Extended Data Figure 2. DDX21 knockdown phenocopies TCS-associated perturbations in X. laevis and zebrafish.

a, Representative immunofluorescence images showing strong nucleolar localization signal for TCOF1 in HeLa cells from n = 3 biologically independent experiments. b, Immunoprecipitation of either GFP–tagged TCOF1 (GFP–TCOF1) or DDX21, followed by western blotting with the indicated antibodies. n = 2 biologically independent experiments. c, Table showing the quantification of injected Xenopus embryos with the indicated morpholinos (MO) or in vitro transcribed mRNAs. d, Efficiency of tcof1 splicing morpholino was determined by PCR. n = 10 injected embryos. e, Representative images of stage 49 Xenopus embryo cartilage stainings with alcian blue. Traces of the mandibular and hyoid streams are shown for clarity. Embryos were collected from n = 3 biologically independent experiments. f, Stage 2 embryos were injected with in vitro transcribed mRNAs encoding wild-type or catalytically defective DDX21. Total mRNA was extracted at stage 31, followed by qPCR to determine the expression levels of injected mRNAs in the anterior part of the embryo (see schematics for details). Bars represent the average of n = 3 independent experiments; error bars, s.e.m. g, Representative images of 5-day-old wild-type (WT), polr1d^−/−, and polr1c^−/− zebrafish embryo cartilage stained with alcian blue from n = 3 independent matings. h, Table showing the quantification of polr1d^−/− and polr1c^−/− crosses. i, Table showing quantification of zebrafish embryos injected with the indicated morpholino or combination of morpholino and mRNA. j, Representative images of 5-day-old zebrafish embryo cartilage stained with alcian blue after injection of ddx21 morpholino at the indicated dosages or ddx21 morpholino and in vitro transcribed human DDX21 mRNA. Traces of the ceratohyal, platoquadrate, and Meckel’s cartilage are shown for clarity. n = 3 biologically independent sets of injections.