AUTHOR=Qi Yue , Xiong Wei , Yu Shukui , Du Zhengde , Qu Tengfei , He Lu , Wei Wei , Zhang Lingjun , Liu Ke , Li Yi , He David Z. , Gong Shusheng 

TITLE=Deletion of C1ql1 Causes Hearing Loss and Abnormal Auditory Nerve Fibers in the Mouse Cochlea

JOURNAL=Frontiers in Cellular Neuroscience

VOLUME=15

YEAR=2021

URL=https://www.frontiersin.org/journals/cellular-neuroscience/articles/10.3389/fncel.2021.713651

DOI=10.3389/fncel.2021.713651

ISSN=1662-5102

ABSTRACT=<p>Complement C1q Like 1 (C1QL1), a secreted component of C1Q-related protein, is known to play an important role in synaptic maturation, regulation, and maintenance in the central nervous system. <italic>C1ql1</italic> is expressed in adult cochlear inner and outer hair cells (IHCs and OHCs) with preferential expression in OHCs. We generated <italic>C1ql1</italic> null mice to examine the role of C1QL1 in the auditory periphery. <italic>C1ql1</italic>-null mice exhibited progressive hearing loss with elevated thresholds of auditory brainstem response and distortion product otoacoustic emission. Confocal microscopy showed that the number of nerve fibers innervating both IHCs and OHCs was significantly reduced. However, spiral ganglion neurons appeared to be normal under electron microscopy. IHC development and survival were not affected by deletion of <italic>C1ql1.</italic> Voltage-clamp recording and immunocytochmistry combined with confocal microscopy showed <italic>C1ql1</italic>-null IHCs showed no significant reduction of pre-synaptic proteins and synaptic vesicle release. This is in contrast to significant OHC loss in the KO mice. Our study suggests that <italic>C1ql1</italic> is essential for development of hair cell innervation and OHC survival. But maturation of presynaptic machinery in IHCs does not depend on C1QL1.</p>