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Thyrotropin-releasing hormone gene expression in normal thyroid parafollicular cells
P J Gkonos1, M A Tavianini, C C Liu
1Geriatric Research, Education, and Clinical Center, American Lake Veterans Administration Medical Center, Tacoma, Washington 98493.
Molecular Endocrinology (Baltimore, Md.)
|December 1, 1989
Summary
Researchers found that the thyrotropin-releasing hormone (TRH) gene is expressed in normal rat thyroid parafollicular cells. This discovery confirms the CA77 cell line as a model for TRH-producing tissues and suggests a local thyroid regulatory role for TRH.
Area of Science:
- Endocrinology
- Molecular Biology
- Neuroendocrinology
Background:
- The rat TRH gene produces preproTRH, a precursor with multiple TRH copies and other peptides.
- TRH gene expression is known in the central nervous system, especially the hypothalamus.
- Thyroid tissue shows TRH immunoreactivity, but its origin (TRH gene vs. other genes) is unclear.
Purpose of the Study:
- To investigate TRH gene expression in normal rat thyroid parafollicular cells.
- To determine if the CA77 neoplastic parafollicular cell line accurately models normal TRH-producing thyroid tissue.
Main Methods:
- Northern analysis of total thyroid RNA using a preproTRH-specific probe.
- Gel filtration and reversed-phase HPLC analysis of thyroid extracts.
- Immunostaining to localize preproTRH53-74 within thyroid parafollicular cells.
Main Results:
- A single hybridizing band of TRH mRNA was detected in thyroid RNA, similar to hypothalamus and CA77 cells.
- Thyroid extracts contained immunoreactive preproTRH53-74 and preproTRH115-151, consistent with TRH gene products.
- PreproTRH53-74 was localized to normal thyroid parafollicular cells.
Conclusions:
- Authentic TRH gene expression occurs in normal rat thyroid parafollicular cells.
- The CA77 cell line serves as a valid model for normal TRH-producing thyroid tissue.
- TRH gene products may have a paracrine regulatory function within the thyroid gland.