15 and 29 were selectively slaughtered for muscular parameters evaluation. Satellite cells isolated from fast (semimembranosus) and slow (semitendinosus) muscles were also selected to investigate differentiation ability variations. We found Lys deficiency significantly hindered muscle development in both fast and slow muscles via the distinct manipulation of myogenic regulatory factors and the Wnt/Ca2+ pathway. In the SC model, Lys deficiency suppressed the Wnt/Ca2+ pathways and myosin heavy chain, myogenin, and myogenic regulatory factor 4 in slow muscle SCs but stimulated them in fast muscle SCs. When sufficient Lys was attained, the fast muscle-derived SCs Wnt/Ca2+ pathway (protein kinase C, calcineurin, calcium/calmodulin-dependent protein kinase II, and nuclear factor of activated T cells 1) was repressed, while the Wnt/Ca2+ pathway of its counterpart was stimulated to further the myogenic differentiation. Lys potentially manipulates the differentiation of porcine slow and fast muscle myofibers via the Wnt/Ca2+ pathway in opposite trends.

Construction of LncRNA-Related ceRNA Networks in Longissimus Dorsi Muscle of Jinfen White Pigs at Different Developmental Stages

The development of skeletal muscle in pigs might determine the quality of pork. In recent years, long non-coding RNAs (lncRNAs) have been found to play an important role in skeletal muscle growth and development. In this study, we investigated the whole transcriptome of the longissimus dorsi muscle (LDM) of Jinfen White pigs at three developmental stages (1, 90, and 180 days) and performed a comprehensive analysis of lncRNAs, mRNAs, and micro-RNAs (miRNAs), aiming to find the key regulators and interaction networks in Jinfen White pigs. A total of 2638 differentially expressed mRNAs (DE mRNAs) and 982 differentially expressed lncRNAs (DE lncRNAs) were identified. Compared with JFW_1d, there were 497 up-regulated and 698 down-regulated DE mRNAs and 212 up-regulated and 286 down-regulated DE lncRNAs in JFW_90d, respectively. In JFW_180d, there were 613 up-regulated and 895 down-regulated DE mRNAs and 184 up-regulated and 131 down-regulated DE lncRNAs compared with JFW_1d. There were 615 up-regulated and 477 down-regulated DE mRNAs and 254 up-regulated and 355 down-regulated DE lncRNAs in JFW_180d compared with JFW_90d. Compared with mRNA, lncRNA has fewer exons, fewer ORFs, and a shorter length. We performed GO and KEGG pathway functional enrichment analysis for DE mRNAs and the potential target genes of DE lncRNAs. As a result, several pathways are involved in muscle growth and development, such as the PI3K-Akt, MAPK, hedgehog, and hippo signaling pathways. These are among the pathways through which mRNA and lncRNAs function. As part of this study, bioinformatic screening was used to identify miRNAs and DE lncRNAs that could act as ceRNAs. Finally, we constructed an lncRNA-miRNA-mRNA regulation network containing 26 mRNAs, 7 miRNAs, and 17 lncRNAs; qRT-PCR was used to verify the key genes in these networks. Among these, XLOC_022984/miR-127/ENAH and XLOC_016847/miR-486/NRF1 may function as key ceRNA networks. In this study, we obtained transcriptomic profiles from the LDM of Jinfen White pigs at three developmental stages and screened out lncRNA-miRNA-mRNA regulatory networks that may provide crucial information for the further exploration of the molecular mechanisms during skeletal muscle development.

lncRNA GPRC5D-AS1 as a ceRNA inhibits skeletal muscle aging by regulating miR-520d-5p

Sarcopenia induced by muscle aging is associated with negative outcomes in a variety of diseases. Long non-coding RNAs are a class of RNAs longer than 200 nucleotides with lower protein coding potential. An increasing number of studies have shown that lncRNAs play a vital role in skeletal muscle development. According to our previous research, lncRNA GPRC5D-AS1 is selected in the present study as the target gene to further study its effect on skeletal muscle aging in a dexamethasone-induced human muscle atrophy cell model. As a result, GPRC5D-AS1 functions as a ceRNA of miR-520d-5p to repress cell apoptosis and regulate the expression of muscle regulatory factors, including MyoD, MyoG, Mef2c and Myf5, thus accelerating myoblast proliferation and differentiation, facilitating development of skeletal muscle. In conclusion, lncRNA GPRC5D-AS1 could be a novel therapeutic target for treating sarcopenia.

