Mitochondrial Characterization in a Mouse Model of Hippocampal Neuron-Specific Iron Deficiency
Early-life iron deficiency (ID) is the insufficient uptake of iron within the first 1000 days of life causing persistent neurobehavioral deficits in adulthood despite iron repletion. Substantial energy is needed to support the rapid growth of the brain through the iron-dependent electron transport chain of mitochondria. Mitochondrial quality control dynamics (fusion, fission, and mitophagy) are coordinated morphological changes and movements, which are essential for normal bioenergetics. Previous work shows perturbed expression of genes associated with mitochondrial quality control dynamics in ID developing hippocampal neuronal cultures but have not been characterized in vivo. The process of cellular iron uptake is through the transferrin receptor 1 (TfR1). Our transgenic mouse model expresses the non-functional dominant negative TfR1 (DNTfR1) in hippocampal pyramidal neurons under control of a CaMKII transactivator transgene and tet-responsive promoter (tet-off). This produces a hippocampal specific, non-anemic, and reversible iron deficient mouse model. Total RNA was isolated from hippocampal tissue of DNTfR1 (n=3) and wild-type (WT) (n=3) mice and reverse-transcribed into complementary DNA for quantitative polymerase chain reaction (qPCR). The expression of mitochondrial quality control dynamic genes optic atrophy 1 (fusion), fission 1 protein (fission), mitochondrial fission factor (fission), Dynamin 1 (fission), Parkin 7 (mitophagy) and PTEN-induced kinase 1 (mitophagy) were evaluated. All target genes were normalized to Hprt and Tbp identified in RefFinder to be the comparatively stable genes in our samples. The relative expression of quality control genes did not demonstrate a significant difference between DNTfR1 and WT in an unpaired t-test for each gene (α = 0.05). However, bioenergetic assessment of isolated hippocampal mitochondria from DNTfR1 mice still show a trending decrease in oxygen consumption rate compared to WT implicating impairment of mitochondrial function due to ID. Future work will employ electron microscopy to identify potential differences in dynamics, morphology and ultrastructure in hippocampal mitochondria in the DNTfR1 model.