RGN and early-onset autosomal dominant Alzheimer disease: Escalated cellular Ca2+ usually results in mRNA level changes of Ca2+ binding proteins, such as regucalcin,21 VILIP‐1, Calbindin‐D28K.22 Besides, under disturbed Ca2+‐homeostasis condition, reduced expression of HPCAL1 lead to enhanced oxidative stress, and increased the apoptosis in neuron, which will result in Alzheimer's disease.22 Thus, increased expression of HPCAL1 may be protective for neuron against oxidative stress, and promotes neuron cell growth.