No abstract

The intestine is a highly dynamic environment that requires tight control of the various inputs to maintain homeostasis and allow for proper responses to injury. It was recently found that the stem cell niche and epithelium is regenerated after injury by de-differentiated adult cells, through a process that gives rise to Sca1+ fetal-like cells and is driven by a transient population of Clu+ revival stem cells (revSCs). However, the molecular mechanisms that regulate this dynamic process have not been fully defined. Here we show that TNFAIP8 (also known as TIPE0) is a regulator of intestinal homeostasis that is vital for proper regeneration. TIPE0 functions through inhibiting basal Akt activation by the commensal microbiota via modulating membrane phospholipid abundance. Loss of TIPE0 in mice results in injury-resistant enterocytes, that are hyperproliferative, yet have regenerative deficits and are shifted towards a de-differentiated state. Tipe0−/− enterocytes show basal induction of the Clu+ regenerative program and a fetal gene expression signature marked by Sca1, but upon injury are unable to generate Sca-1+/Clu+ revSCs and could not regenerate the epithelium. This work demonstrates the role of TIPE0 in regulating the dynamic signaling that determines the injury response and enables intestinal epithelial cell regenerative plasticity.

Because modern electronic systems are likely to be exposed to high intensity radiated fields (HIRF) environments, there is growing interest in understanding how electronic systems are affected by such environments. Backdoor coupling in particular is an area of concern for all electronics, but there is limited understanding about the mechanisms behind backdoor coupling. In this work, we present a study on printed circuit board (PCB) backdoor coupling and the effects of via fencing. Existing work focuses on ideal stackups and indicates that edge radiation is significantly reduced by via fencing. In this study, both full wave electromagnetic modeling and experimental verification are used to investigate both ideal and practical PCB stackups. In the ideal scenario, we find that via fencing substantially reduces coupling, which is consistent with prior work on emissions. In the practical scenario, we incorporate component footprints and traces which naturally introduce openings in the top ground plane. Both simulation and experimental data indicate that via fencing in the practical scenario does not substantially mitigate coupling, suggesting that PCB edge coupling is not the dominant coupling mechanism, even at varying angles of incidence and polarization.

Background After injury, intestinal epithelial cells can regenerate the epithelium and stem cell niche by de‐differentiating through a process recently defined as paligenosis. In the intestine, this process is marked by the YAP‐dependent‐induction of Sca‐1+/Clu+ regenerative stem cells, but other signaling pathways that regulate this regenerative program are unknown. Here we show that the protein TNFAIP8 (aka TIPE0) is a critical regulator of intestinal homeostasis and functions through the inhibition of basal microbiome‐dependent PI3K/Akt signaling. Results Loss of TIPE0 results in hyperactivation of the Akt pathway, leading to resistance to ischemia/reperfusion (Fig 1A&B) and radiation‐induced injuries. Similar results were recapitulated with enteroid cultures exposed to TNF or hypoxic conditions (Fig 1C&D). However, when the epithelium was disrupted through chemical means, the intestine was unable to regenerate. The loss of TNFAIP8 resulted in a baseline shift to more partially differentiated enterocytes (Fig 1E&F), with inappropriate baseline activation of the Sca‐1+/Clu+ regenerative program, but a lack of appropriate YAP/Sca‐1/Clu induction after injury (Fig 1G). Subsequent cellular signaling analysis demonstrated that PI3K/Akt signaling was enhanced upon loss of TIPE0 (Fig 2A–C by IHC in mice, Fig 2D in freshly isolated epithelium, and Fig 2E in enteroid culture) and that this was responsible both for the resistance to injury and lack of regenerative function. TIPE0 was found to regulate PI3K/Akt signaling by extracting PIP from the plasma membrane, limiting the availability of PI3K to convert Ptdlns(4,5)P2 to PIP3 under basal conditions. Conclusions TNFAIP8 is a critical regulator of PI3K/Akt signaling, inhibiting commensal microbial stimulation by extracting Ptdlns(4,5)P2 from the plasma membrane and inhibiting PIP3 accumulation. TIPE0 is needed for intestinal homeostasis, and loss results in hyperactivation of PI3K/Akt‐mediated signaling, leading to altered differentiation as well as an inability to respond injury, with a gut that fails to regenerate but also resists some injuries. Support or Funding Information R01‐AI121166, R01‐AI136945, and R56‐AI132329 to Y.H.C.; grant F32‐DK116528 to J.R.G.; and grant P30‐DK050306 to Anil Rustgi. J.R.G was partially supported by NIH‐T32‐CA009140. TIPE0 controls intestinal injury responses and differentiation. A) Histological score of mice subjected to 60′ of ischemia and 90′ of reperfusion, with accompanying histology (B). Cell titer glo 3D assays were used to determine 1‐day survival of 7d old enteroids exposed to 100 ng/mL TNF (C) or hypoxic conditions (1% O2, D). Sc‐RNA‐Seq shows changes in enterocyte populations with loss of TIPE0 (E&F). G) The Sca‐1+ injury response program does not induce after injury with loss of TIPE0. Loss of TIPE0 results in basal increases in pAkt signaling. IHC staining for A) pAktS473, B) GSK3βS9, and C) β‐catenin in WT and Tipe0−/− ileums with and without ischemia. D) Western blot of enterocytes isolated from healthy ileu...