Fgf4 maintains Hes7 levels critical for normal somite segmentation clock function.

Area of Science:

• Developmental Biology
• Genetics
• Molecular Biology

Background:

• Vertebrate development involves the segmentation of presomitic mesoderm (PSM) into somites, forming the vertebral column.
• Somitogenesis periodicity is regulated by a segmentation clock mechanism involving oscillating Notch activity.
• Fibroblast growth factors (FGFs), including FGF4 and FGF8, have been shown to redundantly prevent PSM differentiation.

Purpose of the Study:

• To investigate the specific roles of FGF4 and FGF8 in somitogenesis and vertebral development.
• To elucidate the molecular mechanisms by which FGF4 influences the segmentation clock.
• To determine the potential link between FGF4 function and human vertebral segmentation defects.

Main Methods:

• Analysis of mouse mutants lacking either FGF4 or FGF8.
• Quantification of mRNA levels using fluorescent in situ hybridization (FISH) and chain reaction.
• Volumetric tissue analysis using Imaris software.
• Genetic synergy studies involving Hes7 and FGF4/FGF8.

Main Results:

• FGF8 is not essential for somitogenesis, while FGF4 mutants exhibit diverse vertebral defects.
• FGF4 is critical for maintaining Hes7 mRNA levels and normal oscillatory patterns in the segmentation clock.
• Genetic analysis revealed synergy between Hes7 and FGF4, but not FGF8, supporting FGF4's role in regulating Hes7.

Conclusions:

• FGF4 plays a significant role in regulating the segmentation clock by maintaining Hes7 expression and oscillatory dynamics.
• Disruptions in FGF4 signaling can lead to vertebral defects, suggesting a mechanism for certain human segmentation disorders.
• These findings highlight FGF4 as a key regulator of somitogenesis and a potential factor in human vertebral segmentation defects linked to Notch pathway oscillations.