Structure, Expression, and Function of a Novel Intercalated Disc Protein, Xin

Area of Science:

• Molecular Biology
• Cardiovascular Biology
• Developmental Biology

Background:

• The Xin gene family, including chick Xin (cXin), mouse Xin alpha (mXinα), and mouse Xin beta (mXinβ), plays a role in cardiac development.
• Xin proteins share conserved domains, including a novel Xin repeat, DNA binding domain, nuclear localization signal, and proline-rich region.

Purpose of the Study:

• To investigate the function and regulation of Xin genes in cardiac development and function.
• To identify Xin protein interactions and its role in signaling pathways.

Main Methods:

• Gene cloning and characterization (mRNA display, EST database searches, cDNA cloning).
• Gene mapping (radiation hybrid analysis, DNA sequencing).
• Expression analysis (tissue expression profiling, knockout mouse models).
• Protein interaction studies (co-localization, direct interaction assays).

Main Results:

• Xin genes are expressed in striated muscle and are downstream targets of Nkx2.5 and MEF2C transcription factors.
• Xin expression is upregulated in response to cardiac hypertrophy.
• Xin protein co-localizes with N-cadherin and β-catenin and interacts with β-catenin.
• Xin repeats bind to actin filaments, suggesting a role in microfilament organization.

Conclusions:

• Xin proteins are integral to cardiac morphogenesis and function by integrating adhesion and regulating actin filament organization.
• Xin plays a critical role in Wnt/β-catenin and N-cadherin-mediated signaling pathways essential for heart development and function.