Jinwoong Bok

Yonsei University · Department of Anatomy

The cochlea is a complex organ comprising diverse cell types with highly specialized morphology and function. Until now, the molecular underpinnings of its specializations have mostly been studied from a transcriptional perspective, but accumulating evidence points to post-transcriptional regulation as a major source of molecular diversity. Alterna...

The cochlea’s ability to discriminate sound frequencies is facilitated by a special topography along its longitudinal axis known as tonotopy. Auditory hair cells located at the base of the cochlea respond to high-frequency sounds, whereas hair cells at the apex respond to lower frequencies. Gradual changes in morphological and physiological feature...

Primary cilia play pivotal roles in embryonic patterning and organogenesis through transduction of the Hedgehog signaling pathway (Hh). While mutations in Hh morphogens impair the development of the gonads and trigger male infertility, the contribution of Hh and primary cilia in the development of male reproductive ductules, including the epididymi...

Primary cilia have essential roles as signaling centers during development and adult homeostasis. Disruption of ciliary structure or function causes congenital human disorders called ciliopathies. Centriolar distal appendage (DAP) proteins are important for anchoring cilia to the membrane. However, the exact functions of DAP during in vivo ciliogen...

Tubby mice exhibit hearing impairment due to the loss of stereocilin from the tip regions that connect the tallest stereocilia of the outer hair cells (OHCs) to the tectorial membrane. Stereocilin is an essential stereociliary protein in the OHCs, the mutation of which in humans causes autosomal recessive non-syndromic deafness. Map1a is a modifier...

Background Cryopyrin-associated periodic syndrome (CAPS) is an inherited autoinflammatory disease caused by a gain-of-function mutation in NLRP3. Although CAPS patients frequently suffer from sensorineural hearing loss, it remains unclear whether CAPS-associated mutation in NLRP3 is associated with the progression of hearing loss. Methods We gener...

Alternative splicing (AS) refers to the production of multiple mRNA isoforms from a single gene due to alternative selection of exons or splice sites during pre-mRNA splicing. It is a primary mechanism of gene regulation in higher eukaryotes and significantly expands the functional complexity of eukaryotic organisms, contributing to animal developm...

Cilia are highly specialized organelles that extend from the cell membrane and function as cellular signaling hubs. Thus, cilia formation and the trafficking of signaling molecules into cilia are essential cellular processes. TULP3 and Tubby (TUB) are members of the tubby-like protein (TULP) family that regulate the ciliary trafficking of G-protein...

Defective primary cilia cause a range of diseases known as ciliopathies, including hearing loss. The etiology of hearing loss in ciliopathies, however, remains unclear. We analyzed cochleae from three ciliopathy mouse models exhibiting different ciliogenesis defects: Intraflagellar transport 88 ( Ift88 ), Tbc1d32 (a.k.a. bromi ), and Cilk1 (a.k.a....

The mammalian middle ear comprises a chain of ossicles, the malleus, incus, and stapes that act as an impedance matching device during the transmission of sound from the tympanic membrane to the inner ear. These ossicles are derived from cranial neural crest cells that undergo endochondral ossification and subsequently differentiate into their fina...

Significance Our hearing organ, the cochlea, acts as an active sound amplifier rather than a simple detector due to the action of outer hair cells (OHCs). This active sound processing by OHCs requires specific hair bundle architecture in which stereocilia are connected to each other and to the overlying tectorial membrane by nanoscale extracellular...

Background The mammalian middle ear comprises a chain of three ossicles—the malleus, incus, and stapes—each of which has a unique morphology for efficiently transmitting sound information. In particular, the stapes, which is attached to the inner ear, is stirrup‐shaped with a head and base connected by two crural arches, forming the stapedial foram...

The rMAPS2 (RNA Map Analysis and Plotting Server 2) web server, freely available at http://rmaps.cecsresearch.org/, has provided the high-throughput sequencing data research community with curated tools for the identification of RNA binding protein sites. rMAPS2 analyzes differential alternative splicing or CLIP peak data obtained from high-through...

