Transcriptional profiling of human and mouse nephron progenitor cells
Ontology highlight
ABSTRACT: Nephron endowment is determined by the self-renewal and induction of a nephron progenitor pool established at the onset of kidney development. In the mouse, the related transcriptional regulators Six1 and Six2 play non-overlapping roles in nephron progenitors. Transient Six1 activity prefigures, and is essential for, active nephrogenesis. In contrast, Six2 maintains later progenitor self-renewal from the onset of nephrogenesis. We compared Six2’s regulatory actions in mouse and human nephron progenitors by chromatin immunoprecipitation followed by DNA sequencing (ChIP-seq). Surprisingly, SIX1 was identified as a SIX2 target unique to the human nephron progenitors. Further, RNA-seq and immunostaining revealed overlapping SIX1 and SIX2 progenitor activity in the 16 week human fetal kidney. Human SIX1 ChIP-seq revealed a similar set of targets to SIX2, and predicted both factors bind DNA through an identical recognition site. In contrast to the mouse where Six2 binds its own enhancers but doesn’t interact with DNA around Six1, both human SIX1 and SIX2 bind homologous SIX2 enhancers and putative enhancers positioned around SIX1. Transgenic analysis of a putative human SIX1 enhancer in the mouse revealed a transient, mouse-like, pre-nephrogenic, Six1 regulatory pattern. Together, these data demonstrate a divergence in SIX-factor regulation between mouse and human nephron progenitors. In the human, an auto/cross-regulatory loop drives continued SIX1 and SIX2 expression during active nephrogenesis. In contrast, the mouse establishes only an auto-regulatory Six2 loop. It is tempting to speculate that differential SIX-factor regulation may contribute to species differences in the duration of progenitor programs and nephron output.
Project description:Nephron endowment is determined by the self-renewal and induction of a nephron progenitor pool established at the onset of kidney development. In the mouse, the related transcriptional regulators Six1 and Six2 play non-overlapping roles in nephron progenitors. Transient Six1 activity prefigures, and is essential for, active nephrogenesis. In contrast, Six2 maintains later progenitor self-renewal from the onset of nephrogenesis. We compared Six2’s regulatory actions in mouse and human nephron progenitors by chromatin immunoprecipitation followed by DNA sequencing (ChIP-seq). Surprisingly, SIX1 was identified as a SIX2 target unique to the human nephron progenitors. Further, RNA-seq and immunostaining revealed overlapping SIX1 and SIX2 progenitor activity in the 16 week human fetal kidney. Human SIX1 ChIP-seq revealed a similar set of targets to SIX2, and predicted both factors bind DNA through an identical recognition site. In contrast to the mouse where Six2 binds its own enhancers but doesn’t interact with DNA around Six1, both human SIX1 and SIX2 bind homologous SIX2 enhancers and putative enhancers positioned around SIX1. Transgenic analysis of a putative human SIX1 enhancer in the mouse revealed a transient, mouse-like, pre-nephrogenic, Six1 regulatory pattern. Together, these data demonstrate a divergence in SIX-factor regulation between mouse and human nephron progenitors. In the human, an auto/cross-regulatory loop drives continued SIX1 and SIX2 expression during active nephrogenesis. In contrast, the mouse establishes only an auto-regulatory Six2 loop. It is tempting to speculate that differential SIX-factor regulation may contribute to species differences in the duration of progenitor programs and nephron output.
Project description:The vertebrate Six1 and Six2 arose by gene duplication from the Drosophila so (sine oculis) and have since diverged in their developmental expression patterns. Both genes are expressed in nephron progenitors of human fetal kidneys, and mutations in SIX1 or SIX2 cause branchio-oto-renal or renal hypodysplasia respectively. Since ~80% of SIX1 target sites are shared by SIX2, it is speculated that SIX1 and SIX2 may be functionally interchangeable by targeting common downstream genes. In contrast, in mouse kidneys, the expression of Six1 and Six2 only transiently overlaps in the metanephric mesenchyme before the onset of ureteric branching, and only Six2 expression is maintained in the nephron progenitors throughout development. This non-overlapping expression between Six1 and Six2 in mouse nephron progenitors promoted us to examine if Six1 can replace Six2. Surprisingly, forced expression of Six1 failed to rescue Six2-deficient kidney hypoplasia. We found that Six1 mediated Eya1 nuclear translocation and inhibited premature epithelialization of the progenitors but failed to rescue the proliferation defects and cell death caused by Six2-knockout. Genome-wide binding analyses showed that Six1 only bound to a small subset of Six2 target sites, but many Six2-bound loci that are crucial to the renewal and differentiation of nephron progenitors lacked Six1 occupancy. Thus, these data indicate that Six1 cannot substitute Six2 to drive nephrogenesis in mouse kidneys, demonstrating that these two transcription factors have not maintained equivalent biochemical properties since their divergence early in vertebrate evolution.
