# Loss of SPRED3 Causes Primary Hypothyroidism and Alters Thyroidal Expression of Autophagy Regulators LC3, p62, and ATG5 in Mice

## TL;DR

Deleting the SPRED3 gene in mice causes thyroid problems and changes how cells clean up waste in the thyroid.

## Contribution

This study reveals SPRED3's role in thyroid function and autophagy regulation through knockout mouse experiments.

## Key findings

- SPRED3 knockout mice show primary hypothyroidism with elevated TSH and reduced T4.
- Thyroid autophagy regulators like LC3, p62, and ATG5 are dysregulated in SPRED3-deficient mice.
- SPRED3 deficiency leads to altered ERK signaling and disrupted thyroid homeostasis.

## Abstract

Sprouty-related proteins with enabled/vasodilator-stimulated phosphoprotein homology 1 (EVH1) domain (SPREDs) are negative regulators of the Ras/MAPK signaling pathway and are known to modulate developmental and endocrine processes. While the roles of SPRED1 and SPRED2 are increasingly understood, the physiological relevance of SPRED3 remains elusive. To elucidate its function, we generated SPRED3 knockout (KO) mice and performed phenotypic, molecular, and hormonal analyses. SPRED3-deficient mice exhibited growth retardation and a non-Mendelian genotype distribution. X-Gal staining revealed Spred3 promoter activity in the thyroid, adrenal gland, pituitary, cerebral cortex, and kidney. Hormonal profiling identified elevated thyroid-stimulating hormone (TSH) and reduced thyroxine (T4) levels, indicating primary hypothyroidism. Thyroidal extracellular signal-regulated kinase (ERK) signaling was mildly reduced in SPRED3 KO mice, and immunoblotting revealed altered expression of autophagy regulators, including reduced sequestosome 1 (p62), increased autophagy-related gene 5 (ATG5), as well as an elevated microtubule-associated protein 1 light chain 3 (LC3) II/I ratio and a decreased pBeclin/Beclin ratio in SPRED3 KO mice. Our findings indicate that SPRED3 is involved in thyroidal homeostasis and plays a regulatory role in autophagy processes within the thyroid gland.