Radiofrequency regulates the BET-mediated pathways in radial glia differentiation in human cortical development.

The development of the human brain is controlled by a complex genetic program. Several genes have been identified as being associated with neurological developmental disorders, including autism spectrum disorder (ASD), intellectual disability, learning disorders, and neuropsychiatric disorders. Researchers have recently proven that non-genetic factors, such as prenatal stress, infections, and nutrition, also influence brain development. Another environmental factor suspected of influencing brain development is radiofrequency (RF) radiation. The working group uses cortical organoids derived from human embryonic stem cells to study the impact of 2.4 GHz RF radiation on brain development. These cortical organoids exhibit complex 3D architectures and cellular diversity. Their developmental pattern reflects the stages and characteristics of human corticogenesis. This includes the formation of apical radial glial (aRG) cells, which differentiate into excitatory neurons.

Cortical organoids (hCOs) were grown from human embryonic stem cells to serve as 3D models of the developing human brain in its earliest stages. Beginning on day 10 of the patterning stage, the cells were exposed to RF radiation for 12 hours per day or continuously. The field source was a Bluetooth module operating at 2.4 GHz (Bluetooth V2.0 + EDR), which corresponds to the transmission power of low-power Bluetooth devices of 4 dBm (2.4 mW). The maximum measured field strength was 2.5 mW/m². Control hCOs were cultivated in separate incubators, and ambient RF radiation levels were measured. The authors examined a variety of endpoints using various methods, including immunohistochemistry, single-cell RNA sequencing (scRNA-seq), epigenetic methods (single-cell ATAC sequencing to detect chromatin accessibility), electrophysiological recordings (whole-cell patch clamp), calcium imaging, and quantitative PCR (reverse transcription quantitative polymerase chain reaction / RT-qPCR).

Eight days after exposure began, the scientists observed a significant reduction in the size of the hCOs, as well as an irregular surface. Examination of differentiation markers revealed that Bluetooth exposure favors the self-renewal of apical radial glial (aRG) cells (symmetrical cell division). This occurs at the expense of other cell populations, such as deep layer neurons. These findings suggest impairment in the early development of the cerebral cortex. These observations were confirmed using neural stem cells from rhesus monkeys in vitro. Statistically significant transcriptomic changes were observed in hCOs exposed to Bluetooth radiation. Genes associated with neurodevelopment and neuronal projection were among those affected, suggesting that RF radiation may influence the early development of the human brain. Genes associated with autism spectrum disorder (ASD) (including FOXG1, AUTS2, and CPEB4) were also overexpressed in the exposed hCOs. This finding was confirmed using three methods: scRNA-seq, RT-qPCR, and immunohistochemistry. Retrotransposons associated with ASD increased statistically significantly after exposure. In summary, these results suggest that RF radiation from mobile devices or Bluetooth can increase the risk of ASD by increasing ASD-risk genes and retrotransposons associated with ASD. However, these effects were reduced or almost completely prevented by inserting a physical barrier in the form of aluminum foil or Faraday shielding. RF radiation also significantly impacted the organoids morphologically and functionally. A higher synapse density accompanied by increased neuronal activity was documented. Pharmacological inhibition of bromodomain and extraterminal (BET) proteins restored a wide range of Bluetooth-induced damage, including morphological changes, hCO size, ASD-associated genes, differentiation markers, and proliferation dynamics. This "rescue" of the phenotype indicates that the RF effect is mediated by epigenetic signaling pathways controlled by histone acetylation. Further analyses revealed that RF radiation altered chromatin accessibility, presumably through the transcription regulator NRF1.

This study shows that Bluetooth radiation can harm cortical organoids (hCOs), which are excellent models for studying the effects of environmental factors, such as viral infections, ethanol, nicotine, and cannabis, on brain development. Damaging effects of RF radiation include altered differentiation of neural stem cells and characteristics associated with ASD. These effects could be mitigated by physical barriers or pharmacological treatment. These effects are consistent with observations in animal models in which intrauterine RF exposure caused cognitive and behavioral abnormalities such as hyperactivity and memory impairment (Aldad et al., 2012). According to the authors, hCO models bridge the gap between animal models and human neurodevelopment.

Editor's note:

The broad scope of methodologies and endpoints examined in this study enhances its significance. This is particularly evident for endpoints confirmed by various molecular biological methods, such as RT-qPCR, scRNA-seq, and immunohistochemistry, as well as for endpoints observed across different species. The significant improvement in phenotype following pharmacological treatment strengthens the study's findings and provides insight into possible mechanistic relationships. The authors clearly state the study's limitations, including the absence of physical barriers, such as a skull, and the limitations of organoid models compared to in vivo situations. Nevertheless, the meaningful hCO model demonstrates that low field strengths (2.5 mW/m²) impair early neural development. (RH)

Aldad TS, Gan G, Gao XB, Taylor HS (2012). Fetal radiofrequency radiation exposure from 800-1900 Mhz-rated cellular telephones affects neurodevelopment and behavior in mice. Scientific Reports, 2: 312. https://doi.org/10.1038/srep00312