Developmental Iron Deficiency Dysregulates TET Activity and DNA Hydroxymethylation in the Rat Hippocampus and Cerebellum

Abstract

Iron deficiency (ID) during neurodevelopment is associated with lasting cognitive and socioemotional deficits, and increased risk for neuropsychiatric disease throughout the lifespan. These neurophenotypical changes are underlain by gene dysregulation in the brain that outlasts the period of ID; however, the mechanisms by which ID establishes and maintains gene expression changes are incompletely understood. The epigenetic modification 5-hydroxymethylcytosine (5hmC), or DNA hydroxymethylation, is one candidate mechanism because of its dependence on iron-containing TET enzymes. The aim of the present study was to determine the effect of fetal-neonatal ID on regional brain TET activity, Tet expression, and 5hmC in the developing rat hippocampus and cerebellum, and to determine whether changes are reversible with dietary iron treatment. Timed pregnant Sprague-Dawley rats were fed iron deficient diet (ID; 4 mg/kg Fe) from gestational day (G)2 to generate iron deficient anemic (IDA) offspring. Control dams were fed iron sufficient diet (IS; 200 mg/kg Fe). At postnatal day (P)7, a subset of ID-fed litters was randomized to IS diet, generating treated IDA (TIDA) offspring. At P15, hippocampus and cerebellum were isolated for subsequent analysis. TET activity was quantified by ELISA from nuclear proteins. Expression of Tet1, Tet2, and Tet3 was quantified by qPCR from total RNA. Global %5hmC was quantified by ELISA from genomic DNA. ID increased DNA hydroxymethylation (p=0.0105), with a corresponding increase in TET activity (p<0.0001) and Tet3 expression (p<0.0001) in the P15 hippocampus. In contrast, ID reduced TET activity (p=0.0016) in the P15 cerebellum, with minimal effect on DNA hydroxymethylation. Neonatal dietary iron treatment resulted in partial normalization of these changes in both brain regions. These results demonstrate that the TET/DNA hydroxymethylation system is disrupted by developmental ID in a brain region-specific manner. Differential regional disruption of this epigenetic system may contribute to the lasting neural circuit dysfunction and neurobehavioral dysfunction associated with developmental ID.

Tailored pharmacist-led intervention to improve adherence to Iron supplementation in premature infants: a randomized controlled trial in China

“…With specific areas of impairment connected to brain regions that appeared to be most negatively impacted by iron deficiency, including myelination and the hippocampus. neonatal iron deficiency has been repeatedly linked to inferior neurodevelopmental outcomes overall ( 31 – 33 ). It is particularly important to ensure adequate brain iron status in the neonatal period because, specifically for infants, brain iron deficiency develops more rapidly when there is a lack of iron, and the developmental disruptions brought on by the lack of iron are not reversed by later repletion ( 34 ).…”

5-Hydroxymethylcytosine: the many faces of the sixth base of mammalian DNA

“…38 Iron-deficient diets during neurodevelopment result in decreased TET activity and reduced global hydroxymethylation in rat brain. 39 Apart from the reaction substrates, it was found that vitamin C enhances the abundance of ox-mC in various cell cultures, from iPSCs and ESCs to cancer cell lines and also activates histone demethylation by Jhdm. 40 Although it was originally prescribed a role in maintaining iron in the reduced form Fe( ii ), no other reducing agents were found to exert similar stimulation of the oxygenase activity.…”

Chromatin accessibility and H3K9me3 landscapes reveal long-term epigenetic effects of fetal-neonatal iron deficiency in rat hippocampus

“…While these long-term epigenetic changes were found in the hippocampus, a focus of our study, they could also occur in the cerebral cortex and cerebellum as these brain structures have a long developmentally-sensitive window [ 57 ]. Future studies could investigate the epigenomic effects of early-life ID on other developing brain regions as we have in a previous study [ 58 ].…”