Retinoic acid delays murine palatal shelf elevation by inhibiting Wnt5a-mediated noncanonical Wnt signaling and downstream Cdc-42/F-actin remodeling in mesenchymal cells

BACKGROUND

Mammalian palatal shelves erupted from maxillary prominences undergo vertical extention, transient elevation, and horizontal growth to fuse. Previous studies in mice reported that the retinoic acid (RA) contributed to cleft palate in high incidence by delaying the elevating procedure, but little was known about the underlying biological mechanisms.

METHODS

In this study, hematoxylin-eosin and immunofluorescence staining were employed to evaluate the phenotypes and the expression of related markers in the RA-treated mice model. In situ hybridization and RT-qPCR were used to detect the expression of genes involved in Wnt signaling pathway. The palatal mesenchymal cells were cultured in vitro, and stimulated with RA or CASIN, and co-treated with Foxy5. Wnt5a and Ccd42 expression were evaluated by immunofluorescence staining. Phalloidin was used to label the microfilament cytoskeleton (F-actin) in cultured cells.

RESULTS

We revealed that RA resulted in 100% incidence of cleft palate in mouse embryos, and the expression of genes responsible for Wnt5a-mediated noncanonical Wnt signal transduction were specifically downregulated in mesenchymal palatal shelves. The in vitro study of palatal mesenchymal cells indicated that RA treatment disrupted the organized remodeling of cytoskeleton, an indicative structure of cell migration regulated by the small Rho GTPase Cdc42. Moreover, we showed that the suppression of cytoskeleton and cell migration induced by RA was partially restored using the small molecule Foxy-5-mediated activation of Wnt5A, and this restoration was attenuated by CASIN (a selective GTPase Cdc42 inhibitor) again.

CONCLUSIONS

These data identified a crucial mechanism for Wnt5a-mediated noncanonical Wnt signaling in acting downstream of Rho GTPase Cdc42 to regulate cytoskeletal remodeling and cell migration during the process of palate elevation. Our study provided a new explanation for the cause of cleft palate induced by RA.

Development and Regeneration of Muscle, Tendon, and Myotendinous Junctions in Striated Skeletal Muscle

Owing to a rapid increase in aging population in recent years, the deterioration of motor function in older adults has become an important social problem, and several studies have aimed to investigate the mechanisms underlying muscle function decline. Furthermore, structural maintenance of the muscle–tendon–bone complexes in the muscle attachment sites is important for motor function, particularly for joints; however, the development and regeneration of these complexes have not been studied thoroughly and require further elucidation. Recent studies have provided insights into the roles of mesenchymal progenitors in the development and regeneration of muscles and myotendinous junctions. In particular, studies on muscles and myotendinous junctions have—through the use of the recently developed scRNA-seq—reported the presence of syncytia, thereby suggesting that fibroblasts may be transformed into myoblasts in a BMP-dependent manner. In addition, the high mobility group box 1—a DNA-binding protein found in nuclei—is reportedly involved in muscle regeneration. Furthermore, studies have identified several factors required for the formation of locomotor apparatuses, e.g., tenomodulin (Tnmd) and mohawk (Mkx), which are essential for tendon maturation.

