Gene Expression Profiling during Pregnancy in Rat Brain Tissue

Abstract

The neurophysiological changes that occur during pregnancy in the female mammal have led to the coining of the phrases “expectant brain” and “maternal brain”. Although much is known of the hormonal changes during pregnancy, alterations in neurotransmitter gene expression have not been well-studied. We examined gene expression in the ventromedial nucleus of the hypothalamus (VMH) during pregnancy based on the fact that this nucleus not only modulates the physiological changes that occur during pregnancy but is also involved in the development of maternal behavior. This study was designed to identify genes that are differentially expressed between mid- and late-pregnancy in order to determine which genes may be associated with the onset and display of maternal behavior and the development of the maternal brain. A commercially available PCR array containing 84 neurotransmitter receptor and regulator genes (RT2 Profiler PCR array) was used. Brains were harvested from rats on days 12 and 21 of gestation, frozen, and micropunched to obtain the VMH. Total RNA was extracted, cDNA prepared, and SYBR Green qPCR was performed. In the VMH, expression of five genes were reduced on day 21 of gestation compared to day 12 (Chrna6, Drd5, Gabrr2, Prokr2, and Ppyr1) whereas Chat, Chrm5, Drd4, Gabra5, Gabrg2, LOC289606, Nmu5r2, and Npy5r expression was elevated. Five genes were chosen to be validated in an additional experiment based on their known involvement in maternal behavior onset. This experiment confirmed that gene expression for both the CCK-A receptor and the GABAAR γ2 receptor increases at the end of pregnancy. In general, these results identify genes possibly involved in the establishment of the maternal brain in rats and indicate possible new genes to be investigated.

A Bioinformatics Model of Human Diseases on the Basis of Differentially Expressed Genes (of Domestic Versus Wild Animals) That Are Orthologs of Human Genes Associated with Reproductive-Potential Changes

“…Comparing the effects of changes in the expression of orthologous genes on human reproductive potential and on the divergence of the guinea pig and cavy from their nearest common ancestor (NCA) [29]. Human genes CHRNA3 and CHRNA6 correspond to cholinergic receptor nicotinic subunits α3 and α6, deficiencies of which elevate human reproductive potential owing to improvements in finding opposite sex congeners [49] and in maternal behavior [51], respectively, in agreement with expression changes of cavy orthologous genes during microevolution [29]. Conversely, CHRNA3 overexpression and CHRNA6 overexpression worsen human reproductive potential through worse effects of nicotine compounds on primordial oocytes [50] and via a higher risk of social defeats [52], in agreement with the direction of expression change of the guinea pig orthologous genes in microevolution [29] (Table 2).…”

Genetic mechanisms of parenting

“…Even cycling (non-postpartum) females, for whom avoidance is the typical response to pups, show a dopamine increase when exposed to pups that is proportional to their prior pup exposure (Afonso et al, 2008). At the genetic level, early evidence suggests that expression of dopamine receptor genes D1 (DRD1) and D2 (DRD2) is upregulated during pregnancy in the rat (Mann, 2014). Furthermore, there is upregulated expression of dopamine receptor D4 (DRD4) and dopamine transporter DAT1 mRNA in the MPOA following pup exposure, regardless of maternal parity (Akbari et al, 2013).…”

“…Severe prenatal parental stress may also exert substantial influence on the fetus, continuing after birth, and methylation may be one of the mechanisms through which prenatal parenting is transmitted to the fetus. For instance, in pregnant rats, multiple genes are up-or downregulated in the hypothalamus, including genes encoding for dopamine receptors, prolactin, and a number of cholinergic receptors (Mann, 2014). In humans, differential methylation may play a crucial role in intergenerational transmission of the Dutch Hunger Winter effects on birth weight and somatic issues (obesity, cardiovascular risks), and maybe also on patterns of parental behavior.…”

The stability of the transcriptome during the estrous cycle in four regions of the mouse brain

“…Sexually dimorphic gene expression has been shown in multiple rodent brain regions including the hypothalamus (Guerra‐Araiza, Coyoy‐Salgado, & Camacho‐Arroyo, ; Mozhui, Lu, Armstrong, & Williams, ; Nishida, Yoshioka, & St‐Amand, ; Quinnies, Bonthuis, Harris, Shetty, & Rissman, ), hippocampus (Guerra‐Araiza et al, ; Quinnies et al, ; Vied et al, ), cortex (Guerra‐Araiza et al, ; Nishida et al, ) and cerebellum (Guerra‐Araiza et al, ; Quinnies et al, ). Female‐specific gene expression has been examined in the hypothalamus (Chiu & Wise, ; Hagihara, Hirata, Osada, Hirai, & Kato, ; Nagano & Kelly, ; Shima, Yamaguchi, & Yuri, ), hippocampus (Aenlle & Foster, ; Aenlle, Kumar, Cui, Jackson, & Foster, ; Han et al, ; Pechenino & Frick, ; Sárvári et al, ), and cortex (Humphreys, Ziegler, & Nardulli, ; Sárvári et al, ,), as well as during pregnancy (Gómora‐Arrati et al, ; Mann, ; Ray et al, ; Wang, Murata, Narita, Honda, & Higuchi, ). However, gene expression changes associated with the estrous cycle have predominantly focused on one gene (Bale, Dorsa, & Johnston, ; Bauer‐Danton, Hollenberg, & Jameson, ; Guerra‐Araiza, Cerbbn, Morimoto, & Camacho‐Arroyo, ; Schirman‐Hildesheim, Bar, Ben‐Aroya, & Koch, ; Suzuki, Nishihara, & Takahashi, ) or stage of the estrous cycle (Bronikowski et al, ; Brown, Kokay, Herbison, & Grattan, ).…”