Probes for INS

Abstract BACKGROUND: Mitochondrial dysfunction has been implicated in the pathologies of a number of retinal degenerative diseases in both the outer and inner retina. In the outer retina, photoreceptors are particularly vulnerable to mutations affecting mitochondrial function due to their high energy demand and sensitivity to oxidative stress. However, it is unclear how defective mitochondrial biogenesis affects neural development and contributes to neural degeneration. In this report, we investigated the in vivo function of nuclear respiratory factor 1 (Nrf1), a major transcriptional regulator of mitochondrial biogenesis in both proliferating retinal progenitor cells (RPCs) and postmitotic rod photoreceptor cells (PRs). METHODS: We used mouse genetic techniques to generate RPC-specific and rod PR-specific Nrf1 conditional knockout mouse models. We then applied a comprehensive set of tools, including histopathological and molecular analyses, RNA-seq, and electroretinography on these mouse lines to study Nrf1-regulated genes and Nrf1's roles in both developing retinas and differentiated rod PRs. For all comparisons between genotypes, a two-tailed two-sample student's t-test was used. Results were considered significant when P < 0.05. RESULTS: We uncovered essential roles of Nrf1 in cell proliferation in RPCs, cell migration and survival of newly specified retinal ganglion cells (RGCs), neurite outgrowth in retinal explants, reconfiguration of metabolic pathways in RPCs, and mitochondrial morphology, position, and function in rod PRs. CONCLUSIONS: Our findings provide in vivo evidence that Nrf1 and Nrf1-mediated pathways have context-dependent and cell-state-specific functions during neural development, and disruption of Nrf1-mediated mitochondrial biogenesis in rod PRs results in impaired mitochondria and a slow, progressive degeneration of rod PRs. These results offer new insights into the roles of Nrf1 in retinal development and neuronal homeostasis and the differential sensitivities of diverse neuronal tissues and cell types of dysfunctional mitochondria. Moreover, the conditional Nrf1 allele we have generated provides the opportunity to develop novel mouse models to understand how defective mitochondrial biogenesis contributes to the pathologies and disease progression of several neurodegenerative diseases, including glaucoma, age-related macular degeneration, Parkinson's diseases, and Huntington's disease.

RUNX transcription factors play pivotal roles in embryonic development and neoplasia. We previously identified the single missense mutation R122C in RUNX3 from human gastric cancer. However, how RUNX3R122C mutation disrupts stem cell homeostasis and promotes gastric carcinogenesis remained unclear.To understand the oncogenic nature of this mutation in vivo, we generated the RUNX3R122C knock-in mice. Stomach tissues were harvested, followed by histological and immunofluorescence staining, organoid culture, flow cytometry to isolate gastric corpus isthmus and non-isthmus epithelial cells, and RNA extraction for transcriptomic analysis.The corpus tissue of RUNX3R122C/R122C homozygous mice exhibited a precancerous phenotype such as spasmolytic polypeptide-expressing metaplasia (SPEM). We observed mucous neck cell hyperplasia, massive reduction of pit, parietal, and chief cell populations, as well as a dramatic increase in the number of rapidly proliferating isthmus stem/progenitor cells in the corpus of RUNX3R122C/R122C mice. Transcriptomic analyses of the isolated epithelial cells showed that the cell cycle-related MYC target gene signature was enriched in the corpus epithelial cells of RUNX3R122C/R122C mice compared with the wild-type corpus. Mechanistically, RUNX3R122C mutant protein disrupted the regulation of the restriction point where cells decide to enter either proliferative or quiescent state, thereby driving stem cell expansion and limiting the ability of cells to terminally differentiate.RUNX3R122C missense mutation is associated with the continuous cycling of isthmus stem/progenitor cells, maturation arrest and development of a precancerous state. This work highlights the importance of RUNX3 in prevention of metaplasia and gastric cancer.

Obesity is an established risk factor for cancer in many tissues. In the mammalian intestine, a pro-obesity high-fat diet (HFD) promotes regeneration and tumorigenesis by enhancing intestinal stem cell (ISC) numbers, proliferation, and function. Although PPAR (peroxisome proliferator-activated receptor) nuclear receptor activity has been proposed to facilitate these effects, their exact role is unclear. Here we find that, in loss-of-function in vivo models, PPARα and PPARδ contribute to the HFD response in ISCs. Mechanistically, both PPARs do so by robustly inducing a downstream fatty acid oxidation (FAO) metabolic program. Pharmacologic and genetic disruption of CPT1A (the rate-controlling enzyme of mitochondrial FAO) blunts the HFD phenotype in ISCs. Furthermore, inhibition of CPT1A dampens the pro-tumorigenic consequences of a HFD on early tumor incidence and progression. These findings demonstrate that inhibition of a HFD-activated FAO program creates a therapeutic opportunity to counter the effects of a HFD on ISCs and intestinal tumorigenesis.