Biomedical subjects

Gabrielle Kardon

Publications and source records attributed to Gabrielle Kardon.

4 recordsLinked to original sources

PubMed2016

Molecular shifts in limb identity underlie development of feathered feet in two domestic avian species.

Birds display remarkable diversity in the distribution and morphology of scales and feathers on their feet, yet the genetic and developmental mechanisms governing this diversity remain unknown. Domestic pigeons have striking variation in foot feathering within a single species, providing a tractable model to investigate the molecular basis of skin appendage differences. We found that feathered feet in pigeons result from a partial transformation from hindlimb to forelimb identity mediated by cis-regulatory changes in the genes encoding the hindlimb-specific transcription factor Pitx1 and forelimb-specific transcription factor Tbx5. We also found that ectopic expression of Tbx5 is associated with foot feathers in chickens, suggesting similar molecular pathways underlie phenotypic convergence between these two species. These results show how changes in expression of regional patterning genes can generate localized changes in organ fate and morphology, and provide viable molecular mechanisms for diversity in hindlimb scale and feather distribution.

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PubMed2006

Somitic origin of limb muscle satellite and side population cells.

Repair of mature skeletal muscle is mediated by adult muscle progenitors. Satellite cells have long been recognized as playing a major role in muscle repair, whereas side population (SP) cells have more recently been identified as contributing to this process. The developmental source of these two progenitor populations has been considerably debated. We explicitly tested and quantified the contribution of embryonic somitic cells to these progenitor populations. Chick somitic cells were labeled by using replication-defective retroviruses or quail/chick chimeras, and mouse cells were labeled by crossing somite-specific, Pax3-derived Cre driver lines with a Cre-dependent reporter line. We show that the majority of, if not all, limb muscle satellite cells arise from cells expressing Pax3 specifically in the hypaxial somite and their migratory derivatives. We also find that a significant number of, but not all, limb muscle SP cells are derived from the hypaxial somite. Notably, the heterogeneity in the developmental origin of SP cells is reflected in their functional heterogeneity; somitically derived SP cells are intrinsically more myogenic than nonsomitically derived ones. Thus, we show that the somites, which supply embryonic and fetal myoblasts, are also an important source of highly myogenic adult muscle progenitors.

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PubMed2003

A Tcf4-positive mesodermal population provides a prepattern for vertebrate limb muscle patterning.

Nai;ve myogenic cells migrate from the somites into the developing vertebrate limb, where they simultaneously differentiate into myotubes and form distinct anatomical muscles. Limb signals have been hypothesized to direct the pattern of muscles formed, but the molecular nature of these signals and the identity of the cells that produce them have remained unclear. We have identified a population of lateral plate-derived limb mesodermal cells in both chick and mouse that expresses the transcription factor Tcf4 in a muscle-specific pattern independently of the muscle cells themselves. Functional experiments in the chick demonstrate that TCF4 and the Wnt-beta-catenin pathway in these limb mesodermal cells are critical for muscle patterning. We propose that Tcf4-expressing cells establish a prepattern in the limb mesoderm that determines the sites of myogenic differentiation and thus establishes the basic pattern of limb muscles.

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PubMed2002

Local extrinsic signals determine muscle and endothelial cell fate and patterning in the vertebrate limb.

Both the muscle and endothelium of the vertebrate limb derive from somites. We have used replication-defective retroviral vectors to analyze the lineage relationships of these somite-derived cells in the chick. We find that myogenic precursors in the somites or proximal limb are not committed to forming slow or fast muscle fibers, particular anatomical muscles, or muscles within specific proximal/distal or dorsal/ventral limb regions. Somitic endothelial precursors are uncommitted to forming endothelium in particular proximal/distal or dorsal/ventral limb regions. Surprisingly, we also find that myogenic and endothelial cells are derived from a common somitic precursor. Thus, local extrinsic signals are critical for determining muscle and endothelial patterning as well as cell fate in the limb.

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