Microglia (MG), the principal neuroimmune sentinels in the brain, continuously sense changes in their environment and respond to invading pathogens, toxins, and cellular debris, thereby affecting neuroinflammation. Microbial pathogens produce small metabolites that influence neuroinflammation, but the molecular mechanisms that determine whether pat...

Background: Endocrine-cerebro-osteodysplasia (ECO) syndrome is a genetic disorder associated with congenital defects of the endocrine, cerebral, and skeletal systems in humans. ECO syndrome is caused by mutations of the intestinal cell kinase (ICK) gene, which encodes a mitogen-activated protein (MAP) kinase-related kinase that plays a critical ro...

Rationale: Mutations of SLC26A4 that abrogate pendrin, expressed in endolymphatic sac, cochlea and vestibule, are known to cause autosomal recessive sensorineural hearing loss with enlargement of the membranous labyrinth. This is the first study to demonstrate the feasibility of gene therapy for pendrin-related hearing loss. Methods: We used a reco...

Targeting specific cell types in the mammalian inner ear is important for treating genetic hearing loss due to the different cell type-specific functions. Adeno-associated virus (AAV) is an efficient in vivo gene transfer vector, and it has demonstrated promise for treating genetic hearing loss. Although more than 100 AAV serotypes have been identi...

The original article contains an error for a grant number in the Acknowledgements section. © 2019, Springer Science+Business Media, LLC, part of Springer Nature.

Defects in the middle ear ossicles - malleus, incus and stapes - can lead to conductive hearing loss. During development, neural crest cells (NCCs) migrate from the dorsal hindbrain to specific locations in pharyngeal arch (PA) 1 and 2, to form the malleus-incus and stapes, respectively. It is unclear how migratory NCCs reach their proper destinati...

Vitamin A deficiency (VAD) produces various pathologic phenotypes in humans and animals. However, evidence regarding the effect of VAD on hearing function has been inconsistent. In this study, we evaluated the effect of VAD on hearing function in two mouse models of VAD. Hearing ability was evaluated on the basis of auditory brainstem response from...

Mitochondrial NADP⁺-dependent isocitrate dehydrogenase 2 (IDH2) is a major NADPH-producing enzyme which is essential for maintaining the mitochondrial redox balance in cells. We sought to determine whether IDH2 deficiency induces mitochondrial dysfunction and modulates auditory function, and investigated the protective potential of an antioxidant a...

Altered miRNA (miR) expression occurs in various diseases. However, the therapeutic effect of miRNAs in autosomal dominant polycystic kidney disease (ADPKD) is unclear. Genome‐wide analyses of miRNA expression and DNA methylation status were conducted to identify crucial miRNAs in end‐stage ADPKD. miR‐192 and ‐194 levels were down‐regulated with hy...

Mammalian palate separates the oral and nasal cavities for normal feeding, breathing and speech. The palatal shelves are a pair of maxillary prominences that consist of the neural crest-derived mesenchyme and surrounding epithelium. Palatogenesis is completed by the fusion of the midline epithelial seam (MES) after the medial edge epithelium (MEE)...

The exocyst, an octameric protein complex consisting of Exoc1 through Exoc8, was first determined to regulate exocytosis by targeting vesicles to the plasma membrane in yeast to mice. In addition to this fundamental role, the exocyst complex has been implicated in other cellular processes. In this study, we investigated the role of the exocyst in c...

Auditory hair cells play an essential role in hearing. These cells convert sound waves, mechanical stimuli, into electrical signals that are conveyed to the brain via spiral ganglion neurons. The hair cells are located in the organ of Corti within the cochlea. They assemble in a special arrangement with three rows of outer hair cells and one row of...

The inner ear is a complex sensory organ responsible for hearing and balance. Formation of the inner ear is dependent on tight regulation of spatial and temporal expression of genes that direct a series of developmental processes. Recently, epigenetic regulation has emerged as a crucial regulator of the development of various organs. However, what...

In the mouse neural tube, sonic hedgehog (Shh) secreted from the floor plate (FP) and the notochord (NC) regulates ventral patterning of the neural tube, and later is essential for the generation of oligodendrocyte precursor cells (OPCs). During early development, the NC is adjacent to the neural tube and induces ventral domains in it, including th...

