Mir125b-2 imprinted in human but not mouse brain regulates hippocampal function and circuit in mice

Neurodevelopmental effects of prenatal Bisphenol A exposure on the role of microRNA regulating NMDA receptor subunits in the male rat hippocampus

Maternal bisphenol A (BPA) exposure has been reported to cause learning and memory deficits in born offspring. However, little is known that this impairment is potentially caused by epigenetic modulation on the development of NMDA receptor subunits. This study investigates the effect of prenatal BPA exposure on the hippocampal miR-19a and miR-539, which are responsible for regulating NMDA receptor subunits as well as learning and memory functions. Pregnant Sprague Dawley rats were orally administered with 5 mg/kg/day of BPA from pregnancy day 1 (PD1) until gestation day 21 (GD21), while control mothers received no BPA. The mothers were observed daily until GD21 for either a cesarean section or spontaneous delivery. The male offspring were sacrificed when reaching GD21 (fetus), postnatal days 7, 14, 21 (PND7, 14, 21) and adolescent age 35 (AD35) where their hippocampi were dissected from the brain. The expression of targeted miR-19a, miR-539, GRIN2A, and GRIN2B were determined by qRT-PCR while the level of GluN2A and GluN2B were estimated by western blot. At AD35, the rats were assessed with neurobehavioral tests to evaluate their learning and memory function. The findings showed that prenatal BPA exposure at 5 mg/kg/day significantly reduces the expression of miR-19a, miR-539, GRIN2A, and GRIN2B genes in the male rat hippocampus at all ages. The level of GluN2A and GluN2B proteins is also significantly reduced when reaching adolescent age. Consequently, the rats showed spatial and fear memory impairments when reaching AD35. In conclusion, prenatal BPA exposure disrupts the role of miR-19a and miR-539 in regulating the NMDA receptor subunit in the hippocampus which may be one of the causes of memory and learning impairment in adolescent rats.

Manganese-induced miR-125b-2-3p promotes anxiety-like behavior via TFR1-mediated ferroptosis

The toxic effects of excessive manganese (Mn) levels in the environment have led to a severe public health concern. Ferroptosis is a newly form of cell death relying on iron, inherent to pathophysiological processes of psychiatric disorders, such as anxiety and depression-like behaviors. Excessive Mn exposure causes various neurological effects, including neuronal death and mood disorders. Whether Mn exposure causes anxiety and depression-like behaviors, and the underlying mechanisms of Mn-induced ferroptosis have yet to be determined. Here, Mn-exposed mice showed anxiety-like behavior. We also confirmed the accumulation of ferrous ion (Fe2+), lipid peroxidation, and depletion of antioxidant defense system both in vitro and in vivo Mn-exposed models, suggesting that Mn exposure can induce ferroptosis. Furthermore, Mn exposure downregulated the expression of miR-125b-2-3p. In turn, overexpression of miR-125b-2-3p alleviated the Mn-induced ferroptosis by targeting Transferrin receptor protein 1 (TFR1). In summary, this novel study established the propensity of Mn to cause anxiety-like behavior, an effect that was regulated by miR-125b-2-3p and ensuing ferroptosis secondary to the targeting of TFR1. These results offer promising targets for the prevention and treatment of Mn-induced neurotoxicity.

Mir125b-1 is Not Imprinted in Human Brain and Shows Developmental Expression Changes in Mouse Brain

Genomic imprinting is a predominantly brain and placenta-specific epigenetic process that contributes to parent-of-origin-specific gene expression. While microRNAs are highly expressed in the brain, their imprinting status in this tissue remains poorly studied. Previous research demonstrated that Mir125b-2 is imprinted in the human brain and regulates hippocampal circuits and functions in mice. However, the imprinting status of another isoform of miR125b, Mir125b-1, in the human brain, as well as its spatiotemporal expression patterns in mice, have not been elucidated. Here, we show MIR125B1 is not imprinted in the human brain. Moreover, miR-125b-1 was highly expressed in the brains of mice. Furthermore, miR-125b-1 was down-regulated during brain development in mice. Specifically, miR-125b-1 displayed preferential expression in the olfactory bulb, thalamus, and hypothalamus of the mouse brain. Notably, miR-125b-1 was enriched in GABAergic neurons, particularly somatostatin-expressing GABAergic neurons, compared with glutamatergic neurons. Taken together, our findings provide the imprinting status and comprehensive spatiotemporal expression profiling of Mir125b-1 in the brain.