Inflammasome Activation Triggers Blood Clotting and Host Death through Pyroptosis.

Inflammasome activation and subsequent pyroptosis are critical defense mechanisms against microbes. However, overactivation of inflammasome leads to death of the host. Although recent studies have uncovered the mechanism of pyroptosis following inflammasome activation, how pyroptotic cell death drives pathogenesis, eventually leading to death of the host, is unknown. Here, we identified inflammasome activation as a trigger for blood clotting through pyroptosis. We have shown that canonical inflammasome activation by the conserved type III secretion system (T3SS) rod proteins from Gram-negative bacteria or noncanonical inflammasome activation by lipopolysaccharide (LPS) induced systemic blood clotting and massive thrombosis in tissues. Following inflammasome activation, pyroptotic macrophages released tissue factor (TF), an essential initiator of coagulation cascades. Genetic or pharmacological inhibition of TF abolishes inflammasome-mediated blood clotting and protects against death. Our data reveal that blood clotting is the major cause of host death following inflammasome activation and demonstrate that inflammasome bridges inflammation with thrombosis.

Inference of selective forces on house mouse genomes during secondary contact in East Asia.

The house mouse (Mus musculus), which is commensal to humans, has spread globally via human activities, leading to secondary contact between genetically divergent subspecies. This pattern of genetic admixture can provide insights into the selective forces at play in this well-studied model organism. Our analysis of 163 house mouse genomes, with a particular focus on East Asia, revealed substantial admixture between the subspecies castaneus and musculus, particularly in Japan and southern China. We revealed, despite the different level of autosomal admixture among regions, that all Y Chromosomes in the East Asian samples belonged to the musculus-type haplogroup, potentially explained by genomic conflict under sex-ratio distortion owing to varying copy numbers of ampliconic genes on sex chromosomes, Slx and Sly Our computer simulations, designed to replicate the observed scenario, show that the preferential fixation of musculus-type Y Chromosomes can be achieved with a slight increase in the male-to-female birth ratio. We also investigated the influence of selection on the posthybridization of the subspecies castaneus and musculus in Japan. Even though the genetic background of most Japanese samples closely resembles the subspecies musculus, certain genomic regions overrepresented the castaneus-like genetic components, particularly in immune-related genes. Furthermore, a large genomic block (∼2 Mbp) containing a vomeronasal/olfactory receptor gene cluster predominantly harbored castaneus-type haplotypes in the Japanese samples, highlighting the crucial role of olfaction-based recognition in shaping hybrid genomes.

Ribosome-mediated specificity in Hox mRNA translation and vertebrate tissue patterning.

Historically, the ribosome has been viewed as a complex ribozyme with constitutive rather than regulatory capacity in mRNA translation. Here we identify mutations of the Ribosomal Protein L38 (Rpl38) gene in mice exhibiting surprising tissue-specific patterning defects, including pronounced homeotic transformations of the axial skeleton. In Rpl38 mutant embryos, global protein synthesis is unchanged; however the translation of a select subset of Homeobox mRNAs is perturbed. Our data reveal that RPL38 facilitates 80S complex formation on these mRNAs as a regulatory component of the ribosome to confer transcript-specific translational control. We further show that Rpl38 expression is markedly enriched in regions of the embryo where loss-of-function phenotypes occur. Unexpectedly, a ribosomal protein (RP) expression screen reveals dynamic regulation of individual RPs within the vertebrate embryo. Collectively, these findings suggest that RP activity may be highly regulated to impart a new layer of specificity in the control of gene expression and mammalian development.

The 36th International Mammalian Genome Conference: A scientific gathering under the cherry blossoms in Tsukuba.

The 36th International Mammalian Genome Conference (IMGC) was held in a hybrid format at the Tsukuba International Congress Center in Tsukuba, Ibaraki, Japan, for 4 days from March 28 to 31, 2023. This international conference on functional genomics of mouse, human, and other mammalian species attracted 246 participants in total, of which 129 were from outside Japan, including Europe, the United States and Asia, and 117 participants were from Japan. The conference included three technical workshops, keynote lectures by domestic researchers, commemorative lectures for the conference awards, 57 oral presentations, and 97 poster presentations. The event was a great success. Topics included the establishment and analysis of disease models using genetically engineered or spontaneous mutant mice, systems genetic analysis using mouse strains such as wild-derived mice and recombinant inbred mouse strains, infectious diseases, immunology, and epigenetics. In addition, as a joint program, a two-day RIKEN Symposium was held, and active discussions continued over the four-day period. Also, there was a trainee symposium, in which young researchers were encouraged to participate, and excellent papers were selected as oral presentations in the main session.