Autosomal polycystic kidney disease (ADPKD) is a common inherited renal disease characterized by the development of numerous fluid-filled cysts in both kidneys. We investigated miRNA-mediated regulatory systems and networks that play an important role during cystogenesis through integrative analysis of miRNA- and RNA-seq using two ADPKD mouse model...

Clusterin (CLU) is an extracellular chaperone protein that is implicated in diverse physiological and pathophysiological cellular processes. CLU expression is upregulated in response to cellular stress and under certain conditions, such as neurodegenerative disease and cancer. CLU primarily functions as a chaperone that exerts cytoprotective effect...

Hereditary hearing loss (HHL) is a common genetically heterogeneous disorder, which follows Mendelian inheritance in humans. Because of this heterogeneity, the identification of the causative gene of HHL by linkage analysis or Sanger sequencing have shown economic and temporal limitations. With recent advances in next-generation sequencing (NGS) te...

The mammalian inner ear is a complex organ responsible for balance and hearing. Sonic hedgehog (Shh), a member of the Hedgehog (Hh) family of secreted proteins, has been shown to play important roles in several aspects of inner ear development, including dorsoventral axial specification, cochlear elongation, tonotopic patterning, and hair cell diff...

Sound perception via mechano-sensation is a remarkably sensitive and fast transmission process, converting sound as a mechanical input to neural signals in a living organism. Although knowledge of auditory hair cell functions has advanced over the past decades, challenges remain in understanding their biomechanics, partly because of their biophysic...

The vertebrate skeletal system has various functions, including support, movement, protection, and the production of blood cells. The development of cartilage and bones, the core components of the skeletal system, is mediated by systematic inter- and intracellular communication among multiple signaling pathways in differentiating progenitors and th...

Significance Sound frequency discrimination is crucial for daily activities throughout the animal kingdom. This process begins at the auditory peripheral organ known as the organ of Corti in mammals and basilar papilla in birds. This frequency tuning is facilitated by specific anatomical and physiological properties, including gradual changes in th...

Mutations in five unconventional myosin genes have been associated with genetic hearing loss (HL). These genes encode the motor proteins myosin IA, IIIA, VI, VIIA and XVA. To date, most mutations in myosin genes have been found in the Caucasian population. In addition, only a few functional studies have been performed on the previously reported myo...

Significance Endocrine-cerebro-osteodysplasia (ECO) syndrome, a human genetic disorder affecting multiple organs, is caused by a mutation in intestinal cell kinase ( Ick ) gene. In algae and invertebrates, ICK homologs are known to be associated with ciliary formation. However, it is unclear whether this role of ICK is conserved in mammals and whet...

Pendrin mutations cause enlarged vestibular aqueducts and various degrees of sensorineural hearing loss. The selective abolition of pendrin causes dilation of the membranous labyrinth known as endolymphatic hydrops, loss of the endocochlear potential, and consequently loss of hearing function. Because Na+ transport is one of the most important driv...

Pax3 mutations result in malformed inner ears in Splotch mutant mice and hearing loss in humans with Waardenburg's syndrome type I. In the inner ear, Pax3 is thought to be involved mainly in the development of neural crest. However, recent studies have shown that Pax3-expressing cells contribute extensively to multiple inner ear structures, some of...

Methionine sulfoxide reductase B3 (MsrB3) is a protein repair enzyme that specifically reduces methionine-R-sulfoxide to methionine. A recent genetic study showed that the MSRB3 gene is associated with autosomal recessive hearing loss in human deafness DFNB74. However, the precise role of MSRB3 in the auditory system and the pathogenesis of hearing...

Mutation of SLC26A4 is the most common cause of prelingual hearing loss in East Asia. Patients with SLC26A4 mutations have variable phenotypes ranging from non-syndromic hearing loss to Pendred syndrome. Here, we analyzed the correlation between genotype and various inner ear phenotypes and found a possible underlying mechanism. This study included...

Neural precursor cells of the central nervous system undergo successive temporal waves of terminal division, each of which is soon followed by the onset of cell differentiation. The organ of Corti in the mammalian cochlea develops differently, such that precursors at the apex are the first to exit from the cell cycle but the last to begin different...

