Dopamine is an essential neurotransmitter whose key roles include movement control, pleasure and reward, attentional and cognitive skills, and regulation of the sleep/wake cycle. Reuptake is carried out by the dopamine transporter (DAT; DAT1 SLC6A3 gene). In order to study the effects of hyper-dopaminergia syndrome, the gene was silenced in rats. DAT-KO rats show stereotypical behavior, hyperactivity, a deficit in working memory, and an altered circadian cycle. In addition to KO rats, heterozygous (DAT-HET) rats show relative hypofunction of DAT; exact phenotypic effects are still unknown and may depend on whether the sire or the dam was KO. Our goal was to elucidate the potential importance of the parental origin of the healthy or silenced allele and its impact across generations, along with the potential variations in maternal care. We thus generated specular lines to study the effects of (grand) parental roles in inheriting the wild or mutated allele. MAT-HETs are the progeny of a KO sire and a WT dam; by breeding MAT-HET males and KO females, we obtained subjects with a DAT -/- epigenotype, named QULL, to reflect additional epigenetic DAT modulation when embryos develop within a hyper-dopaminergic KO uterus. We aimed to verify if any behavioral anomaly was introduced by a QULL (instead of KO) rat acting as a direct father or indirect maternal grandfather (or both). We thus followed epigenotypes obtained after three generations and observed actual effects on impaired maternal care of the offspring (based on pedigree). In particular, offspring of MAT-HET-dam × QULL-sire breeding showed a compulsive and obsessive phenotype. Although the experimental groups were all heterozygous, the impact of having a sire of epigenotype QULL (who developed in the uterus of a KO grand-dam) has emerged clearly. Along the generations, the effects of the DAT epigenotype on the obsessive/compulsive phenotype do vary as a function of the uterine impact on either allele in one's genealogical line.
Keywords: ADHD; OCD; epigenetic effects; transgenerational inheritance.