PSEN2 gene

The official name of PSEN2 gene is presenilin 2 (Alzheimer disease 4),The PSEN2 gene provides instructions for making a protein called presenilin 2. Presenilin 2 helps process certain proteins that are important for transmitting biochemical signals from the cell membrane into the nucleus of the cell. In the nucleus, these signals turn on (activate) particular genes that are important for cell growth and maturation. Presenilin 2 is also involved in processing amyloid precursor protein, which is found in the brain and other tissues. Research suggests that presenilin 2 works as part of an enzyme complex that cuts amyloid precursor protein into smaller segments (peptides). One of these peptides is called soluble amyloid precursor protein (sAPP) and another is called amyloid beta peptide. Recent evidence suggests that sAPP has growth-promoting properties and may play a role in the formation of nerve cells in both embryonic and adult brain tissue. Other functions of sAPP and amyloid beta peptide are under investigation.

Location:
PSEN gene is present in human chromosome 1 and ts coded from region 225124896 to 225150427, the cytogenetic location 1q31-q42

Disorder:
Mutations in this gene causes Alzheimer's disease 4

Alzheimer's disease (AD) patients with an inherited form of the disease carry mutations in the presenilin proteins (PSEN1 or PSEN2) or the amyloid precursor protein (APP).Researcher have found approxiametly 11 mutaions in PSEN gene have been shown to cause type 4 Alzheimer disease.Two of the most common PSEN2 mutations that cause type 4 Alzheimer disease change one of the building blocks (amino acids) used to make presenilin 2. One mutation replaces the amino acid asparagine with the amino acid isoleucine at position 141 (written as Asn141Ile or N141I). The other mutation changes the amino acid methionine to the amino acid valine at position 239 (written as Met239Val or M239V). These mutations appear to affect the processing of amyloid precursor protein.These disease-linked mutations result in increased production of the longer form of amyloid-beta (main component of amyloid deposits found in AD brains). Presenilins are postulated to regulate APP processing through their effects on gamma-secretase, an enzyme that cleaves APP. Also, it is thought that the presenilins are involved in the cleavage of the Notch receptor such that, they either directly regulate gamma-secretase activity, or themselves act are protease enzymes. Two alternatively spliced transcript variants encoding different isoforms of PSEN2 have been identified.