Wfs1E864K knock-in mice illuminate the fundamental role of Wfs1 in endocochlear potential production

Abstract

Wolfram syndrome (WS) is a rare neurodegenerative disease encompassing diabetes mellitus, diabetes insipidus, optic atrophy, hearing loss (HL) and neurological disorders. None of the animal models of the pathology are presenting with an early onset HL, impeding the understanding of the role of Wolframin (WFS1), the protein responsible for WS, in the auditory pathway. We generated a knock-in mouse, the Wfs1E864K line, presenting a human mutation leading to severe deafness in affected individuals. The homozygous mice showed a profound post-natal HL and vestibular syndrome, associated with a decrease of the endocochlear potential (EP) and a devastating alteration of the stria vascularis and neurosensory epithelium. The mutant protein prevented the localization to the cell surface of the Na+/K+ATPase-β1 subunit, a key protein for the maintenance of the EP. Overall, our data support an important role of WFS1 in the maintenance of the EP and the stria vascularis, via its binding partner, the Na+/K+ATPase β1-subunit.

The Wolfram-like variant WFS1E864Kdestabilizes MAM and compromises autophagy and mitophagy in human and mice

“…One can speculate that the dominant negative effect of missense variant associated with WLS might have increased toxicity in the sensory organs compared to the haploinsufficiency of biallelic nonsense variant associated with WS. Consistent with this hypothesis, in a mouse model, homozygous for the WLS Wfs1 E864K allele 6,7 , we recently showed the devastating effect of this missense variant on the inner ear 8 . The homozygous mutant mice showed a profound post-natal hearing loss, at all tested frequencies, a collapse of the endocochlear potential and an alteration of the stria vascularis and neurosensory epithelium within their first month of age.…”

“…Consistent with this hypothesis, in a mouse model, homozygous for the WLS Wfs1 E864K allele 6,7 , we recently showed the devastating effect of this missense variant on the inner ear 8 . The homozygous mutant mice showed a profound post-natal hearing loss, at all tested frequencies, a collapse of the endocochlear potential and an alteration of the stria vascularis and neurosensory epithelium within their first month of age.…”

“…To determine the functional impact of Wfs1 E864K , a WLS-associated protein 6,7 , we first investigated the mitochondrial respiration, using a Seahorse XFe analyzer, (Figure 1A) of neuronal cultures from the hippocampus and cortex of WT and homozygous mutant mice, Wfs1 E864K , at post-natal day 33, age for which the neurosensorial deficits are at their maximal severity 8 . We recorded a significant decrease of the basal ( p = 0.005 and p < 0.0001; Figure 1B), ATP-related ( p = 0.0018 and p = 0.0002; Figure 1C) and maximal ( p = 0.0025 and p = 0.0004; Figure 1D) oxygen consumption rates of the neuronal cultures from the mutant mice, derived from both structures, compared to those of the cultures derived from WT mice.…”

“…The Wfs1 E864K mice were generated as previously described 8 . Animal care and experimentation were authorized by the National Ethic Committee (Paris) and carried out in strict adherence to the European Union Directive 2010/63 and ARRIVE guidelines 40 .…”

“…In contrast with WS pathophysiology, which has attracted attention in the recent years, little is known about the underlying molecular mechanisms of WLS and the impact of the WLS specific WFS1 variants. In the present study, we put in light the molecular role of WFS1 in a pathophysiological context of WLS in the central nervous system of a mouse model of the disease 8 , Wfs1 E864K , and in patients’ fibroblasts 7 , all harboring the missense variant WFS1E864K.…”