Enrichment of Deleterious Mutated Genes Involved in Ciliary Function and Histone Modification in Brain Cancer Patient-Derived Xenograft Models.

Patient-derived xenograft (PDX) models, which can retain the characteristics of original tumors in an in vivo-mimicking environment, have been developed to identify better treatment options. However, although original tumors and xenograft tissues mostly share oncogenic mutations and global gene expression patterns, their detailed mutation profiles occasionally do not overlap, indicating that selection occurs in the xenograft environment. To understand this mutational alteration in xenografts, we established 13 PDX models derived from 11 brain tumor patients and confirmed their histopathological similarity. Surprisingly, only a limited number of somatic mutations were shared between the original tumor and xenograft tissue. By analyzing deleteriously mutated genes in tumors and xenografts, we found that previously reported brain tumor-related genes were enriched in PDX samples, demonstrating that xenografts are a valuable platform for studying brain tumors. Furthermore, mutated genes involved in cilium movement, microtubule depolymerization, and histone methylation were enriched in PDX samples compared with the original tumors. Even with the limitations of the heterogeneity of clinical lesions with a heterotropic model, our study demonstrates that PDX models can provide more information in genetic analysis using samples with high heterogeneity, such as brain tumors.

Ckb and Ybx2 interact with Ribc2 and are necessary for the ciliary beating of multi-cilia.

BACKGROUND: Motile cilia in a vertebrate are important to sustaining activities of life. Fluid flow on the apical surface of several tissues, including bronchial epithelium, ependymal epithelium, and fallopian tubules is generated by the ciliary beating of motile cilia. Multi-ciliated cells in ependymal tissue are responsible for the circulation of cerebrospinal fluid (CSF), which is essential for the development and homeostasis of the central nervous system, and airway tissues are protected from external contaminants by cilia-driven mucosal flow over the top of the airway epithelium. OBJECTIVE: A previous study reported that reduction of Ribc2 protein leads to disruption of ciliary beating in multi-ciliated cells. However, knowledge regarding the molecular function of Ribc2 is limited, thus currently available information is also limited. Therefore, we evaluated the importance of proteins involved in the interaction with Ribc2 in the process of ciliary beating. METHODS: Immunoprecipitation and mass spectrometry analysis was performed for the discovery of proteins involved in the interaction with Ribc2. Expression of the target gene was inhibited by injection of antisense morpholinos and measurement of the fluid flow on the embryonic epidermis of Xenopus was performed using fluorescent beads for examination of the ciliary beating of multi cilia. In addition, the flag-tagged protein was expressed by injection of mRNA and the changes in protein localization in the cilia were measured by immunostaining and western blot analysis for analysis of the molecular interaction between Ribc2 and Ribc2 binding proteins in multi-cilia. RESULTS: The IP/MS analysis identified Ckb and Ybx2 as Ribc2 binding proteins and our results showed that localization of both Ckb and Ybx2 occurs at the axoneme of multi-cilia on the embryonic epithelium of Xenopus laevis. In addition, our findings confirmed that knock-down of Ckb or Ybx2 resulted in abnormal ciliary beating and reduction of cilia-driven fluid flow on multi-cilia of Xenopus laevis. In addition, significantly decreased localization of Ckb or Ybx2 in the ciliary axoneme was observed in Ribc2-depleted multi-cilia. CONCLUSION: Ckb and Ybx2 are involved in the interaction with Ribc2 and are necessary for the ciliary beating of multi-cilia.

TRIP13 Participates in Immediate-Early Sensing of DNA Strand Breaks and ATM Signaling Amplification through MRE11.

Thyroid hormone receptor-interacting protein 13 (TRIP13) participates in various regulatory steps related to the cell cycle, such as the mitotic spindle assembly checkpoint and meiotic recombination, possibly by interacting with members of the HORMA domain protein family. Recently, it was reported that TRIP13 could regulate the choice of the DNA repair pathway, i.e., homologous recombination (HR) or nonhomologous end-joining (NHEJ). However, TRIP13 is recruited to DNA damage sites within a few seconds after damage and may therefore have another function in DNA repair other than regulation of the pathway choice. Furthermore, the depletion of TRIP13 inhibited both HR and NHEJ, suggesting that TRIP13 plays other roles besides regulation of choice between HR and NHEJ. To explore the unidentified functions of TRIP13 in the DNA damage response, we investigated its genome-wide interaction partners in the context of DNA damage using quantitative proteomics with proximity labeling. We identified MRE11 as a novel interacting partner of TRIP13. TRIP13 controlled the recruitment of MDC1 to DNA damage sites by regulating the interaction between MDC1 and the MRN complex. Consistently, TRIP13 was involved in ATM signaling amplification. Our study provides new insight into the function of TRIP13 in immediate-early DNA damage sensing and ATM signaling activation.

O-GlcNAcylation regulates dopamine neuron function, survival and degeneration in Parkinson disease.

The dopamine system in the midbrain is essential for volitional movement, action selection, and reward-related learning. Despite its versatile roles, it contains only a small set of neurons in the brainstem. These dopamine neurons are especially susceptible to Parkinson's disease and prematurely degenerate in the course of disease progression, while the discovery of new therapeutic interventions has been disappointingly unsuccessful. Here, we show that O-GlcNAcylation, an essential post-translational modification in various types of cells, is critical for the physiological function and survival of dopamine neurons. Bidirectional modulation of O-GlcNAcylation importantly regulates dopamine neurons at the molecular, synaptic, cellular, and behavioural levels. Remarkably, genetic and pharmacological upregulation of O-GlcNAcylation mitigates neurodegeneration, synaptic impairments, and motor deficits in an animal model of Parkinson's disease. These findings provide insights into the functional importance of O-GlcNAcylation in the dopamine system, which may be utilized to protect dopamine neurons against Parkinson's disease pathology.