Biomedical Engineering Reference
In-Depth Information
Burnett, &Mlodzik, 2005; Lu, Yan, & Adler, 2010; Wong et al., 2003 ), and
the evidence for feedback systems ( Tree et al., 2002 ) that are a key for the
functioning of the system. As has proved to be true for so much in
biology, the genes that function in PCP in flies have similar functions in a
wide range of animals (see Goodrich & Strutt, 2011; Wang & Nathans,
2007 ; other articles in this volume).
2. THE CELLULAR BASIS FOR PCP
Three types of adult structures have been the primary focus of exper-
iments on PCP in Drosophila ( Adler, 2002 ). The most important are the
cuticular hairs found over much of the flies body. The wing, which is flat
and where each cell elaborates a relatively long distally pointing hair,
has been the principal tissue for studies on hairs ( Fig. 1.1 )( Gubb &
Garcia-Bellido, 1982; Vinson & Adler, 1987; Wong & Adler, 1993 ),
although they have also been studied in depth on the abdomen ( Casal,
Lawrence, & Struhl, 2006 ).
2.1. Epidermal hairs and the fly wing
The frizzled ( fz ) pathway (also called the starry night ( stan ) pathway, Casal
et al., 2006 ) controls PCP by restricting the site of hair initiation to the distal
most part of wing cells ( Wong & Adler, 1993 )( Fig. 1.2 ). The hairs grow out
away from the distal cell periphery resulting in a distally pointing hair ( Wong
& Adler, 1993 ). Mutations in fz/stan pathway genes lead to hairs forming at
abnormal subcellular locations and having abnormal polarity ( Figs. 1.1 and
1.2 ). In this review, I will focus on the wing with an emphasis on the fz/stan
pathway. The simple cell biology and flat shape of the wing make it an ideal
tissue for studies on PCP, and the principles deduced from studying it have
for the most part proved to be conserved in other tissues in the fly and in
other organisms.
2.2. Sensory bristles
The cuticular surface of the fly is also decorated with many bristle sense
organs. On the dorsal thorax and abdomen, the bristle shaft points posteri-
orly and on appendages they point distally ( Adler, 2002 )( Fig. 1.3A and C ).
In other body regions (e.g., the head), bristles are locally aligned and show a
reproducible polarity. The fz pathway regulates bristle polarity by control-
ling the orientation of the spindle during the determinative cell divisions that
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