Shin-Ichi Horike

Hypophosphatasia (HPP) is a rare inherited disorder caused by inactivating variants in the ALPL gene, resulting in defective mineralization of bone and teeth. Dental manifestations include early exfoliation of fully rooted primary teeth as a result of cementum dysplasia, premature loss of permanent teeth, and hypomineralization of enamel, dentin, and jawbone. However, genotype-dependent dental phenotypes and severity-based treatment strategies remain poorly defined. The aim of this study was to generate knock-in mouse models harboring clinically relevant ALPL variants and to characterize their dental and periodontal phenotypes in relation to serum tissue-nonspecific alkaline phosphatase (TNAP) activity. We analyzed mice that were compound heterozygous for a null variant and a hypomorphic variant (Alplc.1559delT/p.F327L) and mice that were heterozygous for a dominant-negative variant (Alpl+/p.R184W). Dental and alveolar phenotypes were assessed using micro-CT, histological analyses, and periodontal ligament traction experiments. Alplc.1559delT/p.F327L mice exhibited reduced serum TNAP levels, mild skeletal abnormalities, and severe dental defects, including hypomineralization of enamel, dentin, and cementum, decreased alveolar BMD, and an increased distance from the cemento–enamel junction to the alveolar bone crest. In contrast, Alpl+/p.R184W mice showed isolated dental abnormalities characterized by dentin and cementum hypomineralization and decreased alveolar bone BMD without overt skeletal involvement. Periodontal tissue fragility was increased in both models. These knock-in mouse models recapitulate genotype-dependent dental manifestations of HPP and indicate that dental phenotypes are influenced not only by circulating TNAP levels but also by the functional effects of individual ALPL variants. This platform provides a valuable framework for elucidating the mechanisms underlying genotype-dependent dental manifestations and for developing dental treatment strategies tailored to disease severity.

Although it was proposed that cell fusion of cancer cells with leukocytes creates mobile hybrids with a metastatic phenotype, it has been difficult to genetically confirm cell fusion events in human cancer in vivo. Here, we experienced 4 cases of placental site trophoblastic tumor (PSTT) that produced immunoglobulin (Ig). Three cases showed recurrence and responded well to pembrolizumab therapy. Among them, we could analyze temporal changes in the genetic profiles on one case of daughter‐derived PSTT, which relapsed after pembrolizumab therapy. In this case, we found that PSTT incorporated the exogenous genes from host maternal cells. The rearrangement patterns of Ig genes and protein expressions sequentially increased. By analyzing single‐nucleotide variants, PSTT incorporated daughter‐non‐inherited maternal alleles (DNIMA), including the Ig lambda and HLA‐DQA2 loci. Protein expressions of TLR10 and SIGLEC10 increased during tumor progression concomitantly with DNIMA incorporation. DNIMA mapping indicates the incorporation of exogenous maternal genes was widely distributed through the whole chromosomes, suggesting the involvement of cell fusion in gene transfer mechanisms. These findings indicate that PSTT sequentially incorporated exogenous genes from maternal cells to express immune‐related molecules and suggest that cancer cells acquired B cell‐related functions, including Ig production by cell fusion with host immune cells.

Autism spectrum disorder (ASD) is a common neurodevelopmental condition characterized by behavioral abnormalities. Although mouse models have been widely adopted to recapitulate the pathology of ASD, the identification of specific neural abnormalities responsible for autistic-like behavior has remained challenging. Here we provide insight into this causal relation by identifying the critical period and cell type responsible for the development of such behavior in ASD model mice with a Chd8 mutation. We find that Chd8 mutation induced at embryonic day 14.5 gives rise to ASD-like behavioral phenotypes, including abnormal social interaction and increased anxiety-like behavior, as well as to accelerated cell-cycle exit and differentiation in ventral progenitor cells. Restoration of Chd8 expression in ventral progenitor cells ameliorates both the behavioral phenotypes and aberrant ventral differentiation in Chd8 mutant mice. Our findings indicate that Chd8 mutation during the midfetal period—in particular, in ventral progenitor cells—contributes to the development of autistic-like behavior.

The vagus nerve connects the brain and pancreas and enhances postprandial endocrine secretion from the pancreas through cholinergic signaling, such as increasing insulin release immediately after food intake in the cephalic-phase insulin response (CPIR). Here, we investigated how obesity affects vagal regulation of pancreatic endocrine function using designer receptors exclusively activated by designer drugs (DREADDs) to manipulate vagal activity. As expected, the plasma concentration of insulin was increased by vagal activation in mice expressing the excitatory DREADD hM3Dq (M3 mice) and decreased by vagal inactivation in mice expressing inhibitory DREADD hM4Di (M4 mice). However, vagal activation in M3 mice with diet-induced obesity did not elicit an early increase in insulin and instead produced a delayed insulin decrease. Mathematical modeling showed that plasma insulin dynamics in these mice were best explained by a model incorporating both the insulin-increasing and insulin-decreasing effects of the vagus nerve. Furthermore, the insulin-decreasing effect was mediated by nitric oxide (NO)–dependent, noncholinergic signaling and was enhanced in obesity. In obese M3 mice, vagal deficiency of neuronal NO synthase (nNOS) abolished the insulin-decreasing effect and restored insulin release after vagal activation. Vagal nNOS deficiency also enhanced insulin release after voluntary feeding, consistent with the CPIR. These findings suggest that vagal NO action inhibits postprandial insulin release, particularly in obesity.

