Phthalate affects egg formation in C. elegans, resulting in abnormal chromosome numbers.

A recent study conducted on roundworms has discovered that a common plastic ingredient can cause DNA strand breaks, leading to egg cells with an abnormal number of chromosomes. The research, led by Monica Colaiácovo from Harvard Medical School, was recently published in the journal PLOS Genetics.

Benzyl butyl phthalate (BBP) is a chemical that makes plastic more flexible and durable, and is found in many consumer products, including food packaging, personal care products, and children's toys. Previous studies have shown that BBP interferes with the body's hormones and affects human reproduction and development, but the details of how it impacts reproduction have been unclear.

Experimental Approach

In the new study, researchers tested a range of doses of BBP on the nematode Caenorhabditis elegans and looked for abnormal changes in egg cells. They saw that at levels similar to those detected in humans, BBP interferes with how newly copied chromosomes are distributed into the sex cells. Specifically, BBP causes oxidative stress and breaks in the DNA strands, which lead to cell death and egg cells with the wrong number of chromosomes.

Plastic Chemical Causes Causes DNA Breakage and Chromosome Defects in Sex Cells
BBP exposure causes chromosome organization defects in the female germline. Carnoy's fixed and DAPI-stained images of gonads at the pachytene stage following exposure to DMSO or BBP. Images represent examples of gonads with normal germline configuration (first panel) or various chromosome organization defects in the germline including laggers (second panel), aggregates (third panel), and gaps (fourth panel). Yellow arrowheads indicate the respective defect in each panel. N = 27–31 gonads. Three biological repeats. Scale bar, 5 μm. Credit: Henderson et al, 2024, PLOS Genetics, CC-BY 4.0

Based on these findings, the researchers propose that BBP exposure alters gene expression in ways that cause significant damage to the DNA, ultimately leading to lower-quality egg cells with abnormal chromosomes. The study also showed that C. elegans metabolizes BBP in the same way as mammals, and is impacted at similar BBP levels that occur in humans, suggesting that C. elegans is an effective model for studying the impacts in people. Overall, the study underscores the toxic nature of this very common plastic ingredient and the damage it causes to animal reproduction.

The authors summarize: "Here, examining the female germline in the nematode C. elegans, this study found that a level of exposure within the range detected in human serum and urine, alters gene expression linking increased germline oxidative stress with compromised genomic integrity and errors in meiotic chromosome segregation."

Reference: "Exposure to benzyl butyl phthalate (BBP) leads to increased double-strand break formation and germline dysfunction in Caenorhabditis elegans" by Ayana L. Henderson, Rajendiran Karthikraj, Emma L. Berdan, Shannan Ho Sui, Kurunthachalam Kannan and Monica P. Colaiácovo, 24 October 2024, PLOS Genetics.
DOI: 10.1371/journal.pgen.1011434

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