In order to investigate the function of nonmuscle myosin II-A, we created a nonmuscle myosin heavy chain II-A (NMHC II-A) null mouse by inserting the neomycin resistance cassette into the gene at exon 3. Previously, we have shown that ablation of nonmuscle myosin heavy chain II-B in mice results in abnormalities in the development of the heart and brain with the lethality occurring between E12 and the day of birth. The other organs of the B-/- mice appear normal, suggesting that NMHC II-A could substitute for II-B in these organs. In contrast to the NMHC II-B knockout, ablation of the NMHC II-A resulted in lethality at E7.5 or earlier, suggesting a role for NMHC II-A during gastrulation. Immunocytochemistry of wild type mice at E7.5 showed the presence of NMHC II-A in all cell layers. At this stage, however, NMHC II-B was absent from the visceral endoderm. NMHCII-A null mice are lacking or have a severely underdeveloped visceral endoderm suggesting that the absence of both isoforms of NMHC II contributed to the defect.Embryonic stem (ES) cells express both NMHC II-A and II-B. NMHC II-A-/- ES cells were generated by re-electroporation of NMHC II-A+/- cells followed by selection at increased concentrations of G418. NMHC II-A-/- ES cells which only express NMHC II-B appear to proliferate at a faster rate than NMHC II-A+/- or wild type cells and do not form embryonic stem cell colonies.

Agency
National Institute of Health (NIH)
Institute
National Heart, Lung, and Blood Institute (NHLBI)
Type
Intramural Research (Z01)
Project #
1Z01HL004218-10
Application #
6432702
Study Section
(LMC)
Project Start
Project End
Budget Start
Budget End
Support Year
10
Fiscal Year
2000
Total Cost
Indirect Cost
Name
U.S. National Heart Lung and Blood Inst
Department
Type
DUNS #
City
State
Country
United States
Zip Code
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