This happy face belongs to a giant cell, formed when several immune cells (known as macrophages) team up and fuse together. Although they may look like eyes and a mouth, the dark spots are actually the cells’ nuclei – the ‘control centres’ containing their DNA. These unusual cells are created in certain illnesses where the immune system runs out of control and causes inflammation such as arthritis, which affects the joints, or the kidney disease glomerulonephritis. A molecule on the surface of macrophages, called KCNN4, directs this biological get-together in mice and humans by orchestrating a complex interacting network of cellular signals. KCNN4 has previously been implicated in other types of over-enthusiastic immune response, and drugs that block it are already being tested in clinical trials for immune system-related conditions such as inflammatory bowel disease and asthma. So maybe they could be useful for treating other illnesses too.
These dramatic photos come from California, where firefighters are currently battling an out-of-control wildfire in the Sierra Nevada mountains. By Wednesday, it had spread through 111 square miles and was threatening more than 2,000 homes.
It looks like a Day-Glo stone circle, but this picture actually shows bones of mice – ribs, tibia, femur, and scapula – that have been genetically modified to express green fluorescent protein (GFP). The lower half shows bones in which cartilage cells have been tweaked to glow green, while the upper part shows bones in which cartilage cells and bone-forming cells called osteoblasts derived from those cartilage cells are tagged green. It’s long been thought that cartilage cells die off, leaving a tissue scaffold that serves as a template on which osteoblasts lay down bone. But by using GFP to tag cartilage cells and track their offspring, researchers found that they can survive and become bone-forming cells during embryonic development or in adulthood, when bones are repaired. This discovery changes our understanding of the cast of cells that make bones, which has implications for how we view the causes of bone disorders.