The Calcium Sensing Receptor Regulates Proliferation, Apoptosis, Migration And Differentiation Of Neural Stem Cells

BACKGROUND: The calcium sensing receptor (CaSR), belonging to the large superfamily of guanine nucleotide regulatory (G)-protein-coupled receptors (GPCRs), expresses on tissues and organs involved in calcium (Ca²⁺) homeostasis and play a crtical role in maintaining systemic Ca²⁺ homeostasis. It also expresses in central nervous system (CNS) and regulates neural cells functions such as promoting the growth of neurites. Previously, we found that CaSR knockout mice exhibited retarded differentiation and maturation of neurons, astrocytes and oligodendrocytes in the CNS during the postnatal development in vivo.METHODS: To avoid the effect of hypercalcinemia and hyperparathyroidism in vivo and further explore the functions and mechanisms of CaSR on brain development, we cultured and investigated characterization of NSCs derived from newborn CaSR knockout mice. We detected NSCs proliferation and self-renew ability by neurosphere quantitation and BrdU incorporation assay with different concentrations of calcium. We observed NSCs apoptosis by Hoechst staining and TUNEL technology. We also examined migration ability by measuring migration distance. Moreover, we analyzed the differentiation ability of CaSR knockout and control NSCs after induction with 1% fetal bovine serum (FBS) for 6 and 10 days, respectively. Finally, we utilized western blot analysis to investigate phosphorylation level of ERK1/2 and JNK in the processes of NSCs proliferation and differentiation between the two genotype littermates.RESULTS: We found that there was no difference in NSCs proliferation and self-renew ability with 1mM [Ca²⁺]0 between CaSR knockout mice and wild-type mice. Morover, we found that CaSR promoted NSC proliferation and inhibited apoptosis in dose-dependent manners in the range of 1-3mM [Ca²⁺]0. Phosphorylation level of ERK1/2 of CaSR null NSCs is lower than wild-type controls during the proliferation course. CaSR null NSCs showed decreases in migration capability and differentiation into neurons, astrocytes and oligodendrocytes, and CaSR null differentiated neurons had the fewer and shorter neural neuritis, as compared with the wild-type controls. Moreover, in CaSR knockout group, phosphorylation levels of ERK1/2 decreased at 2 and 6 days but increased at 10 days after induction of differentiation, compared with those in the wild-type littermates. There was no difference in phosphorylation ratios of JNK at differentiation between the two genotype littermates.CONCLUSION: Together, these findings suggest that CaSR participates in proliferation, apoptosis, migration and differentiation of NSCs, and mediates proliferation and differentiation mainly through ERK1/2 signal pathway.