CD99 Gene (Mic2) - Role in Ewing Sarcoma and T-Cell Development
Comprehensive genomic and proteomic overview of CD99, a key surface antigen in Ewing sarcoma diagnosis and T-cell biology.
Gene Information Card
| Symbol | CD99 |
|---|---|
| Full Name | CD99 molecule (Xg blood group) |
| Gene Type | protein-coding |
| Chromosomal Location | Xp22.33 and Yp11.32 (pseudoautosomal region 1) |
| NCBI Gene ID | 4267 ncbi.nlm.nih.gov/gene/4267 |
| Ensembl ID | ENSG00000002586 |
| UniProt ID | P14209 |
| OMIM ID | 313470 |
| HGNC ID | 1702 |
| Aliases | MIC2, MIC2X, MIC2Y, HBA71, E2 antigen |
Description
CD99 is a cell surface glycoprotein encoded by the MIC2 gene located in the pseudoautosomal region of chromosomes X and Y. It is involved in T-cell adhesion, migration, and apoptosis, and is a critical diagnostic marker for Ewing sarcoma due to its high expression in these tumors. CD99 also plays a role in leukocyte extravasation and thymocyte development.
Disease Associations
| Disease category | Pathophysiological mechanism | Genomic evidence |
|---|---|---|
| Ewing Sarcoma | CD99 overexpression is a hallmark; used as a diagnostic immunohistochemical marker. The exact mechanism is unclear but involves cell adhesion and signaling pathways. | High expression in >95% of Ewing sarcoma cases (NCBI, OMIM) |
| Lymphoblastic Lymphoma | CD99 expression is associated with T-cell lymphoblastic lymphoma; may contribute to tumor cell adhesion and survival. | Immunohistochemical studies (ClinVar) |
| Xg Blood Group System | CD99 carries the Xg blood group antigen; polymorphisms define the Xg(a) phenotype. | OMIM 313470 |
Expression Profile
Tissue Expression
| Tissue | nTPM | level |
|---|---|---|
| Lymph node | 34.5 nTPM | Medium |
| Spleen | 28.2 nTPM | Medium |
| Thymus | 25.1 nTPM | Medium |
| Bone marrow | 18.7 nTPM | Low |
| Lung | 12.3 nTPM | Low |
| Heart | 8.9 nTPM | Low |
Cell Line Expression
| Cell Line | nTPM | Notes |
|---|---|---|
| A-673 (Ewing sarcoma) | 45.2 nTPM | High expression; diagnostic cell line |
| SK-ES-1 (Ewing sarcoma) | 42.1 nTPM | High expression |
| Jurkat (T-cell leukemia) | 38.5 nTPM | High expression |
| HEK293 (embryonic kidney) | 12.0 nTPM | Low expression |
| HeLa (cervical carcinoma) | 8.3 nTPM | Low expression |
Data source：Human Protein Atlas（proteinatlas.org）
Mutations & Variants
Hotspot Mutations
| Variant | Type | Frequency | Functional Description |
|---|---|---|---|
| c.1A>G (p.Met1?) | Missense | <0.01% | Potential start codon loss; effect unknown |
| c.123C>T (p.Ser41=) | Synonymous | 0.02% | No amino acid change; likely benign |
| c.456G>A (p.Thr152=) | Synonymous | 0.01% | No amino acid change; likely benign |
Mutation functional classification
Loss of Function (LOF)
No confirmed loss-of-function mutations reported in CD99. Knockout studies in mice show impaired T-cell development.
Gain of Function (GOF)
No confirmed gain-of-function mutations reported.
Dominant Negative (DN)
No dominant-negative mutations reported.
View complete mutation data：
Gene Ontology (GO)
| • cell adhesion (GO:0007155) | • plasma membrane (GO:0005886) |
| • protein binding (GO:0005515) | • signal transduction (GO:0007165) |
| • T cell activation (GO:0042110) | • movement of cell or subcellular component (GO:0006928) |
Pathways
• Cell adhesion molecules (CAMs) - Homo sapiens (hsa04514)
• Hematopoietic cell lineage - Homo sapiens (hsa04640)
• T cell receptor signaling pathway - Homo sapiens (hsa04660)
Protein Summary
CD99 is a 32 kDa transmembrane glycoprotein with a single extracellular domain and a short cytoplasmic tail. It is heavily O-glycosylated and expressed on the surface of most leukocytes, thymocytes, and Ewing sarcoma cells. CD99 mediates homotypic cell adhesion and regulates T-cell apoptosis and migration. Its high expression in Ewing sarcoma makes it a key diagnostic marker and a potential therapeutic target.
Related Services
Related Products
| Product name | Cat.No. | Species | Gene ID | |
|---|---|---|---|---|
| CD99 Knockout HEK293 Cell Line | EDJ-KQ2492 | Human | 4267 | Details Get a Quote |
| CD99L2 Knockout HEK293 Cell Line | EDJ-KQ9884 | Human | 83692 | Details Get a Quote |
| CD99 Knockout HCT 116 Cell Line | EDJ-KQ23081 | Human | 4267 | Details Get a Quote |
| CD99 Knockout HeLa Cell Line | EDJ-KQ23082 | Human | 4267 | Details Get a Quote |
| CD99 Knockout A-549 Cell Line | EDJ-KQ21719 | Human | 4267 | Details Get a Quote |
| CD99L2 Knockout A-549 Cell Line | EDJ-KQ36759 | Human | 83692 | Details Get a Quote |
| CD99L2 Knockout HCT 116 Cell Line | EDJ-KQ36760 | Human | 83692 | Details Get a Quote |
| CD99L2 Knockout HeLa Cell Line | EDJ-KQ36761 | Human | 83692 | Details Get a Quote |
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