Egg activation in mammals is triggered by oscillations in egg intracellular calcium (Ca²⁺) level. Ca²⁺ oscillation patterns can be modified in vitro by changing the ionic composition of culture media or in vivo by conditions affecting mitochondrial function, such as obesity and inflammation. In mice, disruption of Ca²⁺ oscillations in vitro impacts embryo development and offspring growth. Here we tested the hypothesis that, even without in vitro manipulation, abnormal Ca²⁺ signaling following fertilization impacts offspring growth. Plasma membrane Ca²⁺ ATPases (PMCA) extrude cytosolic Ca²⁺ to restore Ca²⁺ homeostasis. To disrupt Ca²⁺ signaling in vivo, we conditionally deleted PMCA1 (cKO) in oocytes. As anticipated, in vitro fertilized cKO eggs had increased Ca²⁺ exposure relative to controls. To assess the impact on offspring growth, cKO females were mated to wild type males to generate pups that had high Ca²⁺ exposure at fertilization. Because these offspring would be heterozygous, we also tested the impact of global PMCA1 heterozygosity on offspring growth. Control heterozygous pups that had normal Ca²⁺ at fertilization were generated by mating wild type females to heterozygous males; these control offspring weighed significantly less than their wild type siblings. However, heterozygous offspring from cKO eggs (and high Ca²⁺ exposure) were larger than heterozygous controls at 12 week-of-age and males had altered body composition. Our results show that global PMCA1 haploinsufficiency impacts growth and support that abnormal Ca²⁺ signaling after fertilization in vivo has a long-term impact on offspring weight. These findings are relevant for environmental and medical conditions affecting Ca²⁺ handling and for design of culture conditions and procedures for domestic animal and human assisted reproduction.

Summary Sentence

Plasma membrane calcium ATPase 1 (PMCA1) in eggs regulates calcium homeostasis at fertilization, and offspring derived from PMCA1-null eggs (and excess calcium signal at fertilization) weigh more than controls with normal calcium.

Graphical Abstract