Knockdown of Foxg1 in supporting cells increases the trans-differentiation of supporting cells into hair cells in the neonatal mouse cochlea

• Published in: Cellular and molecular life sciences : CMLS Vol. 77; no. 7; pp. 1401 - 1419
• Main Authors: Zhang, Shasha, Zhang, Yuan, Dong, Ying, Guo, Lingna, Zhang, Zhong, Shao, Buwei, Qi, Jieyu, Zhou, Han, Zhu, Weijie, Yan, Xiaoqian, Hong, Guodong, Zhang, Liyan, Zhang, Xiaoli, Tang, Mingliang, Zhao, Chunjie, Gao, Xia, Chai, Renjie
• Format: Journal Article
• Language: English
• Published: Cham Springer International Publishing 01.04.2020; Springer Nature B.V
• Subjects: Animals; Animals, Newborn; Biochemistry; Biomedical and Life Sciences; Biomedicine; Birth; Cell Biology; Cell Count; Cell cycle; Cell differentiation; Cell fate; Cell Lineage; Cell Proliferation; Cell Survival; Cell Transdifferentiation; Cochlea; Cochlea - cytology; Cochlea - innervation; Differentiation; Forkhead protein; Forkhead Transcription Factors - deficiency; Forkhead Transcription Factors - metabolism; Foxg1 protein; Gene Expression Regulation; Gene Knockdown Techniques; Hair; Hair cells; Hair Cells, Auditory - cytology; Hair Cells, Auditory - ultrastructure; Inner ear; Labyrinth Supporting Cells - cytology; Labyrinth Supporting Cells - ultrastructure; Life Sciences; Mechanotransduction, Cellular; Mice, Transgenic; Morphogenesis; Neonates; Nerve Tissue Proteins - deficiency; Nerve Tissue Proteins - metabolism; Original; Original Article; Receptors, G-Protein-Coupled - metabolism; Regeneration; Signal Transduction - genetics; Stem Cells - metabolism; Synapses; Synapses - metabolism; Supporting cells; Trans-differentiation; Progenitors; Proliferation; Hair cells; Foxg1
• ISSN: 1420-682X; 1420-9071
• DOI: 10.1007/s00018-019-03291-2

Foxg1 is one of the forkhead box genes that are involved in morphogenesis, cell fate determination, and proliferation, and Foxg1 was previously reported to be required for morphogenesis of the mammalian inner ear. However, Foxg1 knock-out mice die at birth, and thus the role of Foxg1 in regulating hair cell (HC) regeneration after birth remains unclear. Here we used Sox2 CreER/+ Foxg1 loxp/loxp mice and Lgr5-EGFP CreER/+ Foxg1 loxp/loxp mice to conditionally knock down Foxg1 specifically in Sox2+ SCs and Lgr5+ progenitors, respectively, in neonatal mice. We found that Foxg1 conditional knockdown (cKD) in Sox2+ SCs and Lgr5+ progenitors at postnatal day (P)1 both led to large numbers of extra HCs, especially extra inner HCs (IHCs) at P7, and these extra IHCs with normal hair bundles and synapses could survive at least to P30. The EdU assay failed to detect any EdU+ SCs, while the SC number was significantly decreased in Foxg1 cKD mice, and lineage tracing data showed that much more tdTomato+ HCs originated from Sox2+ SCs in Foxg1 cKD mice compared to the control mice. Moreover, the sphere-forming assay showed that Foxg1 cKD in Lgr5+ progenitors did not significantly change their sphere-forming ability. All these results suggest that Foxg1 cKD promotes HC regeneration and leads to large numbers of extra HCs probably by inducing direct trans-differentiation of SCs and progenitors to HCs. Real-time qPCR showed that cell cycle and Notch signaling pathways were significantly down-regulated in Foxg1 cKD mice cochlear SCs. Together, this study provides new evidence for the role of Foxg1 in regulating HC regeneration from SCs and progenitors in the neonatal mouse cochlea.