Gasdermin D represses inflammation-induced colon cancer development by regulating apoptosis.

Chronic inflammation is widely recognized as a major risk factor for cancer formation, but the underlying mechanisms are poorly understood. Recently, it was shown that Gasdermin D (GSDMD) protein drives pyroptotic cell death in macrophages on cleavage by inflammatory caspases. Even though the Gsdmd gene is specifically expressed in the intestinal epithelium, the role of Gsdmd in the intestinal tissues remains poorly characterized. In this study, we examined the biological role of Gsdmd in colorectal cancer (CRC) development, employing an azoxymethane/dextran sulfate sodium carcinogenesis model. Results show that GSDMD deficiency enhances CRC development, probably due to decreased apoptosis caused by downregulation of interferon-gamma (IFNγ)-signal transducer and activator 1 (STAT1) signaling. Furthermore, we show that GSDMD protein is diminished in human colorectal cancer, indicating involvement of GSDMD in repression of CRC development in humans. Our findings provide a new insight into functions of Gsdmd/GSDMD in colonic inflammation and human CRC development.

Autoimmune disorders associated with gain of function of the intracellular sensor MDA5.

MDA5 is an essential intracellular sensor for several viruses, including picornaviruses, and elicits antiviral interferon (IFN) responses by recognizing viral dsRNAs. MDA5 has been implicated in autoimmunity. However, the mechanisms of how MDA5 contributes to autoimmunity remain unclear. Here we provide direct evidence that dysregulation of MDA5 caused autoimmune disorders. We established a mutant mouse line bearing MDA5 mutation by ENU mutagenesis, which spontaneously developed lupus-like autoimmune symptoms without viral infection. Inflammation was dependent on an adaptor molecule, MAVS indicating the importance of MDA5-signaling. In addition, intercrossing the mutant mice with type I IFN receptor-deficient mice ameliorated clinical manifestations. This MDA5 mutant could activate signaling in the absence of its ligand but was paradoxically defective for ligand- and virus-induced signaling, suggesting that the mutation induces a conformational change in MDA5. These findings provide insight into the association between disorders of the innate immune system and autoimmunity.

Temporospatial sonic hedgehog signalling is essential for neural crest-dependent patterning of the intrinsic tongue musculature.

The tongue is a highly specialised muscular organ with a complex anatomy required for normal function. We have utilised multiple genetic approaches to investigate local temporospatial requirements for sonic hedgehog (SHH) signalling during tongue development. Mice lacking a Shh cis-enhancer, MFCS4 (ShhMFCS4/-), with reduced SHH in dorsal tongue epithelium have perturbed lingual septum tendon formation and disrupted intrinsic muscle patterning, with these defects reproduced following global Shh deletion from E10.5 in pCag-CreERTM; Shhflox/flox embryos. SHH responsiveness was diminished in local cranial neural crest cell (CNCC) populations in both mutants, with SHH targeting these cells through the primary cilium. CNCC-specific deletion of orofaciodigital syndrome 1 (Ofd1), which encodes a ciliary protein, in Wnt1-Cre; Ofdfl/Y mice led to a complete loss of normal myotube arrangement and hypoglossia. In contrast, mesoderm-specific deletion of Ofd1 in Mesp1-Cre; Ofdfl/Y embryos resulted in normal intrinsic muscle arrangement. Collectively, these findings suggest key temporospatial requirements for local SHH signalling in tongue development (specifically, lingual tendon differentiation and intrinsic muscle patterning through signalling to CNCCs) and provide further mechanistic insight into the tongue anomalies seen in patients with disrupted hedgehog signalling.

MoG+: a database of genomic variations across three mouse subspecies for biomedical research.

