Publications

Cell fate decisions of pluripotent embryonic stem (ES) cells are dictated by activation and repression of lineage-specific genes. Numerous signaling and transcriptional networks progressively narrow and specify the potential of ES cells. Whether specific microRNAs help refine and limit gene expression and, thereby, could be used to manipulate ES cell differentiation has largely been unexplored. Here, we show that two serum response factor (SRF)-dependent muscle-specific microRNAs, miR-1 and miR-133, promote mesoderm formation from ES cells but have opposing functions during further differentiation into cardiac muscle progenitors. Furthermore, miR-1 and miR-133 were potent repressors of nonmuscle gene expression and cell fate during mouse and human ES cell differentiation. miR-1's effects were in part mediated by translational repression of the Notch ligand Delta-like 1 (Dll-1). Our findings indicate that muscle-specific miRNAs reinforce the silencing of nonmuscle genes during cell lineage commitment and suggest that miRNAs may have general utility in regulating cell-fate decisions from pluripotent ES cells.

CONTEXT

Colorectal cancer is the second leading cause of cancer death in the United States. Prevention has focused on the detection and removal of polypoid neoplasms. Data are limited on the significance of nonpolypoid colorectal neoplasms (NP-CRNs).

OBJECTIVES

To determine the prevalence of NP-CRNs in a veterans hospital population and to characterize their association with colorectal cancer.

DESIGN, SETTING, AND PATIENTS

Cross-sectional study at a veterans hospital in California with 1819 patients undergoing elective colonoscopy from July 2003 to June 2004.

MAIN OUTCOME MEASURES

Endoscopic appearance, location, size, histology, and depth of invasion of neoplasms.

RESULTS

The overall prevalence of NP-CRNs was 9.35% (95% confidence interval [95% CI], 8.05%-10.78%; n = 170). The prevalence of NP-CRNs in the subpopulations for screening, surveillance, and symptoms was 5.84% (95% CI, 4.13%-8.00%; n = 36), 15.44% (95% CI, 12.76%-18.44%; n = 101), and 6.01% (95% CI, 4.17%-8.34%; n = 33), respectively. The overall prevalence of NP-CRNs with in situ or submucosal invasive carcinoma was 0.82% (95% CI, 0.46%-1.36%; n = 15); in the screening population, the prevalence was 0.32% (95% CI, 0.04%-1.17%; n = 2). Overall, NP-CRNs were more likely to contain carcinoma (odds ratio, 9.78; 95% CI, 3.93-24.4) than polypoid lesions, irrespective of the size. The positive size-adjusted association of NP-CRNs with in situ or submucosal invasive carcinoma was also observed in subpopulations for screening (odds ratio, 2.01; 95% CI, 0.27-15.3) and surveillance (odds ratio, 63.7; 95% CI, 9.41-431). The depressed type had the highest risk (33%). Nonpolypoid colorectal neoplasms containing carcinoma were smaller in diameter as compared with the polypoid ones (mean [SD] diameter, 15.9 [10.2] mm vs 19.2 [9.6] mm, respectively). The procedure times did not change appreciably as compared with historical controls.

CONCLUSION

In this group of veteran patients, NP-CRNs were relatively common lesions diagnosed during routine colonoscopy and had a greater association with carcinoma compared with polypoid neoplasms, irrespective of size.

BACKGROUND

Tryptases are serine peptidases stored in mast cell granules. Rodents express 2 soluble tryptases, mast cell proteases (MCPs) 6 and 7. Human alpha- and beta-tryptases are orthologs of MCP-6. However, much of the ancestral MCP-7 ortholog was replaced by parts of other tryptases, creating chimeric delta-tryptase. Human delta-tryptase's limited activity is hypothesized to be due to truncation and processing mutations.

OBJECTIVE

We sought to probe the origins and consequences of mutations in primate delta-tryptases.

METHODS

Prosimian (lemur), monkey (macaque), great ape (orangutan, gorilla, and chimpanzee), and human delta-tryptase genes were identified by means of data mining and genomic sequencing. Resulting genes were analyzed phylogenetically and structurally.

RESULTS

The seminal conversion event generating the delta-tryptase chimera occurred early because all primates studied contain delta-tryptase genes. Truncation, resulting from a nonsense mutation of Trp206, occurred much later, after orangutans and other great apes last shared an ancestor. The Arg-3Gln propeptide mutation occurred most recently, being present in humans and chimpanzees but not in other primates. Surprisingly, the major active tryptase in monkeys is full-length delta-tryptase, not beta-tryptase, which is the main active tryptase in human subjects. Models of macaque delta-tryptase reveal that the segment truncated in human subjects contains antiparallel beta-strands coursing through the substrate-binding cleft, accounting for truncation's drastic effect on activity.

CONCLUSIONS

Transformations in the ancestral MCP-7-like gene during primate evolution caused dramatic variations in function. Although delta-tryptases are nearly inactive in humans, they are active and dominant in monkeys.

Vascular endothelial growth factor (VEGF) is a key angiogenic factor and has been used experimentally for induction of neovasculature in ischemic myocardium. However, blood vessels induced by VEGF are immature. Angiopoietin-1 (ang-1) has the ability to recruit and sustain periendothelial support cells and promote vascular maturation. Thus, co-expression of the two may yield a better result than expression of either one alone. Two adeno-associated viral vectors (AAV), CMVVEGF and CMVang-1 with the CMV promoter driving VEGF or ang-1 gene expression, respectively, were injected into ischemic mouse hearts individually or together in different ratios. The results show that co-injected groups had more capillaries than the CMVang-1 group and similar densities of capillaries and alpha-actin positive vessels as the CMVVEGF group. Neovasculature induced by CMVVEGF was leaky. In contrast, neovasculature in CMVang-1-injected or CMVVEGF and CMVang-1 co-injected hearts was less leaky than that in CMVVEGF-injected hearts. The group that received CMVang-1 and CMVVEGF in a 1:1 ratio had the smallest infarct size and best cardiac function and regional wall movement among all the groups. We conclude that ang-1 and VEGF can compensate for each others' shortcomings and yield a better therapeutic effect by acting together.