Prenatal stress decreases Bdnf expression and increases methylation of Bdnf exon IV in rats

Figures & data

Table 2. Litter composition, and body weights of dams and pups

	Control	PNS
Weight Dams (G12, before stress)	278 ± 9.1 g	279 ± 4.4 g
Weight Dams (G21, after stress)	362 ± 5.6 g	345 ± 9.5 g
Litter size at birth	11.8 ± 0.21	11.5 ± 0.90
Male/female ratio at birth	0.61 ± 0.18	0.78 ± 0.14
Average male pup weight (PND1)	7.2 ± 0.21 g	7.6 ± 0.22 g
Average male pup weight (PND21)	52.3 ± 0.25 g	53.1 ± 0.33 g

Figure 1.Bdnf mRNA expression in control and PNS rats. Bdnf expression is expressed as the normalized relative expression to the control proactive chow fed group. A: PND21 offspring, B: PND80 offspring. Control, open bars; PNS, hatched bars; AMY, amygdala; HPC, hippocampus; PFC, prefrontal cortex; *significant difference (P < 0.01).

Figure 2. DNA methylation of Bdnf exon IV promoter. The CpGs analyzed are presented relative to the transcription site (TSS) of Bdnf exon IV promoter. (A‒C) PND21 offspring, (D‒F): PND80 offspring. Control, open bars; PNS, hatched bars; *significant difference (P < 0.01); CRE, cyclic adenosine monophospate (cAMP) response element.

Figure 3. DNA methylation of Bdnf exon VI promoter. The CpGs analyzed are presented relative to the transcription site (TSS) of Bdnf exon VI promoter. (A‒C) PND21 offspring, (D‒F) PND80 offspring. Control, open bars; PNS, hatched bars; *significant difference (P < 0.01); GRE, Glucocorticoid response element.

Figure 4.Dnmt1, Dnmt3a, and Dnmt3b mRNA expression at PND21. Bdnf expression is expressed as the normalized relative expression to the control proactive chow fed group. Control, open bars; PNS, hatched bars; *significant difference (P < 0.01).

Table 1. Schematic overview of stressors applied during Gestation

	Time of Day
Day of Gestation (GD)	Morning	Noon	Afternoon
14	Restraint – 60 min	Swim – 15 min	Restraint – 60 min
15	Cold exposure – 6 h
16	Swim – 15 min	Restraint – 60 min	Swim – 15 min
17		Swim – 15 min	Lights on overnight
18	Social stress 12 h
19	Restraint – 60 min	Swim – 15 min	Restraint – 60 min
20		Cold exposure – 6 h
21	Restraint – 60 min	Swim – 15 min

GD, Gestational day

Table 3. Positions of analyzed CpGs relative to the transcription site

	Gene		Transcription Sequence
	Start	End	Start Site	End Site	CpG	Position	Relative to TSS	Pyro #
Bdnf IV	107389490	107389813	107389553	107389895	1	107389518	–35	1
					2	107389530	–23	1
					3	107389572	+19	2
					4	107389588	+35	2
					5	107389590	+37	2
					6	107389596	+43	2
					7	107389615	+62	3
					8	107389618	+65	3
					9	107389677	+124	4
Bdnf VI	107390787	107390994	107390648	107390996	1	107390838	+190	1
					2	107390841	+193	1
					3	107390843	+195	1
					4	107390875	+227	1
					5	107390890	+242	1
					6	107390913	+265	2
					7	107390921	+273	2
					8	107390925	+277	2
					9	107390942	+294	2
					10	107390957	+309	2

Start and end sites of the genes and transcription sequences are based on the UCSC Genome Browser for Rat (Mar. 2012). TSS, Transcription Start Site.