NTRK2 and ataxia telangiectasia: However, a reduction in BDNF mRNA or BDNF intensity was not shown to be restricted to the synapses on PCs in the cerebella of these mouse models; in pre-onset SCA684Q/84Q mice, BDNF intensity was shown to be reduced in the GC layer [10], and we similarly found that NTRK2 was reduced in the GCs and not PCs of AT patients [11].