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CD3G
CD3 gamma subunit of T-cell receptor complex
The CD3G gene provides instructions for making the CD3-gamma protein, an essential component of the T-cell receptor complex vital for proper immune system function. The CD3G gene plays a critical role in adaptive immunity by encoding the CD3-gamma subunit.
CD3G is located on the long (q) arm of chromosome 11, at band 11q23.3. Arm ratio per GRCh38 - banding schematic.
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Overview
The CD3G gene, or CD3 gamma subunit of T-cell receptor complex, is fundamental to the human immune system. It codes for a protein that forms part of the T-cell receptor (TCR) complex found on the surface of T lymphocytes. This complex is crucial for recognising specific antigens and initiating an immune response.
Disruptions to the CD3G gene can impair T-cell development and function, potentially leading to immunodeficiency conditions. Understanding CD3G is important for elucidating mechanisms of immune regulation and disease.
What the gene does
The protein produced from the CD3G gene, known as the CD3-gamma subunit, is a key component of the T-cell receptor (TCR) complex. This multisubunit protein complex is located on the surface of T cells and is responsible for recognising specific foreign antigens presented by other immune cells. Upon antigen binding by the TCR, the CD3-gamma subunit, along with other CD3 subunits (CD3-delta, CD3-epsilon, and CD3-zeta), transmits activating signals into the T cell.
This signal transduction is critical for initiating a cascade of intracellular events including T-cell activation, proliferation, and differentiation. The proper function of CD3-gamma, particularly its interaction with other CD3 components and downstream signalling molecules, is vital for the adaptive immune system to mount an effective defence against pathogens and abnormal cells.
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Chromosome location
The CD3G gene is situated on chromosome 11, specifically at position 11q23.3. This chromosomal location indicates its precise address within the human genome. The gene's position is a fixed point of reference in genetic mapping and studies.
Protein structure
The CD3-gamma protein, comprising 182 amino acids, features distinct functional domains crucial for its role in the T-cell receptor complex. It includes an Ig-like domain, spanning amino acids 37-94, which is characteristic of immunoglobulin superfamily members. A key signalling motif, the ITAM (Immunoreceptor Tyrosine-based Activation Motif), is located between amino acids 149-177. Additionally, a Di-leucine motif, found at amino acids 153-154, plays a role in intracellular trafficking.
Key variants
Genetic variations within the CD3G gene can affect the structure and function of the CD3-gamma protein. These changes, known as variants, may alter how the T-cell receptor complex functions or assembles. Variants are classified based on their potential impact, ranging from benign to pathogenic, and can influence the gene's association with various immune-related conditions.
Sample of pathogenic variants
5 pathogenic / likely-pathogenic variants from ClinVar, ranked by review status (expert-panel-reviewed first). This is a sample; recurrent founder variants in a specific population may not appear here - see the full ClinVar listing via the link above.
| Variant (HGVS) | Protein change | Classification | Evidence | Associated condition |
|---|---|---|---|---|
c.1A>G | p.Met1Val | Pathogenic/Likely pathogenic | ★★☆☆ | Combined immunodeficiency due to CD3gamma deficiency |
c.13A>T | p.Lys5Ter | Pathogenic | ★☆☆☆ | Combined immunodeficiency due to CD3gamma deficiency |
c.496C>T | p.Arg166Ter | Pathogenic | ★☆☆☆ | Combined immunodeficiency due to CD3gamma deficiency |
c.513C>G | p.Tyr171Ter | Pathogenic | ★☆☆☆ | Combined immunodeficiency due to CD3gamma deficiency |
c.71C>G | p.Ser24Ter | Pathogenic | ★☆☆☆ | Combined immunodeficiency due to CD3gamma deficiency |
Evidence stars indicate ClinVar review status. Individual variant interpretation should always be performed by a qualified clinical laboratory - many variants remain classified as Variants of Uncertain Significance (VUS) pending more research.
Associated conditions
Pathogenic variants in the CD3G gene are associated with conditions that affect the immune system. These conditions generally involve impaired T-cell development or function, leading to immunodeficiencies. The severity and specific clinical presentation can vary depending on the nature of the genetic change.
No disease links recorded for this gene in our reference set.
UK clinical status
The CD3G gene is included in several NHS England Genomic Medicine Service approved panels. It is part of the "COVID-19 research" panel, the "Infantile enterocolitis & monogenic inflammatory bowel disease" panel, and the "Primary immunodeficiency or monogenic inflammatory bowel disease" (R15) panel. Its presence on these panels highlights its recognised involvement in immune system disorders.
Sources: NHS GMS PanelApp · Genomics England PanelApp · NHS National Genomic Test Directory
Frequently asked questions
What is the primary function of the CD3G gene?
The CD3G gene provides instructions for making the CD3-gamma protein, which is an essential part of the T-cell receptor (TCR) complex. This complex is vital for T cells to recognise antigens and initiate an immune response.
How do variants in the CD3G gene affect health?
Variants in the CD3G gene can impair the normal function or assembly of the T-cell receptor complex. This can lead to immunodeficiency conditions, where the body's ability to fight off infections is compromised.
Is the CD3G gene relevant to T-cell development?
Yes, proper functioning of the CD3G gene is crucial for normal T-cell development. Defects can disrupt the signalling pathways necessary for T cells to mature and perform their role effectively in the immune system.