Growing Discovery: How Scientists Use Cells to Study Human Biology
Written and illustrated by Devyn Deschamps and Jimin Lee
In the San Roman Lab, we use a variety of techniques, many of which rely on two key models: Lymphoblastoid Cell Lines (LCL) and Primary Skin Fibroblasts from individuals with natural variation in sex chromosome copy number.
Lymphoblastoid Cell Lines, or LCLs for short, are a crucial model in genetic research as they provide a replenishable source of human DNA, RNA, and protein. They are called “immortalized” because the cells have been altered to grow and divide indefinitely. This is exceptionally important in genetics research because it allows the cell line experiments to be easily reproduced. These lines are important as they allow us to grow cells in the lab, outside of a body, for long periods of time.
LCLs are considered a subcategory within the wider history of cell culturing in science, which originated in the early 1900’s when a Johns Hopkins professor discovered he could grow an amphibian nerve cell outside of a frog's body for weeks. He removed the cell and kept it in a sample of the frog’s lymph, which is a bodily fluid that travels through the body’s lymph nodes. The sample was placed within a small microscopic slide, and the sides were sealed with wax, and then inverted. The cell continued to live for weeks.
The true introduction of LCLs came along later in the century, in 1964, when scientists Anthony Epstein, Yvonne Barr, and Burt Achong published a paper on a virus that could cause cancer, later dubbed the Epstein-Barr Virus (EBV). Then, in 1967, a new team of researchers, Werner and Gertrude Henle, found that they could induce a continuous growth of B-lymphocytes, the type of white blood cells that make antibodies when you to protect you from getting sick, by cultivating them with specially treated cells carrying EBV. This paved the way for other scientists to begin collecting LCLs from white blood cells, obtained from human blood.
LCLs are commonly used in labs across the world, including our own, because they serve as a reliable cellular model in our investigations of sex differences in humans.
Because our lab studies the impact of the X and Y chromosomes, we obtain cells from individuals with natural variation in sex chromosome copy number (see aneuploidies section in our Calico Cats X-plination). We work alongside clinicians to recruit volunteers willing to provide samples. We obtain patient consent and collect blood samples, and send the samples to our lab for processing.
After a blood sample is collected, it is placed in a vial, which is placed in a centrifuge, which spins the sample at high speeds. The speed of the centrifuge forces materials of different densities to separate, leaving layers of different materials. For blood samples, this isolates the white blood cells from the red blood cells, because they are slightly less dense.
We collect our isolated white blood cells and move on to cell transformation. To immortalize the B-cells, we infect them with EBV, which triggers immortalization, allowing the cells to divide and grow indefinitely in this laboratory setting.
This leads to the cell growth stage, where a new cell sample is placed in a nutrient-rich medium, similar to the frog’s lymph covering the nerve cell, that allows the cell to continue growing. For our cell samples, we keep them in an incubator, which keeps the samples in a controlled, stable environment at 98 degrees Fahrenheit and constant CO2 concentrations. These conditions mimic the inside of the body, allowing cells to continue growing.
Look at how LCLs appear under a microscope!
Once this process is complete, LCLs can be used for other methods like RNA sequencing, a cornerstone for our sex chromosome research, because they give us a stable and renewable source of human cells, making it easier to compare gene expression across individuals and better understand differences linked to sex chromosomes.
In addition to LCLs, we also use primary skin fibroblast cells as another important model system. This cell type is often used because it closely mirrors cells in the body that are not transformed to grow rapidly, like the LCLs.
Similar to LCLs, we work alongside clinicians to recruit volunteers with natural variation in sex chromosome copy number. We obtain patient consent and collect a skin biopsy, and send the samples to our lab for processing.
Once this sample is acquired, the tissue must be prepared. Using a scalpel, the sample is sliced into even smaller sections and placed in a container with culture medium, a nutrient-rich broth that contains all the nutrients to keep the cells alive and growing.
The samples rest in a 98-degree Fahrenheit incubator, and over time fibroblast cells to grow out from the tissue. Look at how skin fibroblasts appear under a microscope!
Together, these methods push us toward answering larger biological questions. In the San Roman Lab, we study samples from individuals with natural variation in sex chromosome copy number, which provides a unique opportunity to understand how genes on the X and Y chromosomes function.
By combining cell models like LCLs and fibroblasts with techniques such as RNA sequencing (future x-planation coming soon), we can identify which genes are influenced by sex chromosomes and how they contribute to human differences. This work helps us better understand the genetic basis of sex differences and may ultimately inform research into sex differences human health and disease.
Links to our manuscripts using LCLs and skin fibroblasts:
The human Y and inactive X chromosomes similarly modulate autosomal gene expression
The human inactive X chromosome modulates expression of the active X chromosome
This article is part of the first phase of the X-plainers’ initiative, a team of Duke undergraduate students producing scientific communication within a R1 University. This project has been under the supervision of graduate student, Hannah Kubinski & Dr. Adrianna San Roman. To read more about X-plainers, click below.
