CD90 THY-1 (Thy-1 cell surface antigen)
Molecule TypeAntigen ExpressionMolecular Weight
Min / Max
Non-lineage Restricted Molecule
GPI anchor
Brain
Hematopoietic Cell
Stem Cell
Neuron
Fibroblast
Stromal Cell
Thymocyte
Leukemia cell
Bone Marrow
Lymph Node
T Cell
Leukocyte
Endothelial Cell
Lymphoblastoid cell
Prothymocyte
Lymphocyte
Endothelium
25 / 25
29 / 29
35 / 35

Expression
CD90 is expressed on hematopoietic stem cells and neurons in all species studied.  CD90 is highly expressed in connective tissue, on various fibroblast and stromal cell lines and is expressed on all thymocytes and peripheral T cells in mice.  But in humans, CD90 is expressed only on a small number of fetal thymocytes, 10%-40% of blood CD34+ cells in bone marrow, and <1% of CD3+CD4+ lymphocytes in peripheral circulation.  CD90 is also expressed in the human lymph node HEV endothelium but not on other endothelia and lastly, is expressed on a limited number of lymphoblastoid and leukemic cell lines.  The endothelium of dermal microvascular endothelial cells expresses CD90 when activated by inflammatory mediators.  CD90 expression varies considerably among different species.  It is expressed on the prothymocyte subpopulation of human leukocytes, on all mouse and rat thymocytes, and on mouse but not rat T cells.  Rat bone marrow cells also express CD90.  In all 3 species the antigen is expressed abundantly in the brain and at varying levels in other non-lymphoid tissues. 



Structure
MOLECULAR FAMILY NAME: Belongs to the immunoglobulin gene superfamily.

CD90 is a single-pass GPI-anchored glycoprotein.  It contains an 112 aa extracellular domain  which contains an Ig-like V-like domain and 3 N-linked glycosylation sites.  The complex carbohydrate side chains vary in composition between tissues and species.  The N-terminus and site of addition of the GPI-anchor of rat CD90 has been confirmed.  Although the protein sequence of rat CD90 is invariant, the brain and thymocyte forms of the protein have tissue- and site-specific glycosylation patterns.  In the mouse, the Thy-1 gene maps to a region that also encodes CD3 and CD56 NCAM.  The mouse Thy-1 alloantigens Thy-1.1 and Thy-1.2 differ by 1 aa at residue 89, namely Arg in Thy-1.1 and Gln in Thy-1.2.

MOLECULAR MASS
Cell Type Unreduced Reduced Comment
DHL4 B cell lymphoma line 25-35 kDa 25-29 kDa

POST-TRANSCRIPTIONAL MODIFICATION: No information.

POST-TRANSLATIONAL MODIFICATION

There are 3 N-linked glycosylation sites.  The composition of carbohydrates varies between tissues of  the same animal and within same tissue at different stages of differentiation.

Ligands
CD90 associates non-covalently with the Src family tyrosine kinase Fyn.  CD90 binds CD11b/CD18 (Mac-1) complex.

LIGANDS AND MOLECULES ASSOCIATED WITH CD90
Molecule Comment
CD45 Associated molecule required for activation of murine lymphocytes via CD90
Lck Non-covalently associated cell-signaling molecules
Fyn Non-covalently associated cell-signaling molecules
P100 Non-covalently associated cell-signaling molecules



Function
In the mouse, CD90 associates  with CD45 and may contribute to lymphocyte co-stimulation and to the inhibition of proliferation differentiation of hematopoietic stem cells and neuron memory in the central nervous system.  CD90 mAbs can activate T cells in vitro, which is a feature of other GPI-anchored proteins.  Murine CD90 acts as an adhesion molecule mediating Ca2+ independent cell contact between thymocytes and thymic epithelial cells.  The tyrosine kinase Fyn, that associates with Thy-1, is selectively required for activation through Thy-1.  Thy-1 mAbs can also induce bcl-2-resistant thymocyte apoptosis and a ligand for Thy-1 on thymic epithelial cells has been proposed.  Thy-1 expression on a neural cell line selectively inhibits neurite outgrowth on mature astrocytes in vitro and a Thy-1 ligand on astrocytes is suggested.  Thy-1 knockout mice have provided few clues concerning Thy-1 function.  Such mice appear normal apart from having a slight defect in brain function.  An impairment of long-term potentiation in the hippocampus is accomplished by normal spatial learning.

BIOCHEMICAL ACTIVITY:  No information.

DISEASE RELEVANCE AND FUNCTION OF CD90 IN INTACT ANIMAL

CD90 mAb expression inhibits neurite outgrowth on mature astrocytes.  CD90 mAb blocks the memory formation in chicks in passive avoidance tasks.  CD90 knockout mice showed decreased in vivo formation of long term potentiation in the hippocampal dentate gyrus.  Crosslinking of CD90 at the surface of CD90 positive hematopoietic progenitors inhibits production of primitive hematopoietic colonies.  CD90 is a marker for hemopoietic stem cells when coexpressed with CD34.  CD90 mAbs are a very useful means of identifying CD34+ hematopoietic precursor cells in vitro and in vivo.  CD34+CD90+ cells include hematopoietic stem cells that can serve as autologous grafts to replace the bone marrow in patients with malignancies.  CD90 mAbs inhibit proliferation of CD90+/CD34+ cord blood cells.  CD90 has been demonstrated to be an activation associated cell adhesion molecule on human dermal microvascular endothelial cells.  CD90 expressed on the surface of activated CD11b/CD18 on the surface of myeloid cells, mediating cell-to-cell adhesion and subsequence transendothelial migration recruitment to sites of inflammation, tissue injury and infection.

Comments
MOLECULAR INTERACTIONS -
PROTEINS AND DNA ELEMENTS WHICH REGULATE TRANSCRIPTION OF CD90: No information.

SUBSTRATES: No information.

ENZYMES WHICH MODIFY CD90: No information.

ADDITIONAL INSIGHTS

In human, 2 allelic forms exist in human but the polymorphic site is in 3rd intron and so does not give rise to different allelic proteins.  Both ligands and function of CD90 in the human immune system remain unidentified.

Database accession numbers
AnimalPIRSWISSPROTEMGBL/GENBANK
 
HumanEntrezgene 7070P04216
MouseA02108P01831X03151
RatA02107P01830X03152
Antibodies
5 E10   View Reactivity
DH24A   View Reactivity
DH2A   View Reactivity
DOG14-2   View Reactivity
F-3-20-7   View Reactivity
F15-42-1   View Reactivity
F15.42   View Reactivity
YKIX337.217   View Reactivity

Revised June 25, 2008


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