Giese Arnaud P J, Parker Andrew, Rehman Sakina, Brown Steve D M, Riazuddin Saima, Vander Kooi Craig W, Bowl Michael R, Ahmed Zubair M
Department of Otorhinolaryngology - Head and Neck Surgery, University of Maryland School of Medicine, Baltimore, MD 21201, USA.
MRC Harwell Institute, Mammalian Genetics Unit, Harwell Campus, Oxfordshire OX11 0RD, UK.
Dis Model Mech. 2025 Mar 1;18(3). doi: 10.1242/dmm.052043. Epub 2025 Apr 3.
Humans and mice with mutations in genes encoding CIB2 and whirlin (WHRN) are deaf. We previously reported that CIB2 binds to WHRN and is essential for stereocilia staircase architecture of cochlear hair cells. Here, we refine the interaction domains of both proteins and show that these proteins play unique roles in stereocilia bundle formation and organization. We found that the EF2 domain of CIB2 binds to the HHD2 region of WHRN. AlphaFold2 multimer independently identified the same interacting regions and gave a thorough structural model. Next, we investigated genetic interaction between murine Cib2 and Whrn. Hearing in mice double heterozygous for functionally null alleles (Cib2KO/+;Whrnwi/+) was similar to that in age-matched wild-type mice, indicating that partial deficiency for both Cib2 and Whrn does not impair hearing. Double homozygous mutant mice (Cib2KO/KO;Whrnwi/wi) were deaf, and their cochlear stereocilia exhibited a predominant phenotype seen in single Whrnwi/wi mutants. Overexpression of WHRN in Cib2KO/KO mice did not rescue the stereocilia morphology. These data suggest that CIB2 is multifunctional, with key independent functions in the development and/or maintenance of the stereocilia staircase pattern in auditory hair cells.
编码CIB2和Whirlin（WHRN）的基因突变的人类和小鼠会耳聋。我们之前报道过CIB2与WHRN结合，并且对耳蜗毛细胞的静纤毛阶梯结构至关重要。在这里，我们优化了这两种蛋白质的相互作用结构域，并表明这些蛋白质在静纤毛束的形成和组织中发挥着独特作用。我们发现CIB2的EF2结构域与WHRN的HHD2区域结合。AlphaFold2多聚体独立鉴定出了相同的相互作用区域，并给出了一个完整的结构模型。接下来，我们研究了小鼠Cib2和Whrn之间的基因相互作用。功能缺失等位基因的双杂合小鼠（Cib2KO/+;Whrnwi/+）的听力与年龄匹配的野生型小鼠相似，这表明Cib2和Whrn的部分缺陷不会损害听力。双纯合突变小鼠（Cib2KO/KO;Whrnwi/wi）耳聋，其耳蜗静纤毛表现出在单一Whrnwi/wi突变体中看到的主要表型。在Cib2KO/KO小鼠中过表达WHRN并不能挽救静纤毛形态。这些数据表明CIB2具有多种功能，在听觉毛细胞静纤毛阶梯模式的发育和/或维持中具有关键的独立功能。