Skeletal Muscle Metabolic Alternation Develops Sarcopenia

Sarcopenia is a new type of senile syndrome with progressive skeletal muscle mass loss with age, accompanied by decreased muscle strength and/or muscle function. Sarcopenia poses a serious threat to the health of the elderly and increases the burden of family and society. The underlying pathophysiological mechanisms of sarcopenia are still unclear. Recent studies have shown that changes of skeletal muscle metabolism are the risk factors for sarcopenia. Furthermore, the importance of the skeletal muscle metabolic microenvironment in regulating satellite cells (SCs) is gaining significant attention. Skeletal muscle metabolism has intrinsic relationship with the regulation of skeletal muscle mass and regeneration. This review is to discuss recent findings regarding skeletal muscle metabolic alternation and the development of sarcopenia, hoping to contribute better understanding and treatment of sarcopenia.

MicroRNA-124-3p Plays a Crucial Role in Cleft Palate Induced by Retinoic Acid

Cleft lip with/without cleft palate (CL/P) is one of the most common congenital birth defects, showing the complexity of both genetic and environmental contributions [e.g., maternal exposure to alcohol, cigarette, and retinoic acid (RA)] in humans. Recent studies suggest that epigenetic factors, including microRNAs (miRs), are altered by various environmental factors. In this study, to investigate whether and how miRs are involved in cleft palate (CP) induced by excessive intake of all-trans RA (atRA), we evaluated top 10 candidate miRs, which were selected through our bioinformatic analyses, in mouse embryonic palatal mesenchymal (MEPM) cells as well as in mouse embryos treated with atRA. Among them, overexpression of miR-27a-3p, miR-27b-3p, and miR-124-3p resulted in the significant reduction of cell proliferation in MEPM cells through the downregulation of CP-associated genes. Notably, we found that excessive atRA upregulated the expression of miR-124-3p, but not of miR-27a-3p and miR-27b-3p, in both in vivo and in vitro. Importantly, treatment with a specific inhibitor for miR-124-3p restored decreased cell proliferation through the normalization of target gene expression in atRA-treated MEPM cells and atRA-exposed mouse embryos, resulting in the rescue of CP in mice. Taken together, our results indicate that atRA causes CP through the induction of miR-124-3p in mice.

Genetics and signaling mechanisms of orofacial clefts

Craniofacial development involves several complex tissue movements including several fusion processes to form the frontonasal and maxillary structures, including the upper lip and palate. Each of these movements are controlled by many different factors that are tightly regulated by several integral morphogenetic signaling pathways. Subject to both genetic and environmental influences, interruption at nearly any stage can disrupt lip, nasal, or palate fusion and result in a cleft. Here, we discuss many of the genetic risk factors that may contribute to the presentation of orofacial clefts in patients, and several of the key signaling pathways and underlying cellular mechanisms that control lip and palate formation, as identified primarily through investigating equivalent processes in animal models, are examined.

Wnt5a regulates Ameloblastoma Cell Migration by modulating Mitochondrial and Cytoskeletal Dynamics

Objective: Abnormal expression of Wnt5a has been detected in various tumors, including ameloblastoma (AB). Yet, there is no specific mechanistic evidence for the functional role of Wnt5a in AB. In this study, we aimed to conduct a mechanistic examination of the importance of Wnt5a in AB development. Methods: The expressions of Wnt5a and Coro1A were examined by Western blot and immunohistochemistry both in AB tissues and AM-1 cells. The number and size of mitochondria were detected by electronic transmission microscope and confocal microscope. Gain-of-function and loss-of-function assays were used to explore the biological roles of Wnt5a and Coro1A in organelle dynamics changes and cell migration. Cell migration was detected by wound healing and transwell assay. Results: We found that in AM-1 cells, up-regulation of Wnt5a led to enhanced mitochondrial energy production and altered calcium homeostasis, with elevated calcium levels directly leading to altered mitochondrial dynamics and interactions between the cytoskeleton and the mitochondria. When Wnt5a or its downstream cytoskeleton-associated protein Coro1A was knocked down, the migration capacity of AM-1 cells was markedly impaired. Conclusion: Together, these results suggest that Wnt5a plays mitochondria and cytoskeleton specific roles in regulating the development of human AB, with its down-regulation leading to impaired tumor development, thus highlighting Wnt5a or Coro1A as potentially viable therapeutic targets for the treatment of AB.

