Fezf2 is important for early development of the posterior hypothalamus. (A-E′′ ′) Three-color fluorescent whole-mount in situ hybridization (FISH) of 1-dpf wild-type zebrafish embryos with probes for nkx2.1a, shh, emx2, fezf2, foxb1.2 and otpb. Maximum projections of 10 7mu;m confocal stacks are shown. (A-A′′ ′) The hypothalamic expression domains of fezf2 and foxb1.2 are within the posterior part of the nkx2.1a expression domain. (B-B′′ ′) fezf2 expression in the posterior hypothalamus and shh expression in the anterior hypothalamus do not overlap, whereas foxb1.2 is partially co-expressed with fezf2 and shh. (C-C′′ ′) emx2 is expressed in the posterior-ventral hypothalamus within the fezf2 domain, slightly overlapping with foxb1.2. (D-E′′ ′) The posterior hypothalamic otpb domain is contained within the nkx2.1a and foxb1.2 domain and is also fezf2 positive. emx2 in E is smaller than in C3, as E represents a more lateral plane than C′′. The white dashed lines delineate the hypothalamus as defined by nkx2.1a expression; solid white lines outline the different expression domains. (F-M) WISH at 1 dpf on uninjected (F,H,J,L) and 4 ng fezf2 MO-injected (G,I,K,M) embryos reveals that the emx2 expression domain in the posterior-ventral hypothalamus is severely reduced in fezf2 morphants (arrowheads in F,G), whereas the foxb1.2 expression domain is not reduced (H,I). Reduction in prethalamus is apparent in fezf2 morphants (double-headed arrows in F-I). The black dashed lines delineate the telencephalon-diencephalon border. (J-M) fezf2 morphants show an expansion in the posterior hypothalamic domains of wnt8b and fgf8 (double-headed arrows in J-M). (N,O) Summaries of co-expression of the transcription factors in wild type (N) and in fezf2 morphants (O). Lateral views are shown. Tel, telencephalon; Hyp, hypothalamus; HB, hindbrain; LOF, loss-of-function. Scale bars: 60 μm in A-E′′ 100 μm in F-M.
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