Analysis of the Human Ferrochelatase Promoter in Transgenic Mice
Scott T. Magness,
Antonio Tugores,
Edward S. Diala, and
David A. Brenner
From the University of North Carolina at Chapel Hill, Curriculum in
Genetics and Molecular Biology, the Departments of Medicine, and
Biochemistry and Biophysics, Chapel Hill, NC.
Ferrochelatase catalyzes the chelation of ferrous iron and
protoporphyrin to form heme. It is expressed as a housekeeping gene in
all cells, but is upregulated during erythropoiesis. Ferrochelatase activity is deficient in the inherited disease protoporphyria as a
result of heterogeneous mutations. Although human ferrochelatase is
transcribed from a single promoter in both nonerythroid and erythroid
cells, previous studies using transient transfection assays failed to
demonstrate erythroid-specific increased expression from 4.0 kb of the
human ferrochelatase promoter containing the erythroid
cis-elements, GATA and NF-E2. The present study analyzes the in
vivo regulation of the ferrochelatase gene to provide insights into the
mechanism of its erythroid-specific enhancement. Transgenic (TG) mouse
lines were generated in which the luciferase reporter gene was driven
by either a 150-bp ferrochelatase minimal promoter (
0.15
TG) or by a 4.0 kb extended 5
upstream region
(4.0 TG). Expression of the 4.0 TG transgene was generally
consistent with the endogenous gene during embryonic development and in
nonerythroid and erythroid tissues as demonstrated by Northern blotting
and mRNA in situ hybridization. The 4.0 TG was expressed at a higher level than the 0.15 TG in nonerythroid and erythroid tissues, including during extramedullary erythropoiesis induced by
n-acetylphenylhydrazine injection. The enhanced erythroid expression of
the 4.0 TG correlates with the appearance of a DNase I
hypersensitive site in the 5 flanking region of the transgene.
Therefore, in the context of chromosomal integration, the 5
flanking region of the ferrochelatase gene is necessary and sufficient
to confer high levels of transgene expression in erythroid tissue.
Blood, Vol. 92 No. 1 (July 1), 1998:
pp. 320-328
© 1998 by The American Society of Hematology.