Effects of IC50 dose of retinol on metabolomics of RAW264.7 cells

Vitamin A is one of the most multifunctional vitamins in normal human physiology and is involved in several basic physiological processes from embryonic development to adulthood, such as embryogenesis, vision, immunity, cell differentiation, and proliferation. In this study, we conducted ¹ H- NMR to evaluate the metabolomic changes in RAW264.7 cells after treatment with retinol at an IC₅₀ dose to identify its effects on the differential metabolites and main metabolic pathways. Our results showed that the IC₅₀ dose (140 μM) of retinol affected the metabolism of RAW264.7 cells, with a total of 22 differential metabolites identified via ¹ H-NMR, including amino acids, sugars, organic acids, glutathione, glycerin, and creatine. Additionally, multiple metabolic pathways were affected by retinol treatment, including downregulation of amino acid biosynthesis, protein synthesis, and pyruvate metabolism. We speculate that the cytotoxicity of retinol at the IC₅₀ dose is attributed to mitochondrial dysfunction as a result of oxidative stress or lipid peroxidation. PRACTICAL APPLICATIONS: With the general improvement of people's living standards, people use dietary supplements to improve the level of retinol to prevent non-specific diseases. But there are more and more cases of acute or chronic poisoning caused by excessive intake of vitamin A. Therefore, it is necessary to study the toxicity of vitamin A, and more attention should be paid to the excessive intake of vitamin A. From the perspective of metabolomics, this experiment studies the adverse effects of high dose retinol through the changes of metabolites and metabolic pathways at the cellular level. This study will assist further analyses of the toxic mechanism of excessive retinol as fortified foods and nutrient supplementation.

Quantitative phosphoproteomics to unravel the cellular response to chemical stressors with different modes of action

Damage to cellular macromolecules and organelles by chemical exposure evokes activation of various stress response pathways. To what extent different chemical stressors activate common and stressor-specific pathways is largely unknown. Here, we used quantitative phosphoproteomics to compare the signaling events induced by four stressors with different modes of action: the DNA damaging agent: cisplatin (CDDP), the topoisomerase II inhibitor: etoposide (ETO), the pro-oxidant: diethyl maleate (DEM) and the immunosuppressant: cyclosporine A (CsA) administered at an equitoxic dose to mouse embryonic stem cells. We observed major differences between the stressors in the number and identity of responsive phosphosites and the amplitude of phosphorylation. Kinase motif and pathway analyses indicated that the DNA damage response (DDR) activation by CDDP occurs predominantly through the replication-stress-related Atr kinase, whereas ETO triggers the DDR through Atr as well as the DNA double-strand-break-associated Atm kinase. CsA shares with ETO activation of CK2 kinase. Congruent with their known modes of action, CsA-mediated signaling is related to down-regulation of pathways that control hematopoietic differentiation and immunity, whereas oxidative stress is the most prominent initiator of DEM-modulated stress signaling. This study shows that even at equitoxic doses, different stressors induce distinctive and complex phosphorylation signaling cascades.

Role of noncanonical Wnt ligands and Ror-family receptor tyrosine kinases in the development, regeneration, and diseases of the musculoskeletal system

The Ror-family receptor tyrosine kinases (RTKs), consisting of Ror1 and Ror2, play crucial roles in morphogenesis and formation of various tissues/organs, including the bones and skeletal muscles, the so-called musculoskeletal system, during embryonic development, by acting as receptors or coreceptors for a noncanonical Wnt protein Wnt5a. Furthermore, several lines of evidence have indicated that Ror1 and/or Ror2 play critical roles in the regeneration and maintenance of the musculoskeletal system in adults. Considering the anatomical and functional relationship between the skeleton and skeletal muscles, their structural and functional association might be tightly regulated during their embryonic development, development after birth, and their regeneration after injury in adults. Importantly, in addition to their congenital anomalies, much attention has been paid onto the age-related disorders of the musculoskeletal system, including osteopenia and sarcopenia, which affect severely the quality of life. In this article, we overview recent advances in our understanding of the roles of Ror1- and/or Ror2-mediated signaling in the embryonic development, regeneration in adults, and congenital and age-related disorders of the musculoskeletal system and discuss possible therapeutic approaches to locomotive syndromes by modulating Ror1- and/or Ror2-mediated signaling.

