Examining gene expression in the maternal brain
Expectant mothers undergo vast physiological changes during pregnancy and in the months following the birth of their children. In humans, fat and total body water increase; plasma protein concentrations decrease; and blood volume, cardiac output, and blood flow to the kidneys increase. We know that these processes are controlled by the central nervous system. What we don’t have is a clear understanding of the changes in gene expression and regulation that prepare a woman’s body for pregnancy, childbirth, and early motherhood.
In the latest issue of G3, Ray et al. took a detailed look at gene expression in four different regions of the mouse brain over the course of pregnancy, through birth, and into the early postnatal period. The authors collected data from the hypothalamus (important in hormone regulation), the neocortex and hippocampus (important in learning, memory, and cognition), and the cerebellum (important in motor control but without a strong connection to maternal behaviors).
The authors used RNA-sequencing to get a snapshot of which genes are expressed or repressed in the virgin mouse brain and which genes are up- or down-regulated throughout pregnancy and as part of the early maternal stages. Different groups of genes were both induced and repressed in the different stages and brain regions. When pregnant or postnatal brains were compared to those from virgin females, only seven genes were induced in all four of the regions tested, while fourteen were repressed. Hemoglobin genes and genes required for heme synthesis are among those upregulated in all brain regions during pregnancy and postnatally, suggesting that there is a common need for more hemoglobin in pregnant or maternal mice than in virgins. The fourteen repressed genes include a set ‘early response’ genes that have been shown to be important biological sensors for diverse physiological changes. While the four brain regions shared many molecular changes, they each retained a unique molecular signature. Further, the genes that change during the stages examined were previously implicated in diverse developmental and behavioral processes, including parental behaviors and other behaviors.
These results highlight that the changes in gene expression in the brain during pregnancy and early motherhood are complex. Crucially, they provide the scientific community with detailed information on how the maternal brain changes throughout pregnancy, and they offer a jumping-off point for understanding how genetic and molecular changes influence the development of maternal behaviors and physiological states.
Constantine M.M. 2014. Physiologic and pharmacokinetic changes in pregnancy. Front Pharmacol, 5:65. doi: 10.3389/fphar.2014.00065 http://journal.frontiersin.org/article/10.3389/fphar.2014.00065/full
Ray S., Tzeng R.-Y., DiCarlo L.M., Bundy J.L., Vied C., Tyson G., Nowakowski R., Arbeitman M.N. 2015. An Examination of Dynamic Gene Expression Changes in the Mouse Brain During Pregnancy and the Postpartum Period. G3, 6(1):221-233. doi: 10.1534/g3.115.020982 http://www.g3journal.org/content/6/1/221.full