On the role of ephrinA2 in auditory function

Recent findings suggest that the manipulation of the EphA/ephrinA system can improve hearing threshold sensitivity in the auditory system (Yates et al., 2014). These results appear to open-up the possibility that pharmacological manipulation of this system could lead to the development of treatments to cure some types of hearing loss. As a first step towards this goal, we have performed a further series of auditory brainstem evoked potential recordings on ephrinA2 homozygous knockout mice and their wildtype littermates in order to replicate the previously reported findings. However, we found that ephrinA2 knockout mice had auditory threshold sensitivity for click and 3-42 kHz tone pip frequencies comparable to that of their wildtype littermates. Evoked potential wave amplitudes, latencies and inter-peak intervals were also comparable between ephrinA2 knockout mice and wild type control littermates. Thus in our experiments we could not replicate the findings of Yates et al. (2014). Whilst the EphA/ephrinA system may therefore play a role in the development of innervation of the cochlea and neural circuitry of the auditory brainstem, there appears to be a functional redundancy between members of this family such that loss of ephrinA2 function alone is insufficient to alter auditory function in the mouse.