Fig. 7From: Sox5 is involved in germ-cell regulation and sex determination in medaka following co-option of nested transposable elementsRegulation of PGC numbers by Sox5. a,b As early as stage 22, a drastic reduction of the germ-cell number (vasa in situ hybridization) is observed in sox5-/- mutants compared to wild-type embryos. c For conditional knock-in and rescue of the sox5-/- mutant fish, a transgenic line expressing sox5 was produced. See āMethodsā for details. d,e In vivo visualization of the effective recombination and expression of sox5 is apparent after a switch from red cytoplasmic to green nuclear-localized fluorescence. After Cre recombinase injection at the one-cell stage, an almost total recombination is observed, leading to the expression of the sox5 transcript as monitored by green fluorescence. Stars indicate auto-fluorescent pigment cells and arrows indicate recombined germ cells. f Germ-cell numbers in sox5 mutant medaka after in vivo recombination and expression of sox5. Of note, for that specific experiment, embryos were additionally injected with a GFP-Nanos 3ā² untranslated region (UTR) mRNA construct allowing effective PGC monitoring. Statistical significance was assessed with the WilcoxonāMannāWhitney test (Nā=ā30, 28, and 42 for Sox5-/-, Sox5-/- recombined, and wild-type embryos, respectively; * p valueāā¤ā0.05, ** p valueāā¤ā0.01). GFP green fluorescent protein, ns non-significant, PGC primordial germ cellBack to article page