A locus control region in the T cell receptor alpha/delta locus

Area of Science:

• Immunology
• Molecular Biology
• Genetics

Background:

• A locus control region (LCR) regulates chromatin accessibility for gene expression.
• The T cell receptor (TCR) alpha/delta locus has differential expression and rearrangement patterns.
• Understanding the regulatory elements of the TCR locus is crucial for T cell development.

Purpose of the Study:

• To identify and characterize a potential LCR regulating the TCR alpha/delta locus.
• To investigate the role of this LCR in TCR gene expression and T cell development.
• To propose a model for differential TCR alpha and delta gene regulation.

Main Methods:

• Localization of T cell-specific nuclease hypersensitive domains (HS-1 to HS-8) 3' of the TCR alpha/delta locus.
• Generation and analysis of transgenic mice with a TCR alpha gene linked to the identified region.
• Assessment of transgene expression levels, tissue specificity, developmental timing, and T cell subset distribution.

Main Results:

• An LCR, characterized by eight T cell-specific hypersensitive sites (HS-1 to HS-8), was identified 3' of the TCR alpha/delta locus.
• Transgenic mice showed high-level, integration site-independent expression of the linked TCR alpha gene, correlating with gene copy number.
• The transgene was correctly expressed in alpha beta T cells, not gamma delta T cells, and activated appropriately during development.
• Functional analysis indicated that the region containing HS-2 to HS-6 is essential for proper LCR function.

Conclusions:

• A novel LCR regulating the TCR alpha/delta locus has been identified.
• This LCR controls high-level, developmentally regulated expression of the TCR alpha gene in a specific T cell subset.
• A model of LCR competition is proposed to explain the differential regulation of TCR alpha and delta genes.