CHARGE syndrome is an autosomal dominant congenital disorder known to be caused by the haploinsufficiency of the CHD7 gene. Heterozygous mutations in the CHD7 gene have been identified in approximately 60–70% of patients clinically diagnosed with CHARGE syndrome. Although there have been many reports on the mutational spectrum of the CHD7 gene in p...

Background: Carbonic anhydrases (CAs), which catalyze CO(2) hydration to bicarbonate and protons, have been suggested to regulate potassium homeostasis and endocochlear potential in the mammalian cochlea. Sixteen mammalian CA isozymes are currently known. To understand the specific roles of CA isozymes in the inner ear, a systematic survey was con...

All cellular phenomena and developmental events, including inner ear development, are modulated through harmonized signaling networks. Phosphatase and tensin homolog deleted on chromosome 10 (PTEN), a tumor suppressor, is a major signaling component involved in cross talk with key regulators of development; i.e., Wnt, Notch, and bone morphogenetic...

Neuronal loss of vestibular ganglia in Pten-deficient mice at E16.5. (A) Tuj1 immunoreactivity (green) were reduced in the vestibular ganglion of Pax2Cre/+;PtenloxP/loxP mice. U, utricle; VG, vestibular ganglion. Scale bar: 100 µm. (B) Numbers of vestibular ganglia were significantly reduced compared to wild-type mice (7 cochleae, P<0.01). (TIF)

Apoptotic neurons in the cochleovestibular ganglion (CVG) complex of Pax2Cre/+;PtenloxP/loxP embryos. (A–D ´) Cleaved caspase-3-positive apoptotic cells (red) in the CVG were stained with Tuj1 (green), a neuronal marker, or Sox10 (green), a Schwann cell marker, at E12.5. (B, B ´) Apoptotic cells were co-localized with Tuj1-positive neurons in the C...

Reduction in Pten-positive immunoreactivity in Pax2Cre/+;PtenloxP/loxP mice. Pten immunopositivity (red) in the spiral ganglion at E16.5 was significantly decreased in Pax2Cre/+;PtenloxP/loxP mice compared to wild-type mice. DAPI-stained nuclei (blue) are seen in all images. SG, spiral ganglion. Scale bar: 100 µm (TIF)

Neuronal Pten expression during inner ear development in wild-type mice. (A) In the neurons at E10.5, E14.5, E16.5, and E18.5, the expression of Pten (red) partly overlapped with that of neurofilament (green), which was expressed in both the neuronal cell body and neuritis (arrows in b–d, f–h, j–l, and n–p). Higher magnification images of boxed reg...

Confocal images of the hair bundles of the organ of Corti at E18.5. (A–C) Stereociliary bundle (green) and kinocilia (red) labeling of the surface of the organ of Corti from the basal turn showed the regular pattern of a single row of inner hair cells and three rows of outer hair cells. Scale bars: 50 µm in A–C; 10 µm in Á–Ć. (D–F) In Pax2Cre/+;Pte...

Epithelial phenotype in Neurog1Cre/+;PtenloxP/loxP and Atoh1Cre/+;PtenloxP/loxP mice. The morphological pattern of the epithelium was revealed by whole-mount phalloidin (green) with p75NTR (red) immunofluorescence. (A) At E18.5, normally organized cochlear hair cells were seen in Neurog1Cre/+;PtenloxP/loxP mice injected with tamoxifen between E8.5...

Most X-linked nonsyndromic hearing loss is caused by various types of mutations of the POU domain class 3 transcription factor 4 gene (POU3F4). We found five unique missense and frameshift truncation and extension mutations in Korean patients. Two missense mutations (p.Thr211Met and p.Gln229Arg) disturbed transcriptional activity. Two frameshift ex...

The mammalian cochlear duct is tonotopically organized such that the basal cochlea is tuned to high frequency sounds and the apical cochlea to low frequency sounds. In an effort to understand how this tonotopic organization is established, we searched for genes that are differentially expressed along the tonotopic axis during neonatal development....

