Incorporation of mouse neural progenitors transplanted into the rat embryonic forebrain is developmentally regulated and dependent on regional and adhesive properties.

During development, telencephalic neural progenitors acquire positional specification and give rise to distinct structures such as the striatum and cortex. Here, we examine, in vivo, the influence of developmental stage, cell-surface molecules and regional differences along the dorso-ventral and antero-posterior axes on the selective incorporation of neural progenitors derived from different regions of the developing brain, utilizing a cross-species in utero transplantation paradigm. Striatal progenitors derived from the embryonic day (E) 12-14 mouse lateral ganglionic eminence (LGE) were observed consistently to incorporate into the developing striatum as early as 24-48 h following intraventricular injection into the E15-17 rat host. By removing cell-surface molecules from the LGE progenitors, the pattern of incorporation was remarkably different with no preferential striatal incorporation. Cortical progenitors with intact cell-surface molecules, by contrast, displayed little telencephalic (including striatal) incorporation as compared with precursors from the LGE. However, both progenitors from cortex and LGE incorporated widely into diencephalic and mesencephalic structures. The capacity for integration of precursors derived from the LGE and cortex gradually decreased during development of the host and was minimal in the postnatal day (P) 1 host. Unlike the telencephalic precursors, the vast majority of progenitors derived from the midbrain and cerebellar primordium (with cell-surface molecules intact) incorporated into diencephalic and midbrain nuclei with only a few cells observed in the telencephalon. These results demonstrate that incorporation of neural progenitors across the ventricular wall in the embryonic host is strictly developmentally regulated, dependent on their position along the antero-posterior axes and in the case of progenitors from the LGE is mediated by cell-surface molecules expressed on the transplanted cells.

Region-specific migration of embryonic glia grafted to the neonatal brain.

Cell fate determination and region-specific migration among neurons from the developing brain have been widely studied. Because similar attributes have been mostly unexplored in reference to glia, the present study has characterized the migratory responses of glia from diverse regions of the embryonic mouse brain after their transplantation to the brains of early postnatal (still developing) rats. Through the use of the mouse-specific, glial-specific marker M2, immunocytochemical processing of host tissues three to four weeks after transplantation revealed notable difference in the migratory patterns of phylogenetically diverse populations of glia. While glia from the ventral mesencephalon, cerebral cortex, and cerebellar neuroepithelium all showed a similar affinity for the nigropallidal tract after grafting to the internal capsule, only ventral mesencephalon-derived glia showed restricted migration toward and into the substantia nigra after transplantation to the thalamus or pontine tegmentum. These results suggest the presence of a highly favourable substrate for glial migration along developing fibre tracts, but, more importantly, indicates the potential for certain glia to respond to particular (region-specific) distal cues within the developing brain.

Specific nitrogen-15 labelling of leucine residues in human growth hormone.

Biosynthetic human growth hormone (hGH) specifically 15N labelled in the leucine residues has been obtained by recombinant DNA technology, using 15N-labelled leucine and an E. coli strain that requires leucine. It is shown that, despite the possibility of minor transaminase activity, the labelling on the whole is specific, and that the two-dimensional 1H-15N correlation NMR spectra of hGH can be greatly simplified by this methodology.