SC17: Christoph Lahtz

Christoph is a Biochemist and Epigeneticist having started his career as a cancer scientist with a focus on ionizing radiation and its impact to the epigenome. He developed over the years a huge enthusiasm for human space exploration. In these exciting times of the new space age, he has decided to focus more on the biological problems of human space exploration and human settlements to help to make humanity a multi‐planetary species.

The importance of space biology research to become a true spacefarers and space settlers


We live in exciting times we are on the brink to become a multi celestial species. This time is almost as an important step as our ancestors started to explore the sea in their boats and sailed into the unknown driven by curiosity and the spirit of discovery. Today nothing of this spirit changed and is forgotten. Just the frontier changed. Our ancestors’ journey took place in a highly similar environment in contrast to ours. But even our ancestors had to adapt their food sources, their habits and over time their genomes. And in order to reach and live on other celestial bodies like Moon(s), Mars, Venus or space stations we need to do exactly the same. We need to adapt and to learn how to live there. While the question of “How we get there?” will be answered by engineers and entrepreneurs like Elon Musk, the question of how we live there will be answered by biologists (botanists, geneticists, and microbiologists).

When our ancestors did their journeys their new destination had no other gravitation or radiation levels. This will not be the case for us. Humans and of course all other living organisms evolved on earth from the beginning with a constant of 1g of gravity. Gravity is an important part of the development of animals and plants and so changing this constant has consequences.

To do research of how organisms would react in space, scientists established a new field of scientific research – space biology. Space biology investigates what kind of impact space related environmental changes like weightlessness and radiation have on organisms.

First part: About us

For this purpose, NASA and other space agencies perform a lot of experiments since decades but the most exciting one to answer one of the key questions started on March 27th, 2015 when Scott Kelly started his yearlong space mission at the ISS. This was a novelty; no human being was before one year in space without any interruptions. Additionally, this experiment has a huge advantage which excited all geneticists. This study was an identical twin study. While Scott Kelly was in space his twin brother Mark Kelly stayed on earth. That means that all differences in his body could be traced back on his space habitation. During his space habitation, samples were taken from Scott and Mark to investigate the difference in his physiology parameters and his genome. The question “What influence has a long‐term space habitation on the human genome” could be investigated. The results to this question are highly thrilling and would elucidate the possibility of future space missions to Mars and permanent settlements on other celestial bodies.

The mission ended on February 29th, 2016 and scientists started the research. It has not been published a scientific publication yet, but on Nature.com was a news article published, informing about some of the new findings Nature. In the article, scientists speak about the following preliminary results without going into much detail.

1. Different gene expression levels

2. A change of the telomere length

3. A change in the overall genome methylation level.

We cannot discuss much the first two findings but the finding that DNA methylation is decreased during spaceflight should be more elucidated.

DNA methylations are a chemical marker for DNA which can affect gene expression. It is simply the addition of a methyl group (‐CH3) to 5’‐carbon of the cytosine base in the dinucleotide 5’‐CpG‐3’ in CpG islands in the promoter region  of genes (1‐3). Methylated promotor regions would inactivate the following gene.

Simplified: The region which determined the activity of a gene contains very often an enrichment of the bases cytosine and guanine (the other ones are thymine and adenine) in the specific order cytosine ( C )– guanine ( G ) or CpG (the p describes the phosphate bond between the two bases). These enriched regions called CpG islands. A methylation of the C in many of the CpGs prevents the gene to be active, it is called epigenetically silencing.

This process is reversible and not permanent. So when Scott Kelly’s overall genome experienced a decrease of methylation it is assumed that genes, in general, become more active. This would also explain the first finding of a very different gene activity.

Why is this important? What does it mean when many genes become active which were inactive or silenced before? Imagine the genetic program, especially the epigenetic program as a song played on a piano. Each key is a gene and when you push it down you hear the sound and the gene is active for that moment. In order to play a song on a piano, you have to push and release the keys in a certain combination, order, and length. This illustrates how complicated the genetic program is. Now imagine further that all keys are pushed at the same time in our example it would mean that they are all active, they experience a lack of control, a lack of methylation. This analogy is very simplified but it illustrates the problem a lack of overall methylation will cause.

Conclusion: This shows that a long‐term habitation in microgravity gravity has clearly an influence on our genome after 1 year in space. This means that humans would need gravity on a long‐term space habitation in order to keep a healthy genome and for human settlements; the question occurs how much gravity is needed to keep your genome healthy? And can this genetically change stopped by any medication? These are important questions we need to answer to make human settlement long lasting.

Second part: About our companions

Further, in order to establish a settlement on any celestial body, we need to find a new system to produce food in an environment which is significantly different than the original environment of the food organism. That means we would need several different food plants which are ideally genetically designed for these environments (reduced gravity, arid, radiation). NASA is able now to grow lettuce in microgravity in a limited amount. We need to improve the productivity of such space farms in microgravity and reduced gravity like Mars.

Very helpful and precious organisms for a future celestial settlement would be bacteria which produce all kinds of bioproducts (e.g. medication, chemicals) and for recycling the waste products of the settlement.

Portrait of an underestimated organism for space exploration:

Many people think a settlement on Mars would be powered by solar energy. Actually, because the Mars is further away from the sun, only 50% of solar energy reaches the Mars compared to Earth. Solar energy would be insufficient for a full grown settlement. One idea is to use biofuel produced by cyanobacteria to power engines. Cyanobacteria would need a light source as well to produce the necessary lipids for the biofuel production. Because of the insufficient natural light on Mars and the problem of using it, artificial light would be necessary to culture

A very unmentioned and underestimated candidate to produce lipids is the true slime mold Physarum Polycephalum. It has been shown that this organism has great potential for the biofuel production. Physarum P. has no cell wall like cyanobacteria which would need to be cracked by an energy consuming process to harvest the lipids. This is not necessary with Physarum. Additionally, Physarum does not need a light source and can be cultured with an easy carbon source which could be provided by the waste of the food plants. And it is highly radiation resistant which could lead that the production sites of would not need to be radiation protected.

Final conclusion:

For our goal to become a multi‐planetary species we need to see more excitement, engagement and “out of the box thinking” in space biologically research which is crucial for many parts of a successful, long‐term sustainable celestial settlement. Rockets are necessary but we need more space farmers for sustainability.

In order do so my mission is to nurture and increase the curiosity to explore us, our home planet and the universe and acquire scientific knowledge to help to make a space settlement possible. For that purpose, I am about to establish a lab which conducts relevant research in the field of space biology.

Ad Astra

References:

1. Cheng  JC,  Matsen  CB,  Gonzales  FA,e  W,  Greer S, Marquez VE,  et  al. Inhibition of DNA methylation and reactivation of silenced genes by zebularine. J Natl Cancer Inst 2003;95:399‐ 409.

2. Hendrich B, Bird A. Identification and characterization of a family of mammalian methyl‐CpG binding proteins. Mol Cell Biol 1998;18:6538‐47.

3. Zhu   WG,   Otterson   GA. The   interaction   of   histone   deacetylase   inhibitors   and DNA methyltransferase inhibitors in the treatment of human cancer cells. Curr Med Chem Anticancer Agents 2003;3:187‐99.