Circular RNA SNX29 Sponges miR-744 to Regulate Proliferation and Differentiation of Myoblasts by Activating the Wnt5a/Ca2+ Signaling Pathway

Myogenesis is a complex and precisely orchestrated process that is highly regulated by several non-coding RNAs and signal pathways. Circular RNAs (circRNAs) represent a novel subclass of endogenous non-coding RNAs that have been identified in multiple species and tissues and play a vital role in post-transcriptional regulation in eukaryotes, but the precise molecular mechanism of action remains largely unknown. Here, we screened a candidate circRNA derived from the SNX29 gene, termed circSNX29 from our previous circRNAs sequencing data of bovine skeletal muscle, and further characterized its regulation and function during muscle development. The overexpression of circSNX29 facilitated myoblasts differentiation and inhibited cell proliferation. Computational analysis using RNAhybrid showed the potential for circSNX29 to sponge to miR-744 with nine potential binding sites. We tested this via a luciferase screening assay and found that circSNX29 directly interacted with miR-744 and downregulation of miR-744 efficiently reversed the suppression of Wnt5a and CaMKIIδ. Importantly, through the Kyoto Encyclopedia of Genes and Genomes (KEGG) pathways enrichment analysis, Fluo-4, AM, cell permeant-calcium ion fluorescent probing, and western blotting assays, we found that overexpression of Wnt5a and circSNX29 activated the non-canonical Wnt5a/Ca²⁺ pathway. Overall, the evidence generated by our study elucidates the regulatory mechanisms of circSNX29 to function as a sponge for miRNA-744 in bovine primary myoblasts.

Wnt signaling in orofacial clefts: crosstalk, pathogenesis and models

Diverse signaling cues and attendant proteins work together during organogenesis, including craniofacial development. Lip and palate formation starts as early as the fourth week of gestation in humans or embryonic day 9.5 in mice. Disruptions in these early events may cause serious consequences, such as orofacial clefts, mainly cleft lip and/or cleft palate. Morphogenetic Wnt signaling, along with other signaling pathways and transcription regulation mechanisms, plays crucial roles during embryonic development, yet the signaling mechanisms and interactions in lip and palate formation and fusion remain poorly understood. Various Wnt signaling and related genes have been associated with orofacial clefts. This Review discusses the role of Wnt signaling and its crosstalk with cell adhesion molecules, transcription factors, epigenetic regulators and other morphogenetic signaling pathways, including the Bmp, Fgf, Tgfβ, Shh and retinoic acid pathways, in orofacial clefts in humans and animal models, which may provide a better understanding of these disorders and could be applied towards prevention and treatments.

PTEN downregulates WD repeat‑containing protein 66 in salivary adenoid cystic carcinoma

Salivary adenoid cystic carcinoma (SACC) is one of the most common types of salivary gland cancer that causes substantial morbidity and mortality. Despite the substantial health burden of SACC, the molecular mechanisms underlying its development and progression remain poorly understood. We previously reported the loss of phosphatase and tensin homolog (PTEN) expression to be common among SACC tumors, and the PTEN deficiency to be correlated with enrichment of epithelial-mesenchymal transition (EMT) genes based on expression array analysis. The aim of the present study was to investigate further the functional function of WD repeat-containing protein 66 (WDR66), one of the enriched EMT genes, in the context of PTEN deficiency and SACC pathogenesis. WDR66 was identified to be required to maintain the EMT phenotype and the expression of cancer stem cell genes in the context of PTEN deficiency. Furthermore, knockdown of WDR66 decreased cellular proliferation, migration and invasion. Finally, WDR66 expression was identified to be inversely associated with PTEN expression and negatively correlated with the overall survival of patients with SACC. Collectively, the results of the present study revealed a novel function of WDR66 in mediating the progression of PTEN-deficient SACCs, thereby suggesting WDR66 inhibition to be a potential therapeutic approach towards successful management of SACC disease progression, particularly against tumors with decreased PTEN expression levels.

