The thyroid gland regulates growth and metabolism via production of thyroid hormone in follicles composed of thyrocytes. So far, thyrocytes have been assumed to be a homogenous population. To uncover heterogeneity in the thyrocyte population and molecularly characterize the non‐thyrocyte cells surrounding the follicle, we developed a single‐cell transcriptome atlas of the region containing the zebrafish thyroid gland. The 6249‐cell atlas includes profiles of thyrocytes, blood vessels, lymphatic vessels, immune cells, and fibroblasts. Further, the thyrocytes show expression heterogeneity, including bimodal expression of the transcription factor pax2a. To validate thyrocyte heterogeneity, we generated a CRISPR/Cas9‐based pax2a knock‐in line that monitors pax2a expression in the thyrocytes. A population of pax2a‐low mature thyrocytes interspersed in individual follicles can be distinguished. We corroborate heterogeneity within the thyrocyte population using RNA sequencing of pax2a‐high and pax2a‐low thyrocytes, which demonstrates 20% differential expression in transcriptome between the two subpopulations. Our results identify and validate transcriptional differences within the presumed homogenous thyrocyte population.

中文翻译：

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单细胞转录组分析揭示斑马鱼甲状腺中的甲状腺细胞多样性

甲状腺通过在由甲状腺细胞组成的滤泡中产生甲状腺激素来调节生长和代谢。到目前为止，甲状腺细胞被认为是同质群体。为了揭示甲状腺细胞群体的异质性并从分子角度表征滤泡周围的非甲状腺细胞，我们开发了包含斑马鱼甲状腺的区域的单细胞转录组图谱。6249 细胞图谱包括甲状腺细胞、血管、淋巴管、免疫细胞和成纤维细胞的概况。此外，甲状腺细胞显示出表达异质性，包括转录因子pax2a的双峰表达。为了验证甲状腺细胞的异质性，我们生成了一个基于 CRISPR/Cas9 的pax2a敲入系，用于监测甲状腺细胞中pax2a 的表达。可以区分散布在各个滤泡中的pax2a低成熟甲状腺细胞群。我们使用pax2a高和pax2a低甲状腺细胞的 RNA 测序证实了甲状腺细胞群体内的异质性，这表明两个亚群之间的转录组表达存在 20% 的差异。我们的结果识别并验证了假定的同质甲状腺细胞群体内的转录差异。