Pregnancy at Advanced Maternal Age Affects Behavior and Hippocampal Gene Expression in Mouse Offspring

Abstract

There is growing evidence that advanced maternal age is a risk factor for neurological and neuropsychiatric disorders in offspring. However, it remains unclear whether the altered brain programming induced by advanced maternal age is mediated by pre- or postnatal factors. Here, a mouse model was used to investigate whether pregnancy at advanced age may provoke behavioral and brain gene expression changes in offspring. Swiss Albino mice conceived by 3-month-old males and either 15-18-month-old (n = 11) or 3-month-old control females (n = 5), were delivered by cesarean section, fostered after birth by 3-month-old dams and subjected to a battery of behavioral tests. Furthermore, genome-wide mRNA expression was analyzed in the hippocampi of 4-month-old males offspring using microarrays. Offspring conceived by old mothers exhibited increased ultrasound vocalization activity during separation from the foster mother, increased anxiety-like behaviors in adult life, and altered patterns of hippocampal gene expression, compared to controls. These effects were not reversed by the postnatal maternal care provided by the young foster mothers, suggesting that the altered brain programming is already established at birth, consistent with prenatal effects related to maternal aging.

Keywords: Brain disorders; Delayed motherhood; Maternal effects.

Figure 1.

Advanced maternal age affects isolation-induced ultrasound vocalization (USV) activity in young offspring. (a) Mean number of USVs emitted by pups conceived by old (AMA) and young (YMA) females, on postnatal day 4 (P4), P8, and P12 in response to 5 minutes of maternal separation. Pups conceived by older females tended to vocalize at higher rates compared to pups conceived by young mothers; in particular, differences became statistically significant comparing 8-day-old pups. (b) Mean percentage of high intensity calls did not reveal any significant difference among groups. No significant sex differences were observed, thus data were collapsed across sexes. AMA = advanced maternal age, n = 15; YMA = young maternal age, n = 25. *p < .05. Data are expressed as mean ± SEM.

Figure 2.

Advanced maternal age affects anxiety-related behaviors in adult offspring. Male and female mice conceived by old mothers displayed (a) fewer entries, as well as (b) decreased time spent in the center of an open field, and (c) fewer entries in the open arms of an elevated plus maze, compared to offspring conceived by young females. AMA = advanced maternal age, n = 13/sex; YMA = young maternal age, n = 20/sex. *p < .05. Data are expressed as mean ± SEM.

Figure 3.

Advanced maternal age produces gene expression changes in the offspring hippocampus. Selected genes, which showed differential mRNA expression in microarray analysis, were analyzed by real-time quantitative polymerase chain reaction (qPCR). Genes were randomly selected from the 60 most deregulated transcripts of the microarray data set and relative (to the reference gene Pgk1) mRNA expression was compared between AMA and YMA male offspring. All genes analyzed by qPCR displayed differences in gene expression according to microarray results. Each dot represents an individual animal. AMA = advanced maternal age, n = 9; YMA = young maternal age, n = 9. *p < .001. Data are expressed as mean ± SEM.