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Origin of OSS line
OSS cells are a sub-line of the fGS/OSS line derived from bam-mutant ovaries. The parental line contains both germ-line stem cells and ovarian somatic sheet cells; OSS contains only the somatic sheet cells.
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comments on growing this line
We have limited experience with this line, but we have found it to grow fairly easily if you follow the procedures we have posted. OSS requires a special medium (see Note below). To thaw the cells from a frozen ampoule, use the protocol described for ovarian lines in our protocol for thawing cells (click on the Protocols link to the left). The freshly-thawed cells form very tight clumps, from which they migrate onto the surface over a period of days. Cells adhere to the surface, but can be easily dislodged by blowing medium at the surface from a serological or Pasteur pipet. Once dislodged, they form tight clumps; we know of no simple way to determine the concentration of cells in a culture. We typically dilute the cells 3-fold when they reach a density about double that shown in the photograph on this page, approximately every 3 days.
Recently, we gained more experience of growing this line. We found it is hard to dislodge the cells from the surface of the T-flask without trypsinization. But, once the cells are in the plate, trypsinization is no longer necessary.
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Medium for OSS cells
OSS requires a special medium. A protocol for preparation of this medium is posted in the cell line protocols, accessible through the Protocols link to the left. We find it useful to filter-sterilize each bottle of medium, even though it is made by combining previously sterilized components, because without this extra sterilization step, the frequency of contaminated plates is higher for this line than for others. We suspect that this is a consequence of the high concentration of fly extract, made from flies growing in the presence of yeast, mold, and bacteria.
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Sex
Oss cells are female, by criteria of roX gene expression and Sxl splicing (Stoiber et al., 2016, G3, in press).
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Feedback from users
Frequent mould contamination problem. Every 2-3 months. Despite filter sterilization of all media (ASIFA AKHTAR lab,
MAX-PLANCK INSTITUTE OF IMMUNOBIOLOGY).