Tag: Cells

Investigating the Primary Cilium: Q&A With Xuecai Ge

A headshot of Dr. Xuecai Ge.
Credit: Courtesy of Dr. Xuecai Ge.

The brain is a large and complex organ, but some very small structures guide its development. Xuecai Ge, Ph.D., an associate professor of molecular and cell biology at the University of California, Merced (UC Merced), has devoted her career to understanding one of these structures called the primary cilium. In an interview, Dr. Ge shared how her childhood experience inspired her to study science and what makes the primary cilium fascinating.

Q: How did you first become interested in science?

A: When I was a little kid, my mom was a primary care doctor, and I saw her treat patients in our community. I noticed that no matter who got a particular illness, she could use the same medicine to treat them. My little mind was amazed that the same medicine could work for so many different people! I think this early experience planted the original seed of my interest in life science.

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Science Snippet: Examining Enzymes

An enzyme shown as a connected complex of colored ribbons and flat sheets.
Structure of a pyruvate kinase, an enzyme that adds a phosphate group to adenosine diphosphate (ADP) to make adenosine triphosphate (ATP). Credit: PDB 7UEH.

Every day, our cells must produce all the various molecules they need to stay alive. But the chemical reactions to create these molecules can’t occur without help—which is where enzymes come in. Enzymes are biological catalysts, meaning they speed up the rate of specific chemical reactions by reducing the amount of energy needed for the reaction to occur. Most enzymes are proteins, but some RNA molecules can also act as enzymes.

Thousands of different enzymes catalyze the vast range of reactions that take place within cells, but each enzyme typically supports one of the following types of tasks:

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Cool Images: Radiant in Red


Happy Valentine’s Day! In place of red roses, we hope you’ll accept a bouquet of beautiful scientific images featuring rich, red hues. Be sure to click all the way through to see the festive protein flowing through your blood!

For more scientific photos, illustrations, and videos in all the colors of the rainbow, visit our image and video gallery.

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What Is the Immune System?

This post is the first in our miniseries on the immune system. Be sure to check out the other posts in this series!
A sphere with evenly spaced blue projections and a pink core.
A computer-generated image of the rotavirus, a virus that commonly causes illness in children through inflammation of the stomach and intestines. Credit: Bridget Carragher, The Scripps Research Institute, La Jolla, California.

What do antibodies, mucus, and stomach acid have in common? They’re all parts of the immune system!

The immune system is a trained army of cells, tissues, and organs that work together to block, detect, and eliminate harmful insults to your body. It can protect you from invaders like bacteria, viruses, fungi, and parasites.

Innate and Adaptive

The immune system is often thought of as two separate platoons: the innate immune system and the adaptive immune system. Although these two platoons have different jobs and are made up of soldiers with different specialties, they work together to prevent infections.

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Why Do Cells Die?


You might know that tiny individual units called cells make up your body. But did you know some of your cells die every day as a part of their normal life cycle? These deaths are balanced by other cells splitting into two identical cells, a process called mitosis.

Two purple- and orange-speckled ovals (cells). The bottom left cell shrinks and becomes several bright yellow circles. The top right cell morphs into thick, bright yellow strands that align along the center of the cell and then pull apart into two new cells.
A confocal microscope films two cells: The cell on the left undergoes a type of cell death called apoptosis, and the one on the right undergoes mitosis. Credit: Dr. Dylan Burnette, Vanderbilt University School of Medicine.
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Claira Sohn Cultivates Neurons and Diversity in the STEM Community

A headshot of Claira Sohn.
Credit: Courtesy of Claira Sohn.

Claira Sohn credits her grandfather with sparking her interest in science. Although he never studied science at a 4-year university due to financial limitations, he took many community college classes and worked in chemistry labs developing products such as hair dyes and dissolvable stitches. “Every morning, my grandfather would take me to school, and we’d stop to get orange juice and a cookie and talk about science. When I was in elementary school, he bought me a book about quantum mechanics written for kids,” she says. “He inspired me to ask questions and encouraged me to go to college.”

Claira enrolled at Northern Arizona University in Flagstaff after graduating high school. She majored in biomedical sciences and planned to become a medical doctor until her microbiology professor talked to her about the possibility of a research career. “That was an epiphany for me, because while I knew that there was research going on in the world, I didn’t realize there could be a place for me there,” Claira says. During her junior year, she joined the lab of Naomi Lee, Ph.D., where she first experienced what it felt like to be a researcher.

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Molecular Fireworks: How Microtubules Form Inside Cells

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A video depicting red strands of various lengths exploding outward from a focal point at the left. The strands are tipped in neon green.
       Microtubules sprout from one another. Credit: Petry lab, Princeton University.

The red spray pictured here may look like fireworks erupting across the night sky on July 4th, but it’s actually a rare glimpse of tiny protein strands called microtubules sprouting and growing from one another in a lab. Microtubules are the largest of the molecules that form a cell’s skeleton. When a cell divides, microtubules help ensure that each daughter cell has a complete set of genetic information from the parent. They also help organize the cell’s interior and even act as miniature highways for certain proteins to travel along.

As their name suggests, microtubules are hollow tubes made of building blocks called tubulins. Scientists know that a protein called XMAP215 adds tubulin proteins to the ends of microtubules to make them grow, but until recently, the way that a new microtubule starts forming remained a mystery.

Sabine Petry Link to external web site and her colleagues at Princeton University developed a new imaging method for watching microtubules as they develop and found an important clue to the mystery. They adapted a technique called total internal reflection fluorescence (TIRF) microscopy, which lit up only a tiny sliver of a sample from frog egg (Xenopus) tissue. This allowed the scientists to focus clearly on a few of the thousands of microtubules in a normal cell. They could then see what happened when they added certain proteins to the sample.

