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1. Genome-wide analysis of cadmium-induced, germline mutations in a long-term Daphnia pulex mutation-accumulation experiment over 1,123 generations.

   Glaholt, Stephen P ; Young, Kimberly ; Lynch, Michael ; Shaw, Joseph R. ( November 2022 , Environmental health perspectives)

   Germline mutations provide the raw material for all evolutionary processes and contribute to the occurrence of spontaneous human diseases and disorders. Yet despite the daily interaction of humans and other organisms with an increasing number of chemicals that are potentially mutagenic, precise measurements of chemically induced changes to the genome-wide rate and spectrum of germline mutation are lacking. A large-scale mutation-accumulation experiment was propagated in the presence and absence of an environmentally relevant cadmium concentration to quantify the influence of cadmium on germline mutation rates and spectra. Cadmium exposure dramatically changed the genome-wide rates and regional spectra of germline mutations. In comparison with those in control conditions, exposed to cadmium had a higher overall mutation rates and a lower overall mutation rate. exposed to cadmium had a higher intergenic mutation rate and a lower exonic mutation rate. The higher intergenic mutation rate under cadmium exposure was the result of an elevated intergenic rate, whereas the lower exon mutation rate in cadmium was the result of a complete loss of exonic mutations-mutations that are known to be enriched at 5-hydroxymethylcytosine. We experimentally show that cadmium exposure significantly reduced 5-hydroxymethylcytosine levels. These results provide evidence that cadmium changes regional mutation rates and can influence regional rates by interfering with an epigenetic process in the germline. We further suggest these observed cadmium-induced changes to the germline mutation rate may be explained by cadmium's inhibition of zinc-containing domains. The cadmium-induced changes to germline mutation rates and spectra we report provide a comprehensive view of the mutagenic perils of cadmium and give insight into its potential impact on human population health. https://doi.org/10.1289/EHP8932. 

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2. Proteomic responses of the coccolithophore Emiliania huxleyi to zinc limitation and trace metal substitution

   https://doi.org/10.1111/1462-2920.15644  

   Shire, David M. ; Kustka, Adam B. ( June 2021 , Environmental Microbiology)

   Zinc concentrations in pelagic surface waters are within the range that limits growth in marine phytoplankton cultures. However, the influence of zinc on marine primary production and phytoplankton communities is not straightforward due to largely uncharacterized abilities for some phytoplankton to access zinc species that may not be universally bioavailable and substitute zinc with cobalt or cadmium. We used a quantitative proteomic approach to investigate these strategies and other responses to zinc limitation in the coccolithophoreEmiliania huxleyi, a dominant species in low zinc waters. Zinc limitation resulted in the upregulation of metal transport proteins (ZIP, TroA‐like) and COG0523 metallochaperones. Some proteins were uniquely sensitive to growth under replete zinc, substitution of zinc with cobalt, or enhancement of growth with cadmium, and may be useful as biomarkers of zinc stress or substitutionin situ. Several proteins specifically upregulated under cobalt‐supported or cadmium‐enhanced growth appear to reflect stress responses, despite titration of these metals to optimal nutritive levels. Relief from zinc limitation by zinc or cadmium resulted in increased expression of a δ‐carbonic anhydrase. Our inability to detect metal binding enzymes that are specifically induced under cobalt‐ or cadmium‐supported growth suggests cambialism is important for zinc substitution inE. huxleyi.

    

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3. Cadmium Ecotoxic Effects on Embryonic Dmrt1 and Aromatase Expression in Chrysemys picta Turtles May Implicate Changes in DNA Methylation

   https://doi.org/10.3390/genes13081318  

   Mizoguchi, Beatriz ; Topping, Nicholas E. ; Lavin, Andrew M. ; Valenzuela, Nicole ( August 2022 , Genes)

   Temperature-dependent sex determination (TSD) decides the sex fate of an individual based on incubation temperature. However, other environmental factors, such as pollutants, could derail TSD sexual development. Cadmium is one such contaminant of soils and water bodies known to affect DNA methylation, an epigenetic DNA modification with a key role in sexual development of TSD vertebrate embryos. Yet, whether cadmium alters DNA methylation of genes underlying gonadal formation in turtles remains unknown. Here, we investigated the effects of cadmium on the expression of two gene regulators of TSD in the painted turtle, Chrysemys picta, incubated at male-producing and female-producing temperatures using qPCR. Results revealed that cadmium alters transcription of Dmrt1 and aromatase, overriding the normal thermal effects during embryogenesis, which could potentially disrupt the sexual development of TSD turtles. Results from a preliminary DNA methylation-sensitive PCR assay implicate changes in DNA methylation of Dmrt1 as a potential cause that requires further testing (aromatase methylation assays were precluded). 

