Y-complex nucleoporins independently contribute to nuclear pore assembly and gene regulation in neuronal progenitors.

Besides assembling nuclear pore complexes, the conduits of nuclear transport, many nucleoporins also contribute to chromatin organization and gene expression, with critical roles in development and pathologies. We previously reported that Nup133 and Seh1, two components of the Y-complex subassembly of the nuclear pore scaffold, are dispensable for mouse embryonic stem cell viability but required for their survival during neuroectodermal differentiation. Here, a transcriptomic analysis revealed that Nup133 regulates a subset of genes at early stages of neuroectodermal differentiation, including Lhx1 and Nup210l, which encodes a newly validated nucleoporin. These genes are also misregulated in Nup133ΔMid neuronal progenitors, in which nuclear pore basket assembly is impaired. However, a four-fold reduction of Nup133 levels, despite also affecting basket assembly, is not sufficient to alter Nup210l and Lhx1 expression. Finally, these two genes are also misregulated in Seh1-deficient neural progenitors, which only show a mild reduction in nuclear pore density. Together these data reveal a shared function of Y-complex nucleoporins in gene regulation during neuroectodermal differentiation, apparently independent of nuclear pore basket integrity.

A unique coincidence of a 17q12 deletion and duplication in a Czech family led to a refined genotype-phenotype correlation.

Chromosomal band 17q12 is a gene-rich region flanked by segmental duplications, making the region prone to deletions and duplications via the non-allelic homologous recombination mechanism. While deletions cause a well-described disorder with a specific phenotype called renal cysts and diabetes mellitus, the phenotype caused by reciprocal duplications is less specific, primarily because of variable expressivity, and incomplete penetrance. We present an unusual family with four children carrying the 17q12 microduplication inherited from their clinically healthy mother, who was a carrier of both the duplication and, interestingly, also of an atypical deletion of the 17q12 region. The duplication was inherited from her diabetic father and the deletion from her diabetic mother who also suffered from a renal disorder. Clinical manifestations in the family were variable, but all children showed some degree of a neurodevelopmental disorder, such as epilepsy, intellectual disability, delayed speech development, or attention deficit disorder. The simultaneous occurrence of a deletion and duplication in the same chromosomal region in one family is very rare, and to our knowledge, individuals carrying both a deletion and a duplication of this region have never been described.

Lhx1 functions together with Otx2, Foxa2, and Ldb1 to govern anterior mesendoderm, node, and midline development.

Gene regulatory networks controlling functional activities of spatially and temporally distinct endodermal cell populations in the early mouse embryo remain ill defined. The T-box transcription factor Eomes, acting downstream from Nodal/Smad signals, directly activates the LIM domain homeobox transcription factor Lhx1 in the visceral endoderm. Here we demonstrate Smad4/Eomes-dependent Lhx1 expression in the epiblast marks the entire definitive endoderm lineage, the anterior mesendoderm, and midline progenitors. Conditional inactivation of Lhx1 disrupts anterior definitive endoderm development and impedes node and midline morphogenesis in part due to severe disturbances in visceral endoderm displacement. Transcriptional profiling and ChIP-seq (chromatin immunoprecipitation [ChIP] followed by high-throughput sequencing) experiments identified Lhx1 target genes, including numerous anterior definitive endoderm markers and components of the Wnt signaling pathway. Interestingly, Lhx1-binding sites were enriched at enhancers, including the Nodal-proximal epiblast enhancer element and enhancer regions controlling Otx2 and Foxa2 expression. Moreover, in proteomic experiments, we characterized a complex comprised of Lhx1, Otx2, and Foxa2 as well as the chromatin-looping protein Ldb1. These partnerships cooperatively regulate development of the anterior mesendoderm, node, and midline cell populations responsible for establishment of the left-right body axis and head formation.

The T-box transcription factor Eomesodermin is essential for AVE induction in the mouse embryo.