Complete list of genes in each group (Groups A to H), classified based on spatial and temporal expression patterns. (XLSX)

Expression patterns of A2m and Kcnj10 in the cochlea during embryonic and neonatal development. Expression patterns of A2m (A,B) and Kcnj10 (C,D) were examined by in situ hybridization at P0 (A,C) and P8 (B,D). (A,B) A2m was classified in Group I showing decreasing gradients towards the apex at both P0 and P8. Consistent with the microarray data, A...

Primer sets used for qRT-PCR. (DOCX)

Expression patterns of Tectb, Chrna10, and Ptprq in the cochlea during neonatal development. Expression patterns of Tectb (A,B), Chrna1 (C,D) and Ptprq (E, F) were examined by in situ hybridization at P0 (A,C,E) and P8 (B,D,F). (A,B) Tectb was classified in Group E showing increasing gradients towards the apex at both P0 and P8. Consistent with the...

Complete list of the differentially expressed genes between apex and base of the mouse cochlear at P0 or P8. (XLSX)

To date, 135 loci and 50 genes have been identified as causes of nonsyndromic hearing loss. Until recently, four loci (DFN2, DFN3, DFN4, and DFN6) had been implicated in nonsyndromic X-linked hearing loss; however, a new classification (DFNX1-5) has been proposed to reduce confusion in the terminology. The different types of nonsyndromic X-linked h...

Temporal bone CT and temporal MRI findings of patient 10 demonstrating enlarged vestibular aqueduct in a circular shape. (A–F) Axial view of temporal bone CT shows enlarged vestibular aqueduct (black arrows) observed as a circular shape with a diameter significantly larger than that of the posterior semicircular canal (black arrowhead in Fig. S1A)....

Exon-trapping analysis of the novel splice site variation, c.5210+5G>C. For the c.5210+5G>C variation, exons 22 and 23 of CHD7 were introduced into the pSPL3 vector and analyzed by the in vitro splicing assay. For the wild type, normal 623-bp mRNA was identified. For the mutant type, 463-bp mRNA variant was seen together with the normal 623-bp mRNA...

Comparison of the clinical features of patients with CHARGE syndrome who have the same mutations of the CHD7 gene. Of the three mutations identified in this study that had previously been reported, clinical features were provided for only two patients in the previous reports. TE: tracheoesophageal. (DOC)

Primers and PCR conditions used for CHD7 sequencing analysis. (DOC)

Exon-trapping analysis of splice site variation, c.5405-7G>A. For the c.5405-7G>A variation, exon 26 of CHD7 was introduced into the pSPL3 vector and analyzed by the in vitro splicing assay. For the wild type, normal 393-bp mRNA was identified, while the mutant type demonstrated only the 398-bp mRNA variant (A). Sequencing analysis of the wild type...

Splicing variants for in vitro splicing assay. * The exon directly associated with the splice variation is presented in bold. Exon 22 of Patient 5 is closely located to exon 23 and was inserted into the pSPL3 vector together. Restriction enzyme recognition sites of the primer sequences are underlined. (DOC)

In silico analysis through splice site prediction programs. * Values in bold represent scores of the new splice site that is introduced by the intronic variation. (DOC)

Otologic manifestations are one of the most consistent findings of CHARGE syndrome found in more than 90%. Since genetic analysis of the CHD7 gene has rarely been performed in previous reports dealing with ear abnormalities, the genotypic spectrum of CHD7 mutations was analyzed in deaf patients with CHARGE syndrome, and the clinical considerations...

MS/MS spectra of unique peptide sequences for unnamed protein product (gi|28590) revealed by LC-MS/MS. A: MS/MS spectrum of amino acid sequence from 311-337 (peptide sequence: SHCIAEVENDEMPADLPSLAADFVESK, ion socre:45). B: MS/MS spectrum of amino acid sequence from 438-452 (peptide sequence: KVPEVSTPTLVEVSR, ion score:57). C: MS/MS spectrum of amin...

Albumin-like proteins identified by LC-MS/MS except unnamed protein product (gi|28590) in each sample from part of spot 1 ( Fig. 5 ) and trypsinized protein of patients 1. (XLS)

Albumin or albumin-like proteins identified by LC-MS/MS in the luminal fluid from a normal endolymphatic sac. (XLS)

The endolymphatic sac (ES) is an inner ear organ that is connected to the cochleo-vestibular system through the endolymphatic duct. The luminal fluid of the ES contains a much higher concentration of proteins than any other compartment of the inner ear. This high protein concentration likely contributes to inner ear fluid volume regulation by creat...

