Identification of putative GATA3 regulatory elements and comparison of GATA3 distribution in cochleae of mice, rats, macaques, and humans.

The transcription factor GATA3 plays a critical role in the development of neurons and sensory epithelia of the inner ear. In mouse cochleae, GATA3 is downregulated in certain supporting cells (SCs) and in type I spiral ganglion neurons (SGNs) after development. This reduction of GATA3 in SCs severely limits Atoh1-induced hair cell (HC) regeneration and suggests that a similar downregulation in human cochleae may be limiting for regenerative therapies. However, it is unknown whether GATA3 is similarly or differentially regulated in primates versus rodents. Using CAGE-seq data, we compared over 40 putative GATA3 regulatory elements across species and found both conserved and non-conserved sequences. To assess whether cochlear GATA3 distribution is similar or different between rodents and primates, we immunostained cochleae from mice, rats, macaques, and humans using antibodies raised against highly conserved GATA3 peptide sequences. GATA3 immunostaining in the organs of Corti from all four species revealed a large degree of conservation, where SCs medial and lateral to cochlear HCs exhibited robust nuclear GATA3 immunolabeling, but pillar and Deiters cells had significantly reduced GATA3 immunoreactivity. In all four species, GATA3 was expressed in a subset of SGNs that largely co-expressed peripherin suggesting they were type II SGNs. Only one difference emerged, wherein human cochlear inner hair cells were not GATA3 immunoreactive despite being so in the other species. Overall, the pattern of GATA3 expression in primates appears similar to rodents and reinforces the notion that ATOH1 mediated regenerative therapies may be limited by reduced GATA3 expression in adult SCs.