Yutaka Takaoka

Transthyretin amyloidosis is caused by destabilization, dissociation, and tissue deposition of transthyretin (TTR). Although several transgenic and knock-in mouse models have been generated, many models are limited by nonphysiological copy number, low expression, or the formation of hybrid tetramers between mouse and human TTR. We previously generated TTR exon-humanized mice in which mouse Ttr exons were replaced with corresponding human TTR exons while preserving the mouse genomic structure. In the present study, we introduced the Val30Met mutation into the TTR exon-humanized allele and generated three genotypes: TtrhTTRV30e/hTTRV30e, TtrhTTRM30e/hTTRM30e, and TtrhTTRV30e/hTTRM30e mice. We examined non-fibrillar human TTR deposition by immunohistochemistry in ileum, kidney, and sciatic nerve at 26 and 52 weeks of age, using a semi-quantitative scoring system. Genotype-dependent TTR deposition was observed in multiple tissues. TTR deposition was prominent in V30/V30 and V30/M30 mice, whereas M30/M30 mice consistently showed lower deposition scores. Notably, TTR-positive deposits were detected in the sciatic nerve at 52 weeks of age. Direct fast scarlet staining did not detect amyloid fibrils, indicating that the observed deposits represented non-fibrillar or pre-amyloid TTR deposition. Serum human TTR levels showed modest genotype-dependent differences, whereas serum mouse RBP4 levels differed markedly among genotypes. Supportive computer simulation analysis suggested that the predicted binding stability between mouse RBP4 and TTR was highest for mouse TTR, intermediate for human TTR Met30, and lowest for human TTR Val30. These findings indicate that TTR exon-humanized mice provide a useful model for evaluating genotype-dependent TTR deposition and support the possibility that RBP4 functions as a natural stabilizer of circulating TTR.

Dystrophinopathy is caused by alterations in the dystrophin gene. The severe phenotype, Duchenne muscular dystrophy (DMD), is caused by a lack of dystrophin in skeletal muscles, resulting in necrosis and regenerating fibers, inflammatory cells, and muscle fibrosis. Progressive muscle weakness is a characteristic finding of this condition. Here, we encountered a rare case of a 10‐year‐old patient with asymptomatic dystrophinopathy with no dystrophin expression and investigated the reason for the absence of muscle weakness to obtain therapeutic insights for DMD. Using RNA‐seq analysis, gene expression in skeletal muscles was compared among patients with asymptomatic dystrophinopathy, three patients with typical DMD, and two patients without dystrophinopathy who were leading normal daily lives. Cathepsin K (CTSK), myosin heavy chain 3 (MYH3), and nodal modulator 3‐like genes exhibited a >8‐fold change, whereas crystallin mu gene (CRYM) showed a 16‐fold change (P < 0.01), whereas CRYM expression showed a P < 0.01) in patients with typical DMD compared with their expression in those without dystrophinopathy. CTSK plays an essential role in skeletal muscle loss, fibrosis, and inflammation in response to muscles injected with cardiotoxin, one of the most common reagents that induce muscle injury. Increased CTSK expression is associated with muscle injury or necrosis in patients with DMD. The lack of muscle weakness in the patient with asymptomatic dystrophinopathy might be attributed to the low CTSK expression in the muscles. To the best of our knowledge, this is the first report to demonstrate that CTSK expression was significantly higher in the skeletal muscles of patients with DMD with a typical phenotype than in those without dystrophinopathy.

Aldosterone-producing adenomas (APAs) are the commonest curable cause of hypertension. Most have gain-of-function somatic mutations of ion channels or transporters. Herein we report the discovery, replication and phenotype of mutations in the neuronal cell adhesion gene CADM1. Independent whole exome sequencing of 40 and 81 APAs found intramembranous p.Val380Asp or p.Gly379Asp variants in two patients whose hypertension and periodic primary aldosteronism were cured by adrenalectomy. Replication identified two more APAs with each variant (total, n = 6). The most upregulated gene (10- to 25-fold) in human adrenocortical H295R cells transduced with the mutations (compared to wildtype) was CYP11B2 (aldosterone synthase), and biological rhythms were the most differentially expressed process. CADM1 knockdown or mutation inhibited gap junction (GJ)-permeable dye transfer. GJ blockade by Gap27 increased CYP11B2 similarly to CADM1 mutation. Human adrenal zona glomerulosa (ZG) expression of GJA1 (the main GJ protein) was patchy, and annular GJs (sequelae of GJ communication) were less prominent in CYP11B2-positive micronodules than adjacent ZG. Somatic mutations of CADM1 cause reversible hypertension and reveal a role for GJ communication in suppressing physiological aldosterone production.

