Liu Rongrong, Shang Wenjing, Liu Yingying, Xie Yi, Luan Jun, Zhang Ting, Ma Ying, Wang Zengxian, Sun Yan, Song Xicheng, Han Fengchan
Department of Biochemistry and Molecular Biology, and Key Laboratory for Genetic Hearing Disorders in Shandong, Binzhou Medical University, 346 Guanhai Road, Yantai, 264003, Shandong, PR China.
Department of Otorhinolaryngology-Head and Neck Surgery, Affiliated Yantai Yuhuangding Hospital of Qingdao University, Yantai, 264000, PR China.
Cell Death Discov. 2024 Feb 19;10(1):89. doi: 10.1038/s41420-024-01851-5.
The Fscn2 (Fascin2) gene encodes an actin cross-linking protein that is involved in the formation of hair cell stereocilia and retina structure. Mutations in Fscn2 gene have been linked to hearing impairment and retinal degeneration in humans and mice. To understand the function of the Fscn2 gene, we generated the Fscn2 knockout mice, which showed progressive loss of hearing and hair cells. Our goal of the present study was to investigate the mechanism underlying cochlear cell death in the Fscn2 knockout mice. Microarray analysis revealed upregulation of expression of PARVB, a local adhesion protein, in the inner ears of Fscn2 knockout mice at 8 weeks of age. Further studies showed increased levels of PARVB together with cleaved-Caspase9 and decreased levels of ILK, p-ILK, p-AKT, and Bcl-2 in the inner ears of Fscn2 knockout mice of the same age. Knockdown of Fscn2 in HEI-OCI cells led to decreased cell proliferation ability and migration rate, along with increased levels of PARVB and decreased levels of ILK, p-ILK, p-AKT, Bcl-2 and activated Rac1 and Cdc42. Overexpression of Fscn2 or inhibition of Parvb expression in HEI-OC1 cells promoted cell proliferation and migration, with increased levels of ILK, p-ILK, p-AKT, and Bcl-2. Finally, FSCN2 binds with PPAR-γ to reduce its nuclear translocation in HEI-OC1 cells, and inhibition of PPAR-γ by GW9662 decreased the level of PARVB and increased the levels of p-AKT, p-ILK, and Bcl-2. Our results suggest that FSCN2 negatively regulates PARVB expression by inhibiting the entry of PPAR-γ into the cell nucleus, resulting in inhibition of ILK-AKT related pathways and of cochlear cell survival in Fscn2 knockout mice. Our findings provide new insights and ideas for the prevention and treatment of genetic hearing loss.
Fscn2（肌动蛋白成束蛋白2）基因编码一种肌动蛋白交联蛋白，该蛋白参与毛细胞静纤毛和视网膜结构的形成。Fscn2基因突变与人类和小鼠的听力障碍及视网膜变性有关。为了解Fscn2基因的功能，我们培育了Fscn2基因敲除小鼠，这些小鼠表现出渐进性听力丧失和毛细胞缺失。本研究的目的是探究Fscn2基因敲除小鼠耳蜗细胞死亡的潜在机制。基因芯片分析显示，8周龄Fscn2基因敲除小鼠内耳中局部粘附蛋白PARVB的表达上调。进一步研究表明，相同年龄的Fscn2基因敲除小鼠内耳中PARVB水平升高，同时伴有裂解的Caspase9水平升高，而ILK、p-ILK、p-AKT和Bcl-2水平降低。在HEI-OCI细胞中敲低Fscn2导致细胞增殖能力和迁移率降低，同时PARVB水平升高，ILK、p-ILK、p-AKT、Bcl-2水平降低，Rac1和Cdc42活化。在HEI-OC1细胞中过表达Fscn2或抑制Parvb表达可促进细胞增殖和迁移，同时ILK、p-ILK、p-AKT和Bcl-2水平升高。最后，FSCN2与PPAR-γ结合以减少其在HEI-OC1细胞中的核转位，并且用GW9662抑制PPAR-γ可降低PARVB水平并增加p-AKT、p-ILK和Bcl-2水平。我们的结果表明，FSCN2通过抑制PPAR-γ进入细胞核来负向调节PARVB表达，从而导致Fscn2基因敲除小鼠中ILK-AKT相关通路及耳蜗细胞存活受到抑制。我们的研究结果为遗传性听力损失的预防和治疗提供了新的见解和思路。
