TMBIM4 affects left-right patterning via pluripotency exit during gastrulation

Area of Science:

• Developmental Biology
• Genetics
• Cell Biology

Background:

• Congenital heart disease (CHD) is the most common birth defect, yet its genetic underpinnings are not fully understood.
• Transmembrane BAX inhibitor motif-containing protein 4 (TMBIM4) is a candidate gene for CHD, linked to left-right (LR) patterning defects like cardiac heterotaxy.
• The precise developmental role of TMBIM4, particularly in early embryogenesis and cardiac development, requires further investigation.

Purpose of the Study:

• To investigate the developmental function of tmbim4 in Xenopus tropicalis.
• To determine tmbim4's role in left-right (LR) patterning and cardiac asymmetry.
• To elucidate the molecular mechanisms by which TMBIM4 influences embryonic development and cell fate.

Main Methods:

• Depletion of tmbim4 in Xenopus tropicalis embryos.
• Assessment of cardiac asymmetry and LR patterning defects.
• Analysis of gastrulation, pluripotency marker expression, and cell membrane potential (V_m).
• Rescue experiments using human and viral TMBIM4 orthologs and choline application.

Main Results:

• tmbim4 depletion in Xenopus caused cardiac asymmetry defects, mirroring human CHD phenotypes.
• Gastrulation was impaired in tmbim4-depleted embryos, affecting pluripotency marker expression and exit.
• tmbim4 depletion led to embryo depolarization, which was rescued by choline, suggesting an ion channel function.
• Evidence suggests TMBIM4 localizes to the plasma membrane, potentially regulating V_m.

Conclusions:

• tmbim4 is essential for proper LR patterning and gastrulation during embryonic development.
• TMBIM4 functions as a putative ion channel, influencing cell membrane potential and cell fate.
• These findings establish tmbim4 as a plausible gene associated with congenital heart disease and provide novel insights into its developmental roles.