京都大学 / 新制・課程博士 / 博士(医学) / 甲第25487号 / 医博第5087号 / 新制||医||1073(附属図書館) / 京都大学大学院医学研究科医学専攻 / (主査)教授 小濱 和貴, 教授 妹尾 浩, 教授 寺田 智祐 / 学位規則第4条第1項該当 / Doctor of Medical Science / Kyoto University / DFAM

Zebrafish thrombocytes exhibit characteristics of human platelets and megakaryocytes, making them valuable for studying megakaryopoiesis and thrombopoiesis. Using single-cell RNA sequencing, we analyzed gene expression in young and mature zebrafish thrombocytes. We identified 394 protein-coding genes unique to young thrombocytes, many corresponding with human orthologs, suggesting shared regulatory mechanisms in zebrafish and humans. We hypothesized knocking down these 394 genes should identify the novel regulatory genes that control thrombocyte maturation. To address this, we used the piggyback knockdown method to knock down these genes to study their biological functions in zebrafish thrombopoiesis. We first found the knockdown of nfe2, nfe2l1a, and nfe2l3 reduced both young and mature thrombocyte counts, confirming their role in thrombopoiesis. A comprehensive knockdown screening of the uniquely expressed genes in young thrombocytes identified 7 candidate genes associated with thrombopoiesis. We selected the spi1b gene for further mutant characterization, which revealed its critical role in young thrombocyte development, with homozygous mutations leading to embryonic lethality. Considering megakaryocyte properties in thrombocytes, we studied the potential for polyploidization in zebrafish thrombocytes. The inhibition of AURKA led to the development of polyploid thrombocytes resembling mammalian megakaryocytes, suggesting the retention of genetic programs for megakaryocyte development in zebrafish thrombocytes and providing insights into the evolutionary basis of thrombopoiesis. Thus, our study reveals critical gene expression patterns and regulatory factors in zebrafish thrombocyte development, offering insights into conserved mechanisms relevant to developmental biology and research in thrombosis and hemostasis disorder.

Apple scab (causal organism: Venturia inaequalis) is an economically devastating disease of apples that is predominantly controlled with fungicides. Of the chemical classes currently available, the sterol-inhibiting (SI) and strobilurin (QoI) fungicides are the most commonly used. Recent observations indicate that V. inaequalis populations in Virginia have developed resistance to myclobutanil and other SIs. However, little is known about the frequency and distribution of SI and QoI resistance in Virginia's scab populations. The first objective of this research was to evaluate V. inaequalis populations in Virginia for SI and QoI resistance. Fungal isolates were collected from experimental orchards at the Alson H. Smith Jr., Agricultural Research and Extension Center (AHS AREC) and from commercial orchards in Virginia and Maryland. Sensitivities were determined by assessing colony growth at 19°C on potato dextrose agar (PDA) amended with 0 or 1.0 µg ml-1 of myclobutanil (SI) (N=87) or trifloxystrobin (QoI) (N=25) at 28 days. A range of fungicide sensitivity was observed for both chemical classes. The second objective of this research was to monitor the temporal dynamics of SI resistance over five sequential field seasons. To monitor shoot growth, neon rubber bands were placed over actively growing shoot tips following myclobutanil application or sample collection. Fungal isolates were collected from the same trees from 2007 through 2010 (N=176) and compared with isolates collected from wild apple seedlings (N=3). A continuum of SI resistance was observed for each year, and the V. inaequalis population exhibited a baseline shifted toward reduced sensitivity. The third objective of this research was to examine the spatial distribution of SI fungicide resistance within the tree canopy in a lower-density orchard (less than 150 trees A-1). Leaves collected from larger trees (>8m) in a lower-density orchard at the AHS AREC were analyzed for manganese deposition, pre- and post-mancozeb application. Fungal isolates (N=105) were collected from several locations within the canopy in replicated trees in the same orchard. Weather sensors also monitored the microclimates within those tree canopies. Spray deposition, microclimate and SI resistance were influenced by canopy location. The fourth objective of this research was to investigate potential SI resistance mechanisms. Previously classified isolates were screened for point mutations within the CYP51A1 gene (Appendix C), differences in polymorphic bands (alleles) (Appendix D), and differences in metabolism of myclobutanil (Appendix E). The consensus sequences for the CYP51A1 gene were identical for all isolates tested (N=9), and results from amplified fragment length polymorphism experiment (N=82) were inconclusive. There were, however, significant differences among incubation time and myclobutanil concentration in the bioassay (N=11). Our results indicate that myclobutanil is still an effective compound for control of apple scab in many areas of Virginia. / Ph. D.

