Single-cell RNA sequencing of human nail unit defines RSPO4 onychofibroblasts and SPINK6 nail epithelium

Abstract

Research on human nail tissue has been limited by the restricted access to fresh specimen. Here, we studied transcriptome profiles of human nail units using polydactyly specimens. Single-cell RNAseq with 11,541 cells from 4 extra digits revealed nail-specific mesenchymal and epithelial cell populations, characterized by RSPO4 (major gene in congenital anonychia) and SPINK6, respectively. In situ RNA hybridization demonstrated the localization of RSPO4, MSX1 and WIF1 in onychofibroblasts suggesting the activation of WNT signaling. BMP-5 was also expressed in onychofibroblasts implicating the contribution of BMP signaling. SPINK6 expression distinguished the nail-specific keratinocytes from epidermal keratinocytes. RSPO4+ onychofibroblasts were distributed at close proximity with LGR6+ nail matrix, leading to WNT/β-catenin activation. In addition, we demonstrated RSPO4 was overexpressed in the fibroblasts of onychomatricoma and LGR6 was highly expressed at the basal layer of the overlying epithelial component, suggesting that onychofibroblasts may play an important role in the pathogenesis of onychomatricoma.

Integrated Analysis of Single-Cell and Spatial Transcriptomics in Keloids: Highlights on Fibrovascular Interactions in Keloid Pathogenesis

“…Preparation of single-cell suspensions Tissue biopsies were collected from the central areas of the keloid scar but not from the keloid periphery to avoid any confounding effects due to site-specific factors (Supplementary Figure S1a and b) . Singlecell suspensions were generated immediately after resection as previously described (Kim et al, 2021). Briefly, the keloid tissue was washed in PBS.…”

The presence of RSPO4‐expressing onychofibroblasts in the onychodermis

“…Previously, we discovered the presence of specialized mesenchyme and mesenchymal cells below the nail matrix and nail bed in human nail unit, and we proposed to call them onychodermis (of Dongyoun) and onychofibroblasts, respectively 4,5 . Very recently, we conducted single‐cell RNA sequencing in human nail units and confirmed the presence of onychofibroblasts within the onychodermis 6 . Onychofibroblasts showed mRNA expressions of RSPO4 and MSX1 in polydactyly as well as adult nail units; however, there was no expression in dermal fibroblasts elsewhere around the nail unit.…”

Failure of digit tip regeneration in the absence of Lmx1b suggests Lmx1b functions disparate from dorsoventral polarity

“…To get some insights into the transcriptional state of the mutant dorsal dermis, we explored in our DEGs the expression of characteristic genes such as Rspo4, Sfrp2 , and Crabp1 and all of them were found downregulated in the mutant blastema (Supplemental Fig. 4F; Han et al 2008; Storer et al 2020; Kim et al 2021). Using ISH we validated Rspo4 , an activator of the canonical Wnt signaling pathway, normally expressed along the nail dermis in the WT but that was undetectable in the mutant digit (Fig.…”

“…Interestingly, recent scRNA-seq analyses have identified a distinct transcriptional signature specific of this dermal population, different from that of the rest of mesenchyme (Storer et al 2020;Kim et al 2021). To get some insights into the transcriptional state of the mutant dorsal dermis, we explored in our DEGs the expression of characteristic genes such as Rspo4, Sfrp2,and Crabp1 and all of them were found downregulated in the mutant blastema (Supplemental Fig.…”