Cell-line misidentification and contamination with microorganisms, such as
mycoplasma, together with instability, both genetic and phenotypic, are among
the problems that continue to affect cell culture. Many of these problems are
avoidable with the necessary foresight, and these Guidelines have been prepared
to provide those new to the field and others engaged in teaching and instruction
with the information necessary to increase their awareness of the problems and
to enable them to deal with them effectively. The Guidelines cover areas such as
development, acquisition, authentication, cryopreservation, transfer of cell
lines between laboratories, microbial contamination, characterisation,
instability and misidentification. Advice is also given on complying with
current legal and ethical requirements when deriving cell lines from human and
animal tissues, the selection and maintenance of equipment and how to deal with
problems that may arise.
Fat is an atypical cadherin that controls both cell growth and planar polarity. Atrophin is a nuclear co-repressor that is also essential for planar polarity; however, it is not known what genes Atrophin controls in planar polarity, or how Atrophin activity is regulated during the establishment of planar polarity. We show that Atrophin binds to the cytoplasmic domain of Fat and that Atrophin mutants show strong genetic interactions with fat. We find that both Atrophin and fat clones in the eye have non-autonomous disruptions in planar polarity that are restricted to the polar border of clones and that there is rescue of planar polarity defects on the equatorial border of these clones.Both fat and Atrophin are required to control four-jointed expression. In addition our mosaic analysis demonstrates an enhanced requirement for Atrophin in the R3 photoreceptor. These data lead us to a model in which fat and Atrophin act twice in the determination of planar polarity in the eye: first in setting up positional information through the production of a planar polarity diffusible signal, and later in R3 fate determination.
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