In current work, we are studying the role of BMP signaling as effectors of normal programmed cell death that occurs in mesenchymal interdigit cells, thus removing them and sculpting the final digit pattern in animals that are born without webbed limbs. In previous work produced genetic evidence for a novel model in which the surface ectoderm must receive a BMP signal, resulting in down regulation of Fgfs which in turn induces apoptosis of the underlying mesenchyme. Thus we demonstrated that BMPs control programmed cell death indirectly, by regulating FGF signaling. However, it is important to emphasize that this insight does not exclude a direct role for BMP signaling in controlling cell death in the developing limb. Therefore we are extended these studies by studying the role of BMP and FGF signaling in various aspects of limb development using mouse lines that express Cre in specific region of the developing limb. For example the only way to test the hypothesis that BMPs act as direct effectors of cell death is to inactivate BMPs receptors only in the lineage that undergoes cells death, without affecting FGF expression in nearby cells. We have achieved this using new Cre lines that allow Cre-mediated gene inactivation in these lineages. With these lines are asking: are BMPs are direct effectors of normal programmed cell death? If not, how is programmed cell death controlled? If so, how do BMPs achieve this endpont? In a serendipitous discovery, we have found that removal of a BMP signal to the limb bud interdigit zone rescues the requirement for a BMP signal to the digit region of the developing limb. Our efforts to understand this rescue may lead to a fundamental understanding of patterning in the developing limb. In another study, we have uncovered an important node of signaling between FGFs and BMP that is essential for normal development of the limb skeleton. Our previous work, cited above, demonstrates that specific FGFs, secreted from a distal structure in the limb bud, regulate the normal outgrowth and patterning of the limb. In current work, we are generating genetic evidence that BMP signaling to the progenitor population of the skeletal elements regulates this FGF signal by controlling the expression of an FGF antagonist. This linking of the two signaling pathways is not only a unique insight into how the limb is patterned but may provide a model for how the two pathways interact in other developmental contexts or during cancer.

Agency
National Institute of Health (NIH)
Institute
National Cancer Institute (NCI)
Type
Investigator-Initiated Intramural Research Projects (ZIA)
Project #
1ZIABC010518-13
Application #
9153593
Study Section
Project Start
Project End
Budget Start
Budget End
Support Year
13
Fiscal Year
2015
Total Cost
Indirect Cost
Name
Basic Sciences
Department
Type
DUNS #
City
State
Country
Zip Code
Kaltcheva, Maria M; Lewandoski, Mark (2016) Evolution: Enhanced Footing for Snake Limb Development. Curr Biol 26:R1237-R1240
Hung, Irene H; Schoenwolf, Gary C; Lewandoski, Mark et al. (2016) A combined series of Fgf9 and Fgf18 mutant alleles identifies unique and redundant roles in skeletal development. Dev Biol 411:72-84
Kaltcheva, Maria M; Anderson, Matthew J; Harfe, Brian D et al. (2016) BMPs are direct triggers of interdigital programmed cell death. Dev Biol 411:266-76
Mackem, Susan; Lewandoski, Mark (2011) Development. Limb cells don't tell time. Science 332:1038-9
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Zhang, Zhen; O'Rourke, Jason R; McManus, Michael T et al. (2011) The microRNA-processing enzyme Dicer is dispensable for somite segmentation but essential for limb bud positioning. Dev Biol 351:254-65
Lewandoski, Mark; Mackem, Susan (2011) Developmental biology: extending the limb and body with vectors and scalars. Curr Biol 21:R34-6
Mackem, Susan; Lewandoski, Mark (2009) Limb development takes a measured step toward systems analysis. Sci Signal 2:pe33
Tzchori, Itai; Day, Timothy F; Carolan, Peter J et al. (2009) LIM homeobox transcription factors integrate signaling events that control three-dimensional limb patterning and growth. Development 136:1375-85

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