Mutations in the gap junction β2 (GJB2) gene, encoding the connexin26 (CX26) protein, are the most common cause of non-syndromic hearing loss (HL) in many populations. In the East Asian population, two variants, p.V27I (c.79G>A) and p.E114G (c.341G>A), are considered benign polymorphisms since these variants have been identified in both HL patients...

The inner ear is composed of a cochlear duct and five vestibular organs in which mechanosensory hair cells play critical roles in receiving and relaying sound and balance signals to the brain. To identify novel genes associated with hair cell differentiation or function, we analyzed an archived gene expression dataset from embryonic mouse inner ear...

DFN3, the most prevalent X-linked hearing loss, is caused by mutations in the POU3F4 gene. Previous studies in Pou3f4 knockout mice suggest that defective otic fibrocytes in the spiral ligament of the cochlear lateral wall may underlie the hearing loss in DFN3. To better understand the pathological mechanisms of the DFN3 hearing loss, we analyzed i...

Vertebrate hearing and balance are based in complex asymmetries of inner ear structure. Here, we identify retinoic acid (RA) as an extrinsic signal that acts directly on the ear rudiment to affect its compartmentalization along the anterior-posterior axis. A rostrocaudal wave of RA activity, generated by tissues surrounding the nascent ear, induces...

Song MH, Lee HK, Choi JY, Kim S, Bok J, Kim U-K. Clinical evaluation of DFN3 patients with deletions in the POU3F4 locus and detection of carrier female using MLPA. X-linked deafness type 3 (DFN3), the most prevalent X-linked form of hereditary deafness, is caused by mutations of the POU3F4 locus in the Xq21 region. We evaluated two Korean families...

Hoxc8 is a member of Hox family transcription factors that play crucial roles in spatiotemporal body patterning during embryogenesis. Hox proteins contain a conserved 61 amino acid homeodomain, which is responsible for recognition and binding of the proteins onto Hox-specific DNA binding motifs and regulates expression of their target genes. Previo...

The mammalian cochlea is a highly intricate organ responsible for hearing. Numerous specialized cell types residing in the cochlear participate in processing and relaying sound information to the brain. In general, cells in the cochlea are divided into three major types: sensory, neural, and non-sensory. Sensory cells are a group of cells in the or...

Proper regulation of bone morphogenetic protein (BMP) signaling is critical for correct patterning and morphogenesis of various tissues and organs. A well known feedback mechanism is a BMP-mediated induction of Smad6, an inhibitor of BMP signaling. Hoxc8, one of the Hox family transcription factors, has also been shown to negatively regulate BMP-me...

A mature inner ear is a complex structure consisting of vestibular and auditory components. Microsurgical ablations, rotations, and translocations were performed in ovo to identify the tissues that control inner ear morphogenesis. We show that mesenchyme/ectoderm adjacent to the developing ear specifically governs the shape of vestibular components...

X-linked deafness type 3 (DFN3), the most prevalent X-linked form of hereditary deafness, is caused by mutations in the POU3F4 locus, which encodes a member of the POU family of transcription factors. Despite numerous reports on clinical evaluations and genetic analyses describing novel POU3F4 mutations, little is known about how such mutations aff...

Mutations in the GJB2 gene, which encodes the gap junction (GJ) protein connexin26 (Cx26), are the most common cause of inherited non-syndromic hearing loss (NSHL). We identified two missense mutations, p.D46E (c.138T>G) and p.T86R (c.257C>G), of GJB2 in Korean HL families. The novel p.D46E mutation exhibited autosomal dominant inheritance, while t...

Previously, we have demonstrated that purified Hoxc8 homeoprotein has the ability to penetrate the cellular membrane and can be transduced efficiently into COS-7 cells. Moreover, the Hoxc8 protein is able to form a complex with DNA molecules in vitro and helps the DNA be delivered intracellularly, serving as a gene delivery vehicle. Here, we furthe...