Laboratory mouse strains have mosaic genomes derived from at least three major subspecies that are distributed in Eurasia. Here, we describe genomic variations in ten inbred strains: Mus musculus musculus-derived BLG2/Ms, NJL/Ms, CHD/Ms, SWN/Ms, and KJR/Ms; M. m. domesticus-derived PGN2/Ms and BFM/Ms; M. m. castaneus-derived HMI/Ms; and JF1/Ms and MSM/Ms, which were derived from a hybrid between M. m. musculus and M. m. castaneus. These strains were established by Prof. Moriwaki in the 1980s and are collectively named the "Mishima Battery". These strains show large phenotypic variations in body size and in many physiological traits. We resequenced the genomes of the Mishima Battery strains and performed a comparative genomic analysis with dbSNP data. More than 81 million nucleotide coordinates were identified as variant sites due to the large genetic distances among the mouse subspecies; 8,062,070 new SNP sites were detected in this study, and these may underlie the large phenotypic diversity observed in the Mishima Battery. The new information was collected in a reconstructed genome database, termed MoG+ that includes new application software and viewers. MoG+ intuitively visualizes nucleotide variants in genes and intergenic regions, and amino acid substitutions across the three mouse subspecies. We report statistical data from the resequencing and comparative genomic analyses and newly collected phenotype data of the Mishima Battery, and provide a brief description of the functions of MoG+, which provides a searchable and unique data resource of the numerous genomic variations across the three mouse subspecies. The data in MoG+ will be invaluable for research into phenotype-genotype links in diverse mouse strains.

Mouse resources at the RIKEN BioResource Research Center and the National BioResource Project core facility in Japan.

The RIKEN BioResource Research Center (BRC) was established in 2001 as a comprehensive biological resource center in Japan. The Experimental Animal Division, one of the BRC infrastructure divisions, has been designated as the core facility for mouse resources within the National BioResource Project (NBRP) by the Japanese government since FY2002. Our activities regarding the collection, preservation, quality control, and distribution of mouse resources have been supported by the research community, including evaluations and guidance on advancing social and research needs, as well as the operations and future direction of the BRC. Expenditure for collection, preservation, and quality-control operations of the BRC, as a national core facility, has been funded by the government, while distribution has been separately funded by users' reimbursement fees. We have collected over 9000 strains created mainly by Japanese scientists including Nobel laureates and researchers in cutting-edge fields and distributed mice to 7000 scientists with 1500 organizations in Japan and globally. Our users have published 1000 outstanding papers and a few dozen patents. The collected mouse resources are accessible via the RIKEN BRC website, with a revised version of the searchable online catalog. In addition, to enhance the visibility of useful strains, we have launched web corners designated as the "Mouse of the Month" and "Today's Tool and Model." Only high-demand strains are maintained in live colonies, while other strains are cryopreserved as embryos or sperm to achieve cost-effective management. Since 2007, the RIKEN BRC has built up a back-up facility in the RIKEN Harima branch to protect the deposited strains from disasters. Our mice have been distributed with high quality through the application of strict microbial and genetic quality control programs that cover a globally accepted pathogens list and mutated alleles generated by various methods. Added value features, such as information about users' publications, standardized phenotyping data, and genome sequences of the collected strains, are important to facilitate the use of our resources. We have added and disseminated such information in collaboration with the NBRP Information Center and the NBRP Genome Information Upgrading Program. The RIKEN BRC has participated in international mouse resource networks such as the International Mouse Strain Resource, International Mouse Phenotyping Consortium, and Asian Mouse Mutagenesis and Resource Association to facilitate the worldwide use of high-quality mouse resources, and as a consequence it contributes to reproducible life science studies and innovation around the globe.

Asian Mouse Mutagenesis Resource Association (AMMRA): mouse genetics and laboratory animal resources in the Asia Pacific.

The Asian Mouse Mutagenesis Resource Association (AMMRA) is a non-profit organization consisting of major resource and research institutions with rodent expertise from within the Asia Pacific region. For more than a decade, aiming to support biomedical research and stimulate international collaboration, AMMRA has always been a friendly and passionate ally of Asian and Australian member institutions devoted to sharing knowledge, exchanging resources, and promoting biomedical research. AMMRA is also missioned to global connection by working closely with the consortiums such as the International Mouse Phenotyping Consortium and the International Mouse Strain Resource. This review discusses the emergence of AMMRA and outlines its many roles and responsibilities in promoting, assisting, enriching research, and ultimately enhancing global life science research quality.

SHH signaling mediated by a prechordal and brain enhancer controls forebrain organization.