Project description:SIX2 is expressed by the self-renewing nephron progenitors in the human fetal kidney. We have also discovered that SIX1 is expressed in nephron progenitor population of the human fetal kidney, which is in contrast to the mouse. We performed ChIP-seq of SIX1 and SIX2 in order to identify the target genes of each factor and compare the role that each factor plays in transcriptional regulation of the nephron progenitors. We additionally performed ChIP-seq for p300 and H3K27ac in order to identify active loci and complement the transcription factor data.
Project description:When assembling a nephron during development a multipotent stem cell pool becomes restricted as differentiation ensues. A faulty differentiation arrest in this process leads to transformation and initiation of a Wilms' tumor. Mapping these transitions with respective surface markers affords accessibility to specific cell subpopulations. NCAM1 and CD133 have been previously suggested to mark human renal progenitor populations. Herein, using cell sorting, RNA sequencing, in vitro studies with serum-free media and in vivo xenotransplantation we demonstrate a sequential map that links human kidney development and tumorigenesis; In nephrogenesis, NCAM1+CD133- marks SIX2+ multipotent renal stem cells transiting to NCAM1+CD133+ differentiating segment-specific SIX2- epithelial progenitors and NCAM1-CD133+ differentiated nephron cells. In tumorigenesis, NCAM1+CD133- marks SIX2+ blastema that includes the ALDH1+ WT cancer stem/initiating cells, while NCAM1+CD133+ and NCAM1-CD133+ specifying early and late epithelial differentiation, are severely restricted in tumor initiation capacity and tumor self-renewal. Thus, negative selection for CD133 is required for defining NCAM1+ nephron stem cells in normal and malignant nephrogenesis. Human fetal kidney mRNA profiles of 3 cell populations (NCAM1+/CD133-, NCAM+/CD133+, NCAM-/CD133+) were generated by deep sequencing using Illumina HiSeq.
Project description:Eya1 interacts with Six1/2 to induce nephron fate and promote nephron progenitor self-renewal. Haploinsufficiency for these genes in humans causes kidney agenesis or hypoplasia. However, how the Eya1-centered network operates remains elusive. Here we identify Eya1's interacting factors via mass-spectrometry and show that Eya1 and Six2 interact with Brg1-based SWI/SNF chromatin-remodeling complex in the kidney. Depletion of Brg1 results in lack of metanephric mesenchyme and depletion of nephron progenitor cells, which is linked to loss of Eya1 expression. Transcriptional profiling reveals conspicuous downregulation of the proto-oncogene Pbx1 and the Dchs1/Fat4 signaling but premature upregulation of a large subset of genes for podocyte lineages and aberrant activation of oncogenic factors in Brg1-deficent cell. ChIP-seq identifies Brg1-occupancy to enhancers at Pbx1 to a distal enhancer of Eya1 that drives nephron progenitor-specific expression. We demonstrate Six2-dependent Brg1 enrichment to the proximal-promoter of Mycn and two distal enhancers of Pbx1, all of which govern nephron progenitor-specific expression in response to binding to Six2. Together, our results suggest a possible mechanism through which the functional specificity of Brg1-BAFs and Eya1-Six2 in cell cycle regulation and self-renewal of the nephron progenitors may be in part achieved.
Project description:Self-renewing undifferentiated nephron progenitors express Six2, a transcription factor that is required for their maintenance as undifferentiated progenitors. Differentiation of nephron progenitors is triggered by Wnt/b-catenin signaling. In order to understand how Six2 and Wnt signaling counteract each other, we performed ChIP-seq of Six2 and b-catenin in mesenchymal nephron progenitor cells. Nephron progenitors were FACS-isolated from BAC transgenic Six2GFPcre-positive embryonic kidneys at E16.5. For Six2 ChIP, freshly FACS isolated Six2+ cells were used. For b-catenin ChIP, FACS isolated Six2+ cells were aggregated by centrifugation at 850g for 5min and incubated in 10%FBS/DMEM containing 4uM BIO for 24hrs.
