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Science Policy Around the Web – July 7, 2017

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By: Liu-Ya Tang, PhD

Source: pixabay

Autism

Is There Such a Thing as an Autism Gene?

Autism has become a global burden of disease. In 2015, it was estimated to affect 24.8 million people globally. Significant research efforts are underway to investigate the causes of autism. Autism is highly heritable – there is an 80 percent chance that a child would be autistic if an identical twin has autism. The corresponding rate is about 40 percent for fraternal twins.

However, is there such a thing as a single autism gene? Researchers haven’t found one specific gene that is consistently mutated in every person with autism. Conversely, 65 genes are strongly linked to autism and more than 200 others have weaker ties, many of which are related to important neuronal functions. Mutations in a variety of these genes can collectively lead to autism. The mutations could be from single DNA base pair, or copy number variations, which are deletions or duplications of long stretches of DNA that may involve many genes. Most mutations are inherited, but some mutations could also happen in an egg or sperm, or even after conception.

Besides genetic factors, maternal lifestyle and environmental factors can also contribute to autism. Exposure to air pollution during pregnancy or a maternal immune response in the womb may increase the risk of autism. While there is speculation on the link between vaccines and autism, it is not backed by scientific evidence.

Since both genetic and non-genetic factors play a role in the development of autism, establishing the underlying mechanism is complicated. There is no single specific test that can be used for screening autism. However, some tests are available to detect large chromosomal abnormalities or fragile X syndrome, which is associated with autism. (Nicholette Zeliadt, Washington Post)

STEM Education

New Florida Law Lets any Resident Challenge What’s Taught in Science Classes

A new law was signed by Florida Gov. Rick Scott (R) last week, and has taken effect starting July 1. The law requires school boards to hire an “unbiased hearing officer” to handle complaints about teaching materials that are used in local schools. Any county resident can file a complaint, and the material in question will be removed from the curriculum if the hearing officer thinks that the material is “pornographic,” or “is not suited to student needs and their ability to comprehend the material presented, or is inappropriate for the grade level and age group.”

There are different voices in the new legislation, which affects 2.7 million public school students in Florida. Proponents argue that it gives residents more right in participating in their children’s education. A sponsor, state Rep. Byron Donalds (R-Naples), said that his intent wasn’t to target any particular subject. However, Glenn Branch, deputy director of the National Council for Science Education, is worried that science instruction will be challenged since evolution and climate change have been disputed subjects. A group called Florida Citizens for Science asked people to pay close attention to classroom materials and “be willing to stand up for sound science education.”

Like the new law in Florida, the legislature in Idaho rejected several sections of the state’s new public school science standards related to climate change and requested a resubmission for approval this fall. Since the Trump administration began, there has been “a new wave of bills” targeting science in the classroom. To protect teacher’s “academic freedom,” Alabama and Indiana adopted non-binding resolutions that encourage teachers to discuss the controversy around subjects such as climate change. A supporter of the resolution, state Sen. Jeff Raatz (R-Centerville), told Frontline, “Whether it be evolution or the argument about global warming, we don’t want teachers to be afraid to converse about such things”. (Sarah Kaplan, Washington Post)

 

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Written by sciencepolicyforall

July 7, 2017 at 1:32 pm

Is the human germline off limits?

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By: Thomas Calder, Ph.D.

Licensed via Creative Commons

A new genetic engineering technology, known as CRISPR-Cas9, is allowing scientists to edit the human genome faster and easier than ever thought possible. This technology has the potential to treat and even cure several major diseases such as sickle-cell anemia, HIV, and many forms of cancer. As a result, many labs around the world are rushing to better understand the CRISPR-Cas9 system so they can eventually advance the technology into the clinic. However, such unparalleled potential comes with a risk. CRISPR-Cas9 could be used to alter the genetic code of germline cells, which are reproductive cells that could then pass these alterations onto further generations. This has scientists and the public asking the controversial question: is editing the human germline ethical?