Reciprocal inductive interactions between the embryonic and extraembryonic tissues establish the anterior-posterior (AP) axis of the early mouse embryo. The anterior visceral endoderm (AVE) signaling center emerges at the distal tip of the embryo at embryonic day 5.5 and translocates to the prospective anterior side of the embryo. The process of AVE induction and migration are poorly understood. Here we demonstrate that the T-box gene Eomesodermin (Eomes) plays an essential role in AVE recruitment, in part by directly activating the homeobox transcription factor Lhx1. Thus, Eomes function in the visceral endoderm (VE) initiates an instructive transcriptional program controlling AP identity.

Mechanistic insights from the LHX1-driven molecular network in building the embryonic head.

Development of an embryo is driven by a series of molecular instructions that control the differentiation of tissue precursor cells and shape the tissues into major body parts. LIM homeobox 1 (LHX1) is a transcription factor that plays a major role in the development of the embryonic head of the mouse. Loss of LHX1 function disrupts the morphogenetic movement of head tissue precursors and impacts on the function of molecular factors in modulating the activity of the WNT signaling pathway. LHX1 acts with a transcription factor complex to regulate the transcription of target genes in multiple phases of development and in a range of embryonic tissues of the mouse and Xenopus. Determining the interacting factors and transcriptional targets of LHX1 will be key to unraveling the ensemble of factors involved in head development and building a head gene regulatory network.

A gene regulatory network anchored by LIM homeobox 1 for embryonic head development.

Development of the embryonic head is driven by the activity of gene regulatory networks of transcription factors. LHX1 is a homeobox transcription factor that plays an essential role in the formation of the embryonic head. The loss of LHX1 function results in anterior truncation of the embryo caused by the disruption of morphogenetic movement of tissue precursors and the dysregulation of WNT signaling activity. Profiling the gene expression pattern in the Lhx1 mutant embryo revealed that tissues in anterior germ layers acquire posterior tissue characteristics, suggesting LHX1 activity is required for the allocation and patterning of head precursor tissues. Here, we used LHX1 as an entry point to delineate its transcriptional targets and interactors and construct a LHX1-anchored gene regulatory network. Using a gain-of-function approach, we identified genes that immediately respond to Lhx1 activation. Meta-analysis of the datasets of LHX1-responsive genes and genes expressed in the anterior tissues of mouse embryos at head-fold stage, in conjunction with published Xenopus embryonic LHX1 (Xlim1) ChIP-seq data, has pinpointed the putative transcriptional targets of LHX1 and an array of genetic determinants functioning together in the formation of the mouse embryonic head.

Context-specific function of the LIM homeobox 1 transcription factor in head formation of the mouse embryo.

Lhx1 encodes a LIM homeobox transcription factor that is expressed in the primitive streak, mesoderm and anterior mesendoderm of the mouse embryo. Using a conditional Lhx1 flox mutation and three different Cre deleters, we demonstrated that LHX1 is required in the anterior mesendoderm, but not in the mesoderm, for formation of the head. LHX1 enables the morphogenetic movement of cells that accompanies the formation of the anterior mesendoderm, in part through regulation of Pcdh7 expression. LHX1 also regulates, in the anterior mesendoderm, the transcription of genes encoding negative regulators of WNT signalling, such as Dkk1, Hesx1, Cer1 and Gsc. Embryos carrying mutations in Pcdh7, generated using CRISPR-Cas9 technology, and embryos without Lhx1 function specifically in the anterior mesendoderm displayed head defects that partially phenocopied the truncation defects of Lhx1-null mutants. Therefore, disruption of Lhx1-dependent movement of the anterior mesendoderm cells and failure to modulate WNT signalling both resulted in the truncation of head structures. Compound mutants of Lhx1, Dkk1 and Ctnnb1 show an enhanced head truncation phenotype, pointing to a functional link between LHX1 transcriptional activity and the regulation of WNT signalling. Collectively, these results provide comprehensive insight into the context-specific function of LHX1 in head formation: LHX1 enables the formation of the anterior mesendoderm that is instrumental for mediating the inductive interaction with the anterior neuroectoderm and LHX1 also regulates the expression of factors in the signalling cascade that modulate the level of WNT activity.

