RNA methyltransferases such as METTL3, METTL14, WTAP, and VIR can catalyze the methylation of the N6 position of adenylate (M6A) and are opposed by demethylases which include FTO and ALKBH5.

The nucleosome consists of an octamer composed of four histones (H2A, H2B, H3, and H4) and a DNA entangled with 147 base pairs. The core of the histones constituting the nucleosome are roughly the same, but the free N-terminus can be subjected to various modifications.

Endoplasmic Reticulum Marker

The endoplasmic reticulum is a membrane-bound organelle that is critical to the proper sorting and folding of proteins. Improperly folded proteins are normally allowed to refold into their functional conformation, and if not possible to repair, these unfolded proteins are directed to be degraded to prevent damage to the cell. The P4HB gene encodes a protein disulfide isomerase (PDI) that catalyzes both the formation of disulfide bonds, which form between cysteine residues to stabilize protein structure, and isomerization between or within molecules of secreted proteins. To achieve the natural conformation, this process takes place in the endoplasmic reticulum, so P4HB is often used as an ER marker. Studies on the oxidative folding mechanism indicate that molecular oxygen can oxidize the ER protein Ero1, and Ero1 can oxidize PDI through a disulfide bond. After this activity, PDI catalyzes the folding of proteins to form disulfide bonds.

The extracellular signal-regulated kinases, or ERK1/2 (MAPK1/MAPK3, p44/42MAPK), are signaling molecules belonging to the mitogen-activated protein kinase family (MAPKs) that are commonly located in the cytoplasm of eukaryotic cells. In concert with various other molecules in the signaling cascade acting under different surface or intracellular receptors, ERK1/2 act as catalysts in the phosphorylation of serine/threonine and are negatively regulated by the bispecific (Thr/Tyr) MAPK phosphatase family (called DUSP or MKP) and specific inhibitors to MEK activity (such as U0126 and PD98059).

DNA methyltransferase (DNMT) is an important family of enzymes that catalyze and maintain DNA methylation, a common marker in the epigenetic silencing of target genes. The enzymes play a key role in the regulation of gene expression and genomic imprinting/development.

Astrocytes are specialized glial cells with distinct morphology that are found in the central nervous system, playing a role in brain and nerve cell development and the formation of synapses. Mature astrocytes respond to many stress signals and are responsible for many essential complex functions in the healthy brain, allowing the maintenance of proper homeostasis through ion flow, signaling, and the recycling of neurotransmitters. Astrocytes that are irregularly activated may result in various neurological disorders, including Alzheimer's disease and Huntington's disease. 

Glial fibrillary acidic protein (GFAP) is an intermediate filament protein that is mainly found in astrocytes. It is also expressed in chondrocytes, fibroblasts, myoepithelial cells, lymphocytes, and hepatic stellate cells.