Bagci Enise, Heijlen Marjolein, Vergauwen Lucia, Hagenaars An, Houbrechts Anne M, Esguerra Camila V, Blust Ronny, Darras Veerle M, Knapen Dries
Systemic Physiological and Ecotoxicological Research (SPHERE), Department of Biology, University of Antwerp, B-2020 Antwerpen, Belgium; Zebrafishlab, Veterinary Physiology and Biochemistry, Department of Veterinary Sciences, University of Antwerp, B-2160 Wilrijk, Belgium.
Laboratory of Comparative Endocrinology, Animal Physiology and Neurobiology Section, Department of Biology, KU Leuven, B-3000 Leuven, Belgium.
PLoS One. 2015 Apr 9;10(4):e0123285. doi: 10.1371/journal.pone.0123285. eCollection 2015.
Thyroid hormone (TH) balance is essential for vertebrate development. Deiodinase type 1 (D1) and type 2 (D2) increase and deiodinase type 3 (D3) decreases local intracellular levels of T3, the most important active TH. The role of deiodinase-mediated TH effects in early vertebrate development is only partially understood. Therefore, we investigated the role of deiodinases during early development of zebrafish until 96 hours post fertilization at the level of the transcriptome (microarray), biochemistry, morphology and physiology using morpholino (MO) knockdown. Knockdown of D1+D2 (D1D2MO) and knockdown of D3 (D3MO) both resulted in transcriptional regulation of energy metabolism and (muscle) development in abdomen and tail, together with reduced growth, impaired swim bladder inflation, reduced protein content and reduced motility. The reduced growth and impaired swim bladder inflation in D1D2MO could be due to lower levels of T3 which is known to drive growth and development. The pronounced upregulation of a large number of transcripts coding for key proteins in ATP-producing pathways in D1D2MO could reflect a compensatory response to a decreased metabolic rate, also typically linked to hypothyroidism. Compared to D1D2MO, the effects were more pronounced or more frequent in D3MO, in which hyperthyroidism is expected. More specifically, increased heart rate, delayed hatching and increased carbohydrate content were observed only in D3MO. An increase of the metabolic rate, a decrease of the metabolic efficiency and a stimulation of gluconeogenesis using amino acids as substrates may have been involved in the observed reduced protein content, growth and motility in D3MO larvae. Furthermore, expression of transcripts involved in purine metabolism coupled to vision was decreased in both knockdown conditions, suggesting that both may impair vision. This study provides new insights, not only into the role of deiodinases, but also into the importance of a correct TH balance during vertebrate embryonic development.
甲状腺激素（TH）平衡对于脊椎动物的发育至关重要。1型脱碘酶（D1）和2型脱碘酶（D2）会提高，而3型脱碘酶（D3）会降低局部细胞内最重要的活性TH——T3的水平。脱碘酶介导的TH效应在脊椎动物早期发育中的作用仅得到部分理解。因此，我们利用吗啉代寡核苷酸（MO）敲低技术，在转录组（微阵列）、生物化学、形态学和生理学水平上，研究了脱碘酶在斑马鱼受精后96小时内早期发育过程中的作用。敲低D1 + D2（D1D2MO）和敲低D3（D3MO）均导致腹部和尾部能量代谢和（肌肉）发育的转录调控，同时伴有生长减缓、鳔充气受损、蛋白质含量降低和运动能力下降。D1D2MO中生长减缓及鳔充气受损可能是由于T3水平较低，已知T3可驱动生长和发育。D1D2MO中大量编码ATP生成途径关键蛋白的转录本显著上调，可能反映了对代谢率降低的一种代偿反应，这通常也与甲状腺功能减退有关。与D1D2MO相比，D3MO中的效应更明显或更频繁，预计D3MO中会出现甲状腺功能亢进。更具体地说，仅在D3MO中观察到心率加快、孵化延迟和碳水化合物含量增加。代谢率升高、代谢效率降低以及以氨基酸为底物刺激糖异生作用，可能与D3MO幼虫中观察到的蛋白质含量、生长和运动能力降低有关。此外，在两种敲低条件下，与视觉相关的嘌呤代谢相关转录本的表达均降低，表明两者可能都会损害视力。这项研究不仅为脱碘酶的作用提供了新见解，也为脊椎动物胚胎发育过程中正确的TH平衡的重要性提供了新见解。
