Figure 7. Aberrant physiological responses and corticospinal synaptic inputs in the dorsal horn of Advillin^Cre; Pcdhg^fcon3/fcon3 mice due to reduced functional mechanosensory synapses.

(A) MEA recordings from lumbar spinal cord dorsal horn in mice, while the glabrous skin from right hind paw is indented with a series of forces.

(B) Quantifications of the baseline firing rates in littermate control and Advillin^Cre;Pcdhg^fcon3/fcon3 mice. n = 3 animals per genotype. Student’s unpaired t test.

(C) Summary of representative units responding to indentation of the skin with different forces. The amount of force is labeled on the top. The indentations applied are indicated by the black bars below the force labels. Average firing rates in response to the indentation are shown on the bottom row. n = 187 neurons for 5 controls and n = 207 neurons for 5 mutants.

(D and E) Quantifications of the onset (D) and offset (E) responses in littermate control and Advillin^Cre;Pcdhg^fcon3/fcon3 mice. Two-way ANOVA.

(F) Diagram for mapping the functional receptive fields of the dorsal horn neurons.

(G) Quantifications of the receptive field sizes in littermate control and Advillin^Cre;Pcdhg^fcon3/fcon3 mice.

(H) Diagram showing viral labeling of corticospinal projections in the lumbar spinal cord.

(I) IHC images showing corticospinal terminals labeled with synaptophysin-tdTomato in the dorsal column, and lamina III in control and Advillin^Cre;Pcdhg^fcon3/fcon3 mice. White dotted line outlines the shape of the dorsal column with labeling.

(J) Quantification showing the density of Tomato⁺ corticospinal terminals in lamina III is reduced in the Advillin^Cre;Pcdhg^fcon3/fcon3 mice (number of puncta per 10⁴ μm²). Each dot represents average number for an animal. Student’s unpaired t test.

(K) Quantification showing the number of excitatory synapses (Homer1⁺ puncta) surrounding corticospinal terminals in lamina III is reduced in the Advillin^Cre;Pcdhg^fcon3/fcon3 mice. Student’s unpaired t test.

(L) A schematic summarizing (1) the essential roles of Pcdhg isoform diversity in somatosensory neuron synapse formation (left), peripheral axonal branching (right), and (2) step-wise assembly of central mechanosensory circuitry.

*p < 0.05; **p < 0.01; ***p < 0.001.