Mouse CD90, CD90.1 and CD90.2: Differences, Expression and Applications in Immunology Research

CD90, also known as Thy-1 (Thymus Cell Antigen 1), is a cell surface glycoprotein belonging to the immunoglobulin superfamily. It plays important roles in immune cell biology, cell adhesion, neuronal development and cellular interactions. In mice, CD90 exists in two major allelic forms, CD90.1 (Thy-1.1) and CD90.2 (Thy-1.2). Understanding the differences between these variants is particularly important for immunophenotyping, cell tracking, transplantation studies and experimental immunology.

1. What Is CD90 (Thy-1)?

CD90 is a glycosylphosphatidylinositol (GPI)-anchored cell surface glycoprotein encoded by the Thy1 gene. It belongs to the immunoglobulin superfamily and is involved in several biological processes, including cell-cell interactions, cell adhesion and intracellular signaling.

In mice, CD90 is highly expressed on thymocytes and peripheral T lymphocytes. It is also found on neurons and certain hematopoietic stem cell populations. Its expression varies according to tissue type, cellular differentiation and biological conditions.

Because of its expression on immune and neural cells, CD90 is widely used as a surface marker in studies of T-cell biology, stem cell characterization and neuronal development.

2. What Are CD90.1 and CD90.2?

Mouse CD90 has two major allelic variants:

• CD90.1 (Thy-1.1): An allelic form expressed by certain mouse strains, including AKR/J and PL strains.
• CD90.2 (Thy-1.2): The more widely distributed form, expressed by many commonly used laboratory mouse strains, including C57BL/6 and BALB/c.

These variants are genetically determined and differ by a single amino acid in the protein sequence. Specifically, the difference involves residue 89 of the mature mouse Thy-1 protein: CD90.1 contains arginine, whereas CD90.2 contains glutamine.

Although the structural difference is small, it creates distinct antigenic properties that allow researchers to recognize the two variants using specific antibodies.

3. Main Differences Between CD90.1 and CD90.2

The two variants are forms of the same protein rather than separate cell surface markers. Their allelic differences make them useful for distinguishing cells carrying different Thy1 genotypes.

4. Which Mouse Strains Express CD90.1 and CD90.2?

The distribution of CD90.1 and CD90.2 differs among mouse strains. Most commonly used laboratory strains carry the Thy-1.2 (CD90.2) allele, while Thy-1.1 (CD90.1) is associated with a more restricted group of strains.

Mouse Strains Commonly Associated with CD90.1

• AKR/J
• PL mouse strains

Mouse Strains Commonly Associated with CD90.2

• C57BL/6
• BALB/c
• CBA/J
• C3H/He
• DBA mouse strains
• NZB mouse strains

These examples represent commonly reported strain associations rather than an exhaustive list. Congenic lines, substrains and genetically modified mice may carry different Thy1 alleles. Researchers should verify the genotype and strain background before selecting an allele-specific antibody.

5. Why Are CD90.1 and CD90.2 Important in Cell Tracking?

One of the most important applications of the two CD90 allelic variants is the identification of cells originating from different donor populations.

In transplantation and adoptive cell transfer experiments, researchers may introduce cells from a donor mouse expressing CD90.1 into a recipient mouse expressing CD90.2, or vice versa. Allele-specific antibodies can then distinguish donor-derived cells from recipient-derived cells.

This approach helps researchers monitor cell distribution, survival, proliferation and differentiation in experimental models.

6. Applications of CD90 in Immunology and Cell Biology

CD90 is an important marker in several areas of biomedical research.

• T-cell research: Identification and characterization of thymocytes and peripheral T lymphocytes.
• Stem cell research: Characterization of hematopoietic stem cell populations using appropriate combinations of markers.
• Transplantation studies: Monitoring donor-derived and recipient-derived immune cells.
• Cell tracking: Distinguishing genetically different cell populations in experimental models.
• Neuroscience: Investigation of neuronal development, cell adhesion and neural cell interactions.
• Immunophenotyping: Analysis of immune cell populations using flow cytometry and other antibody-based methods.

7. How to Select the Right CD90 Antibody

Selecting the appropriate antibody depends on the experimental objective and the genetic background of the biological sample.

Important selection criteria include:

• Allele specificity: Determine whether the experiment requires CD90.1-specific or CD90.2-specific detection.
• Species reactivity: Confirm that the antibody recognizes mouse CD90.
• Antibody clone: Check the clone and its specificity for the intended CD90 variant.
• Application validation: Verify whether the antibody is validated for flow cytometry, immunohistochemistry or another intended technique.
• Sample characteristics: Consider the mouse strain, cell type and expected antigen expression.

For cell tracking experiments, using allele-specific antibodies is particularly important because a general CD90 antibody may recognize both variants and therefore cannot reliably distinguish donor and recipient populations.

8. Conclusion

CD90 is an important cell surface glycoprotein involved in immune cell biology, neuronal function and cellular interactions. Its two major mouse allelic variants, CD90.1 and CD90.2, differ by a single amino acid but have distinct antigenic properties.

These differences provide valuable tools for immunophenotyping, transplantation research and experimental cell tracking. Understanding mouse strain backgrounds and selecting the appropriate allele-specific antibody are essential steps for accurate identification and analysis of cell populations.

Scientific References

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2. Chang HC, Seki T, Moriuchi T, Silver J. Isolation and characterization of mouse Thy-1 genomic clones. Proceedings of the National Academy of Sciences. 1985;82(11):3819–3823.
DOI: 10.1073/pnas.82.11.3819
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3. Letarte M. Thy-1.1 and Thy-1.2 alloantigens: an overview. Methods in Enzymology. 1984;108:642–653.
DOI: 10.1016/S0076-6879(84)08124-6
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4. Rege TA, Hagood JS. Roles and regulation of Thy-1, a context-dependent modulator of cell phenotype. Biochimica et Biophysica Acta. 2006.
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5. Moriuchi T, Chang HC, Denome R, Silver J. Thy-1 cDNA sequence suggests a novel regulatory mechanism. Nature. 1983;301:80–82.
DOI: 10.1038/301080a0
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