Das B et al. (2006), Gene expression changes at metamorphosis induce...

XB-ART-744

Dev Biol 2006 Mar 15;2912:342-55. doi: 10.1016/j.ydbio.2005.12.032.

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Gene expression changes at metamorphosis induced by thyroid hormone in Xenopus laevis tadpoles.

Das B , Cai L , Carter MG , Piao YL , Sharov AA , Ko MS , Brown DD .

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Thyroid hormone (TH) controlled gene expression profiles have been studied in the tail, hind limb and brain tissues during TH-induced and spontaneous Xenopus laevis metamorphosis. Amplified cRNA probes mixed with a universal standard were hybridized to a set of 21,807-sense strand 60-mer oligonucleotides on each slide representing the entries in X. laevis UniGene Build 48. Most of the up-regulated genes in hind limb and brain are the same. This reflects in part the fact that the initial response to TH induction in both tissues is cell proliferation. A large number of up-regulated genes in the limb and brain programs encode common components of the cell cycle, DNA and RNA metabolism, transcription and translation. Notch is one of the few genes that is differentially expressed exclusively in the brain in the first 48 h of TH induction studied in these experiments. The TH-induced gene expression changes in the tail are different from the limb and brain programs. Distinct muscle and fibroblast programs were identified in the tail. Dying muscle fibers in tail (marked by active caspase-3) up-regulate a group of genes that include proteolytic enzymes. At the climax of metamorphosis, tail muscle down-regulates more than half of the genes that encode the glycolytic enzymes in the cytoplasm and the tricarboxylic acid pathway and all five complexes of the electron transport system in mitochondria. These changes in gene expression precede the activation of caspase-3. Some of these same energy metabolism-related genes are up-regulated in the limb and brain programs by TH. A prominent feature of the tail fibroblasts is the down-regulation of several collagen and other extra cellular matrix genes and the up-regulation of hydrolytic enzymes that are responsible for dissolving the notochord and resorbing the tail.

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Species referenced: Xenopus laevis
Genes referenced: aldoc atp5f1a casp3.2 col9a1 dan4l dpepe eno3 hyal2 mcm7 mmut notch1 trhd ucp1 ucp2

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GSE3404: NCBI
GSE3405: NCBI

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	Fig. 2. In situ hybridization of tail cross sections with a collagen (BG553552) and a hyaluronidase [hyal2] (BQ735978) probe at NF55 and NF62. The notochord is surrounded and lined with fibroblasts.
	Fig. 3. In situ hybridization of tail cross sections using probes expressed in muscle. (A) Mitochondrial uncoupling protein-2 (UCP-2, BC044682) at 3 stages of development. (B) UCP-2, aldolase C (BC054264), and a dipeptidase (BC056069) are up-regulated at NF62 in dying muscle. They have been hybridized to adjacent tail sections at NF62. The section used for the dipeptidase was immunostained for active caspase-3.
	Fig. 5. In situ hybridization of NF55 and 62 tail cross sections using probes for two down-regulated genes. ATPase (BQ383639)is a mitochondrial gene; enolase (BQ736040) is a gene from the glycolysis pathway.
	Fig. 7. In situ hybridization of frontal sections of NF54 brain (A, B) and hind limb (C, D) control (A, C) and 3 day treatment with 5 nM T3 (B, D). The probe is MCM 7 (U66710).