Deficiency in Crumbs homolog 2 (Crb2) affects gastrulation and results in embryonic lethality in mice.

The Crumbs family of transmembrane proteins has an important role in the differentiation of the apical membrane domain in various cell types, regulating such processes as epithelial cell polarization. The mammalian Crumbs protein family is composed of three members. Here, we inactivated the mouse Crb2 gene with gene-targeting techniques and found that the protein is crucial for early embryonic development with severe abnormalities appearing in Crb2-deficient embryos at late-gastrulation. Our findings indicate that the primary defect in the mutant embryos is disturbed polarity of the epiblast cells at the primitive streak, which affects epithelial to mesenchymal transition (EMT) during gastrulation, resulting in impaired mesoderm and endoderm formation, and embryonic lethality by embryonic day 12.5. These findings therefore indicate a novel role for the Crumbs family of proteins.

Myo1e impairment results in actin reorganization, podocyte dysfunction, and proteinuria in zebrafish and cultured podocytes.

BACKGROUND: Podocytes serve as an important constituent of the glomerular filtration barrier. Recently, we and others identified Myo1e as a key molecular component of the podocyte cytoskeleton. RESULTS: Myo1e mRNA and protein was expressed in human and mouse kidney sections as determined by Northern blot and reverse transcriptase PCR, and its expression was more evident in podocytes by immunofluorescence. By specific knock-down of MYO1E in zebrafish, the injected larvae exhibited pericardial edema and pronephric cysts, consistent with the appearance of protein in condensed incubation supernate. Furthermore, specific inhibition of Myo1e expression in a conditionally immortalized podocyte cell line induced morphological changes, actin cytoskeleton rearrangement, and dysfunction in cell proliferation, migration, endocytosis, and adhesion with the glomerular basement membrane. CONCLUSIONS: Our results revealed that Myo1e is a key component contributing to the functional integrity of podocytes. Its impairment may cause actin cytoskeleton re-organization, alteration of cell shape, and membrane transport, and podocyte drop-out from the glomerular basement membrane, which might eventually lead to an impaired glomerular filtration barrier and proteinuria.

Effects of cobalt-60 gamma-radiation on the synthesis of adrenomedullin and endothelin in rat vascular smooth muscle cells.

We studied the effects of cobalt-60 Gamma-radiation on the gene expression and secretion of adrenomedullin (Adm) and endothelin (ET) in cultured rat vascular smooth muscle cells (VSMCs). Rat VSMCs cultured in Dulbecoo's modified Eagle's medium containing 10% FBS were radiated with cobalt-60 Gamma-radiation at doses of 1, 14, and 25 Gy, respectively. Then the mRNA of Adm and ET in VSMCs were detected by the reverse-transcriptative competitive polymerase chain reaction. Adm and ET levels in rat VSMCs were measured by radioimmunoassay. As compared with that of the control, the secretions of Adm in rat VSMCs radiated at doses of 14 and 25 Gy were increased by 270% (P < 0.05) and 233% (P < 0.05), respectively. The mRNA levels of Adm were increased by 82.4% (P < 0.01) and 101% (P <0.01), respectively. Meanwhile, the secretions of ET were decreased by 27.3% (P < 0.01) and 58.0% (P < 0.01) in VSMCs radiated at doses of 14 and 25 Gy, respectively. In parallel, the mRNA levels of ET were decreased by 47.1% (P < 0.01) and 40.2% (P < 0.01), respectively. Radiation at a dose of 1 Gy had no significant effect on Adm and ET at the gene and protein levels. As compared with the control, the Adm/ET ratios in VSMCs increased by 65% (P > 0.05), 409% (P < 0.01), and 693% (P < 0.01), respectively, with radiation at doses of 1,14 and 25 Gy, respectively. The balance of Adm/ET in VSMCs could be changed by cobalt-60 Gamma-radiation, which might play an important role in the use of radiotherapy for restenosis.