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To clarify the molecular pathways governing hematopoietic stem cell (HSC) development, we screened a fetal liver (FL) HSC cDNA library and identified a unique gene, hematopoietic expressed mammalian polycomb ( hemp ), encoding a protein with a zinc-finger domain and four malignant brain tumor (mbt) repeats. To investigate its biological role, we generated mice lacking Hemp ( hemp −/− ). Hemp −/− mice exhibited a variety of skeletal malformations and died soon after birth. In the FL, hemp was preferentially expressed in the HSC and early progenitor cell fractions, and analyses of fetal hematopoiesis revealed that the number of FL mononuclear cells, including HSCs, was reduced markedly in hemp −/− embryos, especially during early development. In addition, colony-forming and competitive repopulation assays demonstrated that the proliferative and reconstitution abilities of hemp −/− FL HSCs were significantly impaired. Microarray analysis revealed alterations in the expression levels of several genes implicated in hematopoietic development and differentiation in hemp −/− FL HSCs. These results demonstrate that Hemp, an mbt-containing protein, plays essential roles in HSC function and skeletal formation. It is also hypothesized that Hemp might be involved in certain congenital diseases, such as Klippel-Feil anomaly.

Gastrointestinal stromal tumors (GISTs) are mesenchymal tumors that originate from the gastrointestinal tract, mostly from the stomach. GISTs are derived from the myenteric interstitial cells of Cajal and are caused by several mutations in the c-kit and platelet-derived growth factor receptor genes. Clinically, GISTs are detected by endoscopic and imaging findings and are diagnosed by immunostaining. Surgery is the first line of treatment, and if the tumor is relatively small, minimally invasive surgery such as laparoscopy is performed. In recent years, neoadjuvant therapy has been administered to patients with GISTs that are suspected of having a large size or infiltration to other organs. Postoperative adjuvant imatinib is the standard therapy for high-risk GISTs. It is important to assess the risk of recurrence after GIST resection. However, the effect of tyrosine kinase inhibitor use will vary by the mutation of c-kit genes and the site of mutation. Furthermore, information regarding gene mutation is indispensable when considering the treatment policy for recurrent GISTs. This article reviews the clinicopathological characteristics of GISTs along with the minimally invasive and multidisciplinary treatment options available for these tumors. The future perspectives for diagnostic and treatment approaches for these tumors have also been discussed.

p130Cas, Crk-associated substrate (Cas), is an adaptor/scaffold protein that plays a central role in actin cytoskeletal reorganization. We previously showed that mice in which Cas was deleted (Cas 2/2 ) died in utero because of early cardiovascular maldevelopment. To further investigate the in vivo roles of Cas, we generated mice with a hypomorphic Cas allele lacking the exon 2-derived region (Cas Dex2/Dex2 ), which encodes Src homology domain 3 (SH3) of Cas. Cas Dex2/Dex2 mice again died as embryos, but they particularly showed progressive liver degeneration with hepatocyte apoptosis. Because Cas expression in the liver is preferentially detected in sinusoidal endothelial cells (SECs), the observed hepatocyte apoptosis was most likely ascribable to impaired function of SECs. To address this possibility, we stably introduced a Cas mutant lacking the SH3 domain (Cas DSH3) into an SEC line (NP31). Intriguingly, the introduction of Cas DSH3 induced a loss of fenestrae, the characteristic cell-penetrating pores in SECs that serve as a critical route for supplying oxygen and nutrients to hepatocytes. The disappearance of fenestrae in Cas DSH3-expressing cells was associated with an attenuation of actin stress fiber formation, a marked reduction in tyrosine phosphorylation of Cas, and defective binding of Cas to CrkII. Conclusion: Cas plays pivotal roles in liver development through the reorganization of the actin cytoskeleton and formation of fenestrae in SECs. (HEPATOLOGY 2010;52:1089-1099 Abbreviations:: Cas, p130 Crk-associated substrate; Cas Dex2, exon 2-deleted p130 Crk-associated substrate; Cas DSH3, p130 Crk-associated substrate mutant lacking Src homology domain 3; Cas FL, full-length p130 Crk-associated substrate; cDNA, complementary DNA; Cre, cyclization recombination; dpc, days post coitum; FN, fibronectin; HA, hemagglutinin; HE, hematoxylin and eosin; loxP, locus of X-over P1; MEF, mouse embryonic fibroblast; Neo, neomycin resistance; NS, not significant; PCR, polymerase chain reaction; SBD, Src-binding domain; SD, substrate domain; SEC, sinusoidal endothelial cell; SH2, Src homology domain 2; SH3, Src homology domain 3; Stab2, stabilin 2; TUNEL, terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate nick-end labeling; WT, wild-type; YxxP, Tyr-x-x-Pro.From the

p130Cas (Cas, Crk‐associated substrate) is an adaptor molecule composed of a Src homology 3 (SH3) domain, a substrate domain (SD) and a Src binding domain (SBD). The SH3 domain of Cas associates with focal adhesion kinase (FAK), but its role in cellular function has not fully been understood. To address this issue, we established and analyzed primary fibroblasts derived from mice expressing a truncated Cas lacking exon 2, which encodes the SH3 domain (Cas Δexon 2). In comparison to wild‐type cells, Cas exon 2Δ/Δ cells showed reduced motility, which could be due to impaired tyrosine‐phosphorylation of FAK and Cas, reduced FAK/Cas/Src/CrkII binding, and also impaired localization of Cas Δexon 2 to focal adhesions on fibronectin. In addition, to analyze downstream signaling pathways regulated by Cas exon 2, we performed microarray analyses. Interestingly, we found that a deficiency of Cas exon 2 up‐regulated expression of CXC Chemokine Receptor‐4 and CC Chemokine Receptor‐5, which may be regulated by IκBα phosphorylation. These results indicate that the SH3‐encoding exon of Cas participates in cell motility, tyrosine‐phosphorylation of FAK and Cas, FAK/Cas/Src/CrkII complex formation, recruitment of Cas to focal adhesions and regulation of cell motility‐associated gene expression in primary fibroblasts.