Abstract
To analyze the effect of gravity on the structure of germinal tissues, we examined tissues of the testes and duct deferens of mice that were exposed to space flight conditions for 21–24 days (experiment Rodent Research-4, SpaceX-10 mission, February 2017, USA). We evaluated the levels of cytoskeletal proteins, sperm-specific proteins, and epigenetic events; in particular, we evaluated levels of 5-hydroxymethylcytosine and of enzymes that regulate DNA methylation/demethylation. We did not detect changes in the levels of cytoskeletal proteins, sperm-specific proteins, DNA-methylases, DNA demethylases, DNA acetylases, or histone deacetylases. However, there were changes at the gene expression level. In particular, there was an increase in the demethylase Tet2 and a decrease in the histone deacetylase Hdac1. These gene expression changes may be of key importance during the early period of readaptation since they could lead to an increase in the expression of target genes.
Highlights
The role of gravity in the early development of mammals, during prenatal development, remains unclear despite a number of previous studies[1,2,3,4,5,6,7,8]
It is known that the exposure of female rats to zero gravity in the second half of pregnancy does not cause significant changes in embryos[3,6], which may be due to the damping of the external mechanical field by the amniotic fluid
It is known that the speed of the movement of the mouse spermatozoa decreases after a 7-day antiorthostatic hanging, which simulates the effects of weightlessness[9]; for the sperm of sea urchin in space flight (STS-81, STS-84), FP130 protein phosphorylation, which is associated with the activation of motility, occurred 3–4 times faster than in conditions of 1 g10
Summary
The role of gravity in the early development of mammals, during prenatal development, remains unclear despite a number of previous studies[1,2,3,4,5,6,7,8]. It is known that the speed of the movement of the mouse spermatozoa decreases after a 7-day antiorthostatic hanging, which simulates the effects of weightlessness[9]; for the sperm of sea urchin in space flight (STS-81, STS-84), FP130 protein phosphorylation, which is associated with the activation of motility, occurred 3–4 times faster than in conditions of 1 g10. It is known that the external mechanical field plays an important role in establishing the patterns of expression of various genes, primarily those encoding cytoskeletal proteins and the associated signaling cascades, in different cell types, including stem cells[16,17,18,19,20,21,22].
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