Morphhologic changes in mouse EKLF and KLF2 double knockout 9 day embryo and yolk sac

Abstract

Krüppel‐like factors (KLFs) are a family of DNA‐binding transcription factors with 3 Cys2/His2 zinc fingers that regulate cell proliferation, differentiation, and development. EKLF (KLF1) and KLF2 have been implicated in primitive (embryonic) erythropoiesis. In this study, the morphology of 9 day yolk sac blood cells, blood vessels and epithelial cells from EKLF/KLF2 double knockout (KO) embryos were compared to single KO and wild type, using light and electron microscopy. Double KO yolk sacs had thickened mesothelial and endothelial intercellular spaces, pleiomorphic erythroid cells with abnormal cytoplasmic protrusions, and epithelial cell ingrowths, when compared to wildtype. Also, endothelial and mesothelial cells were bulbous and less squamous in the double KO yolk sac. There was a higher percentage of irregular erythroid and endothelial cells in double KO than in normal yolk sacs. Preliminary results suggest that in the double KO embryo, erythroid and endothelial cells of the dorsal aorta show abnormal shapes consistent with the yolk sac. These changes in both endodermally and mesodermally derived cells, absent in single KO embryos, suggest that one KLF may compensate for the other. While KLF2 is present in most cell types, EKLF is expressed only in erythroid cells. This points to a possible problem in cell‐cell communication, stemming from the loss of these two KLF genes. Support: NIH DK62154