Car9, also known as carbonic anhydrase IX, is an enzyme involved in acid-base balance and intercellular communication. It is highly active and has adhesion capacity, with its normal presence in basolateral membranes of gastrointestinal epithelial cells and ectopic expression in various carcinomas. The study of Car9 knockout (KO) mouse models has been valuable for understanding its functions [2].

In Car9 -/- mice, morphological analysis revealed vacuolar degenerative changes in the brain, which became visible at eight to ten months. Behavioral tests showed abnormal locomotor activity and poor memory performance. Transcriptomic analyses indicated that genes related to RNA metabolism were up-regulated, while genes involved in cellular ion homeostasis, behavior, and locomotory behavior were down-regulated [1]. In addition, Car9 -/- mice developed gastric hyperplasia of the glandular epithelium with numerous cysts, overproduction of mucus-secreting pit cells, and depletion of pepsinogen-positive chief cells [2].

In conclusion, Car9 plays crucial roles in the normal physiological functions of the brain and gastric epithelium. The Car9 KO mouse models have revealed its importance in maintaining normal brain histology and behavior, as well as in the morphogenesis and homeostasis of the glandular gastric epithelium. These findings contribute to understanding the mechanisms underlying related diseases in these specific areas.

References:

1. Pan, Pei-wen, Parkkila, Anna-Kaisa, Autio, Salla, Haapasalo, Hannu, Parkkila, Seppo. 2011. Brain phenotype of carbonic anhydrase IX-deficient mice. In Transgenic research, 21, 163-76. doi:10.1007/s11248-011-9520-z. https://pubmed.ncbi.nlm.nih.gov/21547424/

2. Gut, Marta Ortova, Parkkila, Seppo, Vernerová, Zdeòka, Horak, Ivan, Pastoreková, Silvia. . Gastric hyperplasia in mice with targeted disruption of the carbonic anhydrase gene Car9. In Gastroenterology, 123, 1889-903. doi:. https://pubmed.ncbi.nlm.nih.gov/12454846/