Loss of Kif26b function causes renal agenesis or hypoplasia in mice, and a KIF26B mutation resulting in deletion of the C‐terminal region has been identified in a human patient with a congenital kidney disorder. However, the role of this region during kidney development is unclear; thus, to investigate this, we generated mice lacking the C‐terminal region of KIF26B (Kif26b‐C) using CRISPR/Cas9. Homozygous Kif26b‐C mice showed bilateral renal agenesis, resembling Kif26b knockout mice. Histological analysis revealed loss of the nephrogenic zone and impaired nephron progenitor condensation at embryonic day 18.5. In situ hybridization showed reduced Gdnf in the metanephric mesenchyme and reduced Wnt11 in ureteric buds, indicating disruption of the Gdnf‐Wnt11 signaling loop. These findings suggest a key role for the KIF26B C‐terminal region in kidney morphogenesis.

Zwitterions, which have low cytotoxicity among ionic liquids, are expected to be adopted in various applications across life sciences. We previously reported that zwitterions can be used as cryoprotectants, and that zwitterion/dimethyl sulfoxide (DMSO) aqueous solutions have high cryoprotective effects. Although cryopreservation of established cell lines has been performed using zwitterions, this method has not yet been applied to primary or stem cells. In this study, we verified whether primary haematopoietic stem cells (HSCs) could be efficiently cryopreserved using the zwitterion/DMSO aqueous solutions. The viable number of HSCs cryopreserved using zwitterion/DMSO/water (5/5/90, w/w/w) was comparable with that using LaboBanker™, a commercial freezing medium. The number was also higher than those after cryopreservation with DMSO/albumin solution/0.9% sodium chloride solution (10/20/70, v/v/v), which is commonly used in cryopreservation of HSCs. This suggests that the zwitterion/DMSO aqueous solution can be used for cryopreservation of HSCs. This article is part of the discussion meeting issue ‘Ionic liquids and the future of soft materials’.

Genomic imprinting is a parent‐of‐origin‐dependent epigenetic mechanism with established roles in placental development and fetal growth in mice, whereas its contribution to brain function and evolution remains incompletely understood. Here, we investigated parent‐of‐origin‐biased gene expression in the ferret, a gyrencephalic mammal whose cortical architecture more closely resembles that of humans than mice. Guided by human imprinting datasets, we screened 65 candidate genes in the ferret brain and identified paternal allele‐biased expression of Adam23 , maternal bias of Atp10a , and biallelic expression of genes including Pxdc1 , Wrb , and Ube3a . Adam23 showed paternal bias in the ferret cortex, most prominently in the occipital region, whereas it was biallelically expressed in mouse brain. In human SH‐SY5Y cells, ADAM23 was biallelically expressed in undifferentiated cells but shifted toward allele‐specific bias upon neuronal differentiation. Analysis of CpG islands upstream of Adam23 revealed no detectable promoter methylation, suggesting that canonical promoter methylation does not underlie this bias. Functional perturbation in Neuro‐2aTG cells showed that reduced Adam23 expression enhanced neurite outgrowth, whereas increased dosage promoted cell proliferation. Together, these findings identify Adam23 as a gene with species‐ and context‐dependent parent‐of‐origin expression bias and dosage‐sensitive cellular effects, linking imprinting‐related regulation to neural developmental processes in gyrencephalic brains.

Genomic imprinting is a parent-of-origin–specific epigenetic mechanism with essential roles in placental development and fetal growth in mice, but its contribution to brain function and evolution remains unclear. Here, we investigated genomic imprinting in the ferret, a gyrencephalic mammal whose cortical architecture closely resembles that of humans rather than mice. Guided by human imprinting datasets, we screened 65 candidate genes in ferret brain and identified paternal expression of Adam23 , maternal expression of Atp10a , and biallelic expression of genes including Pxdc1 , Wrb and Ube3a . Adam23 showed paternal expression in ferret cortex, particularly in the occipital region, whereas it was biallelically expressed in mouse brain. In human SH-SY5Y cells, ADAM23 was biallelic in undifferentiated cells but shifted toward monoallelic expression upon neuronal differentiation. CpG analysis of upstream islands indicated that Adam23 imprinting in ferrets is independent of promoter methylation, suggesting a non-canonical mechanism. Functional assays in Neuro-2aTG cells showed that Adam23 knockdown enhances neurite outgrowth, whereas overexpression promotes cell proliferation. These findings identify Adam23 as a non-canonical imprinted gene whose dosage influences stem cell dynamics and neurite development, linking imprinting to the evolution of gyrencephalic cortical structures and highlighting the ferret as a valuable model for imprinting studies in higher-order brain function.