Their specific spatiotemporal expressions further support their role in developmental processes and diseases. In particular, long non-coding RNAs (lncRNAs) have gained widespread attention in recent years due to their important role in gene regulation. The Drosophila imaginal disc has been an excellent model for the study of developmental gene regulation. Finally, we show that this control mechanism fails when perturbations in proliferation rates affect both wing-committed and recruitable cells, providing an experimentally testable hypothesis of our model. When this observation is incorporated in our model, we show that the duration of cell recruitment robustly determines a final wing size even when cell proliferation rates of wing-committed cells are perturbed. A time-course experiment shows that vestigial-expressing cells increase exponentially while recruitment takes place, but slows down when recruitable cells start to vanish, suggesting that undifferentiated cells may be driving proliferation of wing-committed cells. Using a mathematical model, we show that in the developing wing of the fruit fly, Drosophila melanogaster, variations in proliferation rates of wing-committed cells are inversely proportional to the duration of cell recruitment, a differentiation process in which a population of undifferentiated cells adopt the wing fate by expressing the selector gene, vestigial. How organs robustly control their final size despite perturbations in cell proliferation rates throughout development is a long-standing question in biology. As a result, even small variations in proliferation rates, when integrated over a relatively long developmental time, will lead to large differences in size. Organ growth driven by cell proliferation is an exponential process. Parts of the figure were inspired by (Held 2005), where additional details are described For instance, the wing discs contribute both to the wings and the notum in the adult fly, which is not represented here for simplicity. Note that some portions of the head and thorax, including the notum, also originate from imaginal discs. The epidermis of adult structures like the head, thorax, and appendages come from 9 pairs of bilateral discs (here, only one of each pair is shown in the larva), and genitals derive from a middle disc (19 discs in total): 1, clypeolabral 2, eye-antennal 3, labial 4, humeral (or prothoracic) 5, first leg 6, second leg 7, third leg 8, wing 9, haltere 10, genital. T1 to T3 represent thoracic segments, and A1 to A8 correspond to abdominal segments. Axes orientation is indicated by the perpendicular arrows (A anterior, P posterior, D dorsal, V ventral). The location of imaginal tissue primordia is represented at the cellular blastoderm stage (top), with corresponding numbering in larval (middle) and adult (bottom) stages. Imaginal discs, their embryonic primordia, and adult cuticular products.
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