GDF11 Flox Mouse Line

Brief Overview
JHU researchers generated the GDF11 flox mouse line by inserting a loxP site upstream of exon 2 and a floxed neo cassette downstream of exon 3. Cre mediated recombination was then used to remove the neo cassette leaving exons 2 and 3 floxed (Molecular Image Detail).
 
 
Detailed Technology Overview
Myostatin (Mstn) and growth/differentiation factor 11 (Gdf11) play important roles in growth and differentiation. Mstn is predominantly expressed in developing and adult skeletal muscle, while Gdf11 allows differentiation between anterior and posterior (A/P) axial mesoderm identity. In a study to determine whether myostatin and Gdf11 are functionally redundant with respect to control of muscle mass, GDF11 flox mice were generated since the increase in muscle mass in Mstn-/- mice is not present at birth, and GDF11-/- and Mstn-/- GDF11-/- mice die within 24 hours of birth, precluding the direct comparison of the skeletal muscle phenotype. 
 
JHU researchers generated a targeting construct containing a conditional deletion allele of the Gdf11 gene by inserting loxP recombination sites into intron 1 and flanking a neo gene downstream of the Gdf11 3' UTR (Gdf11flox-neo). Following homologous recombination in embryonic stem (ES) cells and injection of the targeted cells into blastocysts, chimeric mice were obtained that transmitted the Gdf11flox-neo allele through the germline. Mice carrying the Gdf11flox-neo allele were then crossed to EIIa-Cre transgenic mice to generate Gdf11flox/+ mice carrying one upstream and one downstream loxP site after removal of the neo gene.
 
Recombination at the remaining loxP sites delete exons 2 and 3 (Gdf112–3), making a functional null by removing the biologically-active carboxy-terminal domain. JHU researchers crossed double heterozygous mice (Mstn +/- Gdf11+/-) to produce Mstn-/- Gdf11-/- and compared the thoracic and lumbar vertebras to examine skeletal development. It was observed that without Mstn, there was an increase in severity of the Gdf11 null phenotype throughout the axis. This demonstrated the myostatin and Gdf11 exhibit similar roles and either one could be addressed in skeletal development. To prove the mystatin effect on muscle mass, Mstn+/+ mice and Mstn-/- mice were examined. Mstn-/- mice had four times the muscle mass than Mstn +/+. Researchers then studied Gdf11 mutations and its effect on muscle mass. Between six different mutations in Gdf11, there was no difference in body weight or muscle mass. Based on the results, myostatin and Gdf11 have redundant functions in regulating skeletal development, and patterning, but not muscle size. This suggests that the either Mstn or Gdf11 can be targeted for skeletal development diseases, however, only Mstn can be used for muscle wasting.
 
Stage of Development:
Fully Developed Mouse Model
 
Publications:
BMC Dev Biol. 2009; 9: 24
 

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