Mutations in OSBPL2 cause hearing loss associated with primary cilia defects via sonic hedgehog signaling
Hairong Shi, Hongshun Wang, Cheng Zhang, Yajie Lu, Jun Yao, Zhibin Chen, Guangqian Xing, Qinjun Wei, Xin Cao
Hairong Shi, Hongshun Wang, Cheng Zhang, Yajie Lu, Jun Yao, Zhibin Chen, Guangqian Xing, Qinjun Wei, Xin Cao
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Research Article Genetics Otology

Mutations in OSBPL2 cause hearing loss associated with primary cilia defects via sonic hedgehog signaling

Abstract

Defective primary cilia cause a range of diseases called ciliopathies, which include hearing loss (HL). Variants in the human oxysterol-binding protein like 2 (OSBPL2/ORP2) are responsible for autosomal dominant nonsyndromic HL (DFNA67). However, the pathogenesis of OSBPL2 deficiency has not been fully elucidated. In this study, we show that the Osbpl2-KO mice exhibited progressive HL and abnormal cochlear development with defective cilia. Further research revealed that OSBPL2 was located at the base of the kinocilia in hair cells (HCs) and primary cilia in supporting cells (SCs) and functioned in the maintenance of ciliogenesis by regulating the homeostasis of PI(4,5)P2 (phosphatidylinositol 4,5-bisphosphate) on the cilia membrane. OSBPL2 deficiency led to a significant increase of PI(4,5)P2 on the cilia membrane, which could be partially rescued by the overexpression of INPP5E. In addition, smoothened and GL13, the key molecules in the Sonic Hedgehog (Shh) signaling pathway, were detected to be downregulated in Osbpl2-KO HEI-OC1 cells. Our findings revealed that OSBPL2 deficiency resulted in ciliary defects and abnormal Shh signaling transduction in auditory cells, which helped to elucidate the underlying mechanism of OSBPL2 deficiency in HL.

Authors

Hairong Shi, Hongshun Wang, Cheng Zhang, Yajie Lu, Jun Yao, Zhibin Chen, Guangqian Xing, Qinjun Wei, Xin Cao

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Figure 2

Osbpl2–/– mice exhibited defective ciliogenesis and abnormal cochlear development.

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Osbpl2–/– mice exhibited defective ciliogenesis and abnormal cochlear d...
(A) Immunofluorescence staining of cilia with anti-acetylated tubulin (red) and stereocilia with phalloidin (green) on the basal turn of sensory epithelium in Osbpl2–/– and WT mice (P1, P3, P10). (B and C) The length of the kinocilia in mouse HCs of P1 and P3 mice (3 mice per genotype, each dot represents a kinocilium; *P < 0.05; **P < 0.01; ***P < 0.001 by 2-tailed Student’s t test.) Scale bars: 5 μm. (D) Immunofluorescence staining of SCs in cochleae of P3 Osbpl2–/– and WT mice. Cilia were stained with anti-acetylated tubulin (red) and cell boundaries are stained with phalloidin (green). (E) The length of SC cilia in cochleae of P3 Osbpl2–/– and WT mice (3 mice per genotype, each dot represents a cilium; **P < 0.01 by 2-tailed Student’s t test). Scale bars: 5 μm. (F) Representative images of the cochleae in Osbpl2–/– and WT mice (P3). (G) The length of otic capsules were analyzed by ImageJ (3 mice per genotype; **P < 0.01 by 2-tailed Student’s t test). Scale bars: 100 μm. (H) Immunofluorescence images of whole sensory epithelium in Osbpl2–/– and WT mice cochleae. (I) The length of whole sensory epithelium in Osbpl2–/– and WT mice cochleae were analyzed by ImageJ (3 mice per genotype; **P < 0.01 by 2-tailed Student’s t test). Scale bars: 500 μm. (J) Osbpl2–/– mice (P1 and P3) showed 5 rows of HCs versus 4 rows of HCs in WT controls at cochlear apex. Scale bars: 5 μm. (K) The number of ectopic HCs in the cochlear apex (6 mice per genotype, each dot represents a mouse cochlea. **P < 0.01 by 1-way ANOVA).