A previous study demonstrated that autism-associated variants L236S, S438P and V176I lack function in astrocytes. In this study, the authors evaluated three previously uncharacterized autism associated NHE9 variants, P117T, D496N, and Q609K and showed that all three were similar to wild-type NHE9 in endosomal expression and function when expressed in HEK293 cells. The data are nicely illustrated and the manuscript is clearly written. However, I have reservation on the experimental design.
Major: A control for the loss-of-function is missing in the functional analysis. The author should add at least any one of three previously characterized variants in this study and test whether loss-of-function can be detected in their system. The result may also argue for the concern of the cell type specificity. At this stage, I am not convinced that the results do support the conclusions.