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4. Cadmium Pollution From Zinc‐Smelters up to Fourfold Higher Than Expected in Western Europe in the 1980s as Revealed by Alpine Ice

   https://doi.org/10.1029/2020GL087537  

   Legrand, M. ; McConnell, J. R. ; Lestel, L. ; Preunkert, S. ; Arienzo, M. ; Chellman, N. J. ; Stohl, A. ; Eckhardt, S. ( May 2020 , Geophysical Research Letters)

   Estimates of past emission inventories suggest that toxic heavy metal pollution in Europe was highest in the mid‐1970s for lead and in the mid‐1960s for cadmium, but these previous estimates have not been compared to observations. Here, alpine ice‐cores were used to document cadmium and lead pollution in western Europe between 1890 and 2000. The ice‐core trends show that while lead pollution largely from leaded gasoline reached a maximum in ~1975 as expected, cadmium pollution primarily from zinc smelters peaked in the early‐1980s rather than in ~1965 and was up to fourfold higher than estimated after 1975. Comparisons between ice‐core trends, estimated past emissions, and state‐of‐the‐art atmospheric aerosol transport and deposition modeling suggest that the estimated decreases in cadmium emissions after 1970 were based on overly optimistic emissions reductions from the introduction of pollution control devices and other technological improvements.

    

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5. Isotopically Light Cd in Sediments Underlying Oxygen Deficient Zones

   https://doi.org/10.3389/feart.2021.623720  

   Chen, Lena ; Little, Susan H. ; Kreissig, Katharina ; Severmann, Silke ; McManus, James ( March 2021 , Frontiers in Earth Science)

   null (Ed.)

   Cadmium is a trace metal of interest in the ocean partly because its concentration mimics that of phosphate. However, deviations from the global mean dissolved Cd/PO 4 relationship are present in oxygen deficient zones, where Cd is depleted relative to phosphate. This decoupling has been suggested to result from cadmium sulphide (CdS) precipitation in reducing microenvironments within sinking organic matter. We present Cd concentrations and Cd isotope compositions in organic-rich sediments deposited at several upwelling sites along the northeast Pacific continental margin. These sediments all have enriched Cd concentrations relative to crustal material. We calculate a net accumulation rate of Cd in margin settings of between 2.6 to 12.0 × 10 7  mol/yr, higher than previous estimates, but at the low end of a recently published estimate for the magnitude of the marine sink due to water column CdS precipitation. Cadmium in organic-rich sediments is isotopically light ( δ 114/110 Cd NIST-3108 = +0.02 ± 0.14‰, n = 26; 2 SD) compared to deep seawater (+0.3 ± 0.1‰). However, isotope fractionation during diagenesis in continental margin settings appears to be small. Therefore, the light Cd isotope composition of organic-rich sediments is likely to reflect an isotopically light source of Cd. Non-quantitative biological uptake of light Cd by phytoplankton is one possible means of supplying light Cd to the sediment, which would imply that Cd isotopes could be used as a tracer of past ocean productivity. However, water column CdS precipitation is also predicted to preferentially sequester light Cd isotopes from the water column, which could obfuscate Cd as a tracer. We also observe notably light Cd isotope compositions associated with elevated solid phase Fe concentrations, suggesting that scavenging of Cd by Fe oxide phases may contribute to the light Cd isotope composition of sediments. These multiple possible sources of isotopically light Cd to sediments, along with evidence for complex particle cycling of Cd in the water column, bring into question the straightforward application of Cd isotopes as a paleoproductivity proxy. 

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