Fig. 1: Missense GRIN2A mutations can impart severe overall gain or loss of function effects on NMDARs.
From: Common synaptic phenotypes arising from diverse mutations in the human NMDA receptor subunit GluN2A
a A pie chart illustrating the proportion of different types of mutations in human GRIN2A. Missense mutations make over 40% of all GRIN2A mutations but their impact on NMDAR function can be hard to predict. b Surface representation of an NMDAR heterotetramer of GluN1 and GluN2 (pink and yellow respectively). The ligand-binding domain (LBD) of GluN2A is boxed out and magnified to illustrate the glutamate (Glu) binding site, the adjacent gating ring and the location of some functionally characterised disease-associated missense mutations (blue spheres)45,47,51,52,53,54,55,56,57,58. NTD = Amino terminal domain. c Raincloud plot showing quantification of the gain (>0) and loss (<0) of function of the mutations shown in (b) with respect to different properties measured for mutant GluN1/2A receptors expressed in HEK cells or oocytes45,47,51,52,53,54,55,56,57,58. The black dashed line at 0 corresponds to WT GluN2A. The tick dashed maroon line corresponds to the K669N mutation, which serves to illustrate that some mutations can be simultaneously gain-of-function (GOF), loss-of-function (LOF), or have no effect across different properties of the receptor. d Stem-and-leaf plot of the loadings (pattern matrix) of the first two components of a principal component analysis after oblique rotation. The loading for first factor is highest for glutamate potency (EC50, Glu−1), while the loading for the second factor is highest for peak current density (Ipeak). e Scatter plot of the scores of the 20 GRIN2A mutations for each of the factors 1 and 2 from d. The graph is annotated with the results of K-means clustering: mutants that are GOF for factor 1 (red, Type 1 GOF); mutants that are mostly LOF for factor 1 (blue, Type 1 LOF); mutants that are LOF mostly for factor 2 (purple, Type 2 LOF); and WT-like mutants (black). Filled symbols represent mutations used for experiments in this study. The graph is annotated with Kendall’s tau-b correlation coefficient accompanied by bootstrap confidence intervals and p-values (see methods). The blue-white-red gradient fill in figure panels (c) and (e) are purely qualitative to illustrate directionality of mutation effect (as LOF-WT-GOF, respectively).
