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GENERATION OF A STABLE TRANSGENIC SWINE MODEL FOR CELL TRACKING AND CHROMOSOME DYNAMICS STUDIES
Renan B. Sper1,2, Sean Simpson1,2, Xia Zhang1,2, Bruce Collins1,2, Jeff Sommer 3 Bob Petters3,Jorge A. Piedrahita1,2
1Department of Molecular Biomedical Sciences, 2Center for Comparative Medicine and Translational Research, 3 Department of Animal Science, College of Veterinary Medicine, North Carolina State University, Raleigh, NC, USA.
Results
Figure 1. (A) Squematic representation of knockin strategy into the 3’UTR of the beta actin locus via
CRISPR-CAS9 system. Drawing shows the actin genomic locus and the donor plasmid containing the
IRES-H2B-GFP flanked by two homology arms of 1Kb each. (B) Porcine fibroblast colonies heterozygous
(male) for the knockin were utilized as donor cells for somatic cell nuclear transfer. Generated transgenic
embryos were transferred to a recipient sow. Three viable piglet (males, P1 generation) were obtained and
use to generate F1 generation via artificial insemination of wild type sows (3 pregnancies obtained).
Introduction Over the last few years transgenic pigs have become an attractive research model in the
field of translational research, regenerative medicine, and stem cell therapy due to their
anatomic, genetic and physiological similarities with humans. The development of
transgenic murine model via fusion of GFP to Histone 2B protein (H2B, a protein of
nucleosome core) allows easier and convenient methods of tracking cell migration and
engraftment levels after transplantation and a opportunity to better understand the
complexity of chromosome dynamics during cell cycle. Up to date, the development of a
stable transgenic swine model expressing H2B-GFP has not been described. Such model
would have multiple applications in the field of stem cell/regenerative medicine. The
objectives of this study include: 1) Developing a viable H2B-GFP transgenic swine model
via CRISPR-CAS9 recombination into the ACTB locus (β actin) and Somatic Nuclear
Transfer (SCNT), and :2) Demonstrating that H2B-GFP fetal liver hematopoietic stem
cells are capable of engrafting porcine severe combined immunedeficient (SCID) fetuses
(42 days) via ultrasound guided in utero hematopoietic stem cell transplantation (IUHCT).
The hypothesis for the described study include: 1) CRISPR-CAS9 driven targeted
integration of IRES-H2B-GFP would allow the development of the first transgenic swine
model with ubiquitous expression of chromatin-bound GFP and :2) H2B-GFP fetal liver
hematopoietic stem cell can be tracked and analyzed when transplanted via IUHCT into
42 days SCID fetuses, reversing the immunedeficient phenotype at birth, resulting in
fully differentiated GFP positive leukocyte in peripheral blood and lymphoid tissue.
B
GENERATION OF β ACTIN H2B-GFP TRANSGENIC PIGS
Material and Methods
Conclusion CRISPR-CAS9 is capable of driving H2B-GFP transgene into β actin locus via homologous recombination, resulting in the
generation of the first described H2B-GFP swine model with ubiquitous expression of chromatin-associated GFP.
Intranuclear GFP allows chromosomes dynamic to be visualized in vivo and in vitro.
H2B-GFP gene transmission on F1 generation was 55.8% (in concordance with Mendel's Law). P1 and F1 generation
animals are healthy and viable at this point.
H2B-GFP fetal liver hematopoietic stem cells are capable of engrafting SCID transgenic developing fetuses via IUHCT and
reversing immunedeficient phenotype. Engrafted cells can be easily tracked via flow cytometry analysis of peripheral blood
and via fluorescence microscopy of lymphoid tissue.
A
A
Figure 4. (A) Flow cytometry analysis of peripheral blood of 80 days old wildtype and SCID H2B-GFP engrafted pigs. When
staining for pig CD45 and pig CD3 (signal on x axis), a distinct GFP + population is evident (y axis).(B) Left image shows 2x
H&E slide of spleen from SCID H2B-GFP engrafted pigs showing tissue architecture. Right image shows Optimal Cutting
Temperature (OCT) frozen section from spleen of same pig. Two X image shows GFP fluorescence microscopy demonstration
multiple white pulp regions containing H2B-GFP engrafted cells (periarteriolar lymphoid sheaths). Forty X image shows blue
circled region amplified and stain for DAPI, engrafted cells demonstrate DAPI and GFP signal while host cells stain for DAPI
only.
H2B-GFP P1 generation H2B-GFP F1 generation
3’ UTR
E1 E2 E3 E4 E5 E6 PolyA signal
* *
IRES-pH2B-eGFP LHa RHa
IN UTERO H2B-GFP HEMATOPOIETIC STEM CELL TRANSPLANTATION INTO 42 DAYS SCID FETUSES
Figure 2 (A) Day 42 H2B-GFP fetal liver hematopoietic stem cell were isolated and cryopreserved until
transplantation. (B) Five randomly picked swine H2B-GFP postive fetuses were selected as donors for
IUHCT, and 5 42 days transgenic SCID fetuses were injected with 3.5 million viable cells/each via
ultrasound guided fetal intrahepatic injection for engraftment. Four viable fetuses were delivered
naturally.
A
B
UBIQUITOUS EXPRESSION OF H2B-GFP TRANSGENIC PIGS
C
Figure 3. A shows intranuclear H2B-GFP expression in OCT-embedded intestines, muscle and skin for DAPI, GFP
and merge (40X) . B shows fluorescence microscopy (40x) of in vitro cultured bone marrow derived mesenchymal
stem cells from H2B-GFP F1 generation, chromosome dynamics through GFP allows cell cycle staging (a cell in
Telophase stage is shown). C shows bright field and GFP images of 8 days in vitro cultured SCNT H2B-GFP
blastocyst (20x ).
H2B-GFP CELL TRACKING INTO SCID PIGS POSTNATALLY
ANTI CD3
A
GF
P
B
WT STAINED PIGLET A STAINED PIGLET B STAINED
Spleen H&E 2x
Spleen GFP 2x
IUHCT day 42 SCID H2B-GFP engrafted pig
H2B-GFP fetal liver hematopoietic stem cells
GFP
Results
40x GFP+DAPI merge
B intestines
DAPI GFP Merge
muscle
DAPI GFP Merge
skin
DAPI GFP Merge ANTI CD45