Xenopus pitx3 target genes lhx1 and xnr5 are identified using a novel three-fluor flow cytometry-based analysis of promoter activation and repression.

BACKGROUND: Pitx3 plays a well understood role in directing development of lens, muscle fiber, and dopaminergic neurons; however, in Xenopus laevis, it may also play a role in early gastrulation and somitogenesis. Potential downstream targets of pitx3 possess multiple binding motifs that would not be readily accessible by conventional promoter analysis. RESULTS: We isolated and characterized pitx3 target genes lhx1 and xnr5 using a novel three-fluor flow cytometry tool that was designed to dissect promoters with multiple binding sites for the same transcription factor. This approach was calibrated using a known pitx3 target gene, Tyrosine hydroxylase. CONCLUSIONS: We demonstrate how flow cytometry can be used to detect gene regulatory changes with exquisite precision on a cell-by-cell basis, and establish that in HEK293 cells, pitx3 directly activates lhx1 and represses xnr5. Developmental Dynamics 246:657-669, 2017. © 2017 Wiley Periodicals, Inc.

Clinical and genetic aspects of Mayer-Rokitansky-Küster-Hauser syndrome.

The Mayer-Rokitansky-Küster-Hauser (MRKH) syndrome [MIM 277000] is characterised by the absence of a uterus and vagina in otherwise phenotypically normal women with karyotype 46,XX. Clinically, the MRKH can be subdivided into two subtypes: an isolated or type I form can be delineated from a type II form, which is characterised by extragenital malformations. The so-called Müllerian hypoplasia, renal agenesis, cervicothoracic somite dysplasia (MURCS) association can be seen as the most severe phenotypic outcome. The MRKH syndrome affects at least 1 in 4000 to 5000 female new-borns. Although most of the cases are sporadic, familial clustering has also been described, indicating a genetic cause of the disease. However, the mode of inheritance is autosomal-dominant inheritance with reduced penetrance. High-resolution array-CGH and MLPA analysis revealed recurrent aberrations in different chromosomal regions such as TAR susceptibility locus in 1q21.1, chromosomal regions 16p11.2, and 17q12 and 22q11.21 microduplication and -deletion regions in patients with MRKH. Sequential analysis of the genes LHX1, TBX6 and RBM8A, which are located in chromosomal regions 17q12, 16p11.2 and 1q21.1, yielded in the detection of MRKH-associated mutations. In a subgroup of patients with signs of hyperandrogenaemia mutations of WNT4 have been found to be causative. Analysis of another member of the WNT family, WNT9B, resulted in the detection of some causative mutations in MRKH patients.

Head formation: OTX2 regulates Dkk1 and Lhx1 activity in the anterior mesendoderm.

The Otx2 gene encodes a paired-type homeobox transcription factor that is essential for the induction and the patterning of the anterior structures in the mouse embryo. Otx2 knockout embryos fail to form a head. Whereas previous studies have shown that Otx2 is required in the anterior visceral endoderm and the anterior neuroectoderm for head formation, its role in the anterior mesendoderm (AME) has not been assessed specifically. Here, we show that tissue-specific ablation of Otx2 in the AME phenocopies the truncation of the embryonic head of the Otx2 null mutant. Expression of Dkk1 and Lhx1, two genes that are also essential for head formation, is disrupted in the AME of the conditional Otx2-deficient embryos. Consistent with the fact that Dkk1 is a direct target of OTX2, we showed that OTX2 can interact with the H1 regulatory region of Dkk1 to activate its expression. Cross-species comparative analysis, RT-qPCR, ChIP-qPCR and luciferase assays have revealed two conserved regions in the Lhx1 locus to which OTX2 can bind to activate Lhx1 expression. Abnormal development of the embryonic head in Otx2;Lhx1 and Otx2;Dkk1 compound mutant embryos highlights the functional intersection of Otx2, Dkk1 and Lhx1 in the AME for head formation.

Transcription factors lhx1/5-1 and pitx are required for the maintenance and regeneration of serotonergic neurons in planarians.

