The Role Of Transcription Factor GATA3 In Supporting Cells Of The Postnatal Mouse Cochlea

In humans,haplo-insufficiency of the Gata3 gene causes hypoparathyroidism,sensorineural hearing loss,and renal disease?HDR?syndrome,also known as Barakat syndrome.Among these three phenotypes,all patients have some form of sensorineural deafness,suggesting GATA3's essential role in cochlear development.Previous studies have shown that Gata3 is required for the development of the prosensory domain and spiral ganglion neurons?SGNs?of the mouse cochlea during embryogenesis.However,the early deletion of Gata3 results in defects of the prosensory domain and the loss of SGNs also affects the morphology of the cochlear duct,which prevent the further study of Gata3's role in the postmitotic sensory epithelium at later stages.Thus the role of Gata3 in hair cells?HCs?and supporting cells?SCs?after cell differentiation is still largely unknown.In this study,we used the tamoxifen-inducible Sox2-CreERT2 to inactivate Gata3in SCs of the postnatal mouse cochlea.The results showed that Gata3 is continuously expressed in mouse postnatal cochlear SCs and the loss of Gata3 resulted in the hypertrophy of SCs and in the expansion of greater epithelium ridge?GER?in neonatal mouse cochlea.In contrast,Gata3 deficiency had no obvious effect on mature cochlear SCs.EdU staining results showed the absence of Gata3 in SCs resulted in the cell cycle reentry of SCs in neonatal mouse cochlea.The Ki67 immunostaining results revealed that the loss of Gata3 resulted in the proliferation of SCs,including the inner pillar cell?IPC?,inner border cell?IBC?,and lateral GER.In addition,loss of Gata3 resulted in the down-regulation of p27^kip1,a cell cycle inhibitor,in the SCs of Gata3-null neonatal cochleae.Chromatin immunoprecipitation analysis revealed that GATA3 directly bind to the promoter of p27^kip1.Taken together,our results indicate that GATA3 maintain the quiescent state of cochlear SCs by directly regulating p27^kip1 expression.Furthermore,the results of RNA-seq,RT-qPCR and in situ hybridization?ISH?revealed several downstream genes of Gata3 in cochlear SCs,including Tectb,Cyp26b1,Slitrk6,Ano1,and Aqp4.The altered expression levels of these genes may contribute to Gata3deficiency-induced sensorineural deafness in HDR syndrome.