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. 2021 Jun 23;17(6):e1009613. doi: 10.1371/journal.pgen.1009613

Fig 3. Compatibility of the unique Rh4 motifs with the proximal core motifs of Rh3 and Rh5.

Fig 3

(A) Schematic comparison of the wild type (wt) Rh4 promoter and hybrids of the distal Rh4 promoter combined with the proximal core promoters of Rh1, Rh3, or Rh5. Note that the RCSI motifs of Rh1 and Rh4 are identical and that Rh3 and Rh4 share a proximal S-box motif for R8 repression. The dotted vertical line indicates the break/fusion point of the hybrids immediately upstream of the respective RCSI motif that is found in a similar position in all Rhs. (B)—(E) Wild type Rh4 vs. hybrid promoters driving GFP reporter expression (green) in the R7 layer. Rh3 (blue) labels pR7s and Rh4 (red) labels yR7s. Bar graphs show GFP co-expression in the Rh3 or Rh4 subset, respectively. (B’)—(E’) Wild type Rh4 vs. hybrid promoters driving GFP reporter expression (green) in the R8 layer. Rh5 (blue) labels pR8s and Rh6 (red) labels yR8s. Bar graphs show GFP co-expression in the Rh5, Rh6, or R1-R6 subset. Green numbers indicate the mean percentage of GFP co-expressing photoreceptors, error bar represents standard error of the mean. (B) and (B’) The wild type Rh4 promoter drives subtype-specific GFP expression in the yR7/Rh4 subset. Green staining in (B’) is from the axons of yR7s that traverse the R8 layer. N = 9 retinas and n = 949 R7s for (B); N = 9 retinas, n = 869 R8s and 5,214 R1-R6 PRs for (B’). (C) and (C’) The Rh4-Rh3 hybrid drives subtype-specific GFP reporter expression in yR7s. Green staining in (C’) is from the axons of yR7s that traverse the R8 layer. N = 11 retinas and n = 1,327 R7s for (C); N = 12 retinas, n = 1,192 R8s and 7,152 R1-R6 PRs for (C’). (D) and (D’) The Rh4-Rh5 hybrid drives subtype-specific GFP expression in yR7s. Green staining in (D’) is from the axons of yR7s that traverse the R8 layer. N = 12 retinas and n = 1,793 R7s for (D); N = 10 retinas, n = 730 R8s and 4,380 R1-R6 PRs for (D’). (E) and (E’) The Rh4-Rh1 hybrid drives broad GFP expression in both R7 and R8 photoreceptor subtypes as well as R1-R6. N = 12 retinas and n = 1,024 R7s for (E); N = 10 retinas, n = 589 R8s and 3,534 R1-R6 PRs for (E’). Scale bars, 10 μm.