SummaryNonsense-mediated RNA decay (NMD) is a highly conserved pathway that selectively degrades specific subsets of RNA transcripts. Here, we provide evidence that NMD regulates early human developmental cell fate. We found that NMD factors tend to be expressed at higher levels in human pluripotent cells than in differentiated cells, raising the possibility that NMD must be downregulated to permit differentiation. Loss- and gain-of-function experiments in human embryonic stem cells (hESCs) demonstrated that, indeed, NMD downregulation is essential for efficient generation of definitive endoderm. RNA-seq analysis identified NMD target transcripts induced when NMD is suppressed in hESCs, including many encoding signaling components. This led us to test the role of TGF-β and BMP signaling, which we found NMD acts through to influence definitive endoderm versus mesoderm fate. Our results suggest that selective RNA decay is critical for specifying the developmental fate of specific human embryonic cell lineages.

Background and Aims Several different types of non-conventional dysplasia have been recently described in inflammatory bowel disease (IBD). Hypermucinous, goblet cell deficient, and crypt cell dysplasias have received more attention, but there is limited information regarding their clinicopathologic features and clinical outcomes. Methods A total of 126 cases of hypermucinous (n = 55), goblet cell deficient (n = 26), and crypt cell (n = 45) dysplasias from 97 IBD patients were collected from 7 different institutions and analyzed. Results The cohort included 62 (64%) men and 35 (36%) women with a mean age of 49 years (range: 20-78). The majority of affected patients had longstanding IBD (mean duration: 18 years). Nineteen (20%) patients had a concurrent history of primary sclerosing cholangitis. As a group, non-conventional dysplasia was predominantly found in patients with ulcerative colitis (UC) (n = 68; 70%) and occurred in the left colon (n = 80; 63%); however, hypermucinous dysplasia (57%) was the least frequently associated with UC compared with goblet cell deficient (74%) and crypt cell (89%) dysplasias (p = 0.016). Fifty (52%) patients had a history of conventional dysplasia, detected in the same colonic segment as non-conventional dysplasia at a rate of 33%. Goblet cell deficient dysplasia (74%) was more frequently associated with conventional dysplasia than hypermucinous (43%) and crypt cell (48%) dysplasias (p = 0.044). While hypermucinous dysplasia often had a polypoid appearance (58%), crypt cell (96%) and goblet cell deficient (65%) dysplasias were more likely to present as flat/invisible lesions (p < 0.001). Most lesions were low-grade (87%) at diagnosis, but goblet cell deficient dysplasia (31%) more often showed high-grade dysplasia (HGD) than hypermucinous (15%) and crypt cell (0%) dysplasias (p = 0.003). Hypermucinous dysplasia usually demonstrated a tubulovillous/villous architecture (76%), whereas goblet cell deficient dysplasia was predominantly tubular (92%). A flat architecture was exclusively associated with crypt cell dysplasia (100%) (p < 0.001). Immunohistochemical stain results for p53 were available for 33 lesions; 14 (42%) showed strong (3+) and patchy (10-50%) to diffuse (> 50%) nuclear overexpression or null staining pattern, including 4 (33%) of 12 hypermucinous, 2 (29%) of 7 goblet cell deficient, and 8 (57%) of 14 crypt cell dysplastic lesions (p = 0.726). Follow-up biopsies or resections were available for 92 low-grade lesions from 71 patients; 55 (60%) lesions, including 19 (49%) of 39 hypermucinous, 10 (59%) of 17 goblet cell deficient, and 26 (72%) of 36 crypt cell dysplastic lesions (p = 0.116), were associated with subsequent detection of HGD (n = 34; 37%) or adenocarcinoma (n = 21; 23%) at the site of previous biopsy or in the same colonic segment within a mean follow-up time of 12 months (range: < 1-73). Conclusions Hypermucinous, goblet cell deficient, and crypt cell dysplasias have distinct clinicopathologic features but appear to have a similar high risk of association with advanced neoplasia (HGD or adenocarcinoma). Greater than half of the lesions (66%) presented as flat/invisible dysplasia, suggesting that IBD patients may benefit from random biopsy sampling in addition to targeted biopsies. Although not uncommonly associated with conventional dysplasia, non-conventional dysplasia may be the only dysplastic subtype identified in IBD patients. Therefore, it is important to recognize these non-conventional subtypes and recommend complete removal and/or careful examination and follow-up.

Maternal obesity results in placental overgrowth and fetal hypoxia as manifested by normoblastemia; it is also associated with an increased incidence of CV and fetal thrombosis, both more prevalent in female placentas. We have shown for the first time that the effect of maternal obesity on placental inflammation is independent of diabetes and hypertension, but significantly affected by fetal sex. Our data also point to the intriguing possibility that CV serves to normalize placental size, and potentially fetal growth, in the setting of maternal obesity.

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SummaryThe differentiation of human pluripotent stem cells (hPSCs) to insulin-expressing beta islet-like cells is a promising in vitro model system for studying the molecular signaling pathways underlying beta cell differentiation, as well as a potential source of cells for the treatment of type 1 diabetes. MicroRNAs (miRNAs) are a class of small non-coding RNAs that regulate many biological processes, including cellular differentiation. We studied the miRNA and mRNA expression profiles of hPSCs at five stages of in vitro differentiation along the pancreatic beta cell lineage (definitive endoderm, primitive gut tube, posterior foregut, pancreatic progenitor and hormone-expressing endocrine cells) in the context of samples of primary human fetal pancreas and purified adult islet cells using microarray analysis. Bioinformatic analysis of the resulting data identified a unique miRNA signature in differentiated beta islet cells, and predicted the effects of key miRNAs on mRNA expression. Many of the predicted miRNA-mRNA interactions involved mRNAs known to play key roles in the epithelial-mesenchymal transition process and pancreatic differentiation. We validated a subset of the predictions using qRT-PCR, luciferase reporter assays and western blotting, including the known interaction between miR-200 and ZEB2 (involved in epithelial-mesenchymal transition) and the novel interaction between miR-200 and SOX17 (a key transcription factor in specification of definitive endoderm). In addition, we found that miR-30d and let-7e, two miRNAs induced during differentiation, regulated the expression of RFX6, a transcription factor that directs pancreatic islet formation. These findings suggest that precise control of target mRNA expression by miRNAs ensures proper lineage specification during pancreatic development.