Project description:PURPOSE. Limbal stem/progenitor cells (LSC) continuously proliferate and differentiate to replenish the corneal epithelium and play a vital role in corneal function and normal vision. Previous study revealed that Paired box 6 (PAX6) is a master transcription factor involved in determining the fate of corneal epithelial cells (CEC). However, the molecular events downstream of PAX6 remain largely unknown. In this study, we aimed to clarify the regulation network of PAX6 in driving CEC differentiation. METHODS. An air-liquid culture system was used to differentiate LSC into mature CEC. Specific targeting PAX6 short-hairpin shRNAs were used to knock down PAX6 in LSC. RNA-seq was used to analyze shPAX6-transfected CEC and CEC differentiation-associated genes to identify the potential downstream targets of PAX6. RNA-seq analysis, quantitative real-time PCR, and immunofluorescence staining were performed to clarify the function of WNK lysine deficient protein kinase 2 (WNK2), a downstream target of PAX6, and its relationship with corneal diseases. RESULTS. WNK2 expression increased during CEC differentiation and decreased upon PAX6 depletion. The distribution of WNK2 was specifically limited to the central corneal epithelium and suprabasal layer of the limbus. Knockdown of WNK2 impaired the expression of CEC-specific markers (KRT12, ALDH3A1, and CLU), disrupted the corneal differentiation process, and activated the terms of keratinization, inflammation, and cell proliferation, consistent with PAX6-depleted CEC and published microbial keratitis. Thus, aberrant expression of WNK2 was linked to corneal ulcers. CONCLUSIONS. As a downstream target of PAX6, WNK2 plays an essential role in corneal epithelial cell differentiation and maintenance of corneal homeostasis.
Project description:Forkhead box C1 (FOXC1) is required for neural crest and ocular development, and mutations in FOXC1 lead to inherited Axenfeld–Rieger syndrome. Here, we find that FOXC1 and paired box 6 (PAX6) are co-expressed in the human limbus and central corneal epithelium. Deficiency of FOXC1 and alternation in epithelial features occur in patients with corneal ulcers. FOXC1 governs the fate of the corneal epithelium by directly binding to lineage-specific open promoters or enhancers marked by H3K4me2. FOXC1 depletion not only activates the keratinization pathway and reprograms corneal epithelial cells into skin-like epithelial cells but also disrupts the collagen metabolic process and interferon signaling pathways. Loss of interferon regulatory factor 1 (IRF1) and PAX6 induced by FOXC1 dysfunction is linked to the corneal ulcer. Collectively, our results reveal a FOXC1-mediated regulatory network responsible for corneal epithelial homeostasis and provide a potential therapeutic target for corneal ulcer.
Project description:PAX6, a paired box transcription factor, is necessary for eye development. However, how it regulates thecell identity of human corneal epithelial cells (CECs) is not well understood. We aimed to clarify thefunction of PAX6 in human CECs using gene knockout via the clustered regularly interspaced shortpalindromic repeats (CRISPR) and CRISPR associated protein 9 (Cas9) system. We designed guide RNAsfor different targets in PAX6. PAX6-depleted CECs maintained the epithelial morphology, but becamelarger. Global analyses using microarray revealed that down-regulated genes were primarily CEC-specificand included keratin 12, keratin 3, clusterin (CLU), aldehyde dehydrogenase 3 family member A1(ALDH3A1), angiopoietin-like 7 (ANGPTL7) and transketolase (TKT), while up-regulated genes wereprimarily epidermis-related and included keratin 10, keratin 1, involucrin (IVL), filaggrin (FLG). Thesefindings suggest that PAX6 maintains CEC identity by regulating differentiation.
Project description:Purpose: We find that Wnt7a-PAX6 axis determine corneal epithelial cell fate. To obtain global evidence for successful cell fate conversion, we performed gene expression profiling by RNA-seq on CECs, SECs, and LSCs after knocking down PAX6 and on SESCs transduced with PAX6 upon 3-D differentiation. Methods: Under 3-D culture condition, limbal stem cell (LSCs) can be differentiated to Cornea epithelial cells (CECs), and skin epithelial stem cells (SESCs) can be differentiated to skin epithelial cells (SECs). Total RNA was isolated from CECs, SECs, and LSCs after knocking down PAX6 (3-D shPAX6 LSCs) and on SESCs transduced with PAX6 (3-D PAX6+ SESCs) upon 3-D differentiation. Libraries were prepared following published standard protocol (Fox-Walsh K et al., 2011, genomics, 266-71). mRNA profiles were generated by deep sequencing, in duplicate, using Illumina HiSeq 2000. Results: Following optimized decoding and mapping workfollow, we mapped about 5 million sequence reads to the human genome and identified more than 23659 transcripts per sample. Conclusions: Hierarchical clustering analysis of differentially expressed gene signatures revealed that the gene expression pattern of SESCs with PAX6 transduction was strikingly similar to that of CECs, whereas the profile of LSCs with PAX6 knockdown was highly related to that in SECs upon differentiation. These data therefore provided global evidence for a decisive role of the WNT7A/PAX6 axis in cell fate conversion from SESCs to CECs. RNA-seq on CECs, SECs, and LSCs after knocking down PAX6 and on SESCs transduced with PAX6 upon 3-D differentiation, using Illumina HiSeq 2000
Project description:Lineage-specific transcription factors (TFs) play key roles in maintaining the unique properties of cells, but the molecular mechanism that regulates the homeostasis of human corneal epithelial cells (CECs) is still poorly understood. We aimed to modulate KLF4 and PAX6 in human CECs using gene knockout system to clarify the regulatory network of KLF4, and then elucidate how KLF4 regulates the transcriptional genes of human CECs compared with PAX6. We performed a functional analysis of KLF4 via gene knockout using a lentivirus vector that carries both Cas9 and guide RNAs. We designed guide RNAs targeted for KLF4 and PAX6, and created KLF4-, PAX6-, and both KLF4- and PAX6-depleted CECs (KLF4-KO, PAX6-KO, and DKO, respectively). An empty vector was used as a control. The morphology of KLF4-KO CECs displayed an epithelial-mesenchymal transition (EMT)-like change, including upregulation of mesenchymal genes and downregulation of epithelial genes, as well as downregulation of keratin (KRT) 3 and KRT12. Global analyses using NGS revealed that the downregulated genes in KLF4-KO CECs were enriched in more widely keratin-related genes than PAX6-KO CECs. DKO cells showed disruption of the epithelial barrier due to downregulation of epithelial genes and showed more increase of KRT1 and KRT10 than PAX6-KO and KLF4-KO CECs, respectively. In conclusion, KLF4 modulates keratin-related genes as well as EMT-related genes and, together with PAX6, co-regulates the human CEC identity.
