June 17. 2019
Introduction: Developmental neurotoxins (DNtxn) are man-made chemicals in our environment, typically used as insecticides/agricultural chemicals, which impair developing brains in fetuses, infants and young children. DNtxn’s can cause impaired cognitive and/or motor development and can lead to behavioral deficits. Because of this potential for damaging young brains, DNtxn’s are commonly regulated and may be banned.
Currently, DNtxn’s are tested in pregnant experimental animals (typically rats and mice), and the offspring are examined pathologically and behaviorally. Because animal testing is slow, expensive, and may be ethically difficult, there is a need for a rapid, efficient in vitro model to screen DNtxn’s. We have approached this problem by proposing to use our human neural stem cell precursors (hNSCP’s) in cell culture as proxies for young brain cells (neurons and glia). We have carried out preliminary experiments (n=1) in which our hNSCP cells in culture were exposed to DNtxn’s at 10 uM for 24 hrs. DMSO vehicle served as CTL.
The cells were then harvested, RNA extracted and sent for RNA sequencing. We analyzed the RNA sequencing files for expression of typical mRNA genes and regulatory microRNA (miRNA) genes.
Findings: Again, these are preliminary experiments that need repeating. We tested the effect of chlorpyrifos, sodium fluoride, manganese chloride, trichloroethylene and propoxur (and dimethyl sulfoxide (DMSO) as vehicle control). All of the chemicals (except DMSO) are known DNtxn’s based on animal experiments.
Figure 1 shows that in general, exposure of hNSCP’s to DNtxn’s led to an increase in mRNA gene expression.
There was also a reduction in microRNA (miRNA) gene expression.
Interpretation: Our preliminary findings support further experiments to confirm these initial findings. hNSCP’s exposed to DNtxn chemicals experience an up-regulation in mRNA expression and a down-regulation in miRNA expression. If these findings repeat, and if additional developmental neurotoxins exhibit similar effects on mRNA and miRNA expressions in hNSCP cells, then it is possible that commonalities of gene expression changes could be found. This could mean that hNSCP’s in culture could serve as proxies for developing brains and be used to screen chemicals for DNtxn potential.