Sonic hedgehog (SHH) signaling plays a pivotal role in 2 different phases during brain development. Early SHH signaling derived from the prechordal plate (PrCP) triggers secondary Shh induction in the forebrain, which overlies the PrCP, and the induced SHH signaling, in turn, directs late neuronal differentiation of the forebrain. Consequently, Shh regulation in the PrCP is crucial for initiation of forebrain development. However, no enhancer that regulates prechordal Shh expression has yet been found. Here, we identified a prechordal enhancer, named SBE7, in the vicinity of a cluster of known forebrain enhancers for Shh This enhancer also directs Shh expression in the ventral midline of the forebrain, which receives the prechordal SHH signal. Thus, the identified enhancer acts not only for the initiation of Shh regulation in the PrCP but also for subsequent Shh induction in the forebrain. Indeed, removal of the enhancer from the mouse genome markedly down-regulated the expression of Shh in the rostral domains of the axial mesoderm and in the ventral midline of the forebrain and hypothalamus in the mouse embryo, and caused a craniofacial abnormality similar to human holoprosencephaly (HPE). These findings demonstrate that SHH signaling mediated by the newly identified enhancer is essential for development and growth of the ventral midline of the forebrain and hypothalamus. Understanding of the Shh regulation governed by this prechordal and brain enhancer provides an insight into the mechanism underlying craniofacial morphogenesis and the etiology of HPE.

Monoallelic, antisense and total RNA transcription in an in vitro neural differentiation system based on F1 hybrid mice.

We developed an in vitro system to differentiate embryonic stem cells (ESCs) derived from reciprocally crossed F1 hybrid mice into neurons, and used it to investigate poly(A)+ and total RNA transcription at different stages of cell differentiation. By comparing expression profiles of transcripts assembled from 20 RNA sequencing datasets [2 alleles×(2 cell lines×4 time-points+2 mouse brains)], the relative influence of strain, cell and parent specificities to overall expression could be assessed. Divergent expression profiles of ESCs converged tightly at neural progenitor stage. Patterns of temporal variation of monoallelically expressed transcripts and antisense transcripts were quantified. Comparison of sense and antisense transcript pairs within the poly(A)+ sample, within the total RNA sample, and across poly(A)+ and total RNA samples revealed distinct rates of pairs showing anti-correlated expression variation. Unique patterns of sharing of poly(A)+ and poly(A)- transcription were identified in distinct RNA species. Regulation and functionality of monoallelic expression, antisense transcripts and poly(A)- transcription remain elusive. We demonstrated the effectiveness of our approach to capture these transcriptional activities, and provided new resources to elucidate the mammalian developmental transcriptome.

House mouse Mus musculus dispersal in East Eurasia inferred from 98 newly determined complete mitochondrial genome sequences.

The Eurasian house mouse Mus musculus is useful for tracing prehistorical human movement related to the spread of farming. We determined whole mitochondrial DNA (mtDNA) sequences (ca. 16,000 bp) of 98 wild-derived individuals of two subspecies, M. m. musculus (MUS) and M. m. castaneus (CAS). We revealed directional dispersals reaching as far as the Japanese Archipelago from their homelands. Our phylogenetic analysis indicated that the eastward movement of MUS was characterised by five step-wise regional extension events: (1) broad spatial expansion into eastern Europe and the western part of western China, (2) dispersal to the eastern part of western China, (3) dispersal to northern China, (4) dispersal to the Korean Peninsula and (5) colonisation and expansion in the Japanese Archipelago. These events were estimated to have occurred during the last 2000-18,000 years. The dispersal of CAS was characterised by three events: initial divergences (ca. 7000-9000 years ago) of haplogroups in northernmost China and the eastern coast of India, followed by two population expansion events that likely originated from the Yangtze River basin to broad areas of South and Southeast Asia, including Sri Lanka, Bangladesh and Indonesia (ca. 4000-6000 years ago) and to Yunnan, southern China and the Japanese Archipelago (ca. 2000-3500). This study provides a solid framework for the spatiotemporal movement of the human-associated organisms in Holocene Eastern Eurasia using whole mtDNA sequences, reliable evolutionary rates and accurate branching patterns. The information obtained here contributes to the analysis of a variety of animals and plants associated with prehistoric human migration.

Enhancer adoption caused by genomic insertion elicits interdigital Shh expression and syndactyly in mouse.

Acquisition of new cis-regulatory elements (CREs) can cause alteration of developmental gene regulation and may introduce morphological novelty in evolution. Although structural variation in the genome generated by chromosomal rearrangement is one possible source of new CREs, only a few examples are known, except for cases of retrotransposition. In this study, we show the acquisition of novel regulatory sequences as a result of large genomic insertion in the spontaneous mouse mutation Hammer toe (Hm). Hm mice exhibit syndactyly with webbing, due to suppression of interdigital cell death in limb development. We reveal that, in the Hm genome, a 150-kb noncoding DNA fragment from chromosome 14 is inserted into the region upstream of the Sonic hedgehog (Shh) promoter in chromosome 5. Phenotyping of mouse embryos with a series of CRISPR/Cas9-aided partial deletion of the 150-kb insert clearly indicated that two different regions are necessary for the syndactyly phenotype of Hm We found that each of the two regions contains at least one enhancer for interdigital regulation. These results show that a set of enhancers brought by the large genomic insertion elicits the interdigital Shh expression and the Hm phenotype. Transcriptome analysis indicates that ectopic expression of Shh up-regulates Chordin (Chrd) that antagonizes bone morphogenetic protein signaling in the interdigital region. Indeed, Chrd-overexpressing transgenic mice recapitulated syndactyly with webbing. Thus, the Hm mutation provides an insight into enhancer acquisition as a source of creation of novel gene regulation.