A newly identified lncRNA MAR1 acts as a miR-487b sponge to promote skeletal muscle differentiation and regeneration

BACKGROUND

Skeletal muscle atrophy induced by either aging (sarcopenia) or mechanical unloading is associated with serious health consequences. Long non-coding RNAs (lncRNAs) are implicated as important regulators in numerous physiological and pathological processes.

METHODS

Microarray analysis was performed to identify the differentially expressed lncRNAs in skeletal muscle between adult and aged mice. The most decreased lncRNA in aged skeletal muscle was identified. The C2C12 mouse myoblast cells were used to assess the biological function of the lncRNA in vitro. The target microRNA of lncRNA and the target protein of microRNA were predicted by bioinformatics analysis and validated in vitro. Furthermore, the biology function of the lncRNA in vivo was investigated by local overexpression or knockdown the lncRNA in skeletal muscle. The therapeutic effect of the lncRNA overexpression in age-related or mechanical unloading-induced muscle atrophy was also evaluated.

RESULTS

We identified a novel lncRNA (muscle anabolic regulator 1, MAR1) which was highly expressed in mice skeletal muscle and positively correlated with muscle differentiation and growth in vitro and in vivo. We predicted and validated that microRNA-487b (miR-487b) was a direct target of MAR1. We also predicted and validated that Wnt5a, an important regulator during myogenesis, was a target of miR-487b in C2C12 cells. Our findings further demonstrated that enforced MAR1 expression in myoblasts led to derepression of Wnt5a. Moreover, MAR1 promoted skeletal muscle mass/strength and Wnt5a protein level in mice. Enforced MAR1 expression in mice attenuated muscle atrophy induced by either aging or unloading.

CONCLUSIONS

The newly identified lncRNA MAR1 acts as a miR-487b sponge to regulate Wnt5a protein, resulting in promoting muscle differentiation and regeneration. MAR1 could be a novel therapeutic target for treating muscle atrophy induced by either aging or mechanical unloading.

How to make a tongue: Cellular and molecular regulation of muscle and connective tissue formation during mammalian tongue development

The vertebrate tongue is a complex muscular organ situated in the oral cavity and involved in multiple functions including mastication, taste sensation, articulation and the maintenance of oral health. Although the gross embryological contributions to tongue formation have been known for many years, it is only relatively recently that the molecular pathways regulating these processes have begun to be discovered. In particular, there is now evidence that the Hedgehog, TGF-Beta, Wnt and Notch signaling pathways all play an important role in mediating appropriate signaling interactions between the epithelial, cranial neural crest and mesodermal cell populations that are required to form the tongue. In humans, a number of congenital abnormalities that affect gross morphology of the tongue have also been described, occurring in isolation or as part of a developmental syndrome, which can greatly impact on the health and well-being of affected individuals. These anomalies can range from an absence of tongue formation (aglossia) through to diminutive (microglossia), enlarged (macroglossia) or bifid tongue. Here, we present an overview of the gross anatomy and embryology of mammalian tongue development, focusing on the molecular processes underlying formation of the musculature and connective tissues within this organ. We also survey the clinical presentation of tongue anomalies seen in human populations, whilst considering their developmental and genetic etiology.

