Hox Gene AbdB controls left right asymmetry in Drosophila – Part I
At first glance, the left and right sides of our bodies are identical to one-another. However, internally, as we dig deeper, some of our visceral organs are displaced to one side. Our hearts are larger on the left than the right, brains also show significant differences and when one take a look at long coil of guts with appendix near one end, it generally folds one side or to the another – but most interesting aspect for biologists in the field is that how things so consistently folds over in the same direction in individual after individual.
Lot of work has gone and going on in this particular field of left right asymmetry and so far a decent understanding is available for the entire mechanism especially in vertebrates.
Nearly all visceral organs of the thorax and abdomen are Left-Right (LR) asymmetrical in their anatomy, placement and, in some cases, physiology. Bilateral symmetry appears mainly in structures such as the brain, nervous system, skin, hair, and nails, and in parts of the eye and ear – all of which arise from the outer germ layer of the embryo called as ectoderm and some structures, including the skeleton and skeletal muscles, tendons, glands, and reproductive organs, which develop from the mesoderm (middle germ layer). The heart, originating in the mesoderm, and the liver, stomach, pancreas, and intestines, which arise from endoderm (the inner germ layer) appear singly to one side of the midline.
Asymmetry plays a vital role in development and any abnormalities in LR asymmetry of internal organs can lead health defects in the individuals. Hence a complete understanding of LR asymmetry is important not only for basic science, but also for the biomedicine of a wide range of birth defects and human genetic syndromes.
Fruit fly, Drosophila melanogaster serves as a excellent model for LR studies and a prominent LR marker is the looping of the spermiduct around the hindgut, which originates from the 360 degrees clockwise or dextral rotation of the male genitalia to which it is connected.
Stephen Noselli’s lab in Nice , France, published some new findings related to role of Hox gene AbdB in LR asymmetry in recent issue of Developmental cell journal. Previous work in the lab of Stephen Noselli’s showed that dextral orientation of the organs depends on the activity of a single gene MyosinID (myoID), as upon mutation of Myosin ID forms a fully inverted LR axis.