Ischemic heart disease (IHD) remains a major global health concern, with ischemia-reperfusion injury exacerbating myocardial damage despite therapeutic interventions. In this study, we investigated the role of tropomyosin 3 (TPM3) in protecting cardiomyocytes against hypoxia-induced injury and oxidative stress. Using the AC16 and H9c2 cell lines, we established a chemical hypoxia model by treating cells with cobalt chloride (CoCl2) to simulate low-oxygen conditions. We found that CoCl2 treatment significantly upregulated the expression of hypoxia-inducible factor 1 alpha (HIF-1α) in cardiomyocytes, indicating the successful induction of hypoxia. Subsequent morphological and biochemical analyses revealed that hypoxia altered cardiomyocyte morphology disrupted the cytoskeleton, and caused cellular damage, accompanied by increased lactate dehydrogenase (LDH) release and malondialdehyde (MDA) levels, and decreased superoxide dismutase (SOD) activity, indicative of oxidative stress. Lentivirus-mediated TPM3 overexpression attenuated hypoxia-induced morphological changes, cellular damage, and oxidative stress imbalance, while TPM3 knockdown exacerbated these effects. Furthermore, treatment with the HDAC1 inhibitor MGCD0103 partially reversed the exacerbation of hypoxia-induced injury caused by TPM3 knockdown. Protein-protein interaction (PPI) network and functional enrichment analysis suggested that TPM3 may modulate cardiac muscle development, contraction, and adrenergic signaling pathways. In conclusion, our findings highlight the therapeutic potential of TPM3 modulation in mitigating hypoxia-associated cardiac injury, suggesting a promising avenue for the treatment of ischemic heart disease and other hypoxia-related cardiac pathologies.

Previously a ring finger protein 20 (RNF20) is found to be essential for meiotic recombination and mediates H2B ubiquitination during spermatogenesis. However, its role in meiotic division is still unknown. Here, it is shown that RNF20 is localized at both centromeres and spindle poles, and it is required for oocyte acentrosomal spindle organization and female fertility. RNF20-depleted oocytes exhibit severely abnormal spindle and chromosome misalignment caused by defective bipolar organization. Notably, it is found that the function of RNF20 in spindle assembly is not dependent on its E3 ligase activity. Instead, RNF20 regulates spindle assembly by recruiting tropomyosin3 (TPM3) to both centromeres and spindle poles with its coiled-coil motif. The RNF20-TPM3 interaction is essential for acentrosomal meiotic spindle assembly. Together, the studies uncover a novel function for RNF20 in mediating TPM3 recruitment to both centromeres and spindle poles during oocyte spindle assembly.

Patients with myopathies caused by pathogenic variants in tropomyosin genes TPM2 and TPM3 usually have muscle hypotonia and weakness, their muscle biopsies often showing fibre size disproportion and nemaline bodies. Here, we describe a series of patients with hypercontractile molecular phenotypes, high muscle tone, and mostly non-specific myopathic biopsy findings without nemaline bodies. Three of the patients had trismus, whilst in one patient, the distal joints of her fingers flexed on extension of the wrists. In one biopsy from a patient with a rare TPM3 pathogenic variant, cores and minicores were observed, an unusual finding in TPM3-caused myopathy. The variants alter conserved contact sites between tropomyosin and actin.

The tropomyosin genes (TPM1-4) contribute to the functional diversity of skeletal muscle fibers. Since its discovery in 1988, the TPM3 gene has been recognized as an indispensable regulator of muscle contraction in slow muscle fibers. Recent advances suggest that TPM3 isoforms hold more extensive functions during skeletal muscle development and in postnatal muscle. Additionally, mutations in the TPM3 gene have been associated with the features of congenital myopathies. The use of different in vitro and in vivo model systems has leveraged the discovery of several disease mechanisms associated with TPM3-related myopathy. Yet, the precise mechanisms by which TPM3 mutations lead to muscle dysfunction remain unclear. This review consolidates over three decades of research about the role of TPM3 in skeletal muscle. Overall, the progress made has led to a better understanding of the phenotypic spectrum in patients affected by mutations in this gene. The comprehensive body of work generated over these decades has also laid robust groundwork for capturing the multiple functions this protein plays in muscle fibers.

