Red blood cells carry oxygen. They are made continuously in the bone marrow from blood stem cells, through a series of steps called erythropoiesis.

Before birth, red blood cells make fetal hemoglobin. In the months after birth the body switches to the adult form. In sickle cell disease the adult form is faulty: it clumps together and pulls the cell out of shape. People who keep making fetal hemoglobin into adulthood have far milder disease, which makes that switch a target for treatment.

This work used CRISPR-Cas9 to recreate, in blood stem cells from patients, the same changes found in people who naturally keep making fetal hemoglobin. Cutting the site where a repressor protein binds released the fetal gene, and the red cells grown from those stem cells no longer sickled.

Macrophages are immune cells that take up residence in tissue rather than circulating. Microglia are the brain's own macrophages: they arrive early in development and stay for life.

Because they are long-lived and divide, microglia accumulate mutations over a lifetime, as other tissues do. A cell carrying a mutation that helps it grow can expand into a clone.

In brain tissue from people who died with Alzheimer's disease, microglia carried more of these mutations than microglia from people of the same age without the disease. The mutations concentrated in one signaling pathway, and cells carrying them switched on a strongly inflammatory program.

Noradrenergic neurons make norepinephrine, a chemical messenger that sets how alert the brain is and shapes attention, memory and the response to stress.

Most of the brain's norepinephrine comes from the locus coeruleus, a nucleus of only a few thousand cells in the brainstem that sends fibers across the whole brain. It is among the first regions to show damage in Alzheimer's and Parkinson's disease.

The hindbrain is the back of the brain, and it becomes the brainstem and cerebellum. Early in development it divides along its length into a row of segments called rhombomeres.

Each segment switches on its own set of genes, and that pattern decides which neurons form where. The nerves that control the face, swallowing, breathing and heart rate all trace back to particular segments.

Sickle cell disease is caused by a single change in one gene, which makes it a candidate for treatments that correct the gene itself. Stem cells are collected from the patient, changed outside the body, and returned.

Two approaches run through this work. Gene addition delivers a working, anti-sickling hemoglobin gene with a lentiviral vector. Genome editing instead cuts the patient's own DNA to lift the brake on fetal hemoglobin.

Getting enough stem cells out of a patient safely is its own problem, since the standard mobilizing drug is dangerous in sickle cell disease. A separate study tested a different drug, plerixafor, after exchange transfusion.

One patient treated with the gene-addition approach is reported in the New England Journal of Medicine.

Neurodegenerative disease is studied here from two directions: tissue from people who had the disease, and models grown from human stem cells.

In Alzheimer's disease, the work points at the brain's immune cells rather than at neurons alone, and finds inflammatory clones of microglia in patient brain tissue.

In ALS, small spinal cord tissues were grown from stem cells carrying the most common ALS mutation. A blood pressure drug, telmisartan, protected the neurons in that model by damping inflammation.