Gap junction signalling mediated through connexin-43 is required for chick limb development.

Area of Science:

• Developmental Biology
• Molecular Biology
• Cell Signaling

Background:

• Connexin-43 (Cx43) is a gap junction protein crucial for chick limb development.
• Cx43 is expressed in specific regions of the apical ectodermal ridge (AER) and zone of polarizing activity.
• Understanding Cx43's role is vital for elucidating limb bud formation mechanisms.

Purpose of the Study:

• To investigate the function of Connexin-43 (Cx43) in chick limb bud development.
• To determine the impact of Cx43 down-regulation on limb morphology and signaling.
• To explore potential feedback mechanisms involving Cx43 and fibroblast growth factors (FGFs).

Main Methods:

• Utilized antisense oligonucleotides (ODNs) delivered via Pluronic F-127 gel for sustained Cx43 inhibition.
• Assessed Cx43 protein levels and confirmed specificity by examining Connexin-32 (Cx32) expression.
• Analyzed limb phenotypes, gene expression (Shh, Bmp-2, Fgf-4, Fgf-8), and AER marker abnormalities.

Main Results:

• Specific antisense ODNs significantly reduced Cx43 protein expression without affecting Cx32.
• Cx43 inhibition led to severe limb defects in ~40% of embryos, including truncation and splitting.
• Down-regulation of Cx43 disrupted Fgf-4 and Fgf-8 expression in the AER, correlating with limb abnormalities.

Conclusions:

• Cx43 plays a critical role in maintaining AER integrity and normal limb outgrowth.
• Loss of Cx43 function mimics AER removal, leading to distal limb truncation.
• A feedback loop likely exists between FGF signaling and Cx43-mediated gap junction communication in limb development.