Local stores of inhibitory neurons

The exact origin of GABAergic (γ-aminobutyric-acid-releasing) interneurons, which are responsible for control the firing of the principal human cortical neurons, has remained unclear. In rodents all interneurons originate from a subcortical area known as the ganglionic eminence. But in 6 June Nature, Kresimir Letinic and colleagues from Yale University School of Medicine, show that in humans most of the GABAergic interneurons arise locally, from the cortical ventricular zone/subventricular zone (Nature 2002, 417:645-649).

Letinic et al. used retroviral labeling in organotypic slice cultures of the embryonic human forebrain and found two types of GABAergic neurons. The first lineage represents 65% of neocortical interneurons in humans, and originates from Mash1-expressing progenitors of the neocortical ventricular and subventricular zone of the dorsal forebrain. The second lineage — characterized by the expression of Dlx1/2 but not Mash1 — forms around 35% of the GABAergic interneurons and originates from the...