Gene expression profiling of the hippocampal dentate gyrus in an adult toxicity study captures a variety of neurodevelopmental dysfunctions in rat models of hypothyroidism.

We previously found that developmental hypothyroidism changed the expression of genes in the rat hippocampal dentate gyrus, a brain region where adult neurogenesis is known to occur. In the present study, we performed brain regionspecific global gene expression profiling in an adult rat hypothyroidism model to see if it reflected the developmental neurotoxicity we saw in the developmental hypothyroidism model. Starting when male rats were 5weeks old, we administered 6-propyl-2-thiouracil at a doses of 0, 0.1 and 10mgkg^-1 body weight by gavage for 28days. We selected four brain regions to represent both cerebral and cerebellar tissues: hippocampal dentate gyrus, cerebral cortex, corpus callosum and cerebellar vermis. We observed significant alterations in the expression of genes related to neural development (Eph family genes and Robo3) in the cerebral cortex and hippocampal dentate gyrus and in the expression of genes related tomyelination (Plp1 and Mbp) inthe hippocampal dentate gyrus. We observed only minor changes in the expression of these genes in the corpus callosum and cerebellar vermis. We used real-time reverse-transcription polymerase chain reaction to confirmChrdl1, Hes5, Mbp, Plp1, Slit1, Robo3 and the Eph family transcript expression changes. The most significant changes in gene expression were found in the dentate gyrus. Considering that the gene expression profile of the adult dentate gyrus closely related to neurogenesis, 28-day toxicity studies looking at gene expression changes in adult hippocampal dentate gyrusmay also detect possible developmental neurotoxic effects. [ABSTRACT FROM AUTHOR]