ABSTRACT: Genome-wide chromatin-immunoprecipitation studies of sympathetic neurons reveals critical direct targets of ISL1 and suggests potential co-factor families for ISL1 action in sympathetic neurons
Project description:Understanding factors that drive development of the sympathetic neuron is crucial to development of potential therapies for neuroblastoma. Here, we identify a key cell autonomous role for the LIM homeodomain transcription factor ISL1 for survival, proliferation and differentiation of sympathetic neurons throughout development. Chromatin immunoprecipitation assays performed utilizing antibody to ISL1 in chromatin extracts from sympathetic neurons demonstrated that ISL1 directly binds genomic regions within several genes critical for sympathetic neuron development and function, including subunits of the Insm1, Lmo1,Tlx3 and Prox1. Our studies represent in vivo ChIP-seq studies for sympathetic neurons which provide a basis for further exploration of factors critical to sympathetic neurons development and function . Overall design: ISL1 ChIP-seq profiling was performed in sympathetic neurons from E12.5-14.5 Embryos .
Project description:Understanding factors that drive development and function of the sympathetic neuron is crucial to development of potential therapies for neuroblastoma. Here, we identify a key cell autonomous role for the LIM homeodomain transcription factor ISL1 for survival, proliferation and differentiation of sympathetic neurons throughout development. Analysis of several Isl1 mutant mouse lines, including one in which Isl1 was specifically ablated in sympathetic neuron (Wnt1-cre;Isl1 f/f) revealed an early requirement for Isl1 within sympathetic neurons for proliferation and surrvial. RNA-seq analyses on sympathetic neurons revealed dysregulation of a number of genes critical for sympathetic neuron development .Our studies demonstrated that ISL1 regulated the peoliferation, surrvial and differentiation. Overall design: Expression profiling of sympathetic ganglion dissected from E11.5 or E14.5 wild-type and isl1 mutant embryos.
Project description:Genome-wide chromatin-immunoprecipitation studies of purified SAN cells reveals critical direct targets of ISL1 and suggests potential co-factor families for ISL1 action in SAN cells
Project description:Striatal projection neurons comprise two populations of striatonigral and striatopallidal neurons. These two neuronal populations play distinct roles in controlling movement-related functions in the basal ganglia circuits. An important issue is how striatal progenitors are developmentally specified into these two distinct neuronal populations. In the present study, we characterized the function of Islet-1 (Isl1), a LIM-homeodomain transcription factor, in striatal development. Genetic fate mapping showed that Isl1(+) progeny specifically developed into a subpopulation of striatonigral neurons that transiently expressed Isl1. In Nestin-Cre;Isl1(f/f) KO mouse brain, differentiation of striatonigral neurons was defective, as evidenced by decreased expression of striatonigral-enriched genes, including substance P, prodynorphin, solute carrier family 35, member D3 (Slc35d3), and PlexinD1. Striatonigral axonal projections were also impaired, and abnormal apoptosis was observed in Isl1 KO striatum. It was of particular interest that striatopallidal-enriched genes, including dopamine D2 receptor (Drd2), proenkephalin, A2A adenosine receptor (A2aR) and G protein-coupled receptor 6 (Gpr6), were concomitantly up-regulated in Isl1 mutant striatum, suggesting derepression of striatopallidal genes in striatonigral neurons in the absence of Isl1. The suppression of striatopallidal genes by Isl1 was further examined by overexpression of Isl1 in the striatum of Drd2-EGFP transgenic mice using in utero electroporation. Ectopic Isl1 expression was sufficient to repress Drd2-EGFP signals in striatopallidal neurons. Taken together, our study suggests that Isl1 specifies the cell fate of striatonigral neurons not only by orchestrating survival, differentiation, and axonal projections of striatonigral neurons but also by suppressing striatopallidal-enriched genes. The dual action of developmental control by Isl1 in promoting appropriate striatonigral but repressing inappropriate striatopallidal genetic profiles may ensure sharpening of the striatonigral identity during development.
Project description:Understanding factors that drive development and function of the sinoatrial node (SAN) is crucial to development of potential therapies for sinus arrhythmias, including potential generation of biological pacemakers. Here, we identify a key cell autonomous role for the LIM homeodomain transcription factor ISL1 for survival, proliferation and function of pacemaker cells throughout development. Chromatin immunoprecipitation assays performed utilizing antibody to ISL1 in chromatin extracts from FACS purified SAN cells demonstrated that ISL1 directly binds genomic regions within several genes critical for normal pacemaker function, including subunits of the L-type calcium channel, Ank2, and Tbx3. Other genes implicated in abnormal heart rhythm in humans were also direct downstream targets of ISL1 in SAN cells. Our studies represent the first in vivo ChIP-seq studies for SAN cells which provide a basis for further exploration of factors critical to SAN formation and function and highlight the potential for utilization of ISL1 in combination with other SAN transcription factors for generating pacemaker cells for therapy or drug screening purposes. ISL1 ChIP-seq profiling was performed in Hcn4-H2BGFP SAN cells purified from neonatal hearts.
Project description:The sinoatrial node (SAN) maintains a rhythmic heartbeat; therefore, a better understanding of factors that drive SAN development and function is crucial to generation of potential therapies, such as biological pacemakers, for sinus arrhythmias. Here, we determined that the LIM homeodomain transcription factor ISL1 plays a key role in survival, proliferation, and function of pacemaker cells throughout development. Analysis of several Isl1 mutant mouse lines, including animals harboring an SAN-specific Isl1 deletion, revealed that ISL1 within SAN is a requirement for early embryonic viability. RNA-sequencing (RNA-seq) analyses of FACS-purified cells from ISL1-deficient SANs revealed that a number of genes critical for SAN function, including those encoding transcription factors and ion channels, were downstream of ISL1. Chromatin immunoprecipitation assays performed with anti-ISL1 antibodies and chromatin extracts from FACS-purified SAN cells demonstrated that ISL1 directly binds genomic regions within several genes required for normal pacemaker function, including subunits of the L-type calcium channel, Ank2, and Tbx3. Other genes implicated in abnormal heart rhythm in humans were also direct ISL1 targets. Together, our results demonstrate that ISL1 regulates approximately one-third of SAN-specific genes, indicate that a combination of ISL1 and other SAN transcription factors could be utilized to generate pacemaker cells, and suggest ISL1 mutations may underlie sick sinus syndrome.
