Figure 3. Target dependence of Aβ-LTMR central arbor morphologies.

A. Generation of a dual recombinase-dependent AP reporter mouse using the Tau (Mapt) locus (Tau^FSF-iAP) for intersectional genetic labeling of Aβ-LTMR types with specific CreER lines and AAV2/1-hSyn-FlpO virus injection to hairy or glabrous skin. Animals with sparse labeling are analyzed to relate peripheral arbor morphologies (left) to central arbor anatomies in the GN or CN (right).

B. Representative examples of reconstructed brainstem arbors of Aβ RA-LTMRs (top), Aβ field/free nerve ending-LTMRs (middle), or Aβ SAI-LTMRs (bottom) that innervate glabrous or hairy paw skin. Across genetic and functional classes, glabrous skin innervating neurons form more elaborate axonal arbors in the GN or CN than most hairy skin innervating neurons. Neurons innervating hair follicles near glabrous skin (<0.5 mm) form complex arbors similar to those formed by glabrous skin innervating neurons (right). A neuron that spanned both glabrous and hairy skin is indicated with asterisks (***).

C. Aβ-LTMRs innervating paw glabrous skin or hairy follicles adjacent to glabrous skin form arbors with more end points in the GN or CN compared to Aβ-LTMRs innervating paw hairy skin that are more than 0.5 mm from glabrous skin (p<0.01 Kruskal-Wallis one-way ANOVA, **p<0.0001 or *p<0.01, Bonferroni corrected Mann-Whitney U test), n=15 neurons from 14 mice for paw glabrous, 10 neurons from 7 mice for paw hairy, 4 neurons from 4 mice for neurons at the edge of paw/glabrous-hairy border.