Molecular and functional characterization of LIMK2-1, a hominidae-specific isoform of LIMK2 associated with intellectual disability

International audienc

Conception, synthèse et évaluation biologique d’inhibiteurs de LIM kinases

National audienc

LIM kinases as new therapeutic targets for the treatment of neurofibromatosis type 1

International audienc

Design, synthesis and biological evaluation of LIMK inhibitors

National audienc

Supplementary Material for: Inhibition of Pathogenic Mutant SOD1 Aggregation in Cultured Motor Neuronal Cells by Prevention of Its SUMOylation on Lysine 75

<br>Amyotrophic lateral sclerosis (ALS) is a fatal neurodegenerative disease characterized by the selective death of motor neurons. Mutations in the <i>SOD1 </i>gene encoding the superoxide dismutase 1 are present in 15% of familial ALS cases and in 2% of sporadic cases. These mutations are associated with the formation of SOD1-positive aggregates. The mechanisms of aggregation remain unknown, but posttranslational modifications of SOD1 may be involved. Here, we report that NSC-34 motor neuronal cells expressing mutant SOD1 contained aggregates positive for small ubiquitin modifier-1 (SUMO-1), and in parallel a reduced level of free SUMO-1. CLEM (correlative light and electron microscopy) analysis showed nonorganized cytosolic aggregates for all mutations tested (SOD1^A4V, SOD1^V31A, and SOD1^G93C). We next show that preventing the SUMOylation of mutant SOD1 by the substitution of lysine 75, the SUMOylation site of SOD1, significantly reduces the number of motor neuronal cells with aggregates. These results support the need for further research on the SUMOylation pathways, which may be a potential therapeutic target in ALS

Exercise, nutrition and immune function

We report on Dutch and Iranian families with affected individuals who present with moderate to severe intellectual disability and additional phenotypes including progressive tremor, speech impairment, and behavioral problems in certain individuals. A combination of exome sequencing and homozygosity mapping revealed homozygous mutations c.484G>A (p.Gly162Arg) and c.1898C>G (p.Pro633Arg) in SLC6A17. SLC6A17 is predominantly expressed in the brain, encodes a synaptic vesicular transporter of neutral amino acids and glutamate, and plays an important role in the regulation of glutamatergic synapses. Prediction programs and 3D modeling suggest that the identified mutations are deleterious to protein function. To directly test the functional consequences, we investigated the neuronal subcellular localization of overexpressed wild-type and mutant variants in mouse primary hippocampal neuronal cells. Wild-type protein was present in soma, axons, dendrites, and dendritic spines. p.Pro633Arg altered SLC6A17 was found in soma and proximal dendrites but did not reach spines. p.Gly162Arg altered SLC6A17 showed a normal subcellular distribution but was associated with an abnormal neuronal morphology mainly characterized by the loss of dendritic spines. In summary, our genetic findings implicate homozygous SLC6A17 mutations in autosomal-recessive intellectual disability, and their pathogenic role is strengthened by genetic evidence and in silico and in vitro functional analyses

Missense variants in DPYSL5 cause a neurodevelopmental disorder with corpus callosum agenesis and cerebellar abnormalities

International audienceThe collapsin response mediator protein (CRMP) family proteins are intracellular mediators of neurotrophic factors regulating neurite structure/spine formation and are essential for dendrite patterning and directional axonal pathfinding during brain developmental processes. Among this family, CRMP5/DPYSL5 plays a significant role in neuronal migration, axonal guidance, dendrite outgrowth, and synapse formation by interacting with microtubules. Here, we report the identification of missense mutations in DPYSL5 in nine individuals with brain malformations, including corpus callosum agenesis and/or posterior fossa abnormalities, associated with variable degrees of intellectual disability. A recurrent de novo p.Glu41Lys variant was found in eight unrelated patients, and a p.Gly47Arg variant was identified in one individual from the first family reported with Ritscher-Schinzel syndrome. Functional analyses of the two missense mutations revealed impaired dendritic outgrowth processes in young developing hippocampal primary neuronal cultures. We further demonstrated that these mutations, both located in the same loop on the surface of DPYSL5 monomers and oligomers, reduced the interaction of DPYSL5 with neuronal cytoskeleton-associated proteins MAP2 and βIII-tubulin. Our findings collectively indicate that the p.Glu41Lys and p.Gly47Arg variants impair DPYSL5 function on dendritic outgrowth regulation by preventing the formation of the ternary complex with MAP2 and βIII-tubulin, ultimately leading to abnormal brain development. This study adds DPYSL5 to the list of genes implicated in brain malformation and in neurodevelopmental disorders

Ptchd1 deficiency induces excitatory synaptic and cognitive dysfunctions in mouse

International audienceSynapse development and neuronal activity represent fundamental processes for the establishment of cognitive function. Structural organization as well as signalling pathways from receptor stimulation to gene expression regulation are mediated by synaptic activity and misregulated in neurodevelopmental disorders such as autism spectrum disorder (ASD) and intellectual disability (ID). Deleterious mutations in the PTCHD1 (Patched domain containing 1) gene have been described in male patients with X-linked ID and/or ASD. The structure of PTCHD1 protein is similar to the Patched (PTCH1) receptor; however, the cellular mechanisms and pathways associated with PTCHD1 in the developing brain are poorly determined. Here we show that PTCHD1 displays a C-terminal PDZ-binding motif that binds to the postsynaptic proteins PSD95 and SAP102. We also report that PTCHD1 is unable to rescue the canonical sonic hedgehog (SHH) pathway in cells depleted of PTCH1, suggesting that both proteins are involved in distinct cellular signalling pathways. We find that Ptchd1 deficiency in male mice (Ptchd1-/y) induces global changes in synaptic gene expression, affects the expression of the immediate-early expression genes Egr1 and Npas4 and finally impairs excitatory synaptic structure and neuronal excitatory activity in the hippocampus, leading to cognitive dysfunction, motor disabilities and hyperactivity. Thus our results support that PTCHD1 deficiency induces a neurodevelopmental disorder causing excitatory synaptic dysfunction