FGF-activated calcium channels control neural gene expression in Xenopus

Area of Science:

• Developmental Biology
• Neuroscience
• Cell Signaling

Background:

• Neural induction initiates nervous system formation in vertebrates during gastrulation.
• Key signaling pathways involved include BMP inhibition, FGF receptor activation, and calcium (Ca2+) signaling.
• Intracellular Ca2+ concentration ([Ca2+]i) increases via dihydropyridine-sensitive Ca2+ channels (DHP-sensitive Ca2+ channels) are necessary for neural fate determination and gene expression.

Purpose of the Study:

• To investigate the mechanism by which DHP-sensitive Ca2+ channels are activated during neural induction.
• To determine the role of FGF signaling in activating Ca2+ channels and subsequent neural gene expression.

Main Methods:

• Experiments were conducted using isolated ectoderm tissue from Xenopus embryos.
• FGF-4 was used to stimulate ectodermal cells, and changes in membrane potential and [Ca2+]i were measured.
• Inhibitors of FGF receptors (SU5402) and DHP-sensitive Ca2+ channels were employed.

Main Results:

• FGF-4 application depolarized ectodermal cell membranes and increased [Ca2+]i.
• This FGF-induced Ca2+ increase was blocked by FGF receptor and DHP-sensitive Ca2+ channel antagonists.
• Inhibition of these pathways also blocked the induction of neural genes.

Conclusions:

• FGF signaling directly activates DHP-sensitive Ca2+ channels in ectodermal cells.
• This activation is a critical step in FGF-mediated neural induction.
• A proposed mechanism involves arachidonic acid and TRPC1 channel activation in the FGF signaling pathway.