Question

If I conditionally knockout FGF8 in the somatic and lateral plate mesoderm of a mouse during the onset of limb bud formation what would the resulting phenotype look like? What about if I knocked out Shh instead?

Answer 1

Fibroblast growth factor is crucial transcription factor, which regulate the limb formation in mouse and particularly controlled by Fgf8 gene. If you make conditional gene knock out (KO) phenotype through deletion of single exon in the gene Fgf8 as complete gene knockout may not be viable in the progeny. The Fgf8 KO mouse will exhibit no cell migration during the embryonic development that is required for expression of other gene Fgf4 and subsequently affect formation of primitive streak region in the embryo.

Hedgehog signaling proteins are also important for the embryonic development of organisms from invertebrate to vertebrate and sonic hedgehog (shh) proteins is one of the three important proteins in this signaling. This signaling molecule (shh) is important for bud formation in the limbs and pattern formation. If you create conditional knock out in shh instead of Fgf8 gene in mouse, then abnormal digit formation (less number of digits) may be observed in the mouse as compared to normal mouse and also abnormal thymus cells (thymocytes) may be seen in KO mouse also.