Choline Rescues Behavioural Deficits in a Mouse Model of Rett Syndrome by Modulating Neuronal Plasticity

Abstract

Rett syndrome (RTT) is a postnatal neurodevelopmental disorder that primarily affects girls, with 95% of RTT cases resulting from mutations in the methyl-CpG-binding protein 2 (MECP2) gene. Choline, a dietary micronutrient found in most foods, has been shown to be important for brain development and function. However, the exact effects and mechanisms are still unknown. We found that 13 mg/day (1.7 × required daily intake) of postnatal choline treatment to Mecp2-conditional knockout mice rescued not only deficits in motor coordination, but also their anxiety-like behaviour and reduced social preference. Cortical neurons in the brains of Mecp2-conditional knockout mice supplemented with choline showed enhanced neuronal morphology and increased density of dendritic spines. Modelling RTT in vitro by knocking down the expression of the MeCP2 protein with shRNA, we found that choline supplementation to MeCP2-knockdown neurons increased their soma sizes and the complexity of their dendritic arbors. Rescue of the morphological defects could lead to enhanced neurotransmission, as suggested by an observed trend of increased expression of synaptic proteins and restored miniature excitatory postsynaptic current frequency in choline-supplemented MeCP2-knockdown neurons. Through the use of specific inhibitors targeting each of the known physiological pathways of choline, synthesis of phosphatidylcholine from choline was found to be essential in bringing about the changes seen in the choline-supplemented MeCP2-knockdown neurons. Taken together, these data reveal a role of choline in modulating neuronal plasticity, possibly leading to behavioural changes, and hence, a potential for using choline to treat RTT.

The influence of choline treatment on behavioral and neurochemical autistic-like phenotype in Mthfr-deficient mice

“…The current study and those cited above found no adverse effects on control animals. Nonetheless, we do report now sex differences in the response to choline in the social tests, an aspect not tested before since solely male rodents were used in the experiments 78,83,84,86 . Given the basal female/male plasma and liver levels ratio of choline (range 1.4-2.75) and betaine (range 1.3-2.9) 61,92 , metabolites effective in supporting the C1-metabolism in a folate-independent pathway 23,24 , it is conceivable that in females, whose basic choline levels are high, choline supplementation dysregulates enzymes of this pathway or of others.…”

“…They report promising results such as improved motor function, reduced blood homocysteine levels, and elevated brain BDNF levels. Similarly, in the methyl-CpG-binding protein 2 (MECP2)-conditional KO mice modelling the genetic basis of Rett syndrome, a brain disorder with high prevalence of autistic features, choline supplementation was associated with improved object-and social-memory tasks along with enhanced complexity of dendrite arbor, spine density and synaptic activity 86 . A possible mechanism mediating choline's effect is enhancing neuroprotective signaling and reducing oxidative stress 83,84 .…”

The role of MeCP2 in learning and memory

“…Similarly, conditional deletion of Mecp2 in forebrain GABAergic inhibitory interneurons results in increased sociability in both the 3-chamber assay and the partition test (Chao et al 2010). In contrast, conditional deletion of Mecp2 in forebrain excitatory neurons of postnatal mice causes reduced sociability using a modified partition test, in addition to impaired social memory in an unrestricted behavioral assay in which mice habituated to a target mouse for 4 d and the target mouse is replaced with a novel mouse on the fifth day (Gemelli et al 2006), as well as lower social preference in the 3-chamber test (Chin et al 2018). This exemplifies the usefulness of conditional KOs in behavioral testing.…”

Neuroprotective Effects of Choline and Other Methyl Donors

“…These molecular changes correlated with a decrease in the levels of the stress hormone cortisol in the cord blood [45]. Changes in choline levels have also been associated with alteration in cognitive functions with aging [46,47], Alzheimer's disease (AD) [48,49], behavioral changes in animal model of prenatal alcohol exposure [17,[50][51][52], and with symptoms of neurodevelopmental disorders such as Rett Syndrome [26,53] and Down Syndrome [25,54,55].…”

“…Supplementation of choline and other methyl-donors such as VitB6, VitB12, folate and methionine may attenuate age-related cognitive decline with aging [21,22]. Choline has also been shown to mitigate symptoms associated with genetically-related neurodevelopmental disorders such as Down Syndrome [23][24][25] and Rett Syndrome [26] and neurodegenerative diseases such as Alzheimer's disease (AD) [27]. These various effects of choline on the functioning of the developing and aging brain often correlated with epigenetic changes such as histone marks changes or DNA methylation changes of key genes related to cognitive functions [28].…”