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CLAMP Helps Lung Cells Pull Together

ALT TEXTCells covered with cilia (red strands) on the surface of frog embryos. Credit: The Mitchell Lab.

The outermost cells that line blood vessels, lungs, and other organs also act like guards, alert and ready to thwart pathogens, toxins, and other invaders that can do us harm. Called epithelial cells, they don’t just lie passively in place. Instead, they communicate with each other and organize their internal structures in a single direction, like a precisely drilled platoon of soldiers lining up together and facing the same way.

Lining up this way is crucial during early development, when tissues and organs are forming and settling into their final positions in the developing body. In fact, failure to line up in the correct way is linked to numerous birth defects. In the lungs, for instance, epithelial cells’ ability to synchronize with one another is important since these cells have special responsibilities such as carrying mucus up and out of lung tissue. When these cells can’t coordinate their functions, disease results.

Some lung epithelial cells are covered in many tiny, hair-like structures called cilia. All the cilia on lung epithelial cells must move uniformly in a tightly choreographed way to be effective in their mucus-clearing job. This is a unique example of a process called planar cell polarity (PCP) that occurs in cells throughout the body. Researchers are seeking to identify the signals cells use to implement PCP. Continue reading “CLAMP Helps Lung Cells Pull Together”

Pericytes: Capillary Guardians in the Brain

The long arms of pericytes cells (red) stretch along capillaries (blue) in a mouse brain. Credit: Andy Shih.

Nerve cells, or neurons, in our brains do amazing work, from telling our hearts to beat to storing our memories. But neurons cannot operate alone. Many kinds of cells support and regulate neurons and—like neurons—they can come under attack due to injuries or disorders, such as stroke or Alzheimer’s disease. Learning what jobs these cells do and how they respond to disease may show researchers new ways to treat central nervous system disorders. One type of support cell, the pericyte, plays some key roles in brain health. These cells are readily adaptable, even in adult brains, and can support a variety of functions.

Pericytes help with blood flow to nerve cells in the brain. They lie wrapped all along the huge networks of capillaries—the tiniest blood vessels—that both feed neurons and form the blood-brain barrier, which filters out certain substances from blood to protect the brain. Pericytes have a body that appears as a bump protruding from a capillary surface. Pericytes also have long thin arms that stretch along each capillary like a snake on a tree branch. These arms, called processes, reach almost to where the next pericyte process begins, without overlapping. This creates a pericyte chain that covers nearly the entire capillary network.

Pericytes are critical for blood vessel stability and blood-brain barrier function. They’re also known to die off as a result of trauma and disease. Andy ShihLink to external web site, Andree-Ann Berthiaume, and colleagues at the Medical University of South Carolina in Charleston, set up an imaging technique in mouse brains that allowed them to see what pericytes do under normal conditions as well as how these cells respond when some are damaged.

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Optogenetics Sparks New Research Tools

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Imagine if scientists could zap a single cell (or group of cells) with a pulse of light that makes the cell move, or even turns on or off the cell’s vital functions.

Scientists are working toward this goal using a technology called optogenetics. This tool draws on the power of light-sensitive molecules, called opsins and cryptochromes, which are naturally occurring molecules found in the cell membranes of a wide variety of species, from microscopic bacteria and algae to plants and humans. These light-reacting molecules change their shape or activity when they sense light, so they can be used to trigger cellular activity, such as turning on or off ion flow into the cell and other regulatory pathways. The ability to induce changes in cells has a broad range of practical applications, from enabling scientists to see how cells function to providing the basis for potential therapeutic applications for blindness, cancer, and epilepsy.

Opsins first gained a foothold in research about a decade ago when scientists began using them to study specific electrical networks in the brain. This research relied on channelrhodopsins, opsins that could be used to control the flow of charged ions into and out of the cell. Normally, when a neuron reaches a certain ion concentration, it is triggered to fire, but neuron firing can be changed by inserting opsins in the membrane. Neuroscientists figured out how to incorporate light-sensitive opsin proteins by inserting the opsin gene into the host’s DNA. The genetically encoded opsin proteins in the neuronal membranes could be turned on or off by shining light into the brain itself, using optical fibers or micro-LEDs, to switch on or off the flow of ions and neuron firing.

Since those early studies in the brain, the optogenetics field has come a long way. But the leap from brain cells to other cells has been challenging. Scientists first needed to find a way to deliver light into tissues deep in the body. And, unlike stationary brain cells, they needed a way to target cells that are on the move (such as immune cells). They also needed to develop a way to study not only cell networks but also individual cells and cell parts. The NIGMS-funded researchers highlighted below are among the scientists working to overcome these obstacles and are using optogenetics in new and inventive ways.

Illustration showing how bridges can be built within a cell using light-reacting molecules
Illustration shows how “bridges” can be built within a cell through the use of light-reacting molecules. The light triggers proteins to line up within the cell, making it easier to shuttle molecules between the membranes of two subcellular organelles. This optogenetic strategy is helping scientists to control cell function with a simple beam of light. Illustration courtesy of Yubin Zhou.

Building Bridges

Yubin ZhouLink to external web site of Texas A&M is using optogenetics to control the way cells communicate and to study immune cell function. In one line of research, Zhou is using light to make it easier for calcium ions to enter cells. The ions carry instructions for the cell and also help tether small cellular structures (called organelles).  Those inter-membrane tethers allow for the movement of  proteins and lipids back and forth across the cell, and are critical for sending chemical messengers to communicate information (see illustration). When this process is disrupted, it can lead to extreme changes in cell function and even cell death. Using this technology to “switch on” normal pathways enables the scientists to better understand how such processes can be disrupted.

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