Table 2 CRISPR/Cas9 utilized in genetic HL modeling
From: The applications of CRISPR/Cas-mediated genome editing in genetic hearing loss
Gene | Pathogenic mechanism | Disease | Model | Significance | Refs. |
|---|---|---|---|---|---|
GJB2 | Encoding Cx26 that affects the ionic and metabolic homeostasis of inner ear | DFNB1 | Cx26-knockout (KO) HeLa cells | HeLa Cx26-KO cells were used to elucidate the pathogenic effect of the c.516G > C GJB2 variant and its association with DFNB1 | [117] |
GPRASP2 | Inhibiting apoptosis-related pathway of hair cells | X-linked recessive syndromic HL | Gprasp2-KO mouse HEI-OC1 auditory cells | Gprasp2-KO HEI-OC1 cells were used to reveal the potential molecular mechanism of GPRASP2 mutation associated with human syndromic HL | [119] |
THUMPD1 | Affecting small RNA N4-acetylcytidine modification | A syndromic form of intellectual disability associated with HL | THUMPD1-KO HeLa cervical carcinoma cells and THUMPD1-KO HEK293T human embryonic kidney cells | Two THUMPD1-KO cell lines were used to corroborate that THUMPD1 defect results in a loss of ac4C modification in small RNAs, highlighting the critical role of tRNA modification in human disease | [120] |
OGDHL | / | Mendelian neurodevelopmental phenotypes including HL | OGDHL-KO human SH-SY5Y neuronal cells | OGDHL-KO SH-SY5Y cells exhibited defects in mitochondrial respiration, indicating the essential role of OGDHL in mitochondrial metabolism in humans | [121] |
MYO7A | Affecting hair bundle via modulating differentiation and development of stereocilia bundles | DFNB2, DFNA11, and USH1B | hiPSC model with compound heterozygous MYO7A mutations (c.1184G > A and c.4118C > T) | These results confirmed the hypothesis that MYO7A functions in the assembly of stereocilia into stereociliary bundles | [122] |
MYO15A | Affecting hair bundle via modulating differentiation and development of stereocilia bundles | DFNB3 | hiPSC model with compound heterozygous MYO15A mutations (c.4642G > A and c.8374G > A) | These findings demonstrated the feasibility of generating inner ear hair cells from hiPSCs and the functional rescue of gene mutation-based deafness by using genetic correction | [123] |
TRMU | Causing mitochondrial dysfunction | A maternally inherited non-syndromic HL | hiPSC model with compound heterozygous TRMU c.28G > T and 12S rRNA m.1555A > G | These results revealed the pathogenesis of TRMU mutations and provided a step toward therapeutic interventions for this disease | [124] |
GJB6 | Encoding Cx30 that may affect the ionic and metabolic homeostasis of inner ear | DFNA3B | Cx30-KO mouse models (Cx30−/−) | The studies of Cx30-KO mouse models suggest that Cx30 may play an important role in hearing development | [134] |
KCNQ4 | Encoding Kv7.4 that affects the ionic homeostasis of inner ear | DFNA2A | Kcnq4 c.683G > A mutation (Kcnq4G229D) knock-in (KI) mouse models | These results suggest KCNQ4 protein p.G228D variant may induce progressive high-frequency HL in DFNA2 through the degeneration of hair cells | [136] |
MYO6 | Affecting hair bundle via modulating differentiation and development of stereocilia bundles | DFNA22 or DFNB37 | Myo6 c.1325G > A mutation (Myo6C442Y) knock-in (KI) mouse models | These results indicate that loss of auditory hair cells and degeneration of stereocilia bundles on vestibular hair cells may underlie the phenotypes of Myo6C442Y homozygous mice | [139] |
TMC1 | Encoding a pore-forming subunit that is crucial for mechanosensory transduction channels | DFNA36 and DFNB7/11 | Tmc1 p.N193I mutation KI mouse models | This mouse line provided an excellent model for studying the mechanism of DFNB7/11-type deafness in humans | [142] |
CDH23 | Affecting intercellular adhesion via causing structural abnormalities in the stereocilia | DFNB12 and Usher syndrome type 1D (USH1D) | Cdh23 c.208 T > C mutation (Cdh23erl2/erl2) and c.235delG mutation (Cdh23V2J2/V2J2) KI mouse models | These two novel mutant mouse strains provide a valuable research tool for the study of human deafness and vestibular dysfunction in CDH23 mutation-related human disease | [143] |
MYO3A | Affecting hair bundle via modulating the intact structure of hair cell stereocilia | DFNB30 | Myo3a c.410A > G mutation KI mouse models | This mouse line provided an excellent model for studying the mechanism of DFNB30-type deafness in humans | [145] |