In this research, we aimed to predict the relative risk of the recent new variants of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) on the basis of our previous research. We first performed molecular docking simulation analyses of the spike proteins with human angiotensin-converting enzyme 2 (ACE2) to determine the binding affinities to human cells of three new variants of SARS-CoV-2: Omicron BQ.1, XBB, and XBB.1.5 We then investigated the three variants to discover the evolutionary distance of the spike protein gene (S gene) from the Wuhan, Omicron BA.1, and Omicron BA.4/5 variants, to understand the changes in the S gene. The results indicated that the XBB.1.5 variant had the highest binding affinity of the spike protein with ACE2 and the longest evolutionary distance of the S gene. This in silico evidence suggested that the XBB.1.5 variant may produce infections that spread more widely and faster than can infections of preexisting variants.

Previously, we developed a mathematical model via molecular simulation analysis to predict the infectivity of six SARS-CoV-2 variants. In this report, we aimed to predict the relative risk of the recent new variants of SARS-CoV-2 based on our previous research. We subjected Omicron BA.4/5 and BA.2.75 variants of SARS-CoV-2 to the analysis to determine the evolutionary distance of the spike protein gene (S gene) of the variants from the Wuhan variant so as to appreciate the changes in the spike protein. We performed molecular docking simulation analyses of the spike proteins with human angiotensin-converting enzyme 2 (ACE2) to understand the docking affinities of these variants. We then compared the evolutionary distances and the docking affinities of these variants with those of the variants that we had analyzed in our previous research. As a result, BA.2.75 has both the highest docking affinity (ratio per Wuhan variant) and the longest evolutionary distance of the S gene from the Wuhan variant. These results suggest that BA.2.75 infection can spread farther than can infections of preexisting variants.

Objectives In our previous research, we have reported mathematical model with molecular simulation analysis to predict the infectivity of seven SARS-CoV-2 variants. In this report, we aimed to predict the relative risk of the recent new variants of SARS-CoV-2 based on our previous research. Methods We subjected Omicron BA.4/5 or BA.2.75 variant of SARS-CoV-2 to the analysis for the evolutionary distance of the spike protein gene (S gene) to appreciate the changes of the spike protein. We performed the molecular docking simulation analyses of the spike protein with human angiotensin-converting enzyme 2 (ACE2) to understand the docking affinity in these variants. We then compared the evolutionary distance and the docking affinity of these variants with that of the seven variants which were analyzed in our previous research. Results The evolutionary distance of the S gene in BA.4/5 or BA.2.75 from the Wuhan variant were longer than the other variants. The highest docking affinity of the spike protein with ACE2 (ratio per Wuhan variant) was observed in BA.2.75. Conclusion It is important to note that BA.2.75 has both the highest docking affinity and the longest evolutionary distance of the S gene. These results suggest that the infection of BA.2.75 can be spread further than preexisting variants.

Variants of a coronavirus (SARS-CoV-2) have been spreading in a global pandemic. Improved understanding of the infectivity of future new variants is important so that effective countermeasures against them can be quickly undertaken. In our research reported here, we aimed to predict the infectivity of SARS-CoV-2 by using a mathematical model with molecular simulation analysis, and we used phylogenetic analysis to determine the evolutionary distance of the spike protein gene (S gene) of SARS-CoV-2. We subjected the six variants and the wild type of spike protein and human angiotensin-converting enzyme 2 (ACE2) to molecular docking simulation analyses to understand the binding affinity of spike protein and ACE2. We then utilized regression analysis of the correlation coefficient of the mathematical model and the infectivity of SARS-CoV-2 to predict infectivity. The evolutionary distance of the S gene correlated with the infectivity of SARS-CoV-2 variants. The coefficient of the mathematical model obtained with results of molecular docking simulation also correlated with the infectivity of SARS-CoV-2 variants. These results suggest that the data from the docking simulation for the receptor binding domain of variant spike proteins and human ACE2 were valuable for prediction of SARS-CoV-2 infectivity. In addition, we developed a mathematical model for prediction of SARS-CoV-2 variant infectivity by using binding affinity obtained via molecular docking and the evolutionary distance of the S gene.

Xeroderma pigmentosum complementation group D (XPD) is a UV-sensitive syndrome and a rare incurable genetic disease which is caused by the genetic mutation of the excision repair cross-complementation group 2 gene (ERCC2). Patients who harbor only XPD R683W mutant protein develop severe photosensitivity and progressive neurological symptoms. Cultured cells derived from patients with XPD (XPD R683W cells) demonstrate a reduced nucleotide excision repair (NER) ability. We hope to ameliorate clinical symptoms if we can identify candidate agents that would aid recovery of the cells’ NER ability. To investigate such candidates, we created in silico methods of drug repurposing (in silico DR), a strategy that utilizes the recovery of ATP-binding in the XPD R683W protein after the induced fit. We chose 4E1RCat and aprepitant as the candidates for our in silico DR, and evaluated them by using the UV-induced unscheduled DNA synthesis (UDS) assay to verify the recovery of NER in XPD R683W cells. UDS values of the cells improved about 1.4–1.7 times after 4E1RCat treatment compared with solvent-only controls; aprepitant showed no positive effect. In this study, therefore, we succeeded in finding the candidate agent 4E1RCat for XPD R683W. We also demonstrated that our in silico DR method is a cost-effective approach for drug candidate discovery.