Haploinsufficiency of autism spectrum disorder candidate gene NUAK1 impairs cortical development and behavior in mice

Abstract

Recently, numerous rare de novo mutations have been identified in patients diagnosed with autism spectrum disorders (ASD). However, despite the predicted loss-of-function nature of some of these de novo mutations, the affected individuals are heterozygous carriers, which would suggest that most of these candidate genes are haploinsufficient and/or lead to expression of dominant-negative forms of the protein. Here, we tested this hypothesis with the candidate ASD gene Nuak1 that we previously identified for its role in the development of cortical connectivity. We report that Nuak1 is haploinsufficient in mice with regard to its function in cortical development. Furthermore Nuak1+/− mice show a combination of abnormal behavioral traits ranging from defective spatial memory consolidation, defects in social novelty (but not social preference) and abnormal sensorimotor gating. Overall, our results demonstrate that Nuak1 haploinsufficiency leads to defects in the development of cortical connectivity and a complex array of behavorial deficits.

The AMPK-related kinase NUAK1 controls cortical axons branching though a local modulation of mitochondrial metabolic functions

“…Furthermore L-Carnitine and VK2 can rescue axon branching in a NUAK1 null background, without affecting significantly axon length (Fig 6). We previously reported that an autism-linked truncated NUAK1 impairs axon branching without affecting axon elongation (V. Courchet et al, 2018), although mitochondrial function has not been explored for this mutant. Taken together these observations suggest that, in cortical axons, mitochondrial function is necessary and sufficient for collateral branching.…”

“…To test this hypothesis, we turned to microscopy-based strategies to directly investigate mitochondrial function. Cortical neuron cultures were performed from floxed NUAK1 embryos (NUAK1 F/F ; (V. Courchet et al, 2018)) in order to achieve sparse, single-cell NUAK1 inactivation. CRE recombinase encoding plasmids were electroporated together with plasmids encoding the fluorescent protein mVenus and the mitochondrial marker mito-BFP.…”

“…We performed a conditional inactivation of NUAK1 in the dorsal telencephalon by breeding with the Nex CRE mouse line (Goebbels et al, 2006) to induce cortex-specific post-mitotic deletion in all cortical PNs. We previously demonstrated that this conditional genomic deletion leads to a significant decrease in terminal axon branching of contralaterally-projecting layer 2/3 axons (V. Courchet et al, 2018). Upon detection of gestation (at E13.5), time pregnant mice were treated with L-Carnitine in the drinking water, while the control group received only regular water.…”

“…Noon following breeding was considered as E0.5. Floxed NUAK1 mice (Nuak1 tm1a(KOMP)Wtsi ) have been described previously (V. Courchet et al, 2018). The NexCRE mouse line (Neurod6 tm1(cre)Kan ) (Goebbels et al, 2006) were provided by Sandrine Humbert (Grenoble Institute of Neuroscience, France).…”

“…Rare de novo mutations of NUAK1 have been associated to several neurodevelopmental disorders including Autism Spectrum Disorders (ASD) (Iossifov et al, 2014;, Attention Deficit / Hyperactivity Disorders (ADHD) (Alemany et al, 2015), cognitive impairment (Johnson et al, 2016) or hydrocephaly (Vojinovic et al, 2018). In mice, NUAK1 heterozygosity affects cortical development, leading to an array of anatomical and behavioral deficits (V. Courchet et al, 2018). So far, the cellular functions of NUAK1 remain incompletely known.…”