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3055152 
Journal Article 
Mechanical stimulation by osmotic and hydrostatic pressure activates Drosophila oocytes in vitro in a calcium-dependent manner 
Horner, VL; Wolfner, MF 
2008 
Yes 
Developmental Biology
ISSN: 0012-1606
EISSN: 1095-564X 
316 
1 
100-109 
English 
18304524 
WOS:000254845200009 
Embryogenesis in vertebrates and marine invertebrates begins when a mature oocyte is fertilized, resulting in a rise in intracellular calcium (Ca(2+)) that activates development. Insect eggs activate without fertilization via an unknown signal imparted to the egg during ovulation or egg laying. One hypothesis for the activating signal is that deformation of eggs as they pass through a tight orifice provides a mechanical stimulus to trigger activation. Ovulation could produce two forms of mechanical stimulus: external pressure resulting from the passage of oocytes from the ovary into the narrow oviducts, and osmotic pressure caused by hydration-induced swelling of the oocyte within the oviducts. Ovulation could also trigger activation by placing the oocyte in a new environment that contains an activating substance, such as a particular ion. Here, we provide the first evidence that Drosophila oocytes require Ca(2+) for activation, and that activation can be triggered in vitro by mechanical stimuli, specifically osmotic and hydrostatic pressure. Our results suggest that activation in Drosophila is triggered by a mechanosensitive process that allows external Ca(2+) to enter the oocyte and drive the events of activation. This will allow exploitation of Drosophila genetics to dissect molecular pathways involving Ca(2+) and the activation of development. 
egg activation; calcium; mechanosensation; pressure; french press; gadolinium