BELL1-like homeobox genes regulate inflorescence architecture and meristem maintenance in rice.

Inflorescence architecture is diverse in angiosperms, and is mainly determined by the arrangement of the branches and flowers, known as phyllotaxy. In rice (Oryza sativa), the main inflorescence axis, called the rachis, generates primary branches in a spiral phyllotaxy, and flowers (spikelets) are formed on these branches. Here, we have studied a classical mutant, named verticillate rachis (ri), which produces branches in a partially whorled phyllotaxy. Gene isolation revealed that RI encodes a BELL1-type homeodomain transcription factor, similar to Arabidopsis PENNYWISE/BELLRINGER/REPLUMLESS, and is expressed in the specific regions within the inflorescence and branch meristems where their descendant meristems would soon initiate. Genetic combination of an ri homozygote and a mutant allele of RI-LIKE1 (RIL1) (designated ri ril1/+ plant), a close paralog of RI, enhanced the ri inflorescence phenotype, including the abnormalities in branch phyllotaxy and rachis internode patterning. During early inflorescence development, the timing and arrangement of primary branch meristem (pBM) initiation were disturbed in both ri and ri ril1/+ plants. These findings suggest that RI and RIL1 were involved in regulating the phyllotactic pattern of the pBMs to form normal inflorescences. In addition, both RI and RIL1 seem to be involved in meristem maintenance, because the ri ril1 double-mutant failed to establish or maintain the shoot apical meristem during embryogenesis.

KNOTTED1 Cofactors, BLH12 and BLH14, Regulate Internode Patterning and Vein Anastomosis in Maize.

Monocot stems lack the vascular cambium and instead have characteristic structures in which intercalary meristems generate internodes and veins remain separate and scattered. However, developmental processes of these unique structures have been poorly described. BELL1-like homeobox (BLH) transcription factors (TFs) are known to heterodimerize with KNOTTED1-like homeobox TFs to play crucial roles in shoot meristem maintenance, but their functions are elusive in monocots. We found that maize (Zea mays) BLH12 and BLH14 have redundant but important roles in stem development. BLH12/14 interact with KNOTTED1 (KN1) in vivo and accumulate in overlapping domains in shoot meristems, young stems, and provascular bundles. Similar to kn1 loss-of-function mutants, blh12 blh14 (blh12/14) double mutants fail to maintain axillary meristems. Unique to blh12/14 is an abnormal tassel branching and precocious internode differentiation that results in dwarfism and reduced veins in stems. Micro-computed tomography observation of vascular networks revealed that blh12/14 double mutants had reduced vein number due to fewer intermediate veins in leaves and precocious anastomosis in young stems. Based on these results, we propose two functions of BLH12/14 during stem development: (1) maintaining intercalary meristems that accumulate KN1 and prevent precocious internode differentiation and (2) preventing precocious anastomosis of provascular bundles in young stems to ensure the production of sufficient independent veins.

Caspase-7 mediates caspase-1-induced apoptosis independently of Bid.

