Project description:In the study we compared migrating embryonic cortical interneurons from control mouse embryos and ones carryng homozygous deletions of either Mtg8 or Lhx6. The aim was to identify genes that are co-regulated by LHX6 and MTG8.
Project description:Cortical interneurons originating in the embryonic medial ganglionic eminence (MGE) diverge into a range of different subtypes found in the adult mouse cerebral cortex. The mechanisms underlying this divergence and the timing when subtype identity is set up remain unclear. We identify the highly conserved transcriptional co-factor MTG8 as being pivotal in the development of a large subset of MGE cortical interneurons that co-expresses Somatostatin (SST) and Neuropeptide Y (NPY). MTG8 interacts with the pan-MGE transcription factor LHX6 and together the two factors are sufficient to promote expression of critical cortical interneuron subtype identity genes. The SST-NPY cortical interneuron fate is initiated early, well before interneurons migrate into the cortex, demonstrating an early onset specification program. Our findings suggest that transcriptional co-factors and modifiers of generic lineage specification programs may hold the key to the emergence of cortical interneuron heterogeneity from the embryonic telencephalic germinal zones.
Project description:There was a remarkable similarity in the molecular properties of the MGE-GFP+ and ES-GFP+ cells. In particular, genes that are important for medial ganglionic eminence (MGE) and cortical interneurons development are both high in expression in both MGE-Lhx6-GFP+ and ES-Lhx6-GFP+ cells (compared to ES-Lhx6-GFP- cells). To investigate how closely ES cells-derived Lhx6-GFP+ cells resembled authentic Lhx6+ MGE cells, and to define the molecular properties of the Lhx6-GFP+ and Lhx6-GFP- cells from differentiated ES cells, we compared their gene expression profiles. We used FACS to purify GFP+ cells from the E12.5 MGE of Lhx6-GFP transgenic mice. ES-Lhx6-GFP+ cells and ES-Lhx6-GFP- cells (both from D12 EB aggregates) were also isolated by fluorescent activated cell sorting (FACS) and all of the RNA samples were subjected to RNA expression microarray analyses.
Project description:Cortical interneuron diversity arises from the interplay of intrinsic developmental patterning and local extrinsic cues. While individual genetic programs underlying cardinal cell type identity are established in immature neurons prior to integration into cortical circuits, it remains unclear whether distinct interneuron subtype identities are pre-established, and if so, how their identity is maintained prior to circuit integration. Sox6 is a transcription factor with an established role in the maturation of interneurons derived from the medial ganglionic eminence and cell-type specification in other neuronal and non-neuronal cells. To determine a possible role in maintaining cortical somatostatin-expressing (Sst+) interneuron subtype identity, we conditionally removed Sox6 (Sox6-cKO) in migrating Sst+ interneurons and assessed the effects on their mature identity. In adolescent animals, five of eight molecular Sst+ subtypes were nearly absent in the cortex of Sox6-cKO mice. This reduced subtype diversity was not due to a decrease in the overall number of Sst+ interneurons and cells displayed electrophysiological maturity and expressed genes enriched within the broad class of Sst+ interneurons. Furthermore, we show that at embryonic day 18.5, prior to cortical integration, mature Sst+ cell subtype identity could already be inferred in both control and Sox6-cKO cortices, suggesting that the loss in subtype diversity observed in the mature cortex is due to a disrupted subtype maintenance. Importantly, Sox6 removal at postnatal day 7, after Sst+ interneurons have finished migrating and begun integration into the network, did not disrupt marker expression of Sst+ subtypes in the mature cortex. Therefore, Sox6 is necessary during this migratory phase for maintenance of Sst+ subtypes identity, indicating that subtype maintenance requires active transcriptional programs during migration.
Project description:GABAergic interneuron in the cortex comprise a very heterogenous group. and it is critical to identify discrete interneuron types to understand how their contributions to behavior can be modulated by external and internal cues. However, molecular difinition of these interneuron cell groups has been difficult. Comparative analysis of different interneuron subtypes can provide us new candidate marker genes which could target more specific interneu?on cell group. Here we identify oxytocin responsive novel class of interneuron through our comparative analysis. We employed the bacTRAP strategy, which uses BAC transgenic mice expressing EGFP-tagged ribosomal protein L10a in specific cell populations, to affinity purify polysome-bound mRNAs from Nek7, Dlx1, Cort, Htr3a, Oxtr expressing cortical interneurons. We show that Oxtr expressing cells are a subtype of somatostatin positive interneurons. Three independent TRAP replicates were collected and total RNA from the immunoprecipitates or flow-through (input) whole cortex lysates were amplified and hybridized. Data were normalized with the GCRMA algorithm and replicates were averaged across conditions. We recommend filtering data to remove probe sets with normalized expression values less than 50 in at least one condition. Because the Nek7 BAC labels non-neuronal cells, we recommend to delete astrocytes and oligodendrocytes genes from the list using GSE13379 data.
Project description:There was a remarkable similarity in the molecular properties of the MGE-GFP+ and ES-GFP+ cells. In particular, genes that are important for medial ganglionic eminence (MGE) and cortical interneurons development are both high in expression in both MGE-Lhx6-GFP+ and ES-Lhx6-GFP+ cells (compared to ES-Lhx6-GFP- cells).
Project description:Epigenetic gene silencing by aberrant DNA methylation leads to loss of key cellular pathways in tumorigenesis. DNA methylation-mediated silenced genes in pancreatic cancer were searched by methyl-CpG targeted transcriptional activation (MeTA) method and LHX6 (LIM homeobox 6), a transcription factor involved in embryogenesis and head development, was selected as one of candidate genes. LHX6 was downregulated in most pancreatic cancer cell lines (83%: 10/12) mainly through promoter hypermethylation and histone deacetylation. Furthermore, LHX6 was also methylated in primary pancreatic cancers in a tumor-specific manner (57%: 16/28). In order to assess the biological significance of LHX6 in pancreatic tumorigenesis, we first performed colony formation assay and found that LHX6 re-expression inhibited colony formation in pancreatic cancer cell lines. Similarly, inducible expression of LHX6 inhibited cell proliferation and migration in LHX6 low-expressing pancreatic cancer cell lines. On the other hand, knockdown of LHX6 accelerated cell proliferation in LHX6 high-expressing pancreatic cancer cell lines. Our present results suggest that epigenetic inactivation of LHX6 plays an important role in pancreatic tumorigenesis by promoting cell proliferation.
Project description:GABAergic interneuron in the cortex comprise a very heterogenous group. and it is critical to identify discrete interneuron types to understand how their contributions to behavior can be modulated by external and internal cues. However, molecular difinition of these interneuron cell groups has been difficult. Comparative analysis of different interneuron subtypes can provide us new candidate marker genes which could target more specific interneuron cell group. Here we identify oxytocin responsive novel class of interneuron through our comparative analysis. We employed the bacTRAP strategy, which uses BAC transgenic mice expressing EGFP-tagged ribosomal protein L10a in specific cell populations, to affinity purify polysome-bound mRNAs from Nek7, Dlx1, Cort, Htr3a, Oxtr expressing cortical interneurons. We show that Oxtr expressing cells are a subtype of somatostatin positive interneurons.
Project description:BackgroundPrecise matching between motoneuron subtypes and the muscles they innervate is a prerequisite for normal behavior. Motoneuron subtype identity is specified by the combination of transcription factors expressed by the cell during its differentiation. Here we investigate the roles of Mnx family transcription factors in specifying the subtypes of individually identified zebrafish primary motoneurons.ResultsZebrafish has three Mnx family members. We show that each of them has a distinct and temporally dynamic expression pattern in each primary motoneuron subtype. We also show that two Mnx family members are expressed in identified VeLD interneurons derived from the same progenitor domain that generates primary motoneurons. Surprisingly, we found that Mnx proteins appear unnecessary for differentiation of VeLD interneurons or the CaP motoneuron subtype. Mnx proteins are, however, required for differentiation of the MiP motoneuron subtype. We previously showed that MiPs require two temporally-distinct phases of Islet1 expression for normal development. Here we show that in the absence of Mnx proteins, the later phase of Islet1 expression is initiated but not sustained, and MiPs become hybrids that co-express morphological and molecular features of motoneurons and V2a interneurons. Unexpectedly, these hybrid MiPs often extend CaP-like axons, and some MiPs appear to be entirely transformed to a CaP morphology.ConclusionsOur results suggest that Mnx proteins promote MiP subtype identity by suppressing both interneuron development and CaP axon pathfinding. This is, to our knowledge, the first report of transcription factors that act to distinguish CaP and MiP subtype identities. Our results also suggest that MiP motoneurons are more similar to V2 interneurons than are CaP motoneurons.