The striatal complex of basal ganglia comprises two functionally distinct districts. The dorsal district controls motor and cognitive functions. The ventral district regulates the limbic function of motivation, reward, and emotion. The dorsoventral parcellation of the striatum also is of clinical importance as differential striatal pathophysiologies occur in Huntington’s disease, Parkinson’s disease, and drug addiction disorders. Despite these striking neurobiologic contrasts, it is largely unknown how the dorsal and ventral divisions of the striatum are set up. Here, we demonstrate that interactions between the two key transcription factors Nolz-1 and Dlx1/2 control the migratory paths of striatal neurons to the dorsal or ventral striatum. Moreover, these same transcription factors control the cell identity of striatal projection neurons in both the dorsal and the ventral striata including the D1-direct and D2-indirect pathways. We show that Nolz-1, through the I12b enhancer, represses Dlx1/2, allowing normal migration of striatal neurons to dorsal and ventral locations. We demonstrate that deletion, up-regulation, and down-regulation of Nolz-1 and Dlx1/2 can produce a striatal phenotype characterized by a withered dorsal striatum and an enlarged ventral striatum and that we can rescue this phenotype by manipulating the interactions between Nolz-1 and Dlx1/2 transcription factors. Our study indicates that the two-tier system of striatal complex is built by coupling of cell-type identity and migration and suggests that the fundamental basis for divisions of the striatum known to be differentially vulnerable at maturity is already encoded by the time embryonic striatal neurons begin their migrations into developing striata.
GABAergic interneurons play an essential role in modulating cortical networks. The progenitor domains of cortical interneurons are localized in developing ventral forebrain, including the medial ganglionic eminence (MGE), caudal ganglionic eminence (CGE), preoptic area (POA) and preoptic hypothalamic border domain (POH). Here, we characterized the expression pattern of Zswim5, an MGE-enriched gene in the mouse forebrain. At E11.5 to E13.5, prominent Zswim5 expression was detected in the subventricular zone (SVZ) of MGE, CGE, POA and POH of ventral telencephalon in which progenitors of cortical interneurons resided. At E15.5 and E17.5, Zswim5 remained detectable in the SVZ of pallidal primordium (MGE). Zswim5 mRNA was markedly decreased after birth and was absent in the adult forebrain. Interestingly, Zswim5 expression pattern resembled the tangential migration pathways of cortical interneurons. Zswim5-positive cells in the MGE appeared to migrate from the MGE through the SVZ of LGE to overlying neocortex. Indeed, Zswim5 was co-localized with Nkx2.1 and Lhx6, markers of progenitos and migratory cortical interneurons. Double labeling showed that Mash1/Ascl1-positive cells did not express Zswim5. Zswim5 expressing cells showed none or at most low levels of Ki67 but co-expressed Tuj1 in the SVZ of MGE. These results suggest that Zswim5 is immediately upregulated as progenitors exiting cell cycle to become postmitotic. Given that recent studies have elucidated that the cell fate of cortical interneurons is determined shortly after postmitotic, the timing of Zswim5 expression in early postmitotic cortical interneurons suggests a potential role of Zswim5 in regulation of neurogenesis and tangential migration of cortical interneurons. Propagation of neuronal information in neural networks is modulated by the balance between excitatory and inhibitory signals. Abnormalities in excitatory/inhibitory (E/I) balance of synaptic activity have been well documented in neurodevelopmental disorders such as autism and schizophrenia (Ramamoorthi and Lin, 2011; Nelson and Valakh, 2015; Canitano and Pallagrosi, 2017; Sohal and Rubenstein, 2019). A large diversity of cortical interneurons with distinct morphology, connectivity, and physiological activity serves to regulate synaptic E/I balance of cortical projection neurons. Understanding the developmental roots of GABAergic interneurons should provide important information to the pathophysiology of the diseases associated with E/I imbalance.GABAergic interneurons in the pallium of telencephalon are well known to be developmentally derived from the subpallium of the telencephalon (Marin and Rubenstein, 2001;Marín, 2015;Bandler et al., 2017;Hu et al., 2017;Lim et al., 2018). In the ventral part of developing mammalian telencephalon (subpallium), there are three structural elevations, the lateral ganglionic eminence (LGE), medial ganglionic eminence (MGE) and the caudal ganglionic eminence (CGE). These three ganglionic eminences consist of heterogeneous progenitor populations that give ri...
The division of the striatum into dorsal and ventral districts is of central clinical importance. The dorsal striatum is differentially affected in Huntington's disease, dopamine in the ventral striatum is differentially spared in Parkinson's disease, and human brain imaging studies implicate the ventral striatum in addictive disorders. If fits that the dorsal striatum contains the cells of origin of the direct and indirect basal ganglia pathways for motor control. The ventral striatum is a node in neural circuits related to motivation and affect. Despite these striking neurobiologic contrasts, there is almost no information about how the dorsal and ventral divisions of the striatum are set up during development. Here, we demonstrate that interactions between the two key transcription factors Nolz-1 and Dlx1/2 control the migratory paths of developing striatal neurons to the dorsal or ventral striatum. Moreover, these same transcription factors control the cell identity of striatal projection neurons in both the dorsal and ventral striatum including the cell origin of the direct and indirect pathways. We show that Nolz-1 suppresses Dlx1/2 expression. Deletion of Nolz-1 or over-expression of Dlx1/2 can produce a striatal phenotype characterized by withered dorsal striatum and a swollen ventral striatum, and that we can rescue this phenotype by manipulating the interactions between Nolz-1 and Dlx1/2 transcription factors. This evidence suggests that the fundamental basis for divisions of the striatum known to be differentially vulnerable at maturity is already encoded by the time embryonic striatal neurons begin their migrations into the developing striatum.
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