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Fig. 4. Expression pattern of HMGN genes during Xenopus embryogenesis. (A) Northern blot analysis was performed as described in Fig. 2. In each lane total RNA of five embryos each of following stages was analyzed: 2-cell, 4-cell, 16-cell embryo, early blastula (stage 6, 5), blastula (stage 8), gastrula (stage 11), neurula (stage 19), stage 25/26 embryos. As a control for the amount of RNA loaded, ethidium bromide staining of the 18S ribosomal RNA is shown. XHMGN1 and XHMGN2 transcripts are first detectable at the blastula stage. (B) Whole-mount in situ hybridization experiments showing the localization of XHMGN1 (a–d) and XHMGN2 (e, f) transcripts in neurula (a, c, e) and tailbud (b, d, f) embryos. Bright field illumination of BB/BA cleared embryos is shown in (a, b) and top illumination of uncleared embryos in (c–f), respectively. HMGN1/N2 genes are expressed in all tissues but are particularly abundant in mesodermal and neuroectodermal regions of the embryos. Abbreviations: ncr, neural crest; s, somite; cg, cement gland; ant, anterior; post, posterior. Bar represents 0.5 mm in (a) and 1.3 mm in (b). (C) NF25/26 embryos were dissected as indicated in the cartoon into mesoderm/neural tube (3, red), brain/head (2, yellow), endoderm (4, green) and ectoderm/skin (1). RNA was isolated from dissected tissues and probed for HMGN1 or HMGN2 expression by RT-PCR. The expression of the pan-neural marker NRP-1 and the mesodermal marker XmyoD were used to show the enrichment of respective tissues in the embryonic fractions. As a control, the expression of the constitutively expressed translation elongation factor EF1-α is shown. Note the elevated expression levels of HMGN1 and HMGN2 in neural and mesodermal tissues. |