Na(+), K(+)-ATPase subunit composition in a human chondrocyte cell line; evidence for the presence of α1, α3, ß1, ß2 and ß3 isoforms.

Membrane transport systems participate in fundamental activities such as cell cycle control, proliferation, survival, volume regulation, pH maintenance and regulation of extracellular matrix synthesis. Multiple isoforms of Na(+), K(+)-ATPase are expressed in primary chondrocytes. Some of these isoforms have previously been reported to be expressed exclusively in electrically excitable cells (i.e., cardiomyocytes and neurons). Studying the distribution of Na(+), K(+)-ATPase isoforms in chondrocytes makes it possible to document the diversity of isozyme pairing and to clarify issues concerning Na(+), K(+)-ATPase isoform abundance and the physiological relevance of their expression. In this study, we investigated the expression of Na(+), K(+)-ATPase in a human chondrocyte cell line (C-20/A4) using a combination of immunological and biochemical techniques. A panel of well-characterized antibodies revealed abundant expression of the α1, ß1 and ß2 isoforms. Western blot analysis of plasma membranes confirmed the above findings. Na(+), K(+)-ATPase consists of multiple isozyme variants that endow chondrocytes with additional homeostatic control capabilities. In terms of Na(+), K(+)-ATPase expression, the C-20/A4 cell line is phenotypically similar to primary and in situ chondrocytes. However, unlike freshly isolated chondrocytes, C-20/A4 cells are an easily accessible and convenient in vitro model for the study of Na(+), K(+)-ATPase expression and regulation in chondrocytes.

Collaboration between PcG proteins and MLL fusions in Leukemogenesis: an emerging paradigm.

PcG and TrxG proteins mostly with opposite transcriptional activities play key roles in normal and malignant development. In this issue of Cancer Cell, Tan et al. report an unexpected collaboration between CBX8 and MLL-AF9 in leukemia, revealing a far more complicated functional crosstalk between these master epigenetic regulators in oncogenesis.

Apoptosis of cultured granulosa-lutein cells is reduced by insulin-like growth factor I and may correlate with embryo fragmentation and pregnancy rate.

OBJECTIVE: To correlate apoptosis of cultured human granulosa-lutein cells (GL cells) with the outcome of IVF (embryo fragmentation and pregnancy rate) and to study the effect of insulin and insulin-like growth factor I (IGF-I) on apoptosis. DESIGN: In vitro assays. SETTING: University laboratory and private IVF center. PATIENT(S): Eighty-one women undergoing IVF. INTERVENTION(S): Purified human GL cells from pooled follicles were cultured for 48 hours in serum-free media with or without insulin and IGF-I. Cumulus cells and mural GL cells were evaluated separately. MAIN OUTCOME MEASURE(S): Detection of apoptosis by using caspACE FITC-VAD-FMK, a fluorescent in situ marker for activated caspases; embryo fragmentation; and pregnancy. RESULT(S): Age younger than 38 years and successful pregnancy were associated with less apoptosis (33.0% +/- 17.2% vs. 43.2% +/- 18.0% and 30.2% +/- 14.0% vs. 40.4% +/- 19.5%, respectively). There was a linear correlation between embryo fragmentation and GL cell apoptosis. Insulin-like growth factor I decreased apoptosis in a dose-dependent fashion. A statistically significant effect (17% decrease) was reached at a dose of 10 nM. Insulin (10 nM) caused a small (8%) decrease in apoptosis, but this effect did not reach statistical significance. Cumulus cells consistently had <3% apoptosis. CONCLUSION(S): [1] Apoptosis of cultured GL cells may be associated with IVF outcome and ovarian reserve and [2] IGF-I decreases apoptosis of cultured GL cells.