Cell nucleus
Cell nuclei contain most of the cell's genetic material, organized as multiple long linear DNA molecules in a complex with a large variety of proteins, such as histones, to form chromosomes. The genes within these chromosomes are the cell's nuclear genome and are structured in such a way to promote cell function. The nucleus maintains the integrity of genes and controls the activities of the cell by regulating gene expression—the nucleus is, therefore, the control center of the cell. The main structures making up the nucleus are the nuclear envelope, a double membrane that encloses the entire organelle and isolates its contents from the cellular cytoplasm, and the nuclear matrix (which includes the nuclear lamina), a network within the nucleus that adds mechanical support, much like the cytoskeleton, which supports the cell as a whole.
Zona limitans intrathalamica
Signaling from the ZLI cooperating with thalamic and prethalamic markers ensures the migration of post-mitotic (neural progenitor) cells to the mantle zone where the cells assemble into nuclei characteristic of the thalamus. These nuclei are the mechanism of the relay of information from the thalamus to the cortex. The thalamus itself is highly diverse, with each nucleus having distinct morphologies and physiologies according to the region of the brain to which it is connected. These differences are thought to originate in differential gene expression in the thalamus and prethalamus, which allows for a single structure with multiple different and separate functions once the two have merged and completed growth and differentiation. So a functional interplay between Shh from the ZLI and the bHLH factor Her6 (homolog to HES1) determines the neuronal identity within the thalamus: Her6 positive cells in the prethalamus and rostral thalamus differentiate into GABAergic inhibitory neurons, whereas her negative cells become glutamatergic relay neurons. Both cell types depend on Shh signal as trigger to initiate the developmental programme.