Case report: Fatal infantile hypertonic myofibrillar myopathy with compound heterozygous mutations in the CRYAB gene.

Background: Fatal infantile hypertonic myofibrillar myopathy (FIHMM) is an autosomal recessive hereditary disease characterized by amyotrophy, progressive flexion contracture and ankylosis of the trunk and limb muscles, apnea and respiratory failure, and increased creatine phosphate levels. It is caused by mutations in the CRYAB gene, and only around 18 cases including genetic mutations have been reported worldwide. All patients with FIHMM develop respiratory distress, progressive stiffness of the limbs, and have a poor prognosis. However, no effective treatment for CRYAB-associated respiratory failure has been reported. Here, we report a case of FIHMM with a novel heterozygous missense mutation. Case Presentation: A 2-year-old female developed scoliosis of the lumbar spine and restrictive ventilatory dysfunction in infancy. She was admitted to the hospital with labored breathing on the third day after the second injection of inactivated poliomyelitis vaccine. Acute respiratory failure, pneumothorax, and cardiac arrest arose in the patient during hospitalization, and progressive stiffness of the trunk and limb muscles appeared, accompanied by obvious abdominal distension and an increase in phosphocreatine kinase levels. Screenings for genetic metabolic diseases in the blood and urine were normal. Electromyography revealed mild myogenic damage. A muscle biopsy indicated the accumulation of desmin, α-crystallin, and myotilin in the musculus biceps brachii, and dense granules were observed in muscle fibers using electron microscopy. Mutation analysis of CRYAB revealed a novel heterozygous missense mutation in the proband, c.302A > C (p.His101Pro) and c.3G > A (p.Met1Ile), which inherited from her asymptomatic, heterozygous carrier parents, respectively. The proband was finally diagnosed as FIHMM. One month after the FIHMM diagnosis, the child died of respiratory failure. Conclusion: We report a case of FIHMM with a novel heterozygous missense mutation of CRYAB. This finding might improve our understanding of FIHMM and highlight a novel mutation in the Chinese population.

Overexpression of hnRNPC2 induces multinucleation by repression of Aurora B in hepatocellular carcinoma cells.

Heterogeneous ribonuclear protein C2 (hnRNPC2), an RNA binding protein, is a component of hnRNPC which is upregulated in many tumors. Multinucleation exists in many tumors and is positively correlated with tumor grade. To uncover the correlation between hnRNPC2 and multi-nucleation in hepatocellular carcinoma SMMC-7721 cells, we constructed a pEGFP-hnRNPC2 vector and transfected it into cancer cells. Our results revealed that overexpression of hnRNPC2 induced multinucleation in SMMC-7721 cells. Tracking tests indicated that the induced multinucleated cells were unable to recover to mononuclear cells and finally died as a result of defects in cell division. Furthermore, Aurora B, which was localized at the midbody and plays a role in cytokinesis, was repressed in hnRNPC2-overexpressing cells, whose knockdown by RNA interference also induced multinucleation in SMMC-7721 cells. Quantitative polymerase chain reaction (qPCR) and mRNA-protein co-immunoprecipitation results revealed that Aurora B mRNA did not decrease in hnRNPC2-overexpressing cells, instead it bound more hnRNPC2 and less eIF4E, an mRNA cap binding protein and translational initiation factor. Moreover, hnRNPC2 bound more eIF4E in hnRNPC2-overexpressing cells. These results indicate that hnRNPC2 repressed Aurora B binding with eIF4F, which must bind with Aurora B mRNA in order to initiate its translation. This induced multinucleation in hepatocellular carcinoma cells. In addition, hnRNPC2 accelerated hepatocellular carcinoma cell proliferation. Collectively, these data suggest that hnRNPC2 may be a potential target for hepatocellular carcinoma cell diagnosis and treatment.

Cancer cell growth suppression by a 62nt AU-rich RNA from C/EBPß 3'UTR through competitive binding with HuR.

AU-rich elements are functional motifs in the 3'untranslated region of mRNA and are binding sites for the RNA binding protein HuR, an mRNA stabilizer and translation enhancer implicated in carcinogenesis. It is not clear whether, and, if so, how the AU-rich elements function in cells when they are separated from their mRNA and form an independent RNA species. Here, we show that a short RNA with AU-rich elements derived from C/EBPß 3'UTR suppressed growth in a human liver cancer cell line. It specifically bound HuR, and it competed with C/EBPß mRNA in order to bind to HuR. Our results provide evidence that the cancer cell growth suppression by this 62nt RNA containing AU-rich elements may be due to competitive binding to HuR. This work may open new options for the development of novel anti-cancer drugs.

Tumor suppression by RNA from C/EBPß 3'UTR through the inhibition of protein kinase Cε activity.

BACKGROUND: Since the end of last century, RNAs from the 3'untranslated region (3'UTR) of several eukaryotic mRNAs have been found to exert tumor suppression activity when introduced into malignant cells independent of their whole mRNAs. In this study, we sought to determine the molecular mechanism of the tumor suppression activity of a short RNA from 3'UTR of C/EBPß mRΝΑ (C/EBPß 3'UTR RNA) in human hepatocarcinoma cells SMMC-7721. METHODOLOGY/PRINCIPAL FINDINGS: By using Western blotting, immunocytochemistry, molecular beacon, confocal microscopy, protein kinase inhibitors and in vitro kinase assays, we found that, in the C/EBPß 3'UTR-transfectant cells of SMMC-7721, the overexpressed C/EBPß 3'UTR RNA induced reorganization of keratin 18 by binding to this keratin; that the C/EBPß 3'UTR RNA also reduced phosphorylation and expression of keratin 18; and that the enzyme responsible for phosphorylating keratin 18 is protein kinase Cε. We then found that the C/EBPß 3'UTR RNA directly inhibited the phosphorylating activity of protein kinase Cε; and that C/EBPß 3'UTR RNA specifically bound with the protein kinase Cε-keratin 18 conjugate. CONCLUSION/SIGNIFICANCE: Together, these facts suggest that the tumor suppression in SMMC-7721 by C/EBPß 3'UTR RNA is due to the inhibition of protein kinase Cε activity through direct physical interaction between C/EBPß 3'UTR RNA and protein kinase Cε. These facts indicate that the 3'UTR of some eukaryotic mRNAs may function as regulators for genes other than their own.