In contrast to most adult organisms, freshwater planarians can regenerate any injured body part, including their entire nervous system. This allows for the analysis of genes required for both the maintenance and regeneration of specific neural subtypes. In addition, the loss of specific neural subtypes may uncover previously unknown behavioral roles for that neural population in the context of the adult animal. Here we show that two homeodomain transcription factor homologs, Smed-lhx1/5-1 and Smed-pitx, are required for the maintenance and regeneration of serotonergic neurons in planarians. When either lhx1/5-1 or pitx was knocked down by RNA interference, the expression of multiple canonical markers for serotonergic neurons was lost. Surprisingly, the loss of serotonergic function uncovered a role for these neurons in the coordination of motile cilia on the ventral epidermis of planarians that are required for their nonmuscular gliding locomotion. Finally, we show that in addition to its requirement in serotonergic neurons, Smed-pitx is required for proper midline patterning during regeneration, when it is required for the expression of the midline-organizing molecules Smed-slit in the anterior and Smed-wnt1 in the posterior.

Lhx1 is required in Müllerian duct epithelium for uterine development.

The female reproductive tract organs of mammals, including the oviducts, uterus, cervix and upper vagina, are derived from the Müllerian ducts, a pair of epithelial tubes that form within the mesonephroi. The Müllerian ducts form in a rostral to caudal manner, guided by and dependent on the Wolffian ducts that have already formed. Experimental embryological studies indicate that caudal elongation of the Müllerian duct towards the urogenital sinus occurs in part by proliferation at the ductal tip. The molecular mechanisms that regulate the elongation of the Müllerian duct are currently unclear. Lhx1 encodes a LIM-homeodomain transcription factor that is essential for male and female reproductive tract development. Lhx1 is expressed in both the Wolffian and Müllerian ducts. Wolffian duct-specific knockout of Lhx1 results in degeneration of the Wolffian duct and consequently the non-cell-autonomous loss of the Müllerian duct. To determine the role of Lhx1 specifically in the Müllerian duct epithelium, we performed a Müllerian duct-specific knockout study using Wnt7a-Cre mice. Loss of Lhx1 in the Müllerian duct epithelium led to a block in Müllerian duct elongation and uterine hypoplasia characterized by loss of the entire endometrium (luminal and glandular epithelium and stroma) and inner circular but not the outer longitudinal muscle layer. Time-lapse imaging and molecular analyses indicate that Lhx1 acts cell autonomously to maintain ductal progenitor cells for Müllerian duct elongation. These studies identify LHX1 as the first transcription factor that is essential in the Müllerian duct epithelial progenitor cells for female reproductive tract development. Furthermore, these genetic studies demonstrate the requirement of epithelial-mesenchymal interactions for uterine tissue compartment differentiation.

HNF1ß, LHX1, and GGNBP2 deletion contributed to kidney and reproductive dysfunction in 17q12 deletion syndrome: evidence from a case report.

17q12 deletion syndrome is a chromosomal abnormality, where there is a small missing piece (deletion) of genetic material on the long arm (q) of chromosome 17. Sign and symptoms can vary widely among different patients. Recently, a patient was diagnosed with 17q12 deletion syndrome in our hospital, and the clinical characteristics presented as absence of the right kidney, compensatory hypertrophy of the left kidney, multiple small cysts in the left kidney, pancreatic atrophy, hypomagnesemia, bowed uterus, multiple follicular cysts in both lobes of the thyroid gland, and maturity-onset diabetes of the young type 5 (MODY-5). A 1.5-Mb deletion with haploinsufficiency for 20 genes within the 17q12 region was found through copy number variation (CNV) analysis based on metagenomic next-generation sequencing (mNGS) technology. In addition to HNF1B absence, the LIM-class homeobox 1 transcription factor (LHX1) and GGNBP2 absence was also involved in regulation of kidney development and the reproductive system through bioinformatics analysis. The inheriting risk of 17q12 deletion syndrome is about 50%, and it is recommended to provide genetic counseling to all patients who are suspected or diagnosed with the syndrome.

