# Effects of TGFBR1 on Proliferation of Dermal Papilla Cells in Fine-Wool Sheep

## TL;DR

This study shows that TGFBR1 suppresses the growth of dermal papilla cells in fine-wool sheep, affecting hair follicle development and wool fiber diameter.

## Contribution

The novel contribution is identifying TGFBR1 as a negative regulator of dermal papilla cell proliferation through multiple signaling pathways in fine-wool sheep.

## Key findings

- TGFBR1 overexpression suppresses dermal papilla cell proliferation in fine-wool sheep.
- TGFBR1 modulates Wnt/β-catenin, BMP, and Notch signaling pathways to influence hair follicle development.
- Downregulation of TGFBR1 in fine-wool sheep correlates with reduced wool fiber diameter.

## Abstract

This study investigates the regulation of dermal papilla cells proliferation by TGFBR1, a differentially expressed gene identified through single-cell transcriptomic sequencing. The aim is to elucidate the molecular mechanisms through which TGFBR1 governs dermal papilla cells and the role of TGFBR1 in hair follicle development of fine-wool sheep. Single-cell transcriptomic sequencing data revealed significant downregulation of TGFBR1 in dermal papilla cells of ultra-fine-wool sheep, suggesting that this gene serves as a key negative regulator for wool fiber diameter. To validate this hypothesis, we constructed TGFBR1 overexpression plasmids and knockdown vectors for transfection into dermal papilla cells. Combined with functional assays such as EDU and CCK-8, we confirmed TGFBR1 exerts negative control over dermal papilla cell proliferation. Mechanistic studies revealed that TGFBR1 modulates the activity of multiple signaling pathways, including Wnt/β-catenin, BMP, and Notch, thereby influencing the proliferative capacity of fine-wool dermal papilla cells and hair follicle development. These findings provide valuable targets and theoretical references for developing molecular breeding strategies for fine-wool sheep.

Dermal papilla cells (DPCs) serve as the signaling hub regulating hair follicle (HF) development and cyclical growth. This study aims to investigate the biological function and molecular mechanisms of TGFBR1 (transforming growth factor β receptor 1), a differentially expressed gene identified through single-cell transcriptomic sequencing (scRNA-seq) in the DPCs from fine-wool sheep. Primary DPCs were isolated and purified using a combination of enzymatic digestion and mechanical dissociation, followed by immunofluorescence identification (α-SMA and SOX2-positive). Following successful transfection with constructed TGFBR1 overexpression plasmids and siRNA interference vectors, cell proliferation was assessed via EDU staining and CCK-8 assays. mRNA expression of key genes in Wnt/β-catenin, BMP, and Notch signaling pathways (PCNA, CCND1, CTNNB1, SFRP2, BMP2, NOTCH3, SMAD4, etc.) was validated by RT-qPCR. Single-cell transcriptomics revealed significant downregulation of TGFBR1 in DPCs from fine-wool sheep. Functional validation demonstrated that TGFBR1 overexpression markedly suppressed DPC proliferation, whereas knockdown of TGFBR1 expression promoted DPC proliferation. Molecular mechanism studies showed that TGFBR1 overexpression significantly downregulated PCNA, CCND1, CTNNB1, NOTCH3, and SMAD4 while upregulating SFRP2, BMP2, and TGFB1 expression. These findings demonstrate that TGFBR1 acts as a negative regulator of DPCs proliferation by modulating the activity of multiple signaling pathways, including Wnt/β-catenin, BMP, and Notch, thereby suppressing the proliferative capacity of DPCs. This study not only provides new theoretical support for elucidating the role of the TGF-β signaling pathway in H development but also offers theoretical reference for in-depth research on molecular breeding in ultra -fine-wool sheep and the molecular mechanisms underlying HF development.