BACKGROUND: Breast cancer (BRCA) is the most common and leading cause of cancer-related death in women. MicroRNAs (miRNAs) are short non-coding RNA fragments that play a role in regulating gene expression including the cancer-related pathways. Although dysregulation of miR-223 has been demonstrated in recent studies to have prognostic value in various cancers, its diagnostic and prognostic role in BRCA remains unknown.
METHODS: The expression and the prognostic value of miR-223 were evaluated using the TCGA data and verified by qRT-PCR. Subsequently, potential oncogenic targets of miR-223 were identified by using three different miRNA target prediction tools and the GEPIA database. In addition to these databases, protein-protein interaction network, molecular functions, prognostic value, and the expression level of miR-223 targets were included by using several other bioinformatics tools and databases; such as, UALCAN, GeneMANIA and Metascape.
RESULTS: The bioinformatic results demonstrated that miR-223 downregulated in BRCA and associated with poor prognosis of patients. In vitro experiments validated that miR-223 significantly downregulated in BRCA cells, MCF-7, SK-BR3, MDA-MB-231 and HCC1500, compared to normal breast cell line hTERT-HME1. Furthermore, ANLN, DYNLT1, LRRC59, SLC12A8 and TPM3 genes were identified as the potential oncogenic target genes of miR-223 based on their expression and prognosis in BRCA. Additionally, protein-protein interaction network of these target genes was mainly enriched in dynein intermediate chain binding, cell division, regulation of cell cycle process, and positive regulation of cellular component biogenesis.
CONCLUSIONS: The results suggests that miR-223 and its targets, ANLN, DYNLT1, LRRC59, SLC12A8 and TPM3, might be reliable potential prognostic biomarkers in BRCA patients.

Species within the genus Equus are valued for their draft ability. Skeletal muscle forms the foundation of the draft ability of Equus species; however, skeletal muscle development-related conserved genes and their target miRNAs are rarely reported for Equus. In this study, a comparative genomics analysis was performed among five species (horse, donkey, zebra, cattle, and goat), and the results showed that a total of 15,262 (47.43%) genes formed the core gene set of the five species. Only nine chromosomes (Chr01, Chr02, Chr03, Chr06, Chr10, Chr18, Chr22, Chr27, Chr29, and Chr30) exhibited a good collinearity relationship among Equus species. The micro-synteny analysis results showed that TPM3 was evolutionarily conserved in chromosome 1 in Equus. Furthermore, donkeys were used as the model species for Equus to investigate the genetic role of TPM3 in muscle development. Interestingly, the results of comparative transcriptomics showed that the TPM3 gene was differentially expressed in donkey skeletal muscle S1 (2 months old) and S2 (24 months old), as verified via RT-PCR. Dual-luciferase test analysis showed that the TPM3 gene was targeted by differentially expressed miRNA (eca-miR-1). Furthermore, a total of 17 TPM3 gene family members were identified in the whole genome of donkey, and a heatmap analysis showed that EaTPM3-5 was a key member of the TPM3 gene family, which is involved in skeletal muscle development. In conclusion, the TPM3 gene was conserved in Equus, and EaTPM3-5 was targeted by eca-miR-1, which is involved in skeletal muscle development in donkeys.

BACKGROUND: Pathogenic variants in the TPM3 gene, encoding slow skeletal muscle α-tropomyosin account for less than 5% of nemaline myopathy cases. Dominantly inherited or de novo missense variants in TPM3 are more common than recessive loss-of-function variants. The recessive variants reported to date seem to affect either the 5\' or the 3\' end of the skeletal muscle-specific TPM3 transcript.
OBJECTIVE: The aim of the study was to identify the disease-causing gene and variants in a Finnish patient with an unusual form of nemaline myopathy.
METHODS: The genetic analyses included Sanger sequencing, whole-exome sequencing, targeted array-CGH, and linked-read whole genome sequencing. RNA sequencing was done on total RNA extracted from cultured myoblasts and myotubes of the patient and controls. TPM3 protein expression was assessed by Western blot analysis. The diagnostic muscle biopsy was analyzed by routine histopathological methods.
RESULTS: The patient had poor head control and failure to thrive, but no hypomimia, and his upper limbs were clearly weaker than his lower limbs, features which in combination with the histopathology suggested TPM3-caused nemaline myopathy. Muscle histopathology showed increased fiber size variation and numerous nemaline bodies predominantly in small type 1 fibers. The patient was found to be compound heterozygous for two splice-site variants in intron 1a of TPM3: NM_152263.4:c.117+2_5delTAGG, deleting the donor splice site of intron 1a, and NM_152263.4:c.117 + 164 C>T, which activates an acceptor splice site preceding a non-coding exon in intron 1a. RNA sequencing revealed inclusion of intron 1a and the non-coding exon in the transcripts, resulting in early premature stop codons. Western blot using patient myoblasts revealed markedly reduced levels of the TPM3 protein.
CONCLUSIONS: Novel biallelic splice-site variants were shown to markedly reduce TPM3 protein expression. The effects of the variants on splicing were readily revealed by RNA sequencing, demonstrating the power of the method.