Eukaryotic organisms require the ability to respond to their environments. They do so by utilizing signal transduction pathways that allow for signals to effect final biological responses. Many times, these final responses require new gene expression events that have been stimulated or repressed within the nucleus. Thus, much of the understanding of signal transduction pathways converges on the understanding of how signaling affects gene expression alterations (Kumar et al., 2004). The regulation of gene expression involves the modification of chromatin between condensed (closed, silent) and expanded (open, active) states. Histone modifications, such as acetylation, can determine the open versus closed status of chromatin. The PHD (Plant HomeoDomain) finger is a structural domain primarily found in nuclear proteins across eukaryotes. This domain specifically recognizes the epigenetic marks H3K4me2 and H3K4me3, which are di- and tri-methylated lysine 4 residues of Histone H3 (Loewith et al., 2000; Kuzmichev et al., 2002; Vieyra et al. 2002; Shiseki et al., 2003; Pedeux et al., 2005, Doyon et al., 2006). It is estimated that there are ~150 proteins that contain the PHD finger in humans (Solimon and Riabowol, 2007). The PHD finger is conserved in yeast and plants, however an analysis of this domain has only been performed done in Arabidopsis thaliana (Lee et al., 2009). The work presented in this report aims to extend the analysis of this domain in plants by identifying the PHD fingers of the crop species Oryza sativa (rice). In addition, a phylogenetic analysis of all PHD fingers in Arabidopsis and rice was undertaken. From these analyses, it was determined that there are 78 PHD fingers in Arabidopsis and 70 in rice. In addition, these domains can be categorized into classes and groups by defining features within the conserved motif. In a separate study, I investigated the function of two of the PHD finger proteins from Arabidopsis, ING1 (INhibitor of Growth1) and ING2. In humans, these proteins can be found in complexes associated with both open and closed chromatin. They facilitate chromatin remodeling by recruiting histone acetyltransferases and histone deacetylases to chromatin (Doyon et al., 2006, Pena et al., 2006). In addition, these proteins recognize H3K4me2/3 marks and are believed to be "interpreters" of the histone code (Pena et al., 2006, Shi et al., 2006). To understand the function of ING proteins in plants, I took a reverse genetics approach and characterized ing1 and ing2 mutants. My analysis revealed that these mutants are altered in time of flowering, as well as their response to nutrient and stress conditions. Lastly, I was able to show that ING2 protein interacts in vitro with SnRK1.1, a nutrient/stress sensor (Baena-Gonzalez et al., 2007). These results indicate a novel function for PHD proteins in plant growth, development and stress response. / Master of Science

Three epoxy-coated reinforcing steel (ECR) types removed from job sites, one shipped directly from the coater's plant, three commercial corrosion inhibitors, and one ECR plus a corrosion inhibitor were evaluated as reinforcing steel corrosion protection systems against chloride induced corrosion. The three corrosion inhibitors were calcium nitrite, an aqueous mixture of esters and amines, and a mixture of alcohol and amine. The ECR was tested in two groups, 0% and 1% coating damage. Corrosion protection performance was evaluated by the amount of visually observed blister surface area, for the ECR, and corroded surface area, for the tested corrosion inhibitors. Results of the ECR testing demonstrated that coating debondment and corrosion of ECR is directly related to the amount of damage present in the coating, as well as coating thickness. For the bare steel tested with and without corrosion inhibitors, the results showed that corrosion increases with increasing chloride concentrations. Corrosion inhibition characteristics were demonstrated only by the calcium nitrite corrosion inhibitor. A corrosion protection evaluation test was developed for concrete corrosion inhibitor admixtures. The test solution is a simulated concrete pore water. Corrosion is accelerated by evaluating the temperature to field conditions of 40 C. The test consists of a 7 day pretreatment period followed by a 90 day test period. The corrosive sodium chloride is added to the solution containing the bare or epoxy-coated reinforcing steel specimens after the 7 day pretreatment period. In addition, the solution is periodically saturated with oxygen. / Master of Science

<p dir="ltr">Cancer is the second leading cause of death worldwide, and there is a continued need for effective treatments to combat the disease. A key challenge in cancer therapy persists in the form of therapeutic resistance. While kinase inhibitors (KIs) have shown promise in treating cancer patients with dysregulated protein kinases, treatment failures are common, highlighting the urgent need to address this issue. Despite the approval of 80 protein kinase inhibitors by the United States Food and Drug Administration (FDA), and numerous others in clinical trials, the chemical space explored for protein kinase inhibitors remains limited. Most FDA-approved kinase inhibitors share common core moieties, such as indazole, quinoline, pyrazole, and pyrimidine, indicating a lack of diversification in drug development in this area.</p><p dir="ltr">Efforts to expand the chemical space have led to the identification of a novel 3<i>H</i>-pyrazolo-[4,3-<i>f</i>]quinoline core by the Sintim group. This scaffold can be efficiently synthesized through the Doebner–Povarov multicomponent reaction using readily available ketones, heteroaromatic aldehydes, and 5-aminoindazole. This multicomponent chemistry affords small molecules which inhibit disease-associated protein kinases with sub-nanomolar IC₅₀ values. Additionally, the scaffold presents a unique opportunity to tune for selectivity via judicious substitution patterns, allowing us to target numerous disease-driving kinases, such as FLT3, haspin, and CLK, with the use of simple multi-component chemistry.</p><p dir="ltr">From this work emerged lead amide-containing compound HSK205, which potently inhibits FLT3 and haspin and shows impressive potencies against FLT3-driven acute myeloid leukemia cell lines, with GI₅₀ values between 2 and 20 nM. Western blot analyses indicate that HSK205 inhibits the phosphorylation of FLT3 and histone H3 (substrate of haspin) in Molm-14 AML cells. Further exploration led to the discovery of lead CLK inhibitors, such as HSK1132 and HSK3110, which inhibit the growth of multiple myeloma cell lines <i>in vitro</i> with GI₅₀ values as low as 17 nM. Additionally, these compounds are orally bioavailable and reduce the growth of multiple myeloma RPMI-8226 xenograft model in mice by 69%.</p>

