Fgf3 and Fgf10 are required for mouse otic placode induction.

Area of Science:

• Developmental Biology
• Genetics
• Otic Development

Background:

• The inner ear, responsible for hearing and balance, develops from an ectodermal placode near the hindbrain.
• Previous studies indicated Fibroblast Growth Factor (FGF) signaling involvement, with Fgf3 affecting later stages of otic vesicle formation.

Purpose of the Study:

• To investigate the role of FGF signaling, specifically Fgf3 and Fgf10, in early otic placode induction and development.
• To determine the origins of FGF signals directing otic placode formation.

Main Methods:

• Analysis of mouse embryos with combined Fgf3 and Fgf10 gene knockouts.
• Examination of otic marker gene expression patterns in mutant embryos.
• Assessment of cell proliferation and survival in double mutant embryos.

Main Results:

• Embryos lacking both Fgf3 and Fgf10 failed to form otic vesicles.
• Aberrant expression of otic marker genes was observed in double mutants.
• FGF signals appear to act directly on the ectoderm, as hindbrain gene expression remained normal.
• Cell proliferation and survival were not significantly impacted, suggesting a role in gene regulation.

Conclusions:

• FGF signals from both the hindbrain and mesenchyme are essential for otic placode induction.
• The primary role of FGF signaling in otic induction is to establish correct gene expression patterns in the prospective placode.
• A quantitative requirement for FGF signaling in otic vesicle formation was suggested by intermediate phenotypes in triple mutant embryos.