Early lysosome defects precede neurodegeneration with Aβ and tau aggregation

Loss‐of‐function mutations in the X‐linked endosomal Na+/H+ Exchanger 6 (NHE6) cause Christianson syndrome (CS) in males. CS involves endosome dysfunction leading to early cerebellar degeneration, as well as later‐onset cortical and subcortical neurodegeneration, potentially including tau deposition as reported in postmortem studies. In addition, there is reported evidence of modulation of amyloid beta (Aβ) levels in experimental models wherein NHE6 expression was targeted. For in vivo studies, rat models may have an advantage over mouse models for the study of neurodegeneration, as rat brain can demonstrate robust deposition of endogenously‐expressed Aβ and tau in certain pathological states. Mouse models generally do not show the accumulation of insoluble, endogenously‐expressed (non‐transgenic) tau or Aβ.