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ABSTRACT Sea urchins are premier model organisms for the study of early development. However, the lengthy generation times of commonly used species have precluded application of stable genetic approaches. Here, we use the painted sea urchin Lytechinus pictus to address this limitation and to generate a homozygous mutant sea urchin line. L. pictus has one of the shortest generation times of any currently used sea urchin. We leveraged this advantage to generate a knockout mutant of the sea urchin homolog of the drug transporter ABCB1, a major player in xenobiotic disposition for all animals. Using CRISPR/Cas9, we generated large fragment deletions of ABCB1 and used these readily detected deletions to rapidly genotype and breed mutant animals to homozygosity in the F2 generation. The knockout larvae are produced according to expected Mendelian distribution, exhibit reduced xenobiotic efflux activity and can be grown to maturity. This study represents a major step towards more sophisticated genetic manipulation of the sea urchin and the establishment of reproducible sea urchin animal resources. 

Halogenated organic compounds are pervasive in natural and built environments. Despite restrictions on the production of many of these compounds in most parts of the world through the Stockholm Convention on Persistent Organic Pollutants (POPs), many “legacy” compounds, including polychlorinated biphenyls (PCBs), are routinely detected in human tissues where they continue to pose significant health risks to highly exposed and susceptible populations. A major concern is developmental neurotoxicity, although impacts on neurodegenerative outcomes have also been noted. Here, we review human studies of prenatal and adult exposures to PCBs and describe the state of knowledge regarding outcomes across domains related to cognition (e.g., IQ, language, memory, learning), attention, behavioral regulation and executive function, and social behavior, including traits related to attention-deficit hyperactivity disorder (ADHD) and autism spectrum disorders (ASD). We also review current understanding of molecular mechanisms underpinning these associations, with a focus on dopaminergic neurotransmission, thyroid hormone disruption, calcium dyshomeostasis, and oxidative stress. Finally, we briefly consider contemporary sources of organohalogens that may pose human health risks via mechanisms of neurotoxicity common to those ascribed to PCBs. 

Naturally synthesized marine organohalogens (MOH) and their anthropo- genic homologs produced as disinfection byproducts (DBP) are an emerging environmental health concern because several have been identified to exhibit potent biological activities in model systems, including cytotoxicity, genotox- icity, carcinogenicity and developmental toxicity. The molecular mechanisms mediating toxicity are poorly understood. Recently we discovered that several specific MOH and DBP measured in environmental and biological samples, including halopyrroles, halobipyrroles, haloindoles, and hydroxylated poly- brominated diphenylethers directly modify ryanodine receptors and SERCA pump activity, two key proteins anchored within sarcoplasmic/endoplasmic reticulum (SR/ER) that work in physiological opposition to tightly regulate net ER/SR Ca2+ dynamics and thereby shape meaningful Ca2+-dependent cel- lular processes. Using intact HEK293 cells null for ryanodine receptors (RyRs) expression and those that stably express RyR1, we demonstrate that tetra- bromopyrrole (TBP) selectively sensitizes RyR1 channels to caffeine-triggered Ca2+ release only in RyR1-expressing cells. TBP at higher concentrations also depletes of SR/ER Ca2+ stores in both null and RyR1 expressing cells com- mensurate with its lower potency to inhibitory SERCA in biochemical assays. Exposure of primary neuronal/glial co-cultures derived from newborn mice shows that TBP inhibits the frequency and amplitude of spontaneous Ca2+ oscillations (IC50=246 and 426nM, respectively), whereas >1μM produces a sustained rise in cytoplasmic Ca2+. Subchronic (24HR) exposure to TBP caused loss of neuronal/glial viability using the MTT assay (EC50=12.4μM). These re- sults show that nM TBP selectively targets RyR-mediated Ca2+ dynamics in a manner that has been shown to affect neurodevelopment, whereas low-μM exposures causes overt neurotoxicity, likely mediated by the combination of RyR activation and SERCA inhibition.