Microarray analysis of up-regulated genes accompanying filial imprinting in domestic chicks (Gallus gallus domesticus)

Newly-hatched domestic chick serves as an important model for studies of neural and behavioral plasticity, particularly with respect to learning and memory such as filial imprinting. Imprinting is assumed to be a unique case of recognition learning with some characteristic features, such as sensitive period and irreversibility. However, the molecules involved in the memory process are yet to be fully identified. To address this issue, we attempted to identify the genes differentially expressed at an earlier phase of filial imprinting than described in our previous report (Brain Res. Bull.76, 275-281 (2008)). One-day-old chicks were trained for imprinting for 1 h and whole brains were collected and used for cDNA microarray analysis and quantitative RT-PCR. We identified 18 genes upregulated accompanying filial imprinting. These results suggested that the increase of these 18 genes associated with filial imprinting might play an important role in the acquisition of memory in the filial imprinting. Total RNA was extracted from whole brains of trained chicks (n=16) and control dark-reared chicks (n=16). Using these total RNAs, we performed RT-PCR to distinguish male chicks from females. Then total RNAs were separated and mixed in four groups (1, male trained (n=8); 2, female trained (n=8); 3, male dark-reared (n=8); and 4, female dark-reared chicks (n=8)), and we performed cDNA microarray expression analysis to identify the upregulated genes following imprinting (1 versus 3 and 2 versus 4).

刚孵化的家鸡是研究神经与行为可塑性的重要模型，尤其适用于探究亲子印记（filial imprinting）这类学习记忆相关机制的研究。亲子印记被认为是识别学习的独特范式，具备敏感期、不可逆性等典型特征。然而，参与该记忆过程的分子尚未得到完全鉴定。为解决这一问题，我们尝试鉴定出相较于本团队此前发表于《Brain Res. Bull.》76卷275-281页（2008年）的研究，在亲子印记更早阶段出现差异表达的基因。本研究对1日龄雏鸡开展1小时的印记训练，随后采集全脑组织，用于cDNA微阵列（cDNA microarray）分析与定量逆转录聚合酶链反应（quantitative RT-PCR）。本研究共鉴定出18个在亲子印记过程中上调表达的基因。上述结果提示，这18个与亲子印记相关的基因表达上调，可能在亲子印记的记忆获取过程中发挥关键作用。我们从16只经训练的雏鸡与16只黑暗饲养对照雏鸡的全脑组织中提取总RNA。利用提取得到的总RNA，我们通过逆转录聚合酶链反应（RT-PCR）对雏鸡进行性别鉴定。随后将总RNA按组混合，共分为四组：1组为经训练的雄性雏鸡（n=8）；2组为经训练的雌性雏鸡（n=8）；3组为黑暗饲养的雄性雏鸡（n=8）；4组为黑暗饲养的雌性雏鸡（n=8）。我们针对上述四组样本开展cDNA微阵列表达分析，通过比较1组与3组、2组与4组的基因表达差异，以鉴定印记过程中上调的基因。