Fingerprints of the Environment on Our Genes, Epigenetics

Introduction

In March this year, researchers at the University of Michigan released a study suggesting that changes in gene expression caused by microplastic exposure in Fathead Minnows 🐟 could be inherited across generations. In other words, even offspring that had never been exposed to microplastics themselves still showed the same gene expression changes as their parents 🧬.

The idea that gene expression can be altered by environmental factors like microplastic exposure — rather than strictly by genetic inheritance — is quite different from what we traditionally learn about genetics. Isn’t it fascinating? The field of research that directly addresses the possibility of these environmentally driven changes being passed down to future generations is called epigenetics.

So today, welcome to the very first episode, where we are going to break down this concept of epigenetics in a fun and approachable way!

Today’s Content – ZOOM IN 🔬

1. Even with identical genes, gene expression can vary?!
2. Tighten it up, loosen it out – the fun of regulating gene expression
3. A zip file of fascinating epigenetics research 🧬
4. Closing thoughts

Even with Identical Genes, Gene Expression Can Vary?

What is gene expression? 🧬
Our bodies are made up of countless proteins, which determine most of our traits. The amount of each protein produced influences everything from visible traits like skin and hair color to invisible ones like hormone levels. The blueprint for all of this is stored in our DNA.

DNA consists of four bases — cytosine (C), guanine (G), adenine (A), and thymine (T). These building blocks are arranged in various sequences. The specific order of these bases determines which of the 20 amino acids will be produced. Amino acids then link together to form proteins. When DNA’s “code” is transcribed into amino acids and then into proteins, we say a gene has been “expressed.” In short, gene expression is the process of turning the DNA’s instructions into actual working molecules that affect our bodies.

*Tip: Think about Lego block. Each Lego block makes the figure, right? Genetic information in our body is 'instruction' of Lego block, they tell us which Lego blocks to use to make this one figure. Then, we make our figure based on the instruction we have, and we finally see the figure as a whole. This is how genetic information, the Lego instruction, transforms into ourselves, the whole figure. 

Why Identical Genes Can Be Expressed Differently 👀

Before the concept of epigenetics emerged, scientists generally believed that people with the same gene would express it in the same way. For example, if both Person A and Person B have a gene that produces a certain enzyme, they would each produce exactly the same amount of that enzyme.

But epigenetics challenged this view. Two people can have the same gene yet express it at different levels — one person might produce 120 units of an enzyme, while another might produce only 50. In other words, identical genes can have different levels of expression.

Tighten it Up, Loosen it Out – Fun Ways to Regulate Gene Expression 🔧

So how does this happen? Even with the same genes, the way they’re expressed can be altered by several mechanisms. For example:

• The stability and lifetime of mRNA in the cytoplasm can influence how much protein is ultimately produced.
• Proteins bound to the promoter region of DNA can enhance or suppress the transcription of certain genes.

One of the most discussed epigenetic mechanisms today is DNA methylation (another important one is histone modification, but we’ll skip that for now to keep things simple).

In eukaryotic cells, DNA is wrapped around proteins called histones. To express a gene, the DNA must be “unwound” from the histone so it can be transcribed into mRNA. If the DNA-histone structure is tightly wound, transcription is more difficult; if it’s loose, it’s easier.

DNA methylation occurs when enzymes called DNA methyltransferases add methyl groups to cytosine bases in the DNA. This tightens the interaction between DNA and histones 🔒, making it harder for mRNA to access the DNA and thus reducing gene expression. Conversely, adding acetyl groups to histones loosens the DNA-histone interaction 🔓, making transcription easier and increasing gene expression.

Epigenetics suggests that environmental factors in our lives can influence these mechanisms. Normally, these changes are “reset” in the early embryonic stage and not passed to the next generation. However, in rare cases, they are not reset — meaning that environmental effects experienced by one generation can be inherited by the next. Fascinating, right?

Fascinating Epigenetics Studies 🧬

Study 1 – Maternal Bisphenol A (BPA) Exposure and Childhood Obesity
Research from Seoul National University and the University of Copenhagen found that higher maternal exposure to BPA was linked to greater methylation of the IGF2R gene in their children at age two. IGF2R plays a key role in metabolism and growth, and its suppression has been linked to an increased risk of childhood obesity.

Study 2 – Epigenetic Factors in PTSD
Brain-derived neurotrophic factor (BDNF) is critical for stress regulation and neural plasticity. A study from Yonsei University compared DNA methylation in the BDNF promoter region between individuals with and without PTSD. Those with PTSD had higher methylation levels, indicating suppressed BDNF expression. This finding raises the possibility that targeting BDNF expression could aid in PTSD prevention or treatment.