BMP-4 inhibits neural differentiation of murine embryonic stem cells

Members of the transforming growth factor-beta superfamily, including bone morphogenetic protein 4 (BMP-4), have been implicated as regulators of neur onal and glial differentiation. To test for a possible role of BMP-1 in ear ly mammalian neural specification, we examined its effect on neurogenesis i n aggregate cultures of mouse embryonic stem (ES) cells. Compared to contro l aggregates, in which up to 20% of the cells acquired immunoreactivity for the neuron-specific antibody TuJ1, aggregates maintained for 8 days in ser um-free medium containing BMP-4 generated 5- to Ill-fold fewer neurons. The action of BMP-4 was dose dependent and restricted to the fifth through eig hth day in suspension. In addition to the reduction in neurons, we observed that ES cell cultures exposed to BMP-4 contained fewer cells that were imm unoreactive for glial fibrillary acidic protein or the HNK-1 neural antigen , Furthermore, under phase contrast, cultures prepared from BMP-4-treated a ggregates contained a significant proportion of nonneuronal cells with a ch aracteristic Bat, elongated morphology. These cells were immunoreactive for antibodies to the intermediate filament protein vimentin; they were rare o r absent in control cultures. Treatment with BMP-4 enhanced the expression of the early mesodermal genes brachyury and tbx6 but had relatively little effect on total cell number or cell death. Coapplication of the BMP-4 antag onist noggin counteracted the effect of exogenous BMP-4, but noggin alone h ad no effect on neuralization in either the absence or presence of retinoid s, Collectively, our results suggest that BMP-4 can overcome the neuralizin g action of retinoic acid to enhance mesodermal differentiation of murine E S cells. (C) 1999 John Wiley gr Sons, Inc. J Neurobiol 40: 271-287, 1999.