Yaoita Y and Nakajima K (2018), Developmental gene expression patterns in the b...

XB-ART-55380

Genes Cells December 1, 2018; 23 (12): 998-1008.

Developmental gene expression patterns in the brain and liver of Xenopus tropicalis during metamorphosis climax.

Yaoita Y , Nakajima K .

Abstract
Thyroid hormones (THs) induce metamorphosis in amphibians, causing dynamic changes, whereas mammalian newborns undergo environmental transition from placenta to open air at birth. The similarity between amphibian metamorphosis and the mammalian perinatal periods has been repeatedly discussed. However, a corresponding developmental gene expression analysis has not yet been reported. In this study, we examined the developmental gene expression profiles in the brain and liver of Xenopus tropicalis during metamorphosis climax and compared them to the respective gene expression profiles of newborn rodents. Many upregulated genes identified in the tadpole brain during metamorphosis are also upregulated in the rodent brain during the first three postnatal weeks when the TH surge occurs. The upregulation of some genes in the brain was inhibited in thyroid hormone receptor α (TRα) knockout tadpoles but not in TRβ-knockout tadpoles, implying that brain metamorphosis is mainly mediated by TRα. The expression of some genes was also increased in the liver during metamorphosis climax. Our data suggest that the rodent brain undergoes TH-dependent remodeling during the first three postnatal weeks as observed in X. tropicalis during the larva-to-adult metamorphosis.

PubMed ID: 30294949
Article link: Genes Cells
Grant support: [+]
Genes referenced: alb arg1 ass1 atp1a2 atp1b3 cadm1 cadm2 cadm3 cdh2 cps1 dlg4 kcnj10 loc100488132 mag mbp nectin1 nectin3 nefl nefm otc scn4b slc12a5 syt2 thra thrb tubb3
GO keywords: metamorphosis

Article Images: [+] show captions

	Figure 1 Developmental expression of neural tissue‐related genes in the X. tropicalis brain. qRT‐PCR was conducted using total cellular brain RNA and gene‐specific primers (Supporting Information Table S2). The relative mRNA expression level of the indicated gene to EF‐1α mRNA is presented. Data are expressed as mean ± SD (biological replicate number = 5–7)
	Figure 2 Developmental expression of synapse‐related genes in the X. tropicalis brain. qRT‐PCR was conducted using total cellular brain RNA and gene‐specific primers (Supporting Information Table S2). The relative mRNA expression level of the indicated gene to EF‐1α mRNA is presented. Data are expressed as mean ± SD (biological replicate number = 5–7)
	Figure 3 Expression of neural tissue‐related and synapse‐related genes in the brain of NF stage 61 wild‐type and TR‐knockout tadpoles. Total cellular RNA was extracted from brains of NF stage 61 wild‐type, TRα‐knockout, and TRβ‐knockout tadpoles, and qRT‐PCR was conducted using gene‐specific primers (Supporting Information Table S2). The relative mRNA expression level of the indicated gene to EF‐1α mRNA is presented. Data are expressed as mean ± SD. Biological replicate numbers of wild‐type, TRα‐knockout, and TRβ‐knockout brain samples are five, five, and four, respectively. Statistical significance by comparison of TRα‐knockout tadpoles with wild‐type and TRβ‐knockout tadpoles were assessed using the Tukey's test. p < 0.05, *p < 0.01
	Figure 4 Developmental expression of albumin and urea cycle enzyme genes in liver of X. tropicalis. qRT‐PCR was conducted using total cellular liver RNA and gene‐specific primers (Supporting Information Table S2). The relative mRNA expression level of the indicated gene to EF‐1α mRNA is represented. Data are expressed as mean ± SD (biological replicate number = 4–6)
	Figure 5 Developmental expression of TRα and TRβ genes in the brain and liver of X. tropicalis. qRT‐PCR was conducted using total cellular brain and liver RNAs and gene‐specific primers (Supporting Information Table S2). The relative mRNA expression level of the indicated gene to EF‐1α mRNA is presented. Data are expressed as mean ± SD. The biological replicate numbers are 5–7 (a, b) and 4–6 (c, d)
	Supplementary Figure 1. Expression of neural tissue-related genes in the brains of stage-61 wild-type and TR-knockout tadpoles. Total cellular RNA was extracted from brains of NF stage-61 wild-type, TRα knockout, and TRβ knockout tadpoles, and qRT-PCR was conducted using gene-specific primers (Table S2 in Supporting Information). The relative mRNA expression level of the indicated gene to EF-1α mRNA is presented. Data are expressed as mean ± SD. Biological replicate numbers of wild-type, TRα-knockout, and TRβ-knockout brain samples are five, five, and four, respectively.
	Supplementary Figure 2. Developmental expression of albumin and urea cycle enzyme genes in liver of R. catesbeiana. qRT-PCR was conducted using total cellular liver RNA and gene-specific primers (Table S2 in Supporting Information). Tadpoles were staged according to the Nieukoop and Faber method. The relative mRNA expression level of the indicated gene to EF-1α mRNA is represented.