Tropomodulin3-null mice are embryonic lethal with anemia due to impaired erythroid terminal differentiation in the fetal liver.

Tropomodulin (Tmod) is a protein that binds and caps the pointed ends of actin filaments in erythroid and nonerythoid cell types. Targeted deletion of mouse tropomodulin3 (Tmod3) leads to embryonic lethality at E14.5-E18.5, with anemia due to defects in definitive erythropoiesis in the fetal liver. Erythroid burst-forming unit and colony-forming unit numbers are greatly reduced, indicating defects in progenitor populations. Flow cytometry of fetal liver erythroblasts shows that late-stage populations are also decreased, including reduced percentages of enucleated cells. Annexin V staining indicates increased apoptosis of Tmod3(-/-) erythroblasts, and cell-cycle analysis reveals that there are more Ter119(hi) cells in S-phase in Tmod3(-/-) embryos. Notably, enucleating Tmod3(-/-) erythroblasts are still in the process of proliferation, suggesting impaired cell-cycle exit during terminal differentiation. Tmod3(-/-) late erythroblasts often exhibit multilobular nuclear morphologies and aberrant F-actin assembly during enucleation. Furthermore, native erythroblastic island formation was impaired in Tmod3(-/-) fetal livers, with Tmod3 required in both erythroblasts and macrophages. In conclusion, disruption of Tmod3 leads to impaired definitive erythropoiesis due to reduced progenitors, impaired erythroblastic island formation, and defective erythroblast cell-cycle progression and enucleation. Tmod3-mediated actin remodeling may be required for erythroblast-macrophage adhesion, coordination of cell cycle with differentiation, and F-actin assembly and remodeling during erythroblast enucleation.

[Expression and significance of membrane skeleton protein 4.1 family in non-small cell lung cancer].

BACKGROUND AND OBJECTIVE: Protein 4.1, a component of cell membrane skeleton, plays a role in maintaining the shape and mechanical stability of erythrocytes. Recent researches showed that protein 4.1 may be associated with the development of tumors. This study was to investigate the expression and significance of membrane skeleton protein 4.1 family members (4.1B, 4.1R, 4.1N and 4.1G) in human non-small cell lung cancer (NSCLC). METHODS: The expression of proteins 4.1B, 4.1R, 4.1N and 4.1G in 147 specimens of NSCLC was detected by EnVision plus immunohistochemistry. The correlations of 4.1B, 4.1R, 4.1N and 4.1G expression to clinicopathologic features of NSCLC were analyzed by Wilcoxon rank sum test and Spearman rank correlation analysis. RESULTS: The protein levels of 4.1B, 4.1R and 4.1N were significantly lower in lung squamous cell carcinoma tissues than in adjacent normal tissues (P<0.01). The protein levels of 4.1B, 4.1R, 4.1N and 4.1G were significantly lower in lung adenocarcinoma tissues than in adjacent normal tissues (P<0.05). The protein levels of 4.1B and 4.1G were significantly lower in lung squamous cell carcinoma tissues than in lung adenocarcinoma tissues (P<0.05). Protein 4.1G expression in squamous cell carcinoma was positively correlated to tumor cell differentiation (rs=0.386,P<0.01). In adenocarcinoma, the expression of proteins 4.1B, 4.1N and 4.1G were positively correlated to tumor cell differentiation (rs=0.276, P<0.05; rs=0.248,P<0.05; rs=0.268, P <0.05). The expression of protein 4.1s in squamous cell carcinoma and adenocarcinoma were not related to lymph node metastasis, tumor size, patients'age and sex (P>0.05). CONCLUSIONS: Protein 4.1s are weakly expressed in NSCLC tissues than in adjacent normal tissues. The expression of proteins 4.1B, 4.1N and 4.1G are related to tumor cell differentiation.