Fig 2: Summary of the patterns of co-expression between protocadherin-20 (Pcdh20) and taste cell markers in taste cells of the circumvallate papillae. The areas of the circles indicate the numbers of taste bud cells expressing Pcdh20, taste receptor type 1 member 3 (T1R3, a sweet or umami taste cell marker), gustducin (Gust, a G protein mediating mainly bitter taste transduction in mouse circumvallate papillae19) and carbonic anhydrase-4 (Car4, a sour taste cell marker) in the circumvallate papillae of mice. The overlapped area indicates the co-expression. This diagram is based on Table 1.

Fig 3: Protocadherin-20 (Pcdh20) expression in taste cells occurs later than taste receptor type 1 member 3 (T1R3) expression during the morphogenesis of taste papillae. (A) In situ hybridization analysis using tissues from infant mice revealed that Pcdh20 mRNA was first detected in the developing mouse circumvallate papillae (CV) at postnatal day 6 (P6), whereas T1R3 and gustducin (Gust) mRNAs were observed from postnatal day 4–5 (P4–5), i.e. before the expression of Pcdh20. Arrows denote Pcdh20, T1R3 and gustducin-positive cells. Dotted lines indicate the outlines of taste buds. Scale bars, 50 µm. (B) The temporal changes in the number of Gust (green), T1R3 (blue) or Pcdh20 (red) positive cells during taste papilla development. Each score is expressed as mean ± standard error of the mean per section [n = 3–10 sections obtained from 1 (P4) to 4 mice (P5–8) per postnatal day, in independent preparations].

Fig 4: Protocadherin-20 (Pcdh20) mRNA is expressed in mouse taste buds and taste ganglia but not in non-taste tongue epithelium. Reverse transcription-polymerase chain reaction (RT-PCR) amplification of the mRNAs of 14 members of the cadherin superfamily detected by GeneChip analysis, the purinergic P2x2 receptor (P2x2), the transient receptor potential channel M5 (Trpm5) and ß-actin from the geniculate ganglion (GG), nodose-petrosal ganglion complex (NPG), circumvallate papillae (CV), fungiform papillae (FP) and tongue epithelium devoid of taste cells (ET). RT+ and RT- conditions are, respectively, with and without reverse transcriptase. M (bp): 100 bp marker ladder. All experiments were performed as follows: 95 °C for 15 min (1 cycle); 94 °C for 30 s, 55 °C for 30 s and 72 °C for 36 s (35 cycles).

Fig 5: Protocadherin-20 (Pcdh20) is expressed in a subset of mouse taste bud cells but not in taste ganglion neurons. In situ hybridization analysis of Pcdh20, taste receptor type 1 member 3 (T1R3), gustducin (Gust) and the purinergic P2x2 receptor (P2x2) in circumvallate papillae (CV), fungiform papillae (FP), geniculate ganglion (GG) and nodose-petrosal ganglion complex (NPG) of B6 mice. The sense probes served as a negative control. Dotted lines indicate the outlines of taste buds. Arrow denotes Pcdh20-positive cells. Scale bars, 50 µm.