Differential and overlapping expression pattern of SOX2 and SOX9 in inner ear development

Area of Science:

• Developmental Biology
• Genetics
• Otolaryngology

Background:

• Inner ear development involves intricate molecular regulation of cell fate.
• SOX2 and SOX9 are crucial SOX family transcription factors implicated in these processes.
• Previous studies noted early SOX9 expression, but its detailed pattern in later development was unclear.

Purpose of the Study:

• To comprehensively map the expression patterns of SOX9 and SOX2 in the developing mouse inner ear from E9.5 to E18.5.
• To compare the spatiotemporal expression of SOX2 and SOX9.
• To elucidate the potential distinct roles of SOX2 and SOX9 in inner ear sensory development.

Main Methods:

• Double fluorescence immunohistochemistry was employed to visualize SOX2 and SOX9 expression.
• Analysis spanned critical developmental stages from E9.5 to E18.5 in mouse inner ear models.

Main Results:

• SOX9 showed broad expression in otic epithelium, mesenchyme, and cartilage.
• SOX2 consistently marked prosensory and sensory epithelia, initially in all cells, then supporting and hair cells, with diminishing hair cell expression after E15.5.
• SOX9 and SOX2 overlapped in prosensory/sensory regions until E14.5, after which SOX9 became restricted to supporting cells.

Conclusions:

• SOX2 and SOX9 exhibit overlapping yet distinct expression dynamics during inner ear sensory development.
• The differential expression patterns suggest SOX2 and SOX9 orchestrate unique molecular pathways for cell fate specification.
• These findings provide insights into the regulatory mechanisms governing inner ear sensory organogenesis.