Single-cell RNA-based phenotyping reveals a pivotal role of thyroid hormone receptor alpha for hypothalamic development

Thyroid hormone and its receptor TR alpha 1 play an important role in brain development. Several animal models have been used to investigate this function, including mice heterozygous for the TR alpha 1R384C mutation, which confers receptor-mediated hypothyroidism. These mice display abnormalities in several autonomic functions, which was partially attributed to a developmental defect in hypothalamic parvalbumin neurons. However, whether other cell types in the hypothalamus are similarly affected remains unknown. Here, we used single-nucleus RNA sequencing to obtain an unbiased view on the importance of TR alpha 1 for hypothalamic development and cellular diversity. Our data show that defective TR alpha 1 signaling has surprisingly little effect on the development of hypothalamic neuronal populations, but it heavily affects hypothalamic oligodendrocytes. Using selective reactivation of the mutant TR alpha 1 during specific developmental periods, we find that early postnatal thyroid hormone action seems to be crucial for proper hypothalamic oligodendrocyte maturation. Taken together, our findings underline the well-known importance of postnatal thyroid health for brain development and provide an unbiased roadmap for the identification of cellular targets of TR alpha 1 action in mouse hypothalamic development.

Automated summary

Thyroid hormone and its receptor TR alpha 1 have a crucial role in brain development. The mutation TR alpha 1R384C in mice causes hypothyroidism and affects autonomic functions, particularly hypothalamic parvalbumin neurons. However, its impact on other hypothalamic cell types is still unknown.