fam49ab mRNA and ndrg1b-MO display a synergistic effect on rag1 expression. (A-D) rag1 expression in 4.5-dpf embryos injected with low doses of fam49ab mRNA or ndrg1b-MO, or both of the above. (E) Plotted thymus area measurements from 3 independent experiments combined. n = 33 to 49 embryos per condition. ***P < .001; ****P < .0001, 1-way ANOVA. (F) Proposed mechanism of Fam49ab signaling: Fam49ab inhibits Ndrg1b, interrupting the positive regulation of PTEN, thereby inhibiting T-cell differentiation.