Histological study of postnatal development of mouse tongues

Numerous factors, including trauma, tumors and myophagism, may lead to tongue defects, which are mostly repaired via muscular flaps. However, these methods cannot restore the muscular function and gustation function of the tongue. Intensive research on tongue development may offer useful clues for tongue regeneration based on tissue engineering or stem cell therapy. In the present study, staining results revealed that tongue muscle fibers became larger, mature and stronger, and the foliate and fungiform papillae also became mature from newborn to adult C57BL/6J genetic background mice. Immunofluorescence staining and polymerase chain reaction results revealed that C-kit was dynamically expressed in muscle cells, as well as in foliate and fungiform papilla cells from newborn to adult stages. The expression level decreased from P1 to P15 and increased at P90. The immunofluorescence staining results revealed that Ki-67 was expressed in muscle cells and papilla cells from newborn to adult stages, and high expression was observed at P6 and P15. In addition, the immunofluorescence staining results also demonstrated that msh homeobox 2 (Msx2) was dynamically expressed in postnatal tongue muscle cells; however, almost no expression was detected in papilla cells. There was relative high expression level of Msx2 at P1 and P6 stages, but this gradually decreased from P15, and it was expressed primarily in the muscle cells located in the marginal zone of the tongue at P90. These findings suggest that the amount of c-kit-expressing precursor cells in tongue muscle and papilla cells increases to promote tongue development at the early postnatal stage and to maintain homeostasis and functional adaptation of the tongue in the adult stage. Furthermore, Msx2 may serve an important role in postnatal tongue muscle development. The present study also suggests that C-kit and Msx2 may be used as cell markers for postnatal tongue regeneration and self-repair, and may provide an approach for developing treatment methods for tongue diseases with a postnatal onset.

Retinoid acid-induced microRNA-31-5p suppresses myogenic proliferation and differentiation by targeting CamkIIδ

BACKGROUND

We previously reported that Wnt5a/CaMKIIδ (calcium/calmodulin-dependent protein kinase II delta) pathway was involved in the embryonic tongue deformity induced by excess retinoic acid (RA). Our latest study found that the expression of miR-31-5p, which was predicted to target the 3'UTR of CamkIIδ, was raised in the RA-treated embryonic tongue. Thus, we hypothesized that the excess RA regulated Wnt5a/CaMKIIδ pathway through miR-31-5p in embryonic tongue.

METHODS

C2C12 myoblast line was employed as an in vitro model to examine the suppression of miR-31-5p on CamkIIδ expression, through which RA impaired the myoblast proliferation and differentiation in embryonic tongue.

RESULTS

RA stimulated the expression of miR-31-5p in both embryonic tongue and C2C12 myoblasts. Luciferase reporter assay confirmed that the 3'UTR of CamkIIδ was a target of miR-31-5p. MiR-31-5p mimics disrupted CamkIIδ expression, C2C12 proliferation and differentiation as excess RA did, while miR-31-5p inhibitor partially rescued these defects in the presence of RA.

CONCLUSIONS

Excess RA can stimulate miR-31-5p expression to suppress CamkIIδ, which represses the proliferation and differentiation of tongue myoblasts.

Retinoid acid-induced microRNA-27b-3p impairs C2C12 myoblast proliferation and differentiation by suppressing α-dystrobrevin

We previously reported that excess retinoic acid (RA) resulted in hypoplastic and derangement of myofilaments in embryonic tongue by inhibiting myogenic proliferation and differentiation through CamKIID pathway. Our further studies revealed that the expression of a series of miRNAs was altered by RA administration in embryonic tongue as well as in C2C12 cells. Thus, if excess RA impairs myogenic proliferation and differentiation through miRNAs is taken into account. In present study, miR-27b-3p was found up-regulated in RA-treated C2C12 cells as in embryonic tongue, and predicted to target the 3'UTR of α-dystrobrevin (DTNA). Luciferase reporter assays confirmed the direct interaction between miR-27b-3p and the 3'UTR of DTNA. MiR-27b-3p mimics recapitulated the RA repression on DTNA expression, C2C12 proliferation and differentiation, while the miR-27b-3p inhibitor circumvented these defects resulting from excess RA. As expected, the effects of siDTNA on C2C12 were coincided with those by RA treatment or miR-27b-3p mimics. Therefore, these findings indicated that excess RA inhibited the myoblast proliferation and differentiation by up-regulating miR-27b-3p to target DTNA, which implied a new mechanism in myogenic hypoplasia.