Glioma is a general malignant tumor with a dismal prognosis. Long noncoding RNAs (lncRNAs) have been implicated in the initiation and processes of tumors. An investigation of the GEPIA database revealed that long noncoding RNA WEE2 antisense RNA 1 (WEE2-AS1) is upregulated in glioma tissues compared to normal brain tissues, and validation with quantitative real-time polymerase chain reaction (qRT-PCR) revealed that WEE2-AS1 expression was consistent with the database prediction. Fluorescence in situ hybridization (FISH) assays revealed that WEE2-AS1 was localized primarily in the cytoplasm. Clone formation experiment and EDU assay were used to detect cell proliferation ability, and Transwell assay was used to detect cell migration and invasion ability, Western-blot assay and immunofluorescence were used to determine TPM3 protein level. Functional experiments revealed that the downregulation of WEE2-AS1 impeded cell proliferation, migration, and invasion in glioma cell lines. Furthermore, downregulation of WEE2-AS1 suppressed tumor growth in vivo. Bioinformatics predictions and integrated experiments indicated that WEE2-AS1 promoted tropomyosin 3 (TPM3) expression by sponging miR-29b-2-5p. A dual-luciferase reporter assay was conducted to uncover the binding of WEE2-AS1 and miR-29b-2-5p and that of miR-29b-2-5p and TPM3. Additionally, a series of rescue assays showed that WEE2-AS1 promotes proliferation, migration, and invasion by targeting miR-29b-2-5p to regulate TPM3 expression. Ultimately, the results of this study indicate that WEE2-AS1 plays an oncogenic role in glioma and may promote further investigations of the diagnostic and prognostic value of WEE2-AS1 in glioma.

BACKGROUND: We report a patient with a novel c.737 C > T variant (p.Ser246Leu) of the TPM3 gene presenting with adult-onset distal myopathy.
METHODS: A 35-year-old Chinese male patient presented with a history of progressive finger weakness. Physical examination revealed differential finger extension weakness, together with predominant finger abduction, elbow flexion, ankle dorsiflexion and toe extension weakness. Muscle MRI showed disproportionate fatty infiltration of the glutei, sartorius and extensor digitorum longus muscles without significant wasting. Muscle biopsy and ultrastructural examination showed a non-specific myopathic pattern without nemaline or cap inclusions. Genetic sequencing revealed a novel heterozygous p.Ser246Leu variant (c.737C>T) of the TPM3 gene which is predicted to be pathogenic. This variant is located in the area of the TPM3 gene where the protein product interacts with actin at position Asp25 of actin. Mutations of TPM3 in these loci have been shown to alter the sensitivity of thin filaments to the influx of calcium ions.
CONCLUSIONS: This report further expands the phenotypic spectrum of myopathies associated with TPM3 mutations, as mutations in TPM3 had not previously been reported with adult-onset distal myopathy. We also discuss the interpretation of variants of unknown significance in patients with TPM3 mutations and summarise the typical muscle MRI findings of patients with TPM3 mutations.

ALK-rearranged renal cell carcinoma (ALK-RCC) is a very rare novel molecularly defined entity in the recently published fifth edition of the World Health Organization classification of tumours. We describe a case of ALK-RCC in a 76-year-old female. The tumour was composed of discohesive rhabdoid cells and pleomorphic, multinucleated cells (equivalent to ISUP/WHO grade 4). The tumour showed expression with PAX8, Keratin 7 and alpha methylacyl CoA racemase. ALK (D5F3 clone) was strongly and diffusely positive. ALK-FISH showed significant split signals of ALK, confirming the diagnosis. RNA sequencing showed TPM3::ALK rearrangement. Including the current case, there are 14 reported ALK-RCC cases with the same TPM3 fusion partner gene. Review of these published cases highlights their morphological heterogeneity and stresses the importance of running ALK immunohistochemistry on difficult cases to classify renal tumours. This is important while identification of ALK-RCC has clinical significance due to the availability of targeted therapy with ALK inhibitors.