Project description:GATA2 transcription factor and LIM homeodomain proteins Islet1 (ISL1) and LIM homeobox 3 (LHX3) are suspected to be involved in gonadotrope cell fate and maintenance. The GnRH receptor gene (Gnrhr), crucial for gonadotrope function, is expressed in the pituitary gland from embryonic day 13.5 onward, well before LH and FSH ?-subunits. This expression pattern together with the presence of WGATAR and TAAT motifs in Gnrhr promoter sequences suggests the involvement of early transcription factors in promoter activation. In this study, using a well-characterized transgenic mouse model, GATA2 was found colocalized with Gnrhr promoter activity in the pituitary. Transient transfection of Gnrhr promoter luciferase fusion constructs together with either GATA2 expression vectors or small interfering RNA in gonadotrope cell lines indicated that GATA2, which typically acts as a trans-activator, unexpectedly repressed Gnrhr promoter activity. Using DNA chromatography affinity and EMSA, we demonstrated that GATA2 operates via a response element containing a peculiar palindromic GATA motif that overlaps a critical TAAT motif involved in LHX3/ISL1 trans-activation. Indeed, despite the inhibitory action of GATA2, this element displayed a clear-cut enhancer activity in gonadotrope cells. Chromatin immunoprecipitation assays indicated that GATA2, LHX3, and ISL1 interact with a Gnrhr promoter fragment encompassing this element. The trans-repressive action of GATA2 on Gnrhr promoter activity is likely balanced or even hindered by trans-activating effects of LIM homeodomain proteins via this novel bifunctional LIM/GATA response element. Such a hierarchical interplay may contribute to finely adjust Gnrhr gene expression in gonadotrope cell lineage during pituitary development as well as in the adult animal.
Project description:The transcription factor STAT3 has been implicated in axon regeneration. Here we investigate a role for STAT3 in sympathetic nerve sprouting after myocardial infarction (MI) - a common injury in humans. We show that NGF stimulates serine phosphorylation (S727) of STAT3 in sympathetic neurons via ERK1/2, in contrast to cytokine phosphorylation of Y705. Maximal sympathetic axon regeneration in vitro requires phosphorylation of both S727 and Y705. Furthermore, cytokine signaling is necessary for NGF-induced sympathetic nerve sprouting in the heart after MI. Transfection studies in neurons lacking STAT3 suggest two independent pools of STAT3, phosphorylated on either S727 or Y705, that regulate sympathetic regeneration via both transcriptional and non-transcriptional means. Additional data identify STAT3-microtubule interactions that may complement the well-characterized role of STAT3 stimulating regeneration associated genes. These data show that STAT3 is critical for sympathetic axon regeneration in vitro and in vivo, and identify a novel non-transcriptional mode of action.
Project description:Understanding factors that drive development and function of the sinoatrial node (SAN) is crucial to development of potential therapies for sinus arrhythmias, including potential generation of biological pacemakers. Here, we identify a key cell autonomous role for the LIM homeodomain transcription factor ISL1 for survival, proliferation and function of pacemaker cells throughout development. Chromatin immunoprecipitation assays performed utilizing antibody to ISL1 in chromatin extracts from FACS purified SAN cells demonstrated that ISL1 directly binds genomic regions within several genes critical for normal pacemaker function, including subunits of the L-type calcium channel, Ank2, and Tbx3. Other genes implicated in abnormal heart rhythm in humans were also direct downstream targets of ISL1 in SAN cells. Our studies represent the first in vivo ChIP-seq studies for SAN cells which provide a basis for further exploration of factors critical to SAN formation and function and highlight the potential for utilization of ISL1 in combination with other SAN transcription factors for generating pacemaker cells for therapy or drug screening purposes. Overall design: ISL1 ChIP-seq profiling was performed in Hcn4-H2BGFP SAN cells purified from neonatal hearts.
Project description:Combinations of LIM homeodomain proteins form a transcriptional "LIM code" to direct the specification of neural cell types. Two paralogous pairs of LIM homeodomain proteins, LIM homeobox protein 3/4 (Lhx3/Lhx4) and Islet-1/2 (Isl1/Isl2), are expressed in developing ventral motor neurons. Lhx3 and Isl1 interact within a well characterized transcriptional complex that triggers motor neuron development, but it was not known whether Lhx4 and Isl2 could participate in equivalent complexes. We have identified an Lhx3-binding domain (LBD) in Isl2 based on sequence homology with the Isl1(LBD) and show that both Isl2(LBD) and Isl1(LBD) can bind each of Lhx3 and Lhx4. X-ray crystal- and small-angle x-ray scattering-derived solution structures of an Lhx4·Isl2 complex exhibit many similarities with that of Lhx3·Isl1; however, structural differences supported by mutagenic studies reveal differences in the mechanisms of binding. Differences in binding have implications for the mode of exchange of protein partners in transcriptional complexes and indicate a divergence in functions of Lhx3/4 and Isl1/2. The formation of weaker Lhx·Isl complexes would likely be masked by the availability of the other Lhx·Isl complexes in postmitotic motor neurons.