Molecular cloning and developmental expression of two chick embryo gap junction proteins

Area of Science:

• Molecular Biology
• Developmental Biology
• Cardiovascular Research

Background:

• Connexins form gap junctions, crucial for cell-to-cell communication.
• Existing connexins have conserved domains but unique cytoplasmic regions.
• Understanding connexin diversity is key to deciphering developmental roles.

Purpose of the Study:

• To identify novel connexins in chick embryos with potential roles in development.
• To characterize the expression patterns of newly identified connexins.

Main Methods:

• Screening of a chick embryo cDNA library using low-stringency hybridization with rat connexin-43 cDNA.
• Isolation and characterization of cDNA clones for new connexins.
• Southern and RNA blot analyses to determine gene copy number and tissue distribution.

Main Results:

• Two novel chick connexins, connexin-45 and connexin-42, were identified.
• Both connexins possess conserved and unique protein regions.
• Connexin-45 and -42 mRNAs are expressed in various chick organs, with unique tissue distributions.
• Connexin-45 mRNA levels dramatically decrease from embryonic to adult heart, unlike connexin-42 and -43.

Conclusions:

• The discovery of multiple connexins (connexin-43, -42, and -45) suggests diverse gap junction channels in cardiac myocytes.
• Differential expression of connexins, especially connexin-45 during heart development, indicates specialized functions.
• These findings provide insights into the formation of communication compartments in the developing myocardium.