Fig. 7

Prdm13 negatively regulates Ptf1a in a feedback loop. a RT-qPCR analysis of prdm13 and ptf1a expression in animal cap explants isolated from embryos injected with ptf1a-GR, mprdm13, lacZ mRNA and morpholinos as indicated, and collected when sibling embryos reach stage 26. Expression levels in non-injected caps have been set to 1. Shown are representative results of one out of two independent experiments. Data are presented as means of technical triplicates ± SD. b RT-qPCR analysis of ptf1a, prdm13 and neurog2 expression in stage 39/40 dissected eyes from control-MO or prdm13-MO injected embryos. Expression level in control caps has been set to 1. The graph represents a pool of 3 to 4 experiments. Data are presented as mean ± SEM. p < 0.05 (*) (Mann-Whitney test). c Drawing illustrating the interactions between ptf1a and prdm13 suggested by our results. As in the neural tube [22], we found that Ptf1a positively regulates prdm13 expression. It has previously been shown that Ptf1a binds, along with an E protein and Rbpj (PTF1-J complex), to a conserved 2.3 kb sequence located 13.4 kb 5′ to the ptf1a coding region and regulates its own transcription [53]. We showed here that Prdm13 negatively regulates its own expression through a negative retro-control of ptf1a expression. The underlying mechanism remains to be investigated. Our results also do not exclude the possibility that Prdm13 could in addition directly repress its own expression