This gene encodes a member of the aquaporin family of intrinsic membrane proteins that function as water-selective channels in the plasma membranes of many cells. This protein is the predominant aquaporin found in brain and has an important role in brain water homeostasis. Alternatively spliced transcript variants encoding different isoforms have been described for this gene. Additional isoforms, resulting from the use of alternative in-frame translation initiation codons, have also been described. Recent studies provided evidence for translational readthrough in this gene, and expression of C-terminally extended isoforms via the use of an alternative in-frame translation termination codon. [provided by RefSeq, Jun 2018]
Forensic Context
A study in human forensic autopsy cases demonstrated that the AQP4 showed higher mRNA expression in prolonged deaths due to severe burns when normalized using three validated reference genes (PES1, POLR2A, IPO8), and higher expression in acute fire deaths when normalized with the unstable reference gene B2M alone [Wang et al. DOI:10.1007/S00414-013-0868-X]. A study in mice and human forensic autopsy cases demonstrated that intrapulmonary expression of the AQP4 was not significantly different between freshwater drowning, saltwater drowning, postmortem immersion, and control groups, indicating it is not a suitable differential marker for drowning diagnosis [Hayashi et al. DOI:10.1007/S00414-008-0235-5]. In a separate experimental study in Wistar rats, myocardial mRNA expression of the AQP4 was found to be upregulated at 12 hours post-scald injury, as detected by gene microarray analysis [Li et al. DOI:10.3906/sag-1401-149].