NK/T-cell lymphoma (NKTCL) and T-cell non-Hodgkin lymphomas ( T-NHL) are highly aggressive lymphomas that lack rationally designed therapies and rely on repurposed chemotherapeutics from other hematological cancers. Histone deacetylases (HDACs) have been targeted in a range of malignancies, including T-cell lymphomas. This study represents exploratory findings of HDAC6 inhibition in NKTCL and T-NHL through a second-generation inhibitor NN-429. With nanomolar in vitro HDAC6 potency and high in vitro and in cellulo selectivity for HDAC6, NN-429 also exhibited long residence time and improved pharmacokinetic properties in contrast to older generation inhibitors. Following unique selective cytotoxicity towards T-NHL and NKTCL, NN-429 demonstrated a synergistic relationship with the clinical agent etoposide and potential synergies with doxorubicin, cytarabine, and SNS-032 in these disease models, opening an avenue for combination treatment strategies.

Brain metastases (BMs) present a formidable obstacle across various primary cancer types, notably small cell lung cancer (SCLC), non-small cell lung cancer (NSCLC), melanomas, and breast cancers. In this investigation, we aim to evaluate the potential of genotype-guided targeted therapy while addressing the challenges of co-existing genomic alterations frequently encountered in BMs. This research explores the efficacy of adagrasib (MRTX849), a KRAS G12C inhibitor, and abemaciclib, a CDK 4/6 inhibitor, both individually and in combination against BMs originating from NSCLC cell lines harboring KRAS G12C and CDKN2A mutations. Utilizing a diverse array of methodologies encompassing cell viability assays, cell death assays, western blot analyses, and in vivo xenograft models, we elucidate both the therapeutic potential and underlying mechanisms. Distinct responses to adagrasib and abemaciclib monotherapies were observed across two different cell lines, underscoring the necessity for tailored treatment strategies. While adagrasib exhibited variable efficacy, abemaciclib consistently inhibited CDK 4/6 activity. Notably, the combination therapy demonstrated synergistic effects, suggesting a promising approach for enhanced therapeutic outcomes. Our findings from both in vitro assays and western blot analyses corroborate targeted pathway inhibition, although the observed pathway reactivation underscores the importance of optimizing dosing strategies. In vivo studies further support our in vitro findings, demonstrating efficacy but also raising concerns regarding toxicity with combination therapy. Pharmacokinetic / pharmacodynamic (PK/PD) analyses underscore potential advantages of combination therapy in terms of systemic exposure and brain penetration. Despite histological evidence of therapeutic effects, discrepancies between in vivo and in vitro caspase-dependent apoptosis results highlight the complexity of tumor biology and the challenges of translation. By Focusing on personalized treatment approaches and addressing therapeutic hurdles, this work establishes the foundation for clinical investigation in advancing the management of BMs and improving treatment outcomes in NSCLC patients.

Malaria, a disease caused by members of the Plasmodium genus, remains a threat to global health. Despite the availability of therapeutics, Plasmodium's propensity for generating resistance-conferring mutations threatens the efficacy of these drugs. Therefore, it is essential to develop novel therapeutics, and one approach to discover such compounds is to repurpose current drugs as antimalarials. Human kinase inhibitors, most of which are developed as antineoplastics, are a valuable source of such novel compounds. Human kinase inhibitor research spans over twenty years, generating a wellspring of knowledge regarding compound design, mechanism, and tolerability that can be leveraged in the quest to develop new antiplasmodial drugs. Furthermore, the plasmodial kinome differs substantially from the human kinome, providing opportunities for selectivity and minimization of off-target effects in the host. To this end, we sought to identify and characterize compounds within human kinase inhibitor collections that have antiplasmodial effects. One library yielded a potent polo-like kinase 1 (PLK1) kinase inhibitor, BI-2536, which possessed potent antiplasmodial activity in both the asexual blood stage and liver stage and likely acts through involvement of amino acid starvation. Another library comprised exclusively of type II kinase inhibitors, designed to target kinases in the inactive conformation, produced several interesting lead compounds – TL5-135, YLIU-06-026-1, and the analog pair XMD13-99 and WZ9-034-2. These compounds were highly active against asexual blood stage parasites, killing rapidly while also possessing favorable selectivity and liver stage activity. In vivo, TL5-135 and YLIU-06-026-1 acted prophylactically by preventing infection, and therapeutically by resolving an established infection. Currently, investigations are underway to determine the mechanism of action of the lead compounds and to improve their druglike properties. In whole, this effort has not only yielded promising antiplasmodial compounds, but it also underscores the value of the repurposing approach in the quest for novel antimalarial drugs.

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