NTRK1 and schwannoma: Using protein lysates from crushed and contralateral intact nerves of conditional knockout animals, we found that the expression of ErbB2, one of the most abundantly expressed receptor tyrosine kinases in human schwannomas [5], was up-regulated in P0-Cre;Nf2fl/fl mice and even more prominently so in P0-Cre;Nefh-Cre;Nf2fl/+ animals (Fig. 5a and Supplementary Fig. 9).