Fig. 1
HLA-B*27:05/hβ2m expressed in Drosophila wing genetically interacts with the activin pathway and binds specific peptidome. (A-H) Nubbin-GAL4 (nub-GAL4) was used to drive transgenes expression in the pouch of imaginal wing disc. Scale bar: 500 μm. eGFP and luciferase were used as controls and have no effect on wing formation. Adult fly wings expressing genotypes: (A) nub > enhanced Green fluorescent protein (eGFP) > luciferase (luc) (nub-GAL4/+; UAS-eGFP/UAS-luc), (B) nub > HLA-B27 > hβ2m > luc (nub-GAL4/+; UAS-HLA-B*27:05, UAS-hβ2m/UAS-luc), (C) nub > eGFP > activinβ (actβ) RNA interference (RNAi) (nub-GAL4/+; UAS-eGFP/UAS-actβRNAi), (D) nub > HLA-B27 > hβ2m > actβRNAi (nub-GAL4/+; UAS-HLA-B*27:05, UAS-hβ2m/UAS-actβRNAi), (E) nub > eGFP > baboon (babo)RNAi (nub-GAL4/+; UAS-eGFP/UAS-baboβRNAi), (F) nub > HLA-B27 > hβ2m > baboRNAi (nub-GAL4/+; UAS-HLA-B*27:05, UAS-hβ2m/UAS-baboRNAi), (G) nub > eGFP > smoxRNAi (nub-GAL4/+; UAS-eGFP/UAS-smoxβRNAi), (H) nub > HLA-B27 > hβ2m > smoxRNAi (nub-GAL4/+; UAS-HLA-B*27:05, UAS-hβ2m/UAS-smoxRNAi), (I) Drosophila wing: longitudinal veins (L I to L V), ACV Anterior CrossVein (black arrow), PCV Posterior CrossVein (green arrow), Scatter plot with bar analysis of PCV/LII length ratio, n > 80, Kruskal-Wallis followed by Dunn’s multiple comparisons test showing only a difference between the control and B*27:05/hβ2m conditions (****: p < 0.0001). Vertical error bars represent SD. (J) HLA-B*27:05 from duplicate samples of Drosophila wing imaginal discs was retained on immunoaffinity column, using w6/32 Ab. Analysis of the peptides eluted from the column, revealed 50 peptides considered as specifically bound to HLA-B27, as present in both B27 Drosophila duplicates and absent from wild-type Drosophila wing imaginal disc (left panel). The logo motif (created with GibbsCluster; right panel) shows a high proportion of peptides carrying an Arginine, R or Glutamine, Q in second position that is characteristic of HLA-B27 peptidome (28/50, 56%). A significantly lower proportion of peptides shared between wild-type imaginal discs and B27 duplicates exhibited similar characteristic (28/721, 3.8%; p < 0.0001) (figures created with BioRender)