Project description:Purpose: We find that Wnt7a-PAX6 axis determine corneal epithelial cell fate. To obtain global evidence for successful cell fate conversion, we performed gene expression profiling by RNA-seq on CECs, SECs, and LSCs after knocking down PAX6 and on SESCs transduced with PAX6 upon 3-D differentiation. Methods: Under 3-D culture condition, limbal stem cell (LSCs) can be differentiated to Cornea epithelial cells (CECs), and skin epithelial stem cells (SESCs) can be differentiated to skin epithelial cells (SECs). Total RNA was isolated from CECs, SECs, and LSCs after knocking down PAX6 (3-D shPAX6 LSCs) and on SESCs transduced with PAX6 (3-D PAX6+ SESCs) upon 3-D differentiation. Libraries were prepared following published standard protocol (Fox-Walsh K et al., 2011, genomics, 266-71). mRNA profiles were generated by deep sequencing, in duplicate, using Illumina HiSeq 2000. Results: Following optimized decoding and mapping workfollow, we mapped about 5 million sequence reads to the human genome and identified more than 23659 transcripts per sample. Conclusions: Hierarchical clustering analysis of differentially expressed gene signatures revealed that the gene expression pattern of SESCs with PAX6 transduction was strikingly similar to that of CECs, whereas the profile of LSCs with PAX6 knockdown was highly related to that in SECs upon differentiation. These data therefore provided global evidence for a decisive role of the WNT7A/PAX6 axis in cell fate conversion from SESCs to CECs.
Project description:Adult stem cell identity, plasticity, and homeostasis are precisely orchestrated by lineage-restricted epigenetic and transcriptional regulatory networks. Here, by integrating super-enhancer and chromatin accessibility landscapes, we delineate core transcription regulatory circuitries (CRCs) of limbal stem/progenitor cells (LSCs) and find that RUNX1 and SMAD3 are required for maintenance of the corneal epithelial identity and homeostasis. RUNX1 or SMAD3 depletion inhibits PAX6 and induces LSCs to differentiate into epidermal-like type. RUNX1, PAX6 and SMAD3 (RPS) interact with each other and synergistically establish a CRC to govern the lineage-specific cis-regulatory atlas. Moreover, RUNX1 shapes LSC chromatin architecture via modulating H3K27ac deposition. Disturbance of RPS cooperation results in cell identity switching and dysfunction of the corneal epithelium, which is strongly linked to various human corneal diseases. Our work highlights CRC TF cooperativity for the establishment of stem cell identity and lineage commitment, and provides comprehensive regulatory principles for human stratified epithelial homeostasis and pathogenesis.
Project description:Adult stem cell identity, plasticity, and homeostasis are precisely orchestrated by lineage-restricted epigenetic and transcriptional regulatory networks. Here, by integrating super-enhancer and chromatin accessibility landscapes, we delineate core transcription regulatory circuitries (CRCs) of limbal stem/progenitor cells (LSCs) and find that RUNX1 and SMAD3 are required for maintenance of the corneal epithelial identity and homeostasis. RUNX1 or SMAD3 depletion inhibits PAX6 and induces LSCs to differentiate into epidermal-like type. RUNX1, PAX6 and SMAD3 (RPS) interact with each other and synergistically establish a CRC to govern the lineage-specific cis-regulatory atlas. Moreover, RUNX1 shapes LSC chromatin architecture via modulating H3K27ac deposition. Disturbance of RPS cooperation results in cell identity switching and dysfunction of the corneal epithelium, which is strongly linked to various human corneal diseases. Our work highlights CRC TF cooperativity for the establishment of stem cell identity and lineage commitment, and provides comprehensive regulatory principles for human stratified epithelial homeostasis and pathogenesis.