3-OST-5 function is required for FGF signaling to regulate cilia length. (A,B) Motor molecule dnah9 mRNA was equivalently expressed in the DFC (white arrows) of tailbud stage in uninjected embryos (A; n=99) and 3-OST-5 MO1-injected embryos (B; n=62). (C,D) Ciliogenic transcription factor gene foxj1a expression in uninjected tailbud stage embryos (C, white arrow; n=111) was diminished or absent in 36% of 3-OST-5 MO1-injected embryos (D, red arrow; n=75). (E,F) Similarly, ciliogenic transcription factor gene rfx2 expression in uninjected 90% epiboly embryos (E, white circle; n=175) was diminished in 3-OST-5 MO1 DFCs (F, red circle; n=92). (G,H) FGF pathway response gene sef expression in DFCs of 90% epiboly uninjected embryos (G, white arrow; n=85) was diminished in 3-OST-5 MO1-injected embryos (H, red arrow; n=44). See Fig. 5 for quantification of in situ hybridization. (I) Schematic of experiments to test interactions between FGF signaling and 3-OST-5 function. Clutches of embryos from heterozygous crosses of fgf8 hypomorphic mutants were divided into two groups: uninjected or injected with sub-threshold dose of 3-OST-5 MO embryos. At 10 SS, individual embryos were fixed, assayed for KV cilia length, and then individually genotyped for fgf8/ace alleles by HRMA. (J) Average cilia length in WT, heterozygous and homozygous fgf8/ace mutants that were not injected or had been injected with a sub-threshold dose of 3-OST-5 MO1. Homozygous fgf8 mutant embryos injected with sub-threshold dose of 3-OST-5 MO1 had statistically shorter cilia length (**P<0.001) compared with all other classes of embryos. Error bars represent s.e.m. (K) Schematic summarizing 3-OST-5 modulation of FGF signaling and ciliogenic transcription factors to control cilia length.
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