Assuntos
Cromatina , Leucemia Linfocítica Crônica de Células B , Epigênese Genética , Epigenômica , Humanos , TempoRESUMO
Chromatin remodeling accompanies differentiation, however, its role in self-renewal is less well understood. We report that in Drosophila, the chromatin remodeler Kismet/CHD7/CHD8 limits intestinal stem cell (ISC) number and proliferation without affecting differentiation. Stem-cell-specific whole-genome profiling of Kismet revealed its enrichment at transcriptionally active regions bound by RNA polymerase II and Brahma, its recruitment to the transcription start site of activated genes and developmental enhancers and its depletion from regions bound by Polycomb, Histone H1, and heterochromatin Protein 1. We demonstrate that the Trithorax-related/MLL3/4 chromatin modifier regulates ISC proliferation, colocalizes extensively with Kismet throughout the ISC genome, and co-regulates genes in ISCs, including Cbl, a negative regulator of Epidermal Growth Factor Receptor (EGFR). Loss of kismet or trr leads to elevated levels of EGFR protein and signaling, thereby promoting ISC self-renewal. We propose that Kismet with Trr establishes a chromatin state that limits EGFR proliferative signaling, preventing tumor-like stem cell overgrowths.
Assuntos
Cromatina/metabolismo , DNA Helicases/metabolismo , Proteínas de Drosophila/metabolismo , Histona-Lisina N-Metiltransferase/metabolismo , Proteínas de Homeodomínio/metabolismo , Animais , Diferenciação Celular/fisiologia , Proliferação de Células/fisiologia , Montagem e Desmontagem da Cromatina/fisiologia , DNA Helicases/fisiologia , Proteínas de Drosophila/fisiologia , Drosophila melanogaster/metabolismo , Receptores ErbB/metabolismo , Histona-Lisina N-Metiltransferase/fisiologia , Histonas/metabolismo , Proteínas de Homeodomínio/fisiologia , RNA Polimerase II/genética , RNA Polimerase II/metabolismo , Receptores de Peptídeos de Invertebrados/metabolismo , Transdução de Sinais/fisiologia , Células-Tronco/metabolismo , Fatores de Transcrição/metabolismoRESUMO
Precise regulation of stem cell self-renewal and differentiation properties is essential for tissue homeostasis. Using the adult Drosophila intestine to study molecular mechanisms controlling stem cell properties, we identify the gene split-ends (spen) in a genetic screen as a novel regulator of intestinal stem cell fate (ISC). Spen family genes encode conserved RNA recognition motif-containing proteins that are reported to have roles in RNA splicing and transcriptional regulation. We demonstrate that spen acts at multiple points in the ISC lineage with an ISC-intrinsic function in controlling early commitment events of the stem cells and functions in terminally differentiated cells to further limit the proliferation of ISCs. Using two-color cell sorting of stem cells and their daughters, we characterize spen-dependent changes in RNA abundance and exon usage and find potential key regulators downstream of spen. Our work identifies spen as an important regulator of adult stem cells in the Drosophila intestine, provides new insight to Spen-family protein functions, and may also shed light on Spen's mode of action in other developmental contexts.
