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Regulation of major histocompatibility complex and TAP gene products in preimplantation mouse stage embryos
J C Cooper1, N Fernandez, E Joly
1Department of Biological Sciences, University of Essex, Colchester, UK.
Problem:
To determine the ontogeny of major histocompatibility complex (MHC) expression and TAP products in mouse embryos.
Method Of Study:
mRNAs encoding MHC and associated molecules were identified by reverse transcriptase-polymerase chain reaction, and the protein products were localized by confocal microscopy.
Results:
mRNAs encoding class Ia (H-2Db) and class Ib (Q7/9) were present in one-cell embryos, whereas beta 2-microglobulin (beta 2-m) transcripts were not detected until the two-cell stage. Transporter TAP1, but not TAP2, transcripts were detected only in blastocysts. H-2 class Ia (classical) protein was detected on the surface of two-cell embryos, H-2 class Ib (nonclassical) protein was detected on one-cell embryos, and beta 2-m transcripts were detected on eight-cell embryos; TAP1 protein was present at low levels in the cytoplasm from the one-cell stage onward, increasing in expression in blastocysts.
Conclusions:
In mice, MHC class I mRNAs encoding the heavy chain of H-2- and Q7/9-encoding Qa2 molecules are synthesized soon after conception prior to implantation. Similarly, the nonpolymorphic MHC class I-associated molecule beta 2-m also is expressed before implantation. TAP1, but not TAP2, is first detected at the blastocyst stage, thus preceding the onset of TAP2 in embryonic development.
Insights
Major histocompatibility complex (MHC) class I and beta 2-microglobulin (beta 2-m) are expressed early in mouse embryonic development. Transporter TAP1 is detected at the blastocyst stage, preceding TAP2.
Area of Science:
- Immunology
- Developmental Biology
- Molecular Biology
Background:
- The major histocompatibility complex (MHC) plays a crucial role in immune responses.
- Understanding the early expression patterns of MHC molecules and associated proteins in embryonic development is essential for comprehending immune system ontogeny.
- Transporter associated with antigen processing (TAP) proteins are critical for MHC class I antigen presentation.
Purpose of the Study:
- To investigate the developmental timeline of major histocompatibility complex (MHC) expression in mouse embryos.
- To determine the ontogeny of transporter associated with antigen processing (TAP) products during early mouse embryonic development.
Main Methods:
- Utilized reverse transcriptase-polymerase chain reaction (RT-PCR) to detect mRNAs encoding MHC and associated molecules.
- Employed confocal microscopy for the localization of protein products.
Main Results:
- MHC class Ia (H-2Db) and class Ib (Q7/9) mRNAs were detected in one-cell embryos; beta 2-microglobulin (beta 2-m) mRNA appeared at the two-cell stage.
- Transporter TAP1 mRNA was found in blastocysts, while TAP2 mRNA was not detected.
- H-2 class Ia protein was present on two-cell embryos, H-2 class Ib on one-cell embryos, and TAP1 protein was observed from the one-cell stage, increasing in blastocysts.
Conclusions:
- MHC class I heavy chain mRNAs and beta 2-m are synthesized before implantation in mouse embryos.
- TAP1 is detected at the blastocyst stage, preceding the onset of TAP2 expression in embryonic development.
- These findings provide insights into the early molecular events governing immune system development in mice.