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PTPRC
protein tyrosine phosphatase receptor type C
PTPRC is located on the long (q) arm of chromosome 1, at band 1q31.3-q32.1. Arm ratio per GRCh38 - banding schematic.
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Overview
PTPRC (protein tyrosine phosphatase receptor type C) is located on chromosome 1 and encodes the CD45 protein, one of the most abundant molecules on the surface of white blood cells. CD45 belongs to the protein tyrosine phosphatase family, enzymes that counterbalance the action of protein tyrosine kinases by removing phosphate groups from tyrosine amino acids on target proteins. This dephosphorylation activity is crucial for controlling signal transduction pathways in immune cells. CD45 plays a particularly important role in the development and function of T lymphocytes and B lymphocytes, the adaptive immune cells responsible for recognising and responding to foreign pathogens. The protein exists in multiple isoforms generated through alternative splicing, with different isoforms expressed at distinct stages of lymphocyte development and activation.
What the gene does
The CD45 protein functions as a receptor-type protein tyrosine phosphatase, meaning it spans the cell membrane with an external receptor portion and an internal catalytic domain. The intracellular portion contains two tandem phosphatase domains, although only the membrane-proximal domain appears to be enzymatically active. CD45 regulates the activity of Src family kinases, particularly Lck and Fyn in T cells, which are essential components of the T cell receptor signalling pathway. By removing inhibitory phosphate groups from these kinases, CD45 generally enables immune cell activation, though it can also have inhibitory effects depending on cellular context. In T cells, CD45 is required for antigen receptor signalling - cells lacking functional CD45 cannot properly activate in response to foreign antigens. The protein also influences B cell receptor signalling and is involved in cytokine receptor pathways. Alternative splicing of exons 4, 5, and 6 generates multiple CD45 isoforms (designated CD45RA, CD45RB, CD45RC, CD45RO, and combinations thereof) with different extracellular domains. These isoforms are expressed in a cell-type-specific and activation-dependent manner, allowing fine-tuned regulation of immune responses throughout lymphocyte maturation and function.
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Chromosome location
PTPRC is located on the long arm of chromosome 1 at position 1q31.3-q32.1. This chromosomal region contains a cluster of genes involved in immune function and cell signalling. The gene spans a substantial genomic region and contains 34 exons that can be assembled through alternative splicing to produce different protein isoforms with varying extracellular structures.
Protein structure
Domain architecture has not been experimentally characterised in detail for this protein.
Key variants
Genetic variants in PTPRC can affect the structure and function of the CD45 protein. Changes that disrupt the phosphatase activity or expression of CD45 can impair immune cell signalling and development. The inheritance pattern for PTPRC-related conditions varies depending on the specific variant and its functional consequences. Some variants may cause recessive conditions requiring changes in both gene copies, while others may have dominant effects.
No pathogenic or likely-pathogenic ClinVar variants recorded yet for this gene.
Associated conditions
Pathogenic variants in PTPRC have been associated with severe combined immunodeficiency (SCID), a group of inherited disorders characterised by profoundly impaired T cell and B cell function. Individuals with PTPRC-related SCID typically present in infancy with recurrent severe infections, failure to thrive, and absent or severely reduced numbers of functional T lymphocytes. The condition represents a rare cause of SCID, with most cases resulting from biallelic loss-of-function variants that eliminate CD45 expression or activity. Research suggests that complete absence of CD45 prevents normal T cell development in the thymus and blocks T cell receptor signalling in peripheral lymphocytes.
No disease links recorded for this gene in our reference set.
UK clinical status
Sources: NHS GMS PanelApp · Genomics England PanelApp · NHS National Genomic Test Directory
Frequently asked questions
What is the difference between PTPRC and CD45?
PTPRC is the name of the gene, while CD45 is the name of the protein that the gene encodes. CD stands for 'cluster of differentiation', a naming system used to identify proteins on the surface of immune cells.
Why does PTPRC have multiple isoforms?
The PTPRC gene undergoes alternative splicing, a process where different combinations of exons are joined together to create different versions of the messenger RNA. This produces multiple CD45 isoforms with different extracellular structures that are expressed at specific stages of lymphocyte development and activation, allowing precise control of immune responses.
How common are PTPRC variants that cause immune deficiency?
Pathogenic PTPRC variants causing severe combined immunodeficiency are very rare. They represent a small fraction of all SCID cases, which themselves are uncommon conditions occurring in approximately 1 in 50,000 to 1 in 100,000 births across different populations.