Sickle Cell Anemia Mice Carrying Chromosomes from Four Human Haplotypes

Children'S Hospital & Res Ctr At Oakland, Oakland CA

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Abstract

Mouse models for sickle cell anemia are useful for testing therapeutic agents for the treatment of sickle cell disease. Previously we have made a sickle cell anemia mouse in which the endogenous alpha and beta-globin genes were knocked out and replaced by a human a-globin transgene and a yeast artificial chromosome (YAC) containing the beta S globin gene. The reason for using YACs is that the embryonic, fetal and adult globin genes and their control regions are in their native contexts. Sequences that are important for binding various transcription factors that regulate globin gene expression remain intact. However, the mouse model that we made was not ideal as the origin of the DNA to make the YAC was from a patient of unknown ethnicity with chronic myeloid leukemia. 13S gene was introduced to replace the 13A gene in yeast by homologous recombination. Hence, DNA sequences farther away from the beta S gene are not from a patient with sickle cell anemia. In the world population, four major chromosome haplotypes contain the beta S gene, some expressing higher fetal hemoglobin than others. Their responses to agents that stimulate fetal hemoglobin expression are also variable. Hence reconstructing mouse models that carry beta-globin gene clusters from sickle cell anemia patients will more closely resemble the human conditions in their response to therapeutic agents. Our aim is to construct sickle cell mice that contain chromosomes derived from patients with the four major sickle haplotypes: Benim, Bantu, Senegal and Saudi Arabia. In collaboration with Pieter de Jong of the Children?s Hospital Oakland Research Institute (CHORI), we have devised a strategy to clone specifically the beta-globin clusters from the DNA of these patients. Transgenic mice will be made with these four BACs and they will be mated with mice that carry a human alpha-globin transgene and those with knockout of the endogenous murine and alpha and beta-globin genes. We will collaborate with Franz Kuypers of CHORI to study pathophysiology and rheology in these mice. We will test these mice for agents that stimulate fetal hemoglobin expression, and make them available to sickle cell anemia investigators at large.