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Mouse
Metabolic Phenotyping
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Laboratory mice are widely used in diabetes research due to
their suitability for genome manipulation by transgenesis and
gene targeting. The metabolic effects of genetic manipulations,
however, are influenced by modifier genes that can alter the
resulting phenotype in subtle or profound ways. The C57BL/6 is
the mouse strain most commonly used in biological research. The
129S1 strain is widely used as a source of embryonic stem cells
for genome manipulation.
We are using these two strains of mice and their hybrid offspring
as a model to study biological variation in hemoglobin glycation.
Our results have shown that many aspects of erythrocyte and whole-body
glucose metabolism are remarkably different in these mice. The
goal of this project is a panel of assays that will better characterize
metabolic phenotypes and the complex genetic interactions that
influence glucose metabolism. Areas of particular interest include
post-challenge glucose and insulin levels and hemoglobin variant
analysis. We are also measuring erythrocyte levels of glycated
hemoglobin, reduced and oxidized glutathione, 2,3-bisphosphoglycerate,
advanced glycation end products, GAPDH levels and activity, and
UDP-N-acetylglucosamine. Example: Mouse Hemoglobin Variants by Capillary Isoelectric Focusing  Hemoglobin variants migrate as αβ dimers by cIEF. Unlike humans,
mice inherit two copies of the β globin gene from each parent. C57
and 129 mice have different β globin haplotypes. C57 mice exhibit
the HbbS (single)
β globin haplotype. They have the same allele at both β globin
loci and produce the same gene product (βS) which migrates as
a single αβ dimer
peak on cIEF. In contrast, 129 mice exhibit the HbbD (diffuse)
β globin haplotype. They have different alleles at each locus
and both alleles
differ from that of the C57 mouse. The two 129 alleles produce
two different gene products, beta major (βD+) and beta minor
(βD-) that migrate as two
different αβ dimer peaks on cIEF. βD+ and βS differ by three
amino acids but have identical isoelectric points so their αβ
dimers migrate together
on cIEF (as shown for the F1 hybrid mouse). βD- and βS differ
by ten amino acids and have different isoelectric points. As
a consequence, αβD- has
a higher pI and elutes earlier than either αβD+ or αβS (as shown
for both the 129 and F1 hybrid mice). The late eluting minor
peaks evident in blood
from both the F1 hybrid and 129 mice are post-translationally
modified hemoglobin variants typically considered to be glutathione
Hb adducts.
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