Abstract
NGFI-A (also known as EGR-1, zif/268, and Krox-24) is a zinc finger transcription factor induced in many cell types by a variety of growth and differentiation stimuli. To determine if NGFI-A plays a requisite role in these processes, we used homologous recombination to mutate both alleles of NGFI-A in embryonic stem (ES) cells and examined its effect on growth and differentiation. We find that ES cells lacking NGFI-A exhibit similar growth rates and serum-induced gene expression profiles compared to wild-type parental cells. They are capable of differentiating into neurons, cardiac myocytes, chondrocytes, and squamous epithelium. Chimeric mice were generated from targeted ES cells, and their progeny were crossed to produce homozygous mutant mice. Growth and histological analyses of mice lacking NGFI-A confirm the finding in ES cells that NGFI-A is not required for many of the processes associated with its expression and suggest that the function of NGFI-A is either more subtle in vivo or masked by redundant expression provided by other gene family members such as NGFI-C, Krox-20, or EGR3.
Highlights
We demonstrate that NGFI-A is not required for the growth and differentiation of embryonic stem (ES) cells
We have eliminated NGFI-A from ES cells by homologous recombination and have examined its effect on proliferative and differentiative processes associated with its expression
Our finding that ES cells proliferate normally without NGFI-A suggests either that NGFI-A has no role in ES cell proliferation, or that redundant mechanisms can compensate for NGFI-A function
Summary
This article must be hereby marked "advertisement" in accordance with 18 U.S.C. Section 1734 solely to indicate this fact. Differentiation paradigms such as embryonal carcinoma cells into myocytes or neurons, pre-osteoblasts into osteoblasts, and myelornonocytic precursors into macrophages [16,17,18,19]. To assess the importance ofNGFI-A in the variety of cellular processes associated with its induction, we used homologous recombination followed by culture in elevated G418 to inactivate both copies ofNGFI-A in embryonic stem (ES) cells. We demonstrate that NGFI-A is not required for the growth and differentiation of ES cells. We confirm and extend these findings by examining homozygous mutant mice derived from the targeted ES cells and find that mice lacking NGFI-A exhibit no overt defects in growth or differentiation
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