Spen limits intestinal stem cell self-renewal

Abstract

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.

Transcriptomic and proteomic signatures of stemness and differentiation in the colon crypt

“…4d). Numb is a regulator of asymmetric cell divisions and a repressor of Notch signaling; Spen regulates early commitment choices of intestinal stem cells with activities that suppress Notch and activate Wnt 68 .…”

Split-ends is modulating lipid droplet content in adultDrosophilaglial cells and is protective against paraquat toxicity

“…We also found that Spen is a positive regulator of Notch signaling in adult Drosophila glial cells. A Spen-dependent activation of the Notch pathway has also been observed in intestinal stem cells of adult flies 42 , further supporting that Spen can act as a positive regulator of Notch in adult tissues. This also raises the possibility that in spen mutant a reduced Notch signaling leads to the accumulation of lipid droplets although we could not modify lipid droplets size and number by knocking down Su(H) in glial cells.…”

Spen modulates lipid droplet content in adult Drosophila glial cells and protects against paraquat toxicity

“…Because Spen/SPEN has been shown to positively or negatively regulate Notch signaling pathway, depending on the molecular context and cell type 25 , 27 , 28 , we next determined how Spen regulates Notch pathway in adult glial cells. To this end, we knocked down spen expression using an Eaat1 (excitatory amino acid transporter 1) driver, which is mainly expressed in astrocyte-like glial cells 34 , 35 , and monitored Notch pathway activation using a reporter transgene, Notch Responsive Element ( NRE)-GFP .…”

“…Conversely, SPEN can act as a positive regulator of Notch signaling by recruiting the lysine methyl transferase 2D (KMT2D) co-activator complex to Notch target genes 27 . Spen has also been shown to promote Notch receptor activation by regulating trafficking of the Notch ligand Delta in intestinal stem cells of adult flies 28 .…”