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Ciona Brachyury proximal and distal enhancers have different FGF dose-response relationships.

ABSTRACT: Many genes are regulated by two or more enhancers that drive similar expression patterns. Evolutionary theory suggests that these seemingly redundant enhancers must have functionally important differences. In the simple ascidian chordate Ciona, the transcription factor Brachyury is induced exclusively in the presumptive notochord downstream of lineage specific regulators and FGF-responsive Ets family transcription factors. Here we exploit the ability to finely titrate FGF signaling activity via the MAPK pathway using the MEK inhibitor U0126 to quantify the dependence of transcription driven by different Brachyury reporter constructs on this direct upstream regulator. We find that the more powerful promoter-adjacent proximal enhancer and a weaker distal enhancer have fundamentally different dose-response relationships to MAPK inhibition. The Distal enhancer is more sensitive to MAPK inhibition but shows a less cooperative response, whereas the Proximal enhancer is less sensitive and more cooperative. A longer construct containing both enhancers has a complex dose-response curve that supports the idea that the proximal and distal enhancers are moderately super-additive. We show that the overall expression loss from intermediate doses of U0126 is not only a function of the fraction of cells expressing these reporters, but also involves graded decreases in expression at the single-cell level. Expression of the endogenous gene shows a comparable dose-response relationship to the full length reporter, and we find that different notochord founder cells are differentially sensitive to MAPK inhibition. Together, these results indicate that although the two Brachyury enhancers have qualitatively similar expression patterns, they respond to FGF in quantitatively different ways and act together to drive high levels of Brachyury expression with a characteristic input/output relationship. This indicates that they are fundamentally not equivalent genetic elements.

SUBMITTER: Harder MJ

PROVIDER: S-EPMC7846015 | biostudies-literature | 2021 Jan

REPOSITORIES: biostudies-literature

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Ciona Brachyury proximal and distal enhancers have different FGF dose-response relationships.

Harder Matthew J MJ Hix Julie J Reeves Wendy M WM Veeman Michael T MT

PLoS genetics 20210119 1

Many genes are regulated by two or more enhancers that drive similar expression patterns. Evolutionary theory suggests that these seemingly redundant enhancers must have functionally important differences. In the simple ascidian chordate Ciona, the transcription factor Brachyury is induced exclusively in the presumptive notochord downstream of lineage specific regulators and FGF-responsive Ets family transcription factors. Here we exploit the ability to finely titrate FGF signaling activity via ...[more]

PMID: 33465083

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Project description:High tibial osteotomy is a common procedure to address unicompartment knee osteoarthritis and other conditions. Regarding the specific surgical methods, medial open wedge osteotomy and lateral close wedge osteotomy are the most used. Both methods have a common disadvantage in that they are not so suitable to correct a severe deformity. Thus, we would like to introduce an anterior proximal-to-posterior distal oblique proximal tibial osteotomy technique, which is especially suitable to correct severe tibial deformity. The most critical point of this technique is to create an osteotomy plane from the most proximal posterior site of the tibial tubercle posteriorly and distally to the posterior cortex of the tibia, with each horizontal osteotomy maneuver in the coronal plane. Combined fibular osteotomy is always needed, and better results can be obtained when it is combined with arthroscopic debridement of the knee. We consider the introduction of this technique will provide a useful option when tibial osteotomy is needed to preserve the knee, especially for a great deformity correction. Technique Video Video 1 Anterior proximal-to-posterior distal oblique proximal tibial osteotomy. This procedure is performed in the right knee. Arthroscopy is performed to confirm the osteoarthritis status of the medial compartment and the healthier status of the lateral compartment. Debridement and other indicated arthroscopic procedures are performed. A K-wire is drilled in the coronal plane from the medial to the lateral side of the tibia at a level approximately 1 cm distal to the joint line, parallels the joint line as far as possible, and is used as a proximal reference wire. Another K-wire is drilled into the tibia also in the coronal plane at a level in the distal one third of the leg and used as a distal reference wire. The angle between the 2 reference wires is controlled being equal to the to-be-corrected angle of the tibia as far as possible. A longitudinal incision is made over the midline of the medial surface of the tibia. The pes anserinus is peeled off from its tibial insertion. A K-wire is placed at the most proximal and posterior site of the tibial tubercle and an osteotomy line is marked posterodistally to the posteromedial ridge of the tibia with 30° angulation to the tibial axis. The posterior osteofascial compartments are opened at the distal end of the osteotomy line. A 2.5-mm K-wire is used to drill through the medial tibial cortex along the osteotomy line to make a line of holes with approximately 5 mm distance between the neighboring holes. An osteotome is used to cut the bone and connect the holes along the osteotomy line at the medial side of the tibia. The lateral tibial cortex is drilled through the medial tibial fissure with each drilling maneuver along the coronal plane, to create a line of holes on the lateral side of the tibia. The osteotome is put into the fissure at the medial side of the tibia to connect the holes on the lateral side of the tibia to create an osteotomy plane. The distal posterior tibial cortex is cut along the osteotomy plane. A K-wire is drilled perpendicular to the coronal plane through the middle of the osteotomy plane. A fibula osteotomy is performed at its middle point with a wire saw. Valgus stress is applied to correct the varus deformity of the tibia till the 2 reference wires parallel to each other. Two additional K-wires are placed across the osteotomy plane for temporary fixation of the fracture. A tibial condyle plate is placed at the medial side of the tibia. Four self-locking screws are placed in respectively at the proximal and distal segments of the tibia for fracture fixation. The K wires for temporary fixation and correction reference are removed. A suction drainage tube is placed to the osteotomy site. The wounds are closed.

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Ciona Brachyury proximal and distal enhancers have different FGF dose-response relationships.

Publications

Ciona Brachyury proximal and distal enhancers have different FGF dose-response relationships.

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