Substitutions in the Conserved C2C Domain of Otoferlin Cause DFNB9, a Form of Nonsyndromic Autosomal Recessive Deafness

Mirghomizadeh, Farhad; Pfister, Markus; Apaydın, Fazıl; Petit, Christine; Kupka, Susan; Pusch, Carsten M.; Zenner, Hans‐Peter; Blin, Nikolaus

doi:10.1006/nbdi.2002.0488

Cited by 59 publications

(63 citation statements)

References 21 publications

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“…However, it is possible that the N-terminal C2 domains play a role that was not detected in our assays or a function found in mammals but not in zebrafish. Indeed, our results seem to conflict with reports of missense mutations in the C2B and C2C domains that have been linked to hearing loss in mammals (51,52) We speculate that these missense mutations may reduce the structural stability of the protein, resulting in lower levels of protein expression. Knockdown of both zebrafish otoferlin genes was required for an observable phenotype in our studies, despite differing in the first N-terminal 183 amino acids, corresponding to the C2A domain, again suggesting that some domains may be dispensable.…”

Section: Discussioncontrasting

confidence: 99%

Otoferlin Deficiency in Zebrafish Results in Defects in Balance and Hearing: Rescue of the Balance and Hearing Phenotype with Full-Length and Truncated Forms of Mouse Otoferlin

Chatterjee

Padmanarayana

Abdullah

et al. 2015

Molecular and Cellular Biology

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Sensory hair cells convert mechanical motion into chemical signals.Otoferlin, a six-C2 domain transmembrane protein linked to deafness in humans, is hypothesized to play a role in exocytosis at hair cell ribbon synapses. To date, however, otoferlin has been studied almost exclusively in mouse models, and no rescue experiments have been reported. Here we describe the phenotype associated with morpholino-induced otoferlin knockdown in zebrafish and report the results of rescue experiments conducted with full-length and truncated forms of otoferlin. We found that expression of otoferlin occurs early in development and is restricted to hair cells and the midbrain. Immunofluorescence microscopy revealed localization to both apical and basolateral regions of hair cells. Knockdown of otoferlin resulted in hearing and balance defects, as well as locomotion deficiencies. Further, otoferlin morphants had uninflated swim bladders. Rescue experiments conducted with mouse otoferlin restored hearing, balance, and inflation of the swim bladder. Remarkably, truncated forms of otoferlin retaining the C-terminal C2F domain also rescued the otoferlin knockdown phenotype, while the individual N-terminal C2A domain did not. We conclude that otoferlin plays an evolutionarily conserved role in vertebrate hearing and that truncated forms of otoferlin can rescue hearing and balance.H air cells couple mechanical motion to neurotransmitter release at synapses (1). In contrast to conventional neural synapses, hair cell synapses release neurotransmitter continuously and, in a graded manner (2), possess synaptic ribbons (2-4), and lack synaptophysin (5), complexin (6-9), Munc13 (10), and the calcium sensors synaptotagmin I and II (11). In place of synaptotagmin, it is believed that otoferlin may confer calcium sensitivity to evoke neurotransmitter release (12, 13). Otoferlin is a six-C2 domain transmembrane protein expressed in inner, outer, and vestibular hair cells, as well as restricted regions of the brain (13-16). In humans, missense mutations in otoferlin have been linked to hearing loss (17,18), and biochemical studies have determined that otoferlin binds calcium and lipids (12,19), as well as membrane trafficking proteins (12,(20)(21)(22)(23). Further, in vitro assays have demonstrated that otoferlin accelerates SNARE-mediated membrane fusion (12). Based upon this evidence, it is hypothesized that otoferlin functions as a calcium-sensitive regulator of neurotransmitter release in sensory hair cells.However, the results of several studies have raised questions related to otoferlin's function. For instance, despite otoferlin expression in vestibular hair cells, knockout mice show no balance defects (24, 25) despite reduced exocytosis in vestibular type I hair cells (24,26). This raises questions as to the importance of otoferlin in this system. Further, otoferlin did not rescue synchronous neurotransmitter release in synaptotagmin I knockout cultured neurons, indicating that otoferlin and synaptotagmin are not functionally redundant (2...

