Zona limitans intrathalamica

The zona limitans intrathalamica (ZLI) is a lineage-restriction compartment and primary developmental boundary in the vertebrate forebrain (which is analogous to the human cerebrum) that serves as a signaling center and a restrictive border between the thalamus (also known as the dorsal thalamus) and the prethalamus (ventral thalamus).

Sonic hedgehog (shh) signaling from the ZLI is crucial in the development of the diencephalon, which develops into the thalamus, the pretectum, and the anterior tegmental structures. The ZLI together with the prethalamus and thalamus make up the mid-diencephalic territory (MDT).

Cell lineage restriction boundaries, across which replicating cells cannot migrate, were first discovered in invertebrates, where the expression of various Hox genes in each compartment confer the differentiation of observable segments in the adult body of Drosophila melanogaster. Analogous structures were discovered in the developing vertebrate brain. Rhombomeres, which extend down the embryo from the hindbrain, contain clear boundaries and each express various Hox genes that are necessary for differentiation of structures within the body. More anterior regions of the brain were examined in search of other cell lineage restriction boundaries, and multiple potential boundaries continue to be studied (see Developmental Boundaries).

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