Project description:When assembling a nephron during development a multipotent stem cell pool becomes restricted as differentiation ensues. A faulty differentiation arrest in this process leads to transformation and initiation of a Wilms' tumor. Mapping these transitions with respective surface markers affords accessibility to specific cell subpopulations. NCAM1 and CD133 have been previously suggested to mark human renal progenitor populations. Herein, using cell sorting, RNA sequencing, in vitro studies with serum-free media and in vivo xenotransplantation we demonstrate a sequential map that links human kidney development and tumorigenesis; In nephrogenesis, NCAM1+CD133- marks SIX2+ multipotent renal stem cells transiting to NCAM1+CD133+ differentiating segment-specific SIX2- epithelial progenitors and NCAM1-CD133+ differentiated nephron cells. In tumorigenesis, NCAM1+CD133- marks SIX2+ blastema that includes the ALDH1+ WT cancer stem/initiating cells, while NCAM1+CD133+ and NCAM1-CD133+ specifying early and late epithelial differentiation, are severely restricted in tumor initiation capacity and tumor self-renewal. Thus, negative selection for CD133 is required for defining NCAM1+ nephron stem cells in normal and malignant nephrogenesis.
Project description:All nephrons in the mammalian kidney arise from a transient nephron progenitor population that is lost after birth. The recreation of nephron progenitors (NPs) and/or their maintenance in culture has been a major focus of renal regenerative strategies. Using a lentiviral screening approach, we previously generated an induced nephron progenitor (iNP) state in vitro using a pool of six transcription factors (SIX1, SIX2, HOXA11, OSR1, EYA1, SNAI2). Here, using an inducible piggyBac transposon system, we demonstrate efficient reprogramming to iNPs with only three transcription factors (SNAI2, EYA1 and SIX1). Coupled with maintenance in culture conditions supportive of this progenitor state, the resulting population can contribute to developing nephrons in vitro, ex vivo and in vivo. This approach provides a rapid and efficient method for the generation of NPs from human somatic cells.
Project description:Self-renewing undifferentiated nephron progenitors express Six2, a transcription factor that is required for their maintenance as undifferentiated progenitors. Differentiation of nephron progenitors is triggered by Wnt/b-catenin signaling. In order to understand how Six2 and Wnt signaling counteract each other, we performed ChIP-seq of Six2 and b-catenin in mesenchymal nephron progenitor cells.
Project description:Our studies demonstrated the critical role of Histone deacetylases (HDACs) in the regulation of nephrogenesis. To better understand the key pathways regulated by HDAC1/2 in early nephrogenesis, we performed chromatin immunoprecipitation sequencing (ChIP-Seq) of Hdac1/2 on isolated nephron progenitor cells (NPCs) from mouse E16.5 kidneys. Our analysis revealed that 11802 (40.4%) of Hdac1 peaks overlap with Hdac2 peaks, further demonstrates the redundant role of Hdac1 and Hdac2 during nephrogenesis. Common Hdac1/2 peaks are densely concentrated close to the transcriptional start site (TSS). GREAT Gene Ontology analysis of overlapping Hdac1/2 peaks reveals that Hdac1/2 are associated with metanephric nephron morphogenesis, chromatin assembly or disassembly, as well as other DNA checkpoints. Pathway analysis shows that negative regulation of Wnt signaling pathway is one of Hdac1/2’s most significant function in NPCs. Known motif analysis indicated that Hdac1 is enriched in motifs for Six2, Hox family, and Tcf family members, which are essential for self-renewal and differentiation of nephron progenitors. Interestingly, we found the enrichment of HDAC1/2 at the enhancer and promoter regions of actively transcribed genes, especially those concerned with NPC self-renewal. Hdac1/2 simultaneously activate or repress the expression of different genes to maintain the cellular state of nephron progenitors. We used the Integrative Genomics Viewer to visualize these target genes associated with each function and found that Hdac1/2 co-bound to the enhancers or/and promoters of genes associated with nephron morphogenesis, differentiation, and cell cycle control. Taken together, our ChIP-Seq analysis demonstrates that Hdac1/2 directly regulate the molecular cascades essential for nephrogenesis.