Cyclic Nucleotides and Fetal Globin Gene Expression

Project: Research project

Project Details

Description

DESCRIPTION (provided by applicant): Pharmacological stimulation of fetal
hemoglobin (Hb F) has been attracting great concerns for many years, but the
molecular mechanisms by which expression of the g-globin gene is induced in
the adult stage still remain unclear. The long-term goal of this proposal is
to develop "novel Hb F inducers" by clarifying intracellular pathways that
regulate g-globin gene expression. We showed that expression of the g-globin
gene is induced in erythroleukemic cells as well as in primary erythroblasts
by activating an intracellular pathway comprising soluble guanylate cyclase
(sGC) and cGMP-dependent protein kinase (PKG). This pathway was also found to
be essential for the induced expression of the g-globin gene by hemin or
butyrate.

In the first specific aim, we will study the molecular mechanisms by which the
sGC-PKG pathway induces g-globin gene expression. First, we will identify and
characterize within the b-globin locus cis-acting and trans-acting elements
that mediate molecular effects of the pathway to the g-globin gene. Next, we
will examine whether the sGC-PKG pathway contributes to the expression of the
gamma-globin gene in beta-thalassemia.

In the second specific aim, we will test using transgenic mice the hypothesis
that expression of the g-globin gene is induced in the adult stage by over-
expressing or activating sGC, which is an obligate heterodimer of a- and b-
subunits. We will first create transgenic mice with DNA constructs carrying
sGC subunit genes driven by the b-globin gene promoter and the LCR, and breed
them with mice carrying the human b-globin locus. Second, we will examine
whether the phenotype of sickle cell mice can be alleviated by expressing sGC
subunits at high levels. Recently we found two normal subjects with no
mutations in the b-globin locus who express 30% Hb F and have high levels of
porphyrins such as protoporphyrin IX (PPIX) and ZnPP, both of which are sGC
activators. Third, we will examine whether g-globin gene expression can be
induced by increasing PPIX concentrations in red cells. This will be
performed by breeding mice carrying the human b-globin locus with those of
ferrochelatase deficiency.

If successfully implemented, this proposal should not only enhance our
understanding of the molecular mechanisms that regulate the expression of the
g-globin gene during development, but also provide important information to
develop novel Hb F inducers for treating the b-globin disorders.
StatusFinished
Effective start/end date9/30/0111/30/06

ASJC

  • Medicine(all)