CIB2 | Abolishing mechanoelectrical transduction currents via affects stereocilia development | DFNB48 and USH1J | Cib1-KO and Cib2-KO mice | The auditory testing results of the two mouse strains reveals that although both CIB1 and CIB2 are readily detected in the cochlea, only loss of CIB2 results in profound HL | [148] |
TPRN | Affecting hair bundle via causing damage to stereociliary bundles | DFNB79 | Tprn-null mice | The studies of Tprn-null mouse line suggest that loss of Tprn causes the disruption of the stereociliary rootlet, which results in damage to stereociliary bundles and HL | [150] |
ELMOD3 | Affecting hair bundle via modulating the actin cytoskeleton dynamics | DFNB88 | Elmod3-KO mice | The study associates the Elmod3 deficiency with the stereocilia dysmorphology and reveals its roles in the actin cytoskeleton dynamics in cochlear hair cells, thus relating to HL | [153] |
GRXCR2 | Affecting hair bundle via the interaction with CLIC5 in stereocilia | DFNB101 | Mice harboring the in-frame deletion in Grxcr2 | The models reveal that the interaction between GRXCR2 and CLIC5 is crucial for normal hearing | [154] |
ARHGEF6 | Causing hair cell stereocilia deficits | Syndromic X-linked intellectual disability (IDXS) including HL | Arhgef6-KO mice | This research shows that and loss of Arhgef6 in mice caused hair cell stereocilia deficits that eventually led to progressive hair cell loss and HL | [156] |
TIMM8A | Causing an abnormal mitochondrial structure in the brain | Deafness-dystonia-optic neuronopathy (DDON) syndrome | Timm8a1 hemizygous mutation (Timm8a1I23fs49X/y) KI mouse models | This study provides a mouse model bearing loss-of-function mutation in Timm8a1 for explore molecular mechanism of DDON syndrome | [157] |
Mafb | Affecting transcriptional regulation in inner ear | / | A mafba-KO (mafba−/−) zebrafish model | The model provides a novel insight into the role Mafb in the maintenance of ionic channel homeostasis and inner-ear development | [160] |
FGFR3 | Inducing cell death via upregulating canonical Wnt/β-catenin signaling | CATSHL syndrome | A fgfr3-KO zebrafish model | The model further reveals some novel phenotypes and underlying developmental mechanism of CATSHL syndrome, which deepens our understanding of the pathogenesis of CATSHL and the role of fgfr3 in skeleton development | [162] |
tmem183a | Affecting the normal state of mechanoelectrical transduction channels | / | Homozygous zebrafish mutants | This study provides an effective approach to obtain zebrafish mutants, and tmem183a is identified as a candidate gene for HL | [163] |
NCOA3 | Causing subtle and abnormal skeletal behavior (cartilage behavior and bone density) in the ears, | Autosomal dominant, non-syndromic, sensorineural HL | A ncoa mutant (ncoa3−/−) zebrafish model | NCOA3 is identified as a potential candidate gene to explain genetic HL, which plays a vital role in skeletal system homeostasis, and the mutations in NCOA3 involves in the pathogenesis of progressive HL | [164] |
THOC1 | Inducing hair cell apoptosis via promoting expression of pro-apoptotic genes in the p53 signaling pathway | Autosomal dominant late-onset, progressive, non-syndromic HL | A Thoc1-KO zebrafish model | The zebrafish model was used to explored the function of THOC1 in inner ear, and deficiency of Thoc1 was shown to lead to hair cell apoptosis through the p53-mediated pathway, which might be associated with hearing disorders | [165] |
OSBPL2 | Inducing degeneration and apoptosis of cochlea hair cells and causing morphological abnormalities in stereocilia | DFNA67 | A OSBPL2-disrupted Bama miniature pig model | The phenotype of progressive HL in OSBPL2-disrupted pigs confirms the implication of OSBPL2 mutation in non-syndromic HL | [169] |
MITF | Encoding a transcription factor that affects the proliferation and differentiation of neural crest-derived melanocytes | Waardenburg syndrome 2A (WS2A) | A MITF bi-allelic KO pig model | CRISPR/Cas9-mediated MITF bi-allelic KO pigs exhibited anophthalmia, hypopigmentation and bilateral HL, which provided an ideal animal model for the research of human WS2A syndrome | [172] |
MYO7A | Affecting hair bundle via modulating differentiation and development of stereocilia bundles | USH1B | A MYO7A-KO female macaque | The lack of a USH1B phenotype in the macaque indicates that maintaining or achieving a population of ~ 50% of cells with functional MYO7A would suffice in treating individuals with USH1B | [175] |