Hypertrophic cardiomyopathy (HCM) is an intractable disease that causes heart failure mainly due to unexplained severe cardiac hypertrophy and diastolic dysfunction. HCM, which occurs in 0.2% of the general population, is the most common cause of sudden cardiac death in young people. HCM has been studied extensively using molecular genetic approaches. Genes encoding cardiac β-myosin heavy chain, cardiac myosin-binding protein C, and troponin complex, which were originally identified as causative genes, were subsequently reported to be frequently implicated in HCM. Indeed, HCM has been considered a disease of sarcomere gene mutations. However, fewer than half of patients with HCM have mutations in sarcomere genes. The others have been documented to have mutations in cardiac proteins in various other locations, including the Z disc, sarcoplasmic reticulum, plasma membrane, nucleus, and mitochondria. Next-generation sequencing makes it possible to detect mutations at high throughput, and it has become increasingly common to identify multiple cardiomyopathy-causing gene mutations in a single HCM patient. Elucidating how mutations in different genes contribute to the disease pathophysiology will be a challenge. In studies using animal models, sarcomere mutations generally tend to increase myocardial Ca²⁺ sensitivity, and some mutations increase the activity of myosin ATPase. Clinical trials of drugs to treat HCM are ongoing, and further new therapies based on pathophysiological analyses of the causative genes are eagerly anticipated.

Early detection of cancer is crucial for its ultimate control and the prevention of malignant progression. In Japan, a nationwide project was conducted between 2014 and 2019 to develop novel cancer detection tools using serum microRNAs (miRNAs). Using the National Cancer Center Biobank, we collected more than 10,000 serum samples from patients with malignant diseases, including rare cancers such as ovarian cancer, gliomas, and sarcomas. Subsequently, comprehensive miRNA microarray analyses were performed for all samples. This serum miRNA database provides insights regarding miRNA biomarker candidates for each cancer type. Here, we summarize the major achievements of this national project. Notably, although circulating miRNAs packaged in extracellular vesicles are thought to be a cell-to-cell communication tool, the functional characteristics of the miRNAs listed in the project are still unknown. We hope that our findings will help elucidate the biological functions of circulating miRNAs.

Imidazole antifungal compounds exert their antipathogenic effects through inhibition of sterol biosynthesis. These drugs have also recently been identified as candidate anticancer agents for several solid tumors including glioblastoma. However, their effects on glioma-initiating cells (GICs), i.e., glioma cells with stemlike properties that are able to initiate tumors, remain unclear. Consequently, we examined the effects of the optically active imidazole compound luliconazole on mouse GICs and GIC-based tumors. Luliconazole impaired in a concentration-dependent manner the growth of spheres formed by GICs in vitro. In contrast to the inhibitory effects of ionizing radiation and temozolomide on sphere growth, that of luliconazole was attenuated by the addition of exogenous cholesterol. Exposure to luliconazole of brain slices derived from mice with orthotopic GIC implants for 4 days in culture resulted in a marked increase in the number of tumor cells positive for cleaved caspase-3, but without a similar effect on normal cells. Furthermore, in brain slices, luliconazole inhibited the expansion of GIC-based tumors and the parenchymal infiltration of tumor cells. Our findings therefore indicate that luliconazole effectively targets GICs, thereby providing further support for the antitumorigenic effects of imidazole antifungal compounds.

The recent advent of methods for high-throughput single-cell and spatial profiling have opened the way to complete the 150-year-old endeavor of identifying all cell types in the human body, by their distinctive molecular profiles, and to relate this information to other cellular descriptions, physiological phenotypes, molecular mechanisms and functions. Our effort to build a comprehensive reference map of the molecular state of cells in healthy human tissues is propelling the systematic study of physiological states, developmental trajectories, regulatory circuitry and interactions of cells, provides a framework for understanding cellular dysregulation in human disease, and suggests the possibility of predicting cell types and behaviors, towards a “periodic table of our cells”. In this talk, I describe our foundational work underlying single cell genomics and the conceptual framework and impact of our understanding of cell and tissue biology in health, as well as how we use it to shed light on rare disease, cancer, and COVID-19.

The behavior of biochemical molecules moving around in cells makes me think of a school of whales wandering in the ocean, captured by the Argus system on the artificial satellite. When bringing a whale back into the sea --- with a transmitter on its dorsal fin, every staff member hopes that it will return safely to a school of its species. A transmitter is now minute in size, but it was not this way before. There used to be some concern that a whale fitted with a transmitter could be given the cold shoulder and thus ostracized by other whales for “wearing something annoying.” How is whale’s wandering related to the tide or a shoal of small fish? What kind of interaction is there among different species of whales? We human beings have attempted to fully understand this fellow creature in the sea both during and since the age of whale fishing.

In a live cell imaging experiment, a luminescent probe replaces a transmitter. We put a luminescent probe on a specific region of a biological molecule and bring it back into a cell. We can then visualize how the molecule behaves in response to external stimulation. Since luminescence is a physical phenomenon, we can extract various kinds of information by making full use of its characteristics.

Cruising inside cells in a supermicro corps, gliding down in a microtubule like a roller coaster, pushing our ways through a jungle of chromatin while hoisting a flag of nuclear localization signal --- we are reminded to retain a playful and adventurous perspective at all times. What matters is mobilizing all capabilities of science and giving full play to our imagination. We believe that such serendipitous findings can arise out of such a sportive mind, a frame of mind that prevails when enjoying whale-watching.