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Genes controlling cellular polarity in Drosophila
1University of Cambridge, Department of Genetics, UK.
Abstract:
The control of cellular polarity is one of the least understood aspects of development. Genes have been identified in Drosophila that affect the polarity of embryonic cells in all three axes, apical-basal, proximodistal and dorsoventral. Mutations that affect adult polarity are also known and mutant flies show several types of pattern alteration, including rotations and mirror-image duplications. Imaginal discs are much greater in size, however, than the embryo, and adult structures contain very large numbers of cells, many of which are not visibly differentiated with respect to their immediate neighbours. In regions where neighbouring cells are similar to each other, the imaginal polarity mutants alter the orientation of bristles and hairs, but do not change cellular fate. Other regions, such as the tarsal segments of the legs, the ommatidia of the eye and the bracketed bristle sockets on the tibia, behave as discrete fields. Within these fields, fine-scale mirror-image reversals and pattern duplications are observed, analogous to those caused by the embryonic segment polarity mutants. Thus, the polarised transmission of information can affect either orientation or fate depending on whether cells are differentiated from their immediate neighbours. Cellular polarity will be critically dependent on both the internal cytoskeletal architecture and the spatial organisation of signal transduction molecules within the cell membrane.
Insights
Cellular polarity, crucial for development, influences cell orientation and fate in Drosophila. Understanding this process involves cytoskeletal architecture and cell membrane signaling.
Area of Science:
- Developmental Biology
- Genetics
- Cell Biology
Background:
- Cellular polarity is a fundamental yet poorly understood aspect of biological development.
- Genes controlling embryonic polarity across three axes (apical-basal, proximodistal, dorsoventral) have been identified in Drosophila.
- Mutations affecting adult polarity in Drosophila lead to pattern alterations like rotations and mirror-image duplications.
Purpose of the Study:
- To investigate how cellular polarity is controlled in Drosophila development.
- To understand the mechanisms by which polarity influences cell fate and pattern formation in adult structures.
- To explore the relationship between cell differentiation and polarity signaling.
Main Methods:
- Analysis of mutations affecting polarity in Drosophila embryos and adult structures.
- Examination of imaginal discs and specific adult fields (tarsal segments, ommatidia, bristle sockets).
- Observation of pattern alterations, including rotations, mirror-image duplications, and changes in bristle/hair orientation.
Main Results:
- In regions with similar neighboring cells, imaginal polarity mutants alter bristle and hair orientation but not cell fate.
- Specific adult fields exhibit fine-scale mirror-image reversals and pattern duplications, similar to embryonic segment polarity mutants.
- Polarity control impacts cell orientation or fate based on cell differentiation relative to neighbors.
Conclusions:
- Cellular polarity's influence on cell fate versus orientation depends on cell differentiation status.
- The control of cellular polarity is intrinsically linked to internal cytoskeletal organization.
- Spatial organization of signal transduction molecules within the cell membrane is critical for cellular polarity.