Genome-wide analysis of alternative splicing during human heart development

Alternative splicing (AS) drives determinative changes during mouse heart development. Recent high-throughput technological advancements have facilitated genome-wide AS, while its analysis in human foetal heart transition to the adult stage has not been reported. Here, we present a high-resolution global analysis of AS transitions between human foetal and adult hearts. RNA-sequencing data showed extensive AS transitions occurred between human foetal and adult hearts, and AS events occurred more frequently in protein-coding genes than in long non-coding RNA (lncRNA). A significant difference of AS patterns was found between foetal and adult hearts. The predicted difference in AS events was further confirmed using quantitative reverse transcription-polymerase chain reaction analysis of human heart samples. Functional foetal-specific AS event analysis showed enrichment associated with cell proliferation-related pathways including cell cycle, whereas adult-specific AS events were associated with protein synthesis. Furthermore, 42.6% of foetal-specific AS events showed significant changes in gene expression levels between foetal and adult hearts. Genes exhibiting both foetal-specific AS and differential expression were highly enriched in cell cycle-associated functions. In conclusion, we provided a genome-wide profiling of AS transitions between foetal and adult hearts and proposed that AS transitions and deferential gene expression may play determinative roles in human heart development.

High frequency of loss of PTEN expression in human solid salivary adenoid cystic carcinoma and its implication for targeted therapy

Salivary gland tumor (SGT) is one of the least studied cancers due to its rarity and heterogeneous histological types. Here, we reported that loss of PTEN expression was most frequently found in the poorly differentiated, high grade solid adenoid cystic carcinomas. Loss of PTEN expression correlated with activation of mTOR by increased phosphorylated S6 ribosome protein. We further functionally studied the role of PTEN in a pair of human SACC cell lines, SACC-83 and SACC-LM. Reduced PTEN level was correlated with the metastasis potential. When we knocked down PTEN in the SACC-83 cell line, we observed increased proliferation and enhanced migration/invasion in vitro, and increased tumor size in vivo. We further tested the therapeutical effect by applying a PI3K/mTOR inhibitor NVP-BEZ235 to both SACC cell lines. Decreased cell proliferation, increased apoptosis, as well as reduced cell migration/invasion were observed in both cell lines upon the NVP-BEZ235 treatment. Moreover, the NVP-BEZ235 treatment in a SGT xenograft mouse model significantly reduced primary tumor size and lung metastasis. Taken together, our results demonstrated that PTEN is a potent tumor suppressor in human SGTs, and targeting PI3K/mTOR pathway may be effective in the targeted therapy for human SGT patients with loss of PTEN expression.

Novel insights into a retinoic-acid-induced cleft palate based on Rac1 regulation of the fibronectin arrangement

Retinoic acid (RA)-induced cleft palate results from both extrinsic obstructions by the tongue and internal factors within the palatal shelves. Our previous study showed that the spatiotemporal expression of Rac1 regulates the fibronectin (FN) arrangement through cell density alterations that play an important role in palate development. In this study, we investigate the involvement of the Rac1 regulation of the FN arrangement in RA-induced cleft palate. Our results demonstrate that RA-induced intrinsic alterations in palatal shelves, including a delayed progress of cell condensation, delay palate development, even after the removal of the tongue. Further analysis shows that RA treatment diminishes the region-distinctive expression of Rac1 within the palatal shelves, which reversely alters the fibrillar arrangement of FN. Furthermore, RA treatment disrupts the formation of lamellipodia, which are indicative structures of cell migration that are regulated by Rac1. These results suggest that the Rac1 regulation of the FN arrangement is involved in RA-induced cleft palate through the regulation of cell migration, which delays the progress of cell condensation and subsequently influences the FN arrangement, inducing a delay in palate development. Our study provides new insights into the RA-induced impairment of palatal shelf elevation based on cell migration dynamics.