Inflammasomes are innate immune mechanisms that activate caspase-1 in response to a variety of stimuli, including Salmonella infection. Active caspase-1 has a potential to induce two different types of cell death, depending on the expression of the pyroptosis mediator gasdermin D (GSDMD); following caspase-1 activation, GSDMD-sufficient and GSDMD-null/low cells undergo pyroptosis and apoptosis, respectively. Although Bid, a caspase-1 substrate, plays a critical role in caspase-1 induction of apoptosis in GSDMD-null/low cells, an additional mechanism that mediates this cell death independently of Bid has also been suggested. This study investigated the Bid-independent pathway of caspase-1-induced apoptosis. Caspase-1 has been reported to process caspase-6 and caspase-7. Silencing of caspase-7, but not caspase-6, significantly reduced the activation of caspase-3 induced by caspase-1, which was activated by chemical dimerization, in GSDMD/Bid-deficient cells. CRISPR/Cas9-mediated depletion of caspase-7 had the same effect on the caspase-3 activation. Moreover, in the absence of GSDMD and Bid, caspase-7 depletion reduced apoptosis induced by caspase-1 activation. Caspase-7 was activated following caspase-1 activation independently of caspase-3, suggesting that caspase-7 acts downstream of caspase-1 and upstream of caspase-3. Salmonella induced the activation of caspase-3 in GSDMD-deficient macrophages, which relied partly on Bid and largely on caspase-1. The caspase-3 activation and apoptotic morphological changes seen in Salmonella-infected GSDMD/Bid-deficient macrophages were attenuated by caspase-7 knockdown. These results suggest that in addition to Bid, caspase-7 can also mediate caspase-1-induced apoptosis and provide mechanistic insights into inflammasome-associated cell death that is one major effector mechanism of inflammasomes.

Sonic hedgehog acts cell-autonomously on muscle precursor cells to generate limb muscle diversity.

How muscle diversity is generated in the vertebrate body is poorly understood. In the limb, dorsal and ventral muscle masses constitute the first myogenic diversification, as each gives rise to distinct muscles. Myogenesis initiates after muscle precursor cells (MPCs) have migrated from the somites to the limb bud and populated the prospective muscle masses. Here, we show that Sonic hedgehog (Shh) from the zone of polarizing activity (ZPA) drives myogenesis specifically within the ventral muscle mass. Shh directly induces ventral MPCs to initiate Myf5 transcription and myogenesis through essential Gli-binding sites located in the Myf5 limb enhancer. In the absence of Shh signaling, myogenesis is delayed, MPCs fail to migrate distally, and ventral paw muscles fail to form. Thus, Shh production in the limb ZPA is essential for the spatiotemporal control of myogenesis and coordinates muscle and skeletal development by acting directly to regulate the formation of specific ventral muscles.

Correction to: A new species of Xenoturbella from the western Pacific Ocean and the evolution of Xenoturbella.

After publication of Nakano et al. (2017) [1], the authors became aware of the fact that the new species-group name erected for the two specimens of a Japanese xenoturbellid species in the article is not available because Nakano et al. (2017) [1] does not meet the requirement of the amendment of Article 8.5.3 of the International Code of Zoological Nomenclature (the Code) [2]. The authors therefore describe the two xenoturbellids as a new species again in this correction article. Methods for morphological observation, DNA extraction and sequencing were as described in Nakano et al. (2017) [1]. The holotype and paratype specimens are deposited in the National Museum of Nature and Science, Tsukuba (NSMT), Japan. The DNA sequences obtained were deposited in the International Nucleotide Sequence Database (INSD).

Heterozygous mutation of Ush1g/Sans in mice causes early-onset progressive hearing loss, which is recovered by reconstituting the strain-specific mutation in Cdh23.

Most clinical reports have suggested that patients with congenital profound hearing loss have recessive mutations in deafness genes, whereas dominant alleles are associated with progressive hearing loss (PHL). Jackson shaker (Ush1gjs) is a mouse model of recessive deafness that exhibits congenital profound deafness caused by the homozygous mutation of Ush1g/Sans on chromosome 11. We found that C57BL/6J-Ush1gjs/+ heterozygous mice exhibited early-onset PHL (ePHL) accompanied by progressive degeneration of stereocilia in the cochlear outer hair cells. Interestingly, ePHL did not develop in mutant mice with the C3H/HeN background, thus suggesting that other genetic factors are required for ePHL development. Therefore, we performed classical genetic analyses and found that the occurrence of ePHL in Ush1gjs/+ mice was associated with an interval in chromosome 10 that contains the cadherin 23 gene (Cdh23), which is also responsible for human deafness. To confirm this mutation effect, we generated C57BL/6J-Ush1gjs/+, Cdh23c.753A/G double-heterozygous mice by using the CRISPR/Cas9-mediated Cdh23c.753A>G knock-in method. The Cdh23c.753A/G mice harbored a one-base substitution (A for G), and the homozygous A allele caused moderate hearing loss with aging. Analyses revealed the complete recovery of ePHL and stereocilia degeneration in C57BL/6J-Ush1gjs/+ mice. These results clearly show that the development of ePHL requires at least two mutant alleles of the Ush1g and Cdh23 genes. Our results also suggest that because the SANS and CDH23 proteins form a complex in the stereocilia, the interaction between these proteins may play key roles in the maintenance of stereocilia and the prevention of ePHL.