1.AIFM1 variants associated with auditory neuropathy spectrum disorder cause apoptosis due to impaired apoptosis-inducing factor dimerization.
Yue QIU ; Hongyang WANG ; Huaye PAN ; Jing GUAN ; Lei YAN ; Mingjie FAN ; Hui ZHOU ; Xuanhao ZHOU ; Kaiwen WU ; Zexiao JIA ; Qianqian ZHUANG ; Zhaoying LEI ; Mengyao LI ; Xue DING ; Aifu LIN ; Yong FU ; Dong ZHANG ; Qiuju WANG ; Qingfeng YAN
Journal of Zhejiang University. Science. B 2023;24(2):172-184
Auditory neuropathy spectrum disorder (ANSD) represents a variety of sensorineural deafness conditions characterized by abnormal inner hair cells and/or auditory nerve function, but with the preservation of outer hair cell function. ANSD represents up to 15% of individuals with hearing impairments. Through mutation screening, bioinformatic analysis and expression studies, we have previously identified several apoptosis-inducing factor (AIF) mitochondria-associated 1 (AIFM1) variants in ANSD families and in some other sporadic cases. Here, to elucidate the pathogenic mechanisms underlying each AIFM1 variant, we generated AIF-null cells using the clustered regularly interspersed short palindromic repeats (CRISPR)/CRISPR-associated protein 9 (Cas9) system and constructed AIF-wild type (WT) and AIF-mutant (mut) (p.T260A, p.R422W, and p.R451Q) stable transfection cell lines. We then analyzed AIF structure, coenzyme-binding affinity, apoptosis, and other aspects. Results revealed that these variants resulted in impaired dimerization, compromising AIF function. The reduction reaction of AIF variants had proceeded slower than that of AIF-WT. The average levels of AIF dimerization in AIF variant cells were only 34.5%‒49.7% of that of AIF-WT cells, resulting in caspase-independent apoptosis. The average percentage of apoptotic cells in the variants was 12.3%‒17.9%, which was significantly higher than that (6.9%‒7.4%) in controls. However, nicotinamide adenine dinucleotide (NADH) treatment promoted the reduction of apoptosis by rescuing AIF dimerization in AIF variant cells. Our findings show that the impairment of AIF dimerization by AIFM1 variants causes apoptosis contributing to ANSD, and introduce NADH as a potential drug for ANSD treatment. Our results help elucidate the mechanisms of ANSD and may lead to the provision of novel therapies.
Humans
;
Apoptosis Inducing Factor/metabolism*
;
NAD/metabolism*
;
Dimerization
;
Apoptosis
Result Analysis
Print
Save
E-mail