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Genes that Control Limb Development – Musculoskeletal System Development

by John McLachlan, PhD
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    00:01 taking place from the ZPA. Indeed, now we’ve been able to identify the genes that are involved.

    00:05 And these are Hox genes, and in particular, Hox-D genes, and these are expressed in sequence across the limb. So, probing for the presence of these genes gives us this kind of pattern which looks very like our postulated gradient of different signals in the development of the limb. And we can confirm this by looking at our grafts of retinoic acid beads which then induce mirror image reduplication of the gene expression patterns, which the limb will interpret as a mirror image reduplication of the limb itself. So we can see that there are signals which are diffusible in the sense that they spread through the body and they can control things like the outgrowth of the limb and the pattern formation from top to bottom of the limb and it therefore seems very likely that the remainder of the musculoskeletal system is patterned by similar signals. We may ask how does a body know how to make an arm or a leg? There is a barcoding of gene expression patterns down the length of the embryo, which has a frontier on it. Again, there’s a gradient of Hox gene expression.

    01:16 If one was to graph an apical ectodermal ridge in the forward part, then you get an arm.

    01:23 If you graphed it in the lower part, you get a leg and if you graphed it at the frontier between the two, you get an unusual structure which is half arm half leg as it straddles the frontier between these parts of the body. So again, cells can interpret what they’re going to do in the light of their position within the embryo. Now, this might sound a


    About the Lecture

    The lecture Genes that Control Limb Development – Musculoskeletal System Development by John McLachlan, PhD is from the course System-Specific Embryology with John McLachlan.


    Author of lecture Genes that Control Limb Development – Musculoskeletal System Development

     John McLachlan, PhD

    John McLachlan, PhD


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