We demonstrate here that epigenetic reprogramming via Somatic Cell Nuclear Transfer (SCNT) can be used as a tool to generate mouse models with pre-defined T cell receptor (TCR) specificities. These transnuclear mice express the corresponding TCR from their endogenous locus under the control of the endogenous promoter.
Lymphocytes, such as T cells, undergo genetic V(D)J recombination, to generate a receptor with a certain specificity1. Mice transgenic for a rearranged antigen-specific T cell receptor (TCR) have been an indispensable tool to study T cell development and function. However, such TCRs are usually isolated from the relevant T cells after long-term culture often following repeated antigen stimulation, which unavoidably selects for T cells with high affinity. Random genomic integration of the TCR α- and β-chain and expression from non-endogenous promoters can lead to variations in expression level and kinetics.
Epigenetic reprogramming via somatic cell nuclear transfer provides a tool to generate embryonic stem cells and mice from any cell of interest. Consequently, when SCNT is applied to T cells of known specificity, these genetic V(D)J rearrangements are transferred to the SCNT-embryonic stem cells (ESCs) and the mice derived from them, while epigenetic marks are reset. We have demonstrated that T cells with pre-defined specificities against Toxoplasma gondii can be used to generate mouse models that express the specific TCR from their endogenous loci, without experimentally introduced genetic modification. The relative ease and speed with which such transnuclear models can be obtained holds promise for the construction of other disease models.
This method was used in the research reported in Kirak et al., Science 328 (5975), 243-248 (2010).
1. Isolation of Donor Cells
Before specific T or B cells can be used as donor cells to generate transnuclear mouse models, mice need to be infected with a pathogen of interest or immunized with an antigen of interest. Since we have used CD8+ cells specific for Toxoplasma gondii, the following protocol will describe the generation and isolation of these cells and needs to be adapted according to personal interest.
2. Somatic Cell Nuclear Transfer
There are a few protocols for Somatic Cell Nuclear Transfer. The one described here makes use of oocytes arrested at Metaphase-II and the inhibition of the second meiotic division using Cytochalasin B. Therefore donor cells are needed which are in G0/G1 phase.
3.Derivation of embryonic stem cells
The SCNT-blastocysts can be used to either transfer them into pseudo-pregnant females (also known as direct or one-step cloning) or to derive embryonic stem cells (also known as indirect or two-step cloning). Since it is much more efficient to generate ES cells, we choose the two-step procedure. In case the scientist is interested in direct cloning, the blastocysts can be transferred directly into pseudo-pregnant females as described in section 5.
There are many protocols describing the derivation of embryonic stem cells. The one described here is a standard technique, which utilizes feeder cells, and fetal calf serum.
4.Blastocyst injection
The injection of blastocysts is a routine technique to generate any kind of transgenic mouse model. It is important to mention that the injection of blastocysts and the subsequent transfer into pseudo-pregnant females needs to be timed well.
5. Embryo Transfer
The transfer of embryos into pseudo-pregnant females represents a surgical procedure, which needs to be carried out very carefully and according to the guidelines of the researcher’s institute.
Figure 1. Somatic cell nuclear transfer of pre-defined T cells in B6CF1 background. Absolute and relative numbers of embryos generated from CD8+ T cells and embryonic stem cells derived from SCNT blastocysts.
Figure 2. Representative flow cytometric analysis of chimeric mice injected with SCNT embryonic stem cells. Gate and number (percent per total CD8+ T cells) indicates the presence of specific CD8+ T cells in chimeric mice.
We have shown here that SCNT can be used to generate transnuclear mice from T cells with pre-defined specificity. Although not shown here, the technique should also be usable to generate transnuclear mice from B cells with pre-defined specificity.
One important thing to consider is the strain and gender of mouse, which is infected or immunized and used to isolate T or B cells of interest. Since T and B cells have a very low reprogramming efficiency in general, we recommend using F1 hybrids of desired haplotype. Because the donor cell also determines the sex, we recommend using T or B cells from male mice. This means that only male chimeric mice would transmit the TCR or BCR through the germline, with male mice being easier and faster to breed.
Taken together, we think that epigenetic reprogramming via SCNT represents a powerful tool to generate a novel type of mouse models, which will be of great advantage for the immunological field.
The authors have nothing to disclose.
The authors are thankful to H. Eisen, M. Gubbels, K. van Grinsven, E. Guillen, A. Drake, V. Mahajan, Q. Gao, and G. Yap for fruitful discussions and reagents. We are thankful to J. Dausman, R. Flannery, and J. Jackson for assistance with the management of the mouse colony. We are thankful to P. Wisniewski for FACSorting. EMF was supported by the Human Frontiers Science Program. R.J. was supported by National Institute of Health grants RO1-HD045022 and R37-CA084198. HLP was supported by grants from the National Institute of Health.
Material Name | Type | Company | Catalogue Number | Comment |
---|---|---|---|---|
Red Blood Cell lysis Buffer | Sigma | R7757 | ||
Cell strainer | BD Falcon | REF 352340 | ||
Pregnant Mare Serum (PMS) | Calbiochem | 367222 | ||
Human Chorionic Gonadotropin (HCG) | Calbiochem | 230734 | ||
Hyaluronidase | Sigma | H4272 | Type IV-S | |
KSOM-AA | Millipore | MR-106-D | ||
HCZB | Millipore | MR-173-D | Customized medium | |
Ca-free medium for activation | Millipore | MR-174-D | Customized medium | |
SrCl2 | Sigma | 255521 | 100mM = 10x | |
AlbuMAX I | Gibco | 11020-021 | ||
PVP | MP Biotech | 102787 | Make 10% solution using HCZB, and add 0.1% AlbuMAX I | |
Cytochalasin B | Sigma | C6762 | 500μg/ml = 100x | |
Trichostatin A | Sigma | T8552 | 5mM = 1000x | |
Mineral Oil | Sigma | M5310 | ||
Holding needle | Humagen | MPH-SM-30 | ||
Injection and transfer needles | Humagen | 4-15, 7-15, 15-15 | ||
Mouth pipette | Sigma | A5177 | ||
Scissors | Fine Science Instruments | 14088-10 | or something similar | |
Forceps | Fine Science Instruments | 11251-10 | or something similar | |
Wound Clip Applicator | BD | 427630 | ||
Wound Clips | BD | 427630 | ||
Suture | Ethicon | K871H | ||
DMEM | Sigma | D6429 | ||
FBS | Hyclone | SH30071.03 | 15% | |
Penicillin/Streptomycin | Lonza | 17-602E | 100x | |
Glutamin | MP Biomedicals | 101806 | 200mM = 100x | |
Non-essential Aminoacids | Gibco | 11140050 | 100x | |
β-Mercaptoethanol | Gibco | 21985-023 | 5μl in 500ml | |
LIF | Millipore | ESG1106 | 1000x | |
MEK inhibitor | Cell Signaling | 9900L | For ES derivation only, add to ES medium (final concentration 50μM) |