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cell biology

A Ray of Molecular Beauty from Cryo-EM

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Rhodopsin

Credit: Subramaniam Lab, National Cancer Institute, NIH

Walk into a dark room, and it takes a minute to make out the objects, from the wallet on the table to the sleeping dog on the floor. But after a few seconds, our eyes are able to adjust and see in the near-dark, thanks to a protein called rhodopsin found at the surface of certain specialized cells in the retina, the thin, vision-initiating tissue that lines the back of the eye.

This illustration shows light-activating rhodopsin (orange). The light photons cause the activated form of rhodopsin to bind to its protein partner, transducin, made up of three subunits (green, yellow, and purple). The binding amplifies the visual signal, which then streams onward through the optic nerve for further processing in the brain—and the ability to avoid tripping over the dog.


Watching Cancer Cells Play Ball

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Credit: Ning Wang, University of Illinois at Urbana-Champaign

As tumor cells divide and grow, they push, pull, and squeeze one another. While scientists have suspected those mechanical stresses may play important roles in cancer, it’s been tough to figure out how. That’s in large part because there hadn’t been a good way to measure those forces within a tissue. Now, there is.

As described in Nature Communications, an NIH-funded research team has developed a technique for measuring those subtle mechanical forces in cancer and also during development [1]. Their ingenious approach is called the elastic round microgel (ERMG) method. It relies on round elastic microspheres—similar to miniature basketballs, only filled with fluorescent nanoparticles in place of air. In the time-lapse video above, you see growing and dividing melanoma cancer cells as they squeeze and spin one of those cell-sized “balls” over the course of 24 hours.


An Architectural Guide to the Nuclear Pore Complex

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Credit: The Rockefeller University, New York

Sixty years ago, folk singer Pete Seeger recorded a song about helping those in need. The song starts like this: “Oh, had I a golden thread/And a needle so fine/I’d weave a magic strand/Of rainbow design.” In this brief animation, it seems like a golden thread and a needle are fast at work. But this rainbow design helps to answer a longstanding need for cell biologists: a comprehensive model of the thousands of pores embedded in the double-membrane barrier, or nuclear envelope, that divides the nucleus and its DNA from the rest of the cell.

These channels, called nuclear pore complexes (NPCs), are essential for life, tightly controlling which large macromolecules get in or out of the nucleus. Such activities include allowing vital proteins to enter the nucleus, blocking out harmful viruses, and shuttling messenger RNAs from the nucleus to the cytoplasm, where they are translated into proteins.

This computer simulation starts with an overhead view of the fully formed NPC structure. From this angle, the pore membrane (gray) appears to be at the base and is embroidered in four rings that are the channel’s main architectural support beams. There’s the cytoplasmic outer ring (yellow), the inner rings (purple, blue), the membrane ring (brown), and the nucleoplasmic outer ring (yellow). Each color represents different protein complexes, not rings per se, and the hole in the middle is the central channel through which molecules are transported. Filling the hole is a selective gating mechanism made of disordered protein (anchored to green) that helps to get the right molecules in and out.


Teaching Computers to “See” the Invisible in Living Cells

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Brain Cell Analysis

Caption: While analyzing brain cells, a computer program “thinks” about which cellular structure to identify.
Credit: Steven Finkbeiner, University of California, San Francisco and the Gladstone Institutes

For centuries, scientists have trained themselves to look through microscopes and carefully study their structural and molecular features. But those long hours bent over a microscope poring over microscopic images could be less necessary in the years ahead. The job of analyzing cellular features could one day belong to specially trained computers.

In a new study published in the journal Cell, researchers trained computers by feeding them paired sets of fluorescently labeled and unlabeled images of brain tissue millions of times in a row [1]. This allowed the computers to discern patterns in the images, form rules, and apply them to viewing future images. Using this so-called deep learning approach, the researchers demonstrated that the computers not only learned to recognize individual cells, they also developed an almost superhuman ability to identify the cell type and whether a cell was alive or dead. Even more remarkable, the trained computers made all those calls without any need for harsh chemical labels, including fluorescent dyes or stains, which researchers normally require to study cells. In other words, the computers learned to “see” the invisible!


Unraveling the Biocircuitry of Obesity

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Mouse neurons

Caption: Mouse neurons (purple), with their nuclei (blue) and primary cilia (green).
Credit: Yi Wang, Vaisse Lab, UCSF

Obesity involves the complex interplay of diet, lifestyle, genetics, and even the bacteria living in the gut. But there are other less-appreciated factors that are likely involved, and a new NIH-supported study suggests one that you probably never would have imagined: antenna-like sensory projections on brain cells.

The study in mice, published in the journal Nature Genetics [1], suggests these neuronal projections, called primary cilia, are a key part of a known “hunger circuit,” which receives signals from other parts of the body to control appetite. The researchers add important evidence in mouse studies showing that changes in the primary cilia can produce a short circuit, impairing the brain’s ability to regulate appetite and leading to overeating and obesity.


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