OSBPL2, also known as oxysterol-binding protein-related protein 2, is an important regulator in cellular lipid metabolism and transport. It is involved in pathways related to cholesterol homeostasis, lipid droplet lipolysis, and may interact with key proteins in hyperkeratosis like Phosphoinositide phospholipase C-beta-3 (PLCB3) [1,6,7]. Animal models such as gene-disrupted pigs and KO mice have been crucial in studying its functions [3,4].

Compound heterozygous variants in OSBPL2 cause Dyschromatosis, Ichthyosis, Deafness, and Atopic Disease (DIDA) syndrome. These variants lead to enhanced ubiquitination and degradation of PLCB3, resulting in epidermal hyperkeratosis [1]. Mutations in OSBPL2 also cause autosomal dominant hearing loss (DFNA67), as mutant OSBPL2 accumulates intracellularly, impairs autophagy, and disrupts endolysosomal homeostasis [2]. OSBPL2-disrupted pigs display progressive hearing loss and hypercholesterolaemia, while Osbpl2-KO mice show progressive hearing loss, abnormal cochlear development with defective cilia, and down-regulation of key molecules in the Sonic Hedgehog (Shh) signaling pathway [3,4]. In age-related hearing loss, OSBPL2 inhibition leads to apoptosis of cochlea hair cells by inhibiting the AKT/FOXG1 signaling pathway [5]. Also, OSBPL2 deficiency upregulates squalene epoxidase (SQLE) expression, increasing intracellular cholesterol and cholesteryl ester through the AMPK/SP1 and SREBF2 signalling pathway [6].

In conclusion, OSBPL2 is essential for maintaining normal cellular lipid metabolism, especially cholesterol homeostasis, and is crucial for normal auditory function and epidermal cell regulation. The use of gene-knockout mouse models and other animal models has significantly contributed to understanding its role in diseases such as DIDA syndrome, autosomal dominant hearing loss, and age-related hearing loss, providing insights into potential therapeutic strategies for these conditions.

References:

1. Wang, Yumeng, Zhao, Anqi, Zhou, Naihui, Li, Ming, Li, Min. 2024. OSBPL2 compound heterozygous variants cause dyschromatosis, ichthyosis, deafness and atopic disease syndrome. In Biochimica et biophysica acta. Molecular basis of disease, 1870, 167207. doi:10.1016/j.bbadis.2024.167207. https://pubmed.ncbi.nlm.nih.gov/38701954/

2. Koh, Young Ik, Oh, Kyung Seok, Kim, Jung Ah, Choi, Jae Young, Gee, Heon Yung. 2022. OSBPL2 mutations impair autophagy and lead to hearing loss, potentially remedied by rapamycin. In Autophagy, 18, 2593-2614. doi:10.1080/15548627.2022.2040891. https://pubmed.ncbi.nlm.nih.gov/35253614/

3. Yao, Jun, Zeng, Huasha, Zhang, Min, Cao, Xin, Dai, Yifan. 2019. OSBPL2-disrupted pigs recapitulate dual features of human hearing loss and hypercholesterolaemia. In Journal of genetics and genomics = Yi chuan xue bao, 46, 379-387. doi:10.1016/j.jgg.2019.06.006. https://pubmed.ncbi.nlm.nih.gov/31451425/

4. Shi, Hairong, Wang, Hongshun, Zhang, Cheng, Wei, Qinjun, Cao, Xin. 2022. Mutations in OSBPL2 cause hearing loss associated with primary cilia defects via sonic hedgehog signaling. In JCI insight, 7, . doi:10.1172/jci.insight.149626. https://pubmed.ncbi.nlm.nih.gov/35041619/

5. Li-Yang, Meina, Ma, Chao, Wang, Xiaoye, You, Jianqiang. 2024. OSBPL2 inhibition leads to apoptosis of cochlea hair cells in age-related hearing loss by inhibiting the AKT/FOXG1 signaling pathway. In Aging, 16, 13132-13144. doi:10.18632/aging.206138. https://pubmed.ncbi.nlm.nih.gov/39475791/

6. Zhang, Cui, Zhang, Hongdu, Zhang, Min, Xing, Guangqian, Cao, Xin. 2019. OSBPL2 deficiency upregulate SQLE expression increasing intracellular cholesterol and cholesteryl ester by AMPK/SP1 and SREBF2 signalling pathway. In Experimental cell research, 383, 111512. doi:10.1016/j.yexcr.2019.111512. https://pubmed.ncbi.nlm.nih.gov/31356817/

7. Wang, Tianming, Wei, Qinjun, Liang, Lihong, Xing, Guangqian, Cao, Xin. 2020. OSBPL2 Is Required for the Binding of COPB1 to ATGL and the Regulation of Lipid Droplet Lipolysis. In iScience, 23, 101252. doi:10.1016/j.isci.2020.101252. https://pubmed.ncbi.nlm.nih.gov/32650117/