High expression of human beta S- and alpha-globins in transgenic mice: hemoglobin composition and hematological consequences.
A line of transgenic mice (alpha H beta S-11; where alpha H is human alpha-globin) was created in which the human beta S and human alpha 2 globin genes, each linked to the beta-globin locus control region, were cointegrated into the mouse genome. On a normal genetic background, the transgenic mice produced 36% human beta S-globin chains with an alpha H/beta S ratio of 1.3. Higher levels of beta S were achieved by breeding the transgenic mice with mutant mice carrying a mouse beta major-globin gene deletion. Mice heterozygous for the beta major deletion (alpha H beta S[beta MD]; MD, mouse deletion) had 54% beta S with an alpha H/beta S ratio of 1.0; mice homozygous for the beta major deletion (alpha H beta S[beta MDD]) had 72.5% beta S and an alpha H/beta S ratio of 0.73. Because mouse alpha chains inhibit hemoglobin (Hb) S polymerization, we bred the mice to heterozygosity for a mouse alpha-globin deletion. These mice (alpha H beta S[alpha MD beta MDD]) had an increased alpha H/beta S ratio of 0.89 but expressed 65% beta S. Expression of the human genes cured the thalassemic phenotype associated with the murine beta major deletion. Transgenic alpha H beta S[beta MDD] mice had normal hematocrit and Hb and somewhat elevated reticulocytes (6% vs. 3% for control), whereas the mice carrying the alpha-globin deletion (alpha H beta S[alpha MD beta MDD]) had a normal hematocrit and Hb and more elevated reticulocytes (10.3 +/- 7.6% vs. 3.4 +/- 1.0%). Expression of the transgene restored a normal distribution of erythrocyte densities when compared to thalassemic mice; however, the average mean corpuscular Hb concentration of alpha H beta S[beta MDD] mice increased to 35.7 g/dl (vs. control 33.7 g/dl) whereas that of alpha H beta S[alpha MD beta MDD] mice was further elevated to 36.3 g/dl. The intrinsic oxygen affinity was increased in transgenic mouse erythrocytes at 280 milliosmolal, and the PO2 at midsaturation of alpha H beta S[alpha MD beta MDD] erythrocytes was higher than that of alpha H beta S[beta MDD] cells (37.4 +/- 2 vs. 33.5 +/- 1 mmHg). The higher values of the mean corpuscular Hb concentration and intrinsic PO2 at midsaturation, which favor in vivo sickling, may explain the slightly more severe hematological picture in alpha H beta S[alpha MD beta MDD] mice. We conclude that the transgenic mouse with high Hb S expression does not exhibit adult anemia but does have abnormal hematological features: increased erythrocyte density, high oxygen affinity, and reticulocytosis with increased stress reticulocytes.
Fabry
M E
ME
Department of Medicine, Albert Einstein College of Medicine/Montefiore Medical Center, Bronx, NY 10461.
Nagel
R L
RL
Pachnis
A
A
Suzuka
S M
SM
Costantini
F
F
D000755:Anemia, Sickle Cell / Q000503:physiopathology*; D000818:Animals; D004195:Disease Models, Animal; D017353:Gene Deletion; D015870:Gene Expression; D005914:Globins / Q000235:genetics*; D006400:Hematocrit; D006454:Hemoglobins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D007526:Isoelectric Point; D051379:Mice; D008815:Mice, Inbred Strains; D008822:Mice, Transgenic; D010100:Oxygen / Q000378:metabolism; D012333:RNA, Messenger / Q000235:genetics; D012995:Solubility; D013329:Structure-Activity Relationship
D006454:Hemoglobins; D012333:RNA, Messenger; D005914:Globins; D010100:Oxygen