Physiological and Evolutionary Genomics Laboratory, Scottish Oceans Institute, School of Biology, University of St Andrews, St Andrews, Scotland, UK.
PLoS One. 2012;7(12):e51884. doi: 10.1371/journal.pone.0051884. Epub 2012 Dec 17.
Initially we characterised growth responses to altered nutritional input at the transcriptional and tissue levels in the fast skeletal muscle of juvenile gilthead sea bream. Fish reared at 21-22°C (range) were fed a commercial diet at 3% body mass d(-1) (non-satiation feeding, NSF) for 4 weeks, fasted for 4d (F) and then fed to satiation (SF) for 21d. 13 out of 34 genes investigated showed consistent patterns of regulation between nutritional states. Fasting was associated with a 20-fold increase in MAFbx, and a 5-fold increase in Six1 and WASp expression, which returned to NSF levels within 16h of SF. Refeeding to satiation was associated with a rapid (<24 h) 12 to 17-fold increase in UNC45, Hsp70 and Hsp90α transcripts coding for molecular chaperones associated with unfolded protein response pathways. The growth factors FGF6 and IGF1 increased 6.0 and 4.5-fold within 16 h and 24 h of refeeding respectively. The average growth in diameter of fast muscle fibres was checked with fasting and significant fibre hypertrophy was only observed after 13d and 21d SF. To investigate developmental plasticity in growth responses we used the same experimental protocol with fish reared at either 17.5-18.5°C (range) (LT) or 21-22°C (range) (HT) to metamorphosis and then transferred to 21-22°C. There were persistent effects of development temperature on muscle growth patterns with 20% more fibres of lower average diameter in LT than HT group of similar body size. Altering the nutritional input to the muscle to stimulate growth revealed cryptic changes in the expression of UNC45 and Hsp90α with higher transcript abundance in the LT than HT groups, whereas there were no differences in the expression of MAFbx and Six1. It was concluded that myogenesis and gene expression patterns during growth are not fixed, but can be modified by temperature during the early stages of the life cycle.
最初，我们在幼年金头鲷快速骨骼肌的转录和组织水平上研究了对营养输入改变的生长反应。在 21-22°C（范围）下饲养的鱼以 3%的体重喂食（非饱食喂养，NSF）4 周，禁食 4d（F），然后饱食（SF）21d。在所研究的 34 个基因中，有 13 个基因在营养状态之间表现出一致的调节模式。禁食导致 MAFbx 增加 20 倍，Six1 和 WASp 增加 5 倍，在 SF 后 16 小时内恢复到 NSF 水平。饱食后，与未折叠蛋白反应途径相关的分子伴侣 UNC45、Hsp70 和 Hsp90α 的转录物迅速（<24 小时）增加 12-17 倍。生长因子 FGF6 和 IGF1 在重新喂食后 16 小时和 24 小时内分别增加 6.0 倍和 4.5 倍。快速肌纤维的平均生长直径通过禁食检查，仅在 SF 后 13d 和 21d 观察到显著的纤维肥大。为了研究生长反应的发育可塑性，我们使用相同的实验方案，在 17.5-18.5°C（范围）（LT）或 21-22°C（范围）（HT）下饲养鱼以进行变态，然后转移到 21-22°C。发育温度对肌肉生长模式有持久的影响，LT 组比 HT 组具有更低平均直径的纤维多 20%。改变肌肉的营养输入以刺激生长，揭示了 UNC45 和 Hsp90α 表达的隐性变化，LT 组的转录物丰度高于 HT 组，而 MAFbx 和 Six1 的表达没有差异。结论是，生长过程中的成肌和基因表达模式不是固定的，而是可以在生命周期的早期阶段通过温度来改变。
