Mouse Models of Hematopoietic Engraftment: Limitations of Transgenic GFP Strains and an HPLC Approach to Analysis of Erythroid Chimerism

¹ Departments of Medicine and Pathology, University of Utah School of Medicine, Salt Lake City, Utah
² Department of Pathology, University of Utah School of Medicine, Salt Lake City, Utah
³ Department of Neurobiology and Anatomy, University of Utah School of Medicine, Salt Lake City, Utah
⁴ Department of Medicine, University of Utah School of Medicine, Salt Lake City, Utah
⁵ Department of Medicine, Division of Hematology and Medical Oncology, Oregon Health & Science University, Portland, Oregon

^* To whom correspondence should be addressed. E-mail: gspangrude{at}mac.com.

	Abstract

Transgenic mouse strains ubiquitously expressing green fluorescent protein (GFP) have enabled investigators to develop in vivo transplant models that can detect donor contributions to many different tissues. However, most GFP transgenics lack expression of the reporter in the erythroid lineage. We evaluated expression of GFP in the bone marrow of the OsbY01 transgenic mouse (B6-GFP) in the context of CD71 and TER-119 expression, and found that GFP fluorescence is lost prior to the basophilic erythroblast stage of development. However, platelets in B6-GFP mice were found to be uniformly positive for GFP. We therefore utilized the GFP transgenic model in combination with allelic variants of CD45 and the hemoglobin beta chain (Hbb) to develop a model system that allows all blood lineages to be followed in a mouse model of bone marrow transplantation (BMT). To detect Hbb variant molecules, we developed a new protocol based on high performance liquid chromatography (HPLC) that is sensitive and precise, allowing rapid and quantitative analysis of erythroid chimerism. Platelet and leukocyte engraftment were detected by flow cytometry. BMT into sub-lethally irradiated (4 Gy) recipients demonstrated the failure of B6-GFP-derived cells to engraft relative to B6-CD45^a-derived cells, suggesting that an immune barrier may prevent efficient engraftment of the transgenic cells in a setting of minimal ablation. These results establish limitations in the use of transgenic GFP expression as a donor marker in transplantation models.