This controversy is not new, as genetic engineering technologies have been around since the 1980’s. Zinc-finger nucleases (ZFNs) were discovered in the 1980’s and were determined to have genome-editing capabilities during 1996-2003. ZFNs are DNA cutting enzymes that can be engineered to target specific segments of DNA, and can thus alter sections of the human genome. Designing ZFNs proved to be difficult, so many scientists were excited when different genome-editing enzymes, TAL effector nucleases (TALENs), were found in 2009-2010 to be easier to engineer than ZFNs. Both ZFNs and TALENs have the same shortcoming though. They require scientists to design proteins specifically for a targeted segment of DNA, which then requires validation of each newly designed protein. Thus, these technologies are highly impractical for editing the genome on a large-scale.

The CRISPR-Cas9 system was first discovered in 1987 by a Japanese lab, but it was not well understood until recent years. Scientists determined in 2005-2007 that bacteria harbor this DNA editing system to digest foreign viral DNA. In 2011-2012, scientists began to understand the basic essentials of this system so they could utilize it for genetic engineering. They discovered that Cas9 is a DNA cutting enzyme that can be targeted to specific DNA fragments with the help of a specially designed guide-RNA molecule. This system proved to be much easier to use that ZFNs and TALENs, because scientists did not have to design different enzymes for each targeted DNA fragment. Instead, they only had to engineer RNA molecules to match with targeted DNA fragments. With this approach, CRISPR-Cas9 can be used to target and alter any gene based on its genetic code, and it can even be used for genome-wide studies.

With the recent characterization of CRISPR-Cas9, a new frontier in science has begun. Scientists have designed guide-RNA molecules for every gene in the genome to determine which genes are essential for various diseases, such as many forms of cancer. This approach is exciting because it may lead to the discovery of new targets for drug-based therapy. Scientists are also creating animal models of various genetic diseases by causing disease-specific alterations in the genome of animals such as mice and monkeys. For humans, this research has focused on non-reproductive cells, but the efficacy of this technology is making the human germline a tempting target. Theoretically, scientists could use CRISPR-Cas9 in an embryo to remove a disease-causing gene and replace it with a healthy version of the gene. This approach has the potential to ward off deadly diseases—but is it ethical? Most importantly, is it safe?

Both questions are controversial. In terms of safety, many scientists currently agree that it is not safe to create a permanent genetic alteration that can be passed onto future children. One concern is that Cas9 could have off-target effects that could damage the human genome in unpredictable ways. Another concern is that scientists do not understand the genome well enough to start making changes to the code. According to a Perspective article in the journal Science, by scientists that attended an ethics discussion in January on the topic of editing the human germline, “there are limits to our knowledge of human genetics, gene-environment interactions, and the pathways of diseases (including the interplay between one disease and other conditions or diseases in the same patient).” Also, side-effects from altering the genetic code of an embryo might not be noticeable until that embryo turns into a grown child, many years into the future. Therefore, more information on the human genome is necessary before genetic engineering of the human germline can be considered safe.

These safety concerns factor into the ethics debate, but other concerns are also drawing attention. While CRISPR-Cas9 is currently being proposed to prevent debilitating diseases, the use of this technology might start a slippery slope that could lead to the creation of “designer-babies.” For example, the genome of an embryo could be altered to impart a different eye color, hair color, or higher level of intelligence. These changes are certainly not worth the risk of side-effects, but some parents might pursue these options to provide their child with a “leg up”. Other ethical questions include:

  • Would the use of this technology be regulated?
  • Would a child be monitored if he/she was genetically modified as an embryo? Would the child’s future offspring be monitored?
  • Which parts of society would have access to this technology? Would use of this technology lead to a greater divide between the poor and wealthy?

The CRISPR-Cas9 technology is advancing quickly, so scientists need to act now to reach a consensus on these ethical issues. Many scientists have already called for a moratorium on editing the human germline in the short-term. This would provide time for scientists to engage with the bioethics community and the public to discuss the ethical, social, and legal implications of altering the human genome.

The genetic engineering capabilities of CRISPR-Cas9 is exciting. Millions of lives could benefit from this new technology. It could cure certain cancers, prevent diabetes, ward of many age-related diseases, and even stop HIV from causing AIDS. But scientists must use extra caution when editing the human germline, because any negative effects that arise could last for many generations into the future.

Sources:

Written by sciencepolicyforall

April 15, 2015 at 11:02 am