Isles, A. | bioRxiv Science

bioRxiv2018

Impulsive choice in mice lacking paternal expression of Grb10 provides evidence for intra-genomic conflict in behavior

Imprinted genes are expressed from one parental allele only as a consequence of epigenetic events that take place in the mammalian germ line and are thought to have evolved through intra-genomic conflict between parental alleles. We demonstrate, for the first time, oppositional effects of imprinted genes on brain and behavior. Specifically, here we show that mice lacking paternal Grb10 make fewer impulsive choices, with no dissociable effects on a separate measure of impulsive action. Taken together with previous work showing that mice lacking maternal Nesp55 make more impulsive choices this suggests that impulsive choice behavior is a substrate for the action of genomic imprinting. Moreover, the contrasting effect of these two genes suggests impulsive choices are subject to intra-genomic conflict and that maternal and paternal interests pull this behavior in opposite directions. Finally, these data may also indicate that an imbalance in expression of imprinted genes contributes to pathological conditions such as gambling and drug addiction, where impulsive behavior becomes maladaptive.

genetics↗

bioRxiv2018

Ehmt1 forebrain haploinsufficiency leads to impaired memory, sensory gating and information processing

Regulators of chromatin dynamics and transcription are increasingly implicated in the aetiology of neurodevelopmental disorders (NDDs). Haploinsufficiency of EHMT1, encoding a histone methyl-transferase, is associated with several NDDs, including Kleefstra syndrome, developmental delay and autism spectrum disorder. Using a mouse model of Ehmt1 haploinsufficiency (Ehmt1D6Cre/+), we examined a number of brain and behavioural endophenotypes of relevance to NDDs. Specifically, we show that Ehmt1D6Cre/+ mice have deficits in information processing, evidenced by abnormal sensory-motor gating, a complete absence of object recognition memory and a reduced magnitude of auditory evoked potentials in both paired-pulse inhibition and mismatch negativity (MMN). The electrophysiological experiments show that differences in magnitude response to auditory stimulus were associated with marked reductions in total and evoked beta- and gamma-band oscillatory activity, as well as significant reductions in phase synchronisation. The pattern of electrophysiological deficits in Ehmt1D6Cre/+ matches those seen in control mice following administration of the selective NMDA-R antagonist, ketamine. This, coupled with reduction of Grin1 mRNA expression in Ehmt1D6Cre/+ hippocampus, suggests that Ehmt1 haploinsufficiency may lead to disruption in NMDA-R. Taken together, these data indicate that reduced Ehmt1 dosage during forebrain development leads to abnormal circuitry formation, which in turn results in profound information processing deficits. Such information processing deficits are likely paramount to our understanding of the cognitive and neurological dysfunctions shared across the NDDs associated with EHMT1 haploinsufficiency.

neuroscience↗