LIM homeobox 1 (LHX1) induces endoplasmic reticulum stress and promotes preterm birth.

Background: Premature birth (PTB) is a major cause of neonatal mortality and has enduring consequences. LIM Homeobox 1 (LHX1) is vital in embryonic organogenesis, while Inositol-Requiring Enzyme 1 (IRE-1) regulates endoplasmic reticulum stress (ERS). This study explores whether IRE-1 impacts PTB via LHX1 modulation. Methods: We analyzed LHX1 expression in placental samples from PTB patients and examined its impact on the viability, migration, invasion, and apoptosis of the human placental trophoblast cell line HTR8/Svneo, particularly when treated with the ERS inducer tunicamycin (TM). We also assessed the levels of ERS-related genes and autophagy activation in response to LHX1 deficiency. To gain mechanistic insights, we evaluated the ERS-mediated activation of the IRE-1/XBP1/CHOP signaling pathway in LHX1-silenced HTR8/Svneo cells. Additionally, we examined the transcriptional activation of IRE-1 and the binding of LHX1 to the IRE-1 promoter in HTR8/Svneo cells. We overexpressed IRE-1 in LHX1-silenced HTR8/Svneo cells to assess its effects on cell viability, migration, invasion, apoptosis, and autophagy. Finally, we induced LHX1 knockdown in mice through intraperitoneal injections of tunicamycin (TM) and Sh-LHX1 over a 24-h period to evaluate PTB symptoms. Results: We observed LHX1 overexpression in placental tissue from PTB cases and TM-induced HTR8/Svneo cells. LHX1 depletion enhanced cell viability, migration, and invasion while reducing autophagy and apoptosis. This reduction in LHX1 led to decreased levels of IRE-1, XBP1, CHOP, and other ERS-related genes, indicating LHX1's role in ERS induction and the activation of the IRE-1/XBP1/CHOP pathway. Mechanistically, LHX1 was found to bind to the IRE-1 promoter, inducing its transcriptional activation. Notably, overexpressing IRE-1 counteracted the impact of LHX1 depletion on trophoblast cell behavior, suggesting that LHX1 modulates IRE-1. In line with our in vitro studies, LHX1 knockdown ameliorated PTB symptoms in TM-treated mice. Conclusion: LHX1 contributes to the progression of PTB by regulating the IRE-1-XBP1-CHOP pathway.

TGF-ß modulates cell fate in human ES cell-derived foregut endoderm by inhibiting Wnt and BMP signaling.

Genetic differences between pluripotent stem cell lines cause variable activity of extracellular signaling pathways, limiting reproducibility of directed differentiation protocols. Here we used human embryonic stem cells (hESCs) to interrogate how exogenous factors modulate endogenous signaling events during specification of foregut endoderm lineages. We find that transforming growth factor ß1 (TGF-ß1) activates a putative human OTX2/LHX1 gene regulatory network which promotes anterior fate by antagonizing endogenous Wnt signaling. In contrast to Porcupine inhibition, TGF-ß1 effects cannot be reversed by exogenous Wnt ligands, suggesting that induction of SHISA proteins and intracellular accumulation of Fzd receptors render TGF-ß1-treated cells refractory to Wnt signaling. Subsequently, TGF-ß1-mediated inhibition of BMP and Wnt signaling suppresses liver fate and promotes pancreas fate. Furthermore, combined TGF-ß1 treatment and Wnt inhibition during pancreatic specification reproducibly and robustly enhance INSULIN+ cell yield across hESC lines. This modification of widely used differentiation protocols will enhance pancreatic ß cell yield for cell-based therapeutic applications.

LHX1 as a potential biomarker regulates EMT induction and cellular behaviors in uterine corpus endometrial carcinoma.

