The helix-loop-helix gene E2A is required for B cell formation

Area of Science:

• Developmental biology
• Immunology
• Genetics

Background:

• Tissue-specific cell fate is determined by heterodimers of basic-helix-loop-helix (bHLH) proteins and E2A gene products.
• Understanding the broad developmental roles of E2A is essential.

Purpose of the Study:

• To investigate the function of E2A in mammalian development by generating and analyzing E2A mutant mice.

Main Methods:

• Homologous recombination in embryonic stem cells to create E2A mutant mice.
• Analysis of postnatal survival, growth, and detailed hematopoiesis in mutant and wild-type mice.

Main Results:

• Homozygous E2A mutant mice exhibit high postnatal death and retarded growth.
• These mice are devoid of B cells, with differentiation blocked before immunoglobulin gene rearrangement and B220 expression.
• Other hematopoietic lineages (T cells, granulocytes, macrophages, erythroid) remain intact.
• Heterozygous embryos have approximately half the number of B cells compared to wild-type, suggesting a dose-dependent effect.

Conclusions:

• E2A is indispensable for B cell development, acting upstream of immunoglobulin gene rearrangement.
• The study suggests a mechanism where E2A levels are translated into B cell numbers, highlighting its role in regulating cell population size.