Final answer:
Astrocytes in the central nervous system are marked by the protein glial fibrillary acidic protein (GFAP).
Step-by-step explanation:
Astrocytes are a type of star-shaped cell in the central nervous system that perform various functions, including the regulation of ions, uptake and breakdown of neurotransmitters, and contributing to the formation of the blood-brain barrier. One protein that is used as a marker for astrocytes is glial fibrillary acidic protein (GFAP). In a micrograph, astrocytes that express GFAP are labeled in green, while neurons are not labeled with GFAP.