OBJECTIVES: To investigate the expression of LHX1 and its role as a biomarker in the diagnosis and prognosis of Uterine Corpus Endometrial Carcinoma (UCEC). METHODS: The Cancer Genome Atlas (TCGA) database was used to detect the expression level of LHX1 in UCEC cells and tissues, and to find out the effect of LHX1 on prognosis. Co-expressed genes were then identified by Spearman correlation analysis, and the protein-protein interaction network was constructed using Cytoscape software. The R "clusterProfiler" package was used to conduct Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment analyses. A series of in vitro experiments were performed to evaluate LHX1 expression and detect UCEC cell proliferation, invasion, and migration. Western blotting was used to determine the effect of LHX1 on expression levels of Epithelial-Mesenchymal Transition (EMT)-related proteins. RESULTS: LHX1 was upregulated in UCEC tissues and correlated with poor overall survival and disease-specific survival outcomes. Functional enrichment analysis suggested that genes co-expressed with LHX1 were enriched in cell adhesion. The expression of LHX1 was positively correlated with the expression levels of genes related to EMT induction and invasion. LHX1 can enhance the proliferation, migration, and invasion activities of UCEC cells in vitro, and alter the expression levels of EMT-related proteins. CONCLUSION: LHX1 expression was highly upregulated in UCEC cells and tissues, which was correlated with the prognosis of patients with UCEC. LHX1 may regulate UCEC progression at least in part by modulating EMT induction.

Differentiation of mouse embryonic stem cells into cells with spermatogonia-like morphology with chemical intervention-dependent increased gene expression of LIM homeobox 1 (Lhx1).

Spermatogonial stem cells (SSCs) originate from gonocytes that differentiate from primordial germ cells (PGCs). In the developing mouse testis, expression of the gene LIM homeobox 1 (Lhx1) marks the most undifferentiated SSCs, which has not yet been reported for spermatogonia-like cells generated in vitro. Previously, it was shown that a chemical intervention in male mouse embryonic stem (ES) cells in serum culture, including Sirtuin 1 (SIRT1) inhibitor Ex-527, DNA methyltransferase (DNMT) inhibitor RG-108 and electrophilic redox cycling compound tert-butylhydroquinone (tBHQ), was associated with molecular markers of PGC to gonocyte differentiation. Here, we report the in vitro differentiation of male mouse ES cells, cultured under dual chemical inhibition of GSK3ß and MEK (2i) with leukemia inhibitory factor (LIF) (2iL) and serum, into cells with spermatogonia-like morphology (CSMs) and population-averaged expression of spermatogonia-specific genes by removal of 2iL and a specific schedule of twice daily partial medium replacement. Combination of this new protocol with the previously reported chemical intervention increased population-averaged gene expression of Lhx1 in the resulting CSMs. Furthermore, we detected single CSMs with strong nuclear LHX1/5 protein signal only in the chemical intervention group. We propose that further investigation of CSMs may provide new insights into male germline development.

Involvement of a Basic Helix-Loop-Helix Gene BHLHE40 in Specification of Chicken Retinal Pigment Epithelium.

The first event of differentiation and morphogenesis in the optic vesicle (OV) is specification of the neural retina (NR) and retinal pigment epithelium (RPE), separating the inner and outer layers of the optic cup, respectively. Here, we focus on a basic helix-loop-helix gene, BHLHE40, which has been shown to be expressed by the developing RPE in mice and zebrafish. Firstly, we examined the expression pattern of BHLHE40 in the developing chicken eye primordia by in situ hybridization. Secondly, BHLHE40 overexpression was performed with in ovo electroporation and its effects on optic cup morphology and expression of NR and RPE marker genes were examined. Thirdly, we examined the expression pattern of BHLHE40 in LHX1-overexpressed optic cup. BHLHE40 expression emerged in a subset of cells of the OV at Hamburger and Hamilton stage 14 and became confined to the outer layer of the OV and the ciliary marginal zone of the retina by stage 17. BHLHE40 overexpression in the prospective NR resulted in ectopic induction of OTX2 and repression of VSX2. Conversely, BHLHE40 was repressed in the second NR after LHX1 overexpression. These results suggest that emergence of BHLHE40 expression in the OV is involved in initