Persistent expression of BMP-4 in embryonic chick adrenal cortical cells and its role in chromaffin cell development
- Equal contributors
1 Neuroanatomy, Interdisciplinary Center for Neurosciences (IZN), University of Heidelberg, INF 307, D-69120 Heidelberg, Germany
2 Max-Planck Institute for Brain Research, Deutschordenstr. 46, D-60528 Frankfurt, Germany
3 Department of Anatomy and Cell Biology, Hebrew University of Jerusalem, Hadassah Medical School, Jerusalem 91120, Israel
Neural Development 2008, 3:28 doi:10.1186/1749-8104-3-28Published: 22 October 2008
Adrenal chromaffin cells and sympathetic neurons both originate from the neural crest, yet signals that trigger chromaffin development remain elusive. Bone morphogenetic proteins (BMPs) emanating from the dorsal aorta are important signals for the induction of a sympathoadrenal catecholaminergic cell fate.
We report here that BMP-4 is also expressed by adrenal cortical cells throughout chick embryonic development, suggesting a putative role in chromaffin cell development. Moreover, bone morphogenetic protein receptor IA is expressed by both cortical and chromaffin cells. Inhibiting BMP-4 with noggin prevents the increase in the number of tyrosine hydroxylase positive cells in adrenal explants without affecting cell proliferation. Hence, adrenal BMP-4 is likely to induce tyrosine hydroxylase in sympathoadrenal progenitors. To investigate whether persistent BMP-4 exposure is able to induce chromaffin traits in sympathetic ganglia, we locally grafted BMP-4 overexpressing cells next to sympathetic ganglia. Embryonic day 8 chick sympathetic ganglia, in addition to principal neurons, contain about 25% chromaffin-like cells. Ectopic BMP-4 did not increase this proportion, yet numbers and sizes of 'chromaffin' granules were significantly increased.
BMP-4 may serve to promote specific chromaffin traits, but is not sufficient to convert sympathetic neurons into a chromaffin phenotype.