EDC mixture disrupts maternal behavior and the hypothalamic control of puberty transgenerationally through epigenetic mechanisms.

Endocrine disrupting chemicals (EDCs) are a rising concern for public health due to their ubiquity as complex mixtures. Our goal was to study the effect of an EDC mixture on female sexual development during 3 generations.
Female rats (F0 generation) were orally exposed to a mixture of 13 anti-androgenic and estrogenic EDCs or corn oil for 2 weeks before gestation until weaning. The mixture was composed of plasticizers, fungicides/pesticides, UV filters, parabens and acetaminophen at doses representing human exposure. Sexual development (vaginal opening, GnRH interpulse-interval, estrous cyclicity and folliculogenesis) and maternal behavior were studied from F0 to F3 generations. At PND21, mediobasal hypothalamus of the F1 and F3 were removed for gene expression, histone modifications and DNA methylation analysis of target genes.
F2 and F3 females showed delayed vaginal opening, decreased percentage of regular estrous cycle, decreased GnRH interpulse interval and altered late stage folliculogenesis. F1 and F2 females showed decreased maternal licking behavior while spending more time resting alone. The phenotype was associated with transcriptional and epigenetic alterations of hypothalamic genes involved in reproductive competence and behavior like kisspeptin (Kiss1), oxytocin (Oxt), estrogen (Esr1), glutamate (Grin2d), dopamine signaling (Th) as well as glucocorticoid activity (Nr3c1 and Crh). We have found alterations in repressive (H3K27me3, H3K9me3) or active (H3K4me3, H3K9ac) histone marks concomitant with transcriptional activity.
Overall, gestational and lactational exposure to an environmentally relevant EDC mixture transgenerationally affects sexual development throughout epigenetic reprogramming of the hypothalamic control of puberty. Such effects could be mediated by alterations of maternal behavior.