Car13, a member of the carbonic anhydrase (CA) gene family, encodes an enzyme that catalyzes the hydration of CO₂ to bicarbonate and protons. Carbonic anhydrases are involved in multiple physiological processes such as potassium homeostasis, endocochlear potential regulation in the mammalian cochlea, acid and bicarbonate secretion in the digestive system, and pH adjustment in gland secretions [1,2,3]. Genetic models like KO mouse models can be valuable in further elucidating its functions.

During mammalian inner ear development, Car13 is among the CA isozymes expressed at higher levels, with its expression pattern showing potential functional relationships with other proteins like Pendrin [1]. In the mouse digestive system, Car13 is detected in seven out of eight tissues examined and shows very high expression levels in certain tissues, suggesting its possible involvement in physiological processes beyond the typical CA catalysis [2]. In the mouse harderian gland, Car13 shows relatively high mRNA expression, contributing to the understanding of CA isozyme distribution and function in this gland [3]. In the neonatal mouse uterus, Car13 mRNA is detected in both endometrial epithelia and stroma, and treatment with a CA inhibitor affects endometrial gland development, indicating a role for Car13 in this process [4].

In conclusion, Car13 plays essential roles in various biological processes including inner ear development, function of the digestive and harderian gland systems, and endometrial gland development in the neonatal uterus. Studies, potentially including those using KO mouse models, contribute to understanding its functions in these areas, which may be relevant to related physiological and pathological conditions.

References:

1. Wu, Ling, Sagong, Borum, Choi, Jae Young, Kim, Un-Kyung, Bok, Jinwoong. 2013. A systematic survey of carbonic anhydrase mRNA expression during mammalian inner ear development. In Developmental dynamics : an official publication of the American Association of Anatomists, 242, 269-80. doi:10.1002/dvdy.23917. https://pubmed.ncbi.nlm.nih.gov/23233153/

2. Pan, Pei-wen, Rodriguez, Alejandra, Parkkila, Seppo. 2007. A systematic quantification of carbonic anhydrase transcripts in the mouse digestive system. In BMC molecular biology, 8, 22. doi:. https://pubmed.ncbi.nlm.nih.gov/17362527/

3. Pan, Pei-wen, Waheed, Abdul, Sly, William S, Parkkila, Seppo. 2010. Carbonic anhydrases in the mouse harderian gland. In Journal of molecular histology, 41, 411-7. doi:10.1007/s10735-010-9290-6. https://pubmed.ncbi.nlm.nih.gov/20820888/

4. Hu, Jianbo, Spencer, Thomas E. 2005. Carbonic anhydrase regulate endometrial gland development in the neonatal uterus. In Biology of reproduction, 73, 131-8. doi:. https://pubmed.ncbi.nlm.nih.gov/15788756/