House Spiders Go High-Tech: CRISPR Swaps DNA for Dazzling Red Silk

The possibility of editing our genes once seemed more like science fiction than reality. Times have changed with the development of CRISPR-Cas9, a gene-editing tool first used in 2012. Gene editing is highly celebrated as a possible solution to health issues and genetic disorders. However, scientists are beginning to explore CRISPR-Cas9 as a way to develop solutions for future societal needs.

A broad variety of animals, from mice to livestock, have already been genetically edited and engineered, many times with food in mind. But a research team from the University of Bayreuth’s Biomaterials division made history with the first-ever successful gene modification of common house spiders (Parasteatoda tepidariorum) that made these spiders capable of producing fluorescent red silk.

What is CRISPR-Cas9?

Before discussing why this study was so impactful, it’s important to explain how gene editing actually works. Genes play a hugely important role in how the body operates, and not just in humans. These DNA-based building blocks influence everything from an animal’s size and health to its behavior and development.

With CRISPR-Cas9, a protein called Cas9 goes to a spot in the DNA and changes it by cutting the DNA. This may cause genes to be removed or “turned off,” activated, or even added.

Gene Editing in Spiders is Challenging

This particular study began when the research team, led by Dr. Thomas Scheibel and doctoral student Edgardo Santiago-Rivera, questioned why gene-editing had never been done in spiders.

Dr. Scheibel writes that he was surprised by this since “CRISPR has been applied in a wide range of studies in developmental and evolutionary biology and for diverse applications such as in material sciences, pest control, and agriculture.”

Spiders are understudied compared to other arthropods. As Dr. Scheibel and Santiago-Rivera soon found out, there are several reasons why spider-related research can be so challenging:

• Cannibalism: Spiders are solitary and will eat each other, which makes it hard to keep many spiders for research.
• Species: Given how many spider species exist, what research shows about one spider may not be true for others.
• Unique genome: Some spiders, like the common house spider, have two copies of several genes.

Study Goals: CRISPR Research in Common House Spiders

The challenges associated with spider-related research meant that Dr. Scheibel and Santiago-Rivera had to come up with a more innovative approach to their study. They began by putting female spiders to sleep (literally, not figuratively!) before using a thin needle to inject a CRISPR solution.

The CRISPR solution permeated the spiders’ eggs. When the female spiders woke up, they were mated with male spiders. The researchers then collected a total of 59 egg sacs to study to see which spider offspring (known as spiderlings) had genetic changes.

Fun fact: Spider egg sacs can contain over 100 eggs!

From these eggs, Dr. Scheibel and Santiago-Rivera wanted to test how effective CRISPR-Cas9 was in gene knock-outs and knock-ins:

• Knock-outs: A knocked-out gene is deactivated and doesn’t work anymore. For the study, scientists targeted the sine oculis gene to see how it would affect spiders’ eye development.
• Knock-ins: To the spiders, the researchers added biological information for a red protein to the MaSp2 gene to see if it would affect silk color.

The Spiders’ Silk Changed, But Not As Much As Scientists Thought

Both the knock-in and knock-out experiments were successful. Knocking out the sine oculis gene prevented the spiderlings’ eyes from developing correctly. But this manifested in different ways. Some nymphs had no eyes at all. Other nymphs developed deformed eyes or lacked proper internal eye structures.

In terms of the silk, the inclusion of the red protein did contribute to the spiderlings having red silk when they grew into adults. The researchers also tested the strength of the silk. They found that, despite the changes to color, there were no real changes to silk production or strength.

What Does This Mean for the Common House Spider?

Genetically oriented research in spiders is still relatively limited. But it is considered a growing and evolving field. For researchers who are interested in gene-edited spiders, studying Parasteatoda tepidariorum is a good place to start.

Scientists have already proven that the editing done during this study did not harm the spiders’ silk production. Since the world is heavily moving towards more sustainable options for everything from clothing to healthcare, spider silk could become valuable. This makes the common house spider even more attractive to research teams since they have already seen success here.

How Could We Use Spider Silk in Future Applications?

Spider silk is notoriously strong, especially relative to its size. It is considered high-tensile, which is a fancy way of saying that spider silk can be heavily stretched or pulled without breaking. By weight, spider silk is around 5x stronger than steel and also stretchier. This is because spider silk is made up of thousands of nanostrands, which make it more elastic and better at absorbing energy.

Much more research is needed, and much more testing must be done, before spider silk can be used widely for different applications. But this research is already starting, mostly using artificial spider silk:

• Scientists are creating artificial spider silk for biodegradable, biocompatible bandages and surgical sutures to promote wound healing.
• Artificial spider silk has been explored as a more eco-friendly option for clothing that can reduce plastic-based fiber use.
• Some researchers question whether spider silk could be woven into super-elastic cords for use in construction settings.

Here is where the German study can help: By proving that spiders can be genetically edited to produce different color silk, the researchers set the stage for future genetic editing that can possibly intensify silk strength or thickness for use in the above fields.

Some critics may argue that this is less ethical than producing artificial spider silk. But regardless, this study highlights the growing interest and possibilities of using gene editing to enhance silk production at the source.