BACKGROUND Amacrine interneurons that modulate synaptic plasticity between bipolar and ganglion cells constitute the most diverse cell type in the retina. Most are inhibitory neurons using either GABA or glycine as neurotransmitters. Although several transcription factors involved in amacrine cell fate determination have been identified, mechanisms underlying amacrine cell subtype specification remain to be further understood. The Prdm13 histone methyltransferase encoding gene is a target of the transcription factor Ptf1a, an essential regulator of inhibitory neuron cell fate in the retina. Here, we have deepened our knowledge on its interaction with Ptf1a and investigated its role in amacrine cell subtype determination in the developing Xenopus retina. METHODS We performed prdm13 gain and loss of function in Xenopus and assessed the impact on retinal cell fate determination using RT-qPCR, in situ hybridization and immunohistochemistry. RESULTS We found that prdm13 in the amphibian Xenopus is expressed in few retinal progenitors and in about 40% of mature amacrine cells, predominantly in glycinergic ones. Clonal analysis in the retina reveals that prdm13 overexpression favours amacrine cell fate determination, with a bias towards glycinergic cells. Conversely, knockdown of prdm13 specifically inhibits glycinergic amacrine cell genesis. We also showed that, as in the neural tube, prdm13 is subjected to a negative autoregulation in the retina. Our data suggest that this is likely due to its ability to repress the expression of its inducer, ptf1a. CONCLUSIONS Our results demonstrate that Prdm13, downstream of Ptf1a, acts as an important regulator of glycinergic amacrine subtype specification in the Xenopus retina. We also reveal that Prdm13 regulates ptf1a expression through a negative feedback loop.

中文翻译：

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Prdm13与Ptf1a形成反馈回路，是非洲爪蟾视网膜中甘氨酸能无长突细胞生成所必需的。

背景技术调节双极和神经节细胞之间的突触可塑性的无长素神经元构成视网膜中最多样化的细胞类型。大多数是使用GABA或甘氨酸作为神经递质的抑制性神经元。尽管已经确定了与无长素细胞命运决定有关的几种转录因子，但无长素细胞亚型规范所依据的机制仍有待进一步理解。Prdm13组蛋白甲基转移酶编码基因是转录因子Ptf1a的靶标，Ptf1a是视网膜中抑制性神经元细胞命运的重要调节剂。在这里，我们加深了其与Ptf1a相互作用的知识，并研究了其在发育中的非洲爪蟾视网膜中无长突蛋白亚型确定中的作用。方法我们在非洲爪蟾中进行了prdm13功能的获得和丧失，并使用RT-qPCR，原位杂交和免疫组织化学评估了对视网膜细胞命运测定的影响。结果我们发现两栖类非洲爪蟾中的prdm13在少数视网膜祖细胞和约40％的成熟无长突细胞中表达，主要在甘氨酸能细胞中表达。视网膜中的克隆分析显示prdm13过表达有助于确定无长突霉素的细胞命运，并偏向于甘氨酸能细胞。相反，敲低prdm13会特异性抑制甘氨酸能无长突细胞的发生。我们还显示，如同在神经管中一样，prdm13在视网膜中会受到负的自动调节。我们的数据表明，这可能是由于其抑制诱导物ptf1a表达的能力所致。结论我们的结果表明Prdm13，Ptf1a的下游，充当非洲爪蟾视网膜中的甘氨酸Amacrine亚型规格的重要调节剂。我们还揭示了Prdm13通过负反馈回路调节ptf1a表达。