Environmental estrogens affect early developmental activity in zebrafish

June 21, 2012

Chemicals in the environment that mimic estrogen can strongly influence the development of humans and other animals. New research to be presented at the 2012 International Zebrafish Development and Genetics Conference, held June 20-24 in Madison, Wisconsin, reveals that these substances may act even earlier than previously realized, at the very beginning stages of embryonic development.

Estrogenic compounds in the environment are both naturally occurring, such as in food plants, and synthetic, such as bisphenol A (BPA), used in making hard plastic bottles, like baby bottles and metal-based food and , including those for baby formula. They are known to affect development of the , but not much is known about other effects, including any at beginning embryonic development. "The timing of exposure is critical. Evidence from animals suggests that there are critical periods of development when endocrine disruptors could be more deleterious than exposure during adulthood," says Daniel Gorelick, Ph.D., a postdoctoral fellow at the Carnegie Institution for Science.

Working with Professor Marnie Halpern, Ph.D., Dr. Gorelick discovered a new and unexpected activity of estrogenic compounds during early stages of . He will present his findings at the conference on Sunday, June 24.

The researchers used zebrafish, which offer several advantages for studying this question. "People have used fish as environmental sentinels for aquatic pollution for decades," Dr. Gorelick says. Most studies, however, have been limited to fairly crude effects such as death or large-scale changes in single genes.

The researchers took advantage of the available for zebrafish to study where and when estrogen receptors are active throughout the body. They genetically developed fish whose cells make a when their estrogen receptors are activated and looked at the fish early in development, during formation of the major tissues and organ systems, including the heart, gut, and central nervous system. Because zebrafish embryos are optically transparent during early development, the researchers were able to see individual estrogen-responsive cells in living, growing embryos.

"We found some things that were expected, which was activity in the liver and parts of the brain known to be estrogen-responsive," Dr. Gorelick says. "The big surprise was finding it in the heart, and specifically in heart valves, which to my knowledge had not been known to be sensitive to estrogens."

In fact, the heart appears to be even more sensitive than other organs to some estrogenic compounds, particularly genistein (a common dietary estrogen found in plants) and BPA.

That finding prompted the researchers to look for possible effects of environmental estrogens. In collaboration with the Fish Health Branch of the U.S. Geological Survey and the University of Maryland School of Medicine, they collected concentrated from in and around the Chesapeake Bay and found that these water samples also activate the zebrafish estrogen receptors, with especially high activation in the heart valves.

Researchers don't yet know what role estrogen sensitivity in the heart may play, nor how the fish's development may be affected by such early exposure to estrogenic compounds. As with many signaling molecules, it's likely that both the timing and the amount of exposure are critical.

"They can respond to estrogens in the lab, but also estrogens in the environment in samples from local rivers and streams," Dr.Gorelick says. "They're everywhere and they're unavoidable, but it's the dose that makes the poison."

Dr. Gorelick and his colleagues are now working to identify specific compounds from the water samples that activate the receptors, as well as to learn what physiological role estrogen receptor activity plays in heart development and function.

Explore further: How neonatal plant estrogen exposure leads to adult infertility

Related Stories

How neonatal plant estrogen exposure leads to adult infertility

May 2, 2012
A paper published today in Biology of Reproduction's Papers-in-Press describes the effects of brief prenatal exposure to plant estrogens on the mouse oviduct, modeling the effects of soy-based baby formula on human infants. ...

Early-life exposure to BPA affects adult learning

April 4, 2012
In testing the effects of the controversial chemical bisphenol A (BPA) on zebrafish, UWM scientist Daniel Weber found himself in familiar territory.

Recommended for you

Forgotten strands of DNA initiate the development of immune cells

September 21, 2017
Intricate human physiological features such as the immune system require exquisite formation and timing to develop properly. Genetic elements must be activated at just the right moment, across vast distances of genomic space.

Genome editing reveals role of gene important for human embryo development

September 20, 2017
Researchers have used genome editing technology to reveal the role of a key gene in human embryos in the first few days of development. This is the first time that genome editing has been used to study gene function in human ...

A piece of the puzzle: Eight autism-related mutations in one gene

September 19, 2017
Scientists have identified a hotspot for autism-related mutations in a single gene.

Scientists identify key regulator of male fertility

September 19, 2017
When it comes to male reproductive fertility, timing is everything. Now scientists are finding new details on how disruption of this timing may contribute to male infertility or congenital illness.

New assay leads to step toward gene therapy for deaf patients

September 18, 2017
Scientists at Oregon State University have taken an important step toward gene therapy for deaf patients by developing a way to better study a large protein essential for hearing and finding a truncated version of it.

Genomic recycling: Ancestral genes take on new roles

September 18, 2017
One often hears about the multitude of genes we have in common with chimps, birds or other living creatures, but such comparisons are sometimes misleading. The shared percentage usually refers only to genes that encode instructions ...

0 comments

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.