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Section: Discussioncontrasting

confidence: 99%

Otoferlin Deficiency in Zebrafish Results in Defects in Balance and Hearing: Rescue of the Balance and Hearing Phenotype with Full-Length and Truncated Forms of Mouse Otoferlin

Chatterjee

Padmanarayana

Abdullah

et al. 2015

Molecular and Cellular Biology

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“…Missense mutations in C2 domains of otoferlin have been reported to underlie several cases of human deafness, including the P490Q and I515T mutations in the C2C domain (Mirghomizadeh et al, 2002), the L1011P mutation in the C2D domain (Tekin et al, 2005), and the P1825A mutation in the C2F domain (Migliosi et al, 2002). Thus, ablations of individual C2 domains by themselves can disrupt the overall function of the protein, indicating that these domains are not simply redundant components that additively increase the Ca 2+ binding property of the protein.…”

Section: Discussionmentioning

confidence: 99%

A missense mutation in the conserved C2B domain of otoferlin causes deafness in a new mouse model of DFNB9

et al. 2007

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Mutations of the otoferlin gene have been shown to underlie deafness disorders in humans and mice. Analysis of genetically engineered mice lacking otoferlin have demonstrated an essential role for this protein in vesicle exocytosis at the inner hair cell afferent synapse. Here, we report on the molecular and phenotypic characterization of a new ENU-induced missense mutation of the mouse otoferlin gene designated Otof deaf5Jcs . The mutation is a single T to A base substitution in exon 10 of Otof that causes a non-conservative amino acid change of isoleucine to asparagine in the C2B domain of the protein. Although strong immunoreactivity with an otoferlin-specific antibody was detected in cochlear hair cells of wild type mice, no expression was detected in mutant mice, indicating that the missense mutation has a severe effect on the stability of the protein and potentially its localization. Auditory brainstem response (ABR) analysis demonstrated that mice homozygous for the missense mutation are profoundly deaf, consistent with an essential role for otoferlin in inner hair cell neurotransmission. Vestibular-evoked potentials (VsEPs) of mutant mice, however, were equivalent to those of wild type mice, indicating that otoferlin is unnecessary for vestibular function even though it is highly expressed in both vestibular and cochlear hair cells.

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“…Pathological missense mutations in the C2C (Mirghomizadeh et al, 2002), C2D (Tekin et al, 2005), and C2F domains (Migliosi et al, 2002) of otoferlin have been linked to profound deafness in several human patients. Interestingly, in each case, a single amino acid change in a single C2 domain results in deafness; in some cases, this appears to be caused by degradation of the entire protein in response to misfolding of single domains.…”

Section: Point Mutations Disrupt the Function Of Otoferlin C2 Domainsmentioning

confidence: 99%

Otoferlin is a calcium sensor that directly regulates SNARE-mediated membrane fusion

Johnson¹,

Chapman²

2010

J Gen Physiol

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Substitutions in the Conserved C2C Domain of Otoferlin Cause DFNB9, a Form of Nonsyndromic Autosomal Recessive Deafness

Cited by 59 publications

References 21 publications

Otoferlin Deficiency in Zebrafish Results in Defects in Balance and Hearing: Rescue of the Balance and Hearing Phenotype with Full-Length and Truncated Forms of Mouse Otoferlin

Otoferlin Deficiency in Zebrafish Results in Defects in Balance and Hearing: Rescue of the Balance and Hearing Phenotype with Full-Length and Truncated Forms of Mouse Otoferlin

A missense mutation in the conserved C2B domain of otoferlin causes deafness in a new mouse model of DFNB9

Otoferlin is a calcium sensor that directly regulates SNARE-mediated membrane fusion

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