IP3R2 null mice display a normal acquisition of somatic and neurological development milestones

Abstract

Astrocytes are key players in the regulation of brain development and function. They sense and respond to the surrounding activity by elevating their intracellular calcium (Ca²⁺) levels. These astrocytic Ca²⁺ elevations emerge from different sources and display complex spatio-temporal properties. Ca²⁺ elevations are spatially distributed in global (soma and main processes) and/or focal regions (microdomains). The inositol 1,4,5-trisphosphate receptor type 2 knockout (IP<inf>3</inf>R2 KO) mouse model lacks global Ca²⁺ elevations in astrocytes, and it has been used by different laboratories. However, the constitutive deletion of IP<inf>3</inf>R2 during development may trigger compensating phenotypes, which could bias the results of experiments using developing or adult mice. To address this issue, we performed a detailed neurodevelopmental evaluation of male and female IP<inf>3</inf>R2 KO mice, during the first 21 days of life, as well as an evaluation of motor function, strength and neurological reflexes in adult mice. Our results show that male and female IP<inf>3</inf>R2 KO mice display a normal acquisition of developmental milestones, as compared with wild-type (WT) mice. We also show that IP<inf>3</inf>R2 KO mice display normal motor coordination, strength and neurological reflexes in adulthood. To exclude a potential compensatory overexpression of other IP<inf>3</inf>Rs, we quantified the relative mRNA levels of all 3 subtypes, in brain tissue. We found that, along with the complete deletion of Itpr2, there is no compensatory expression of Itpr1 or Itrp3. Overall, our results show that the IP<inf>3</inf>R2 KO mouse is a reliable model to study the functional impact of global IP<inf>3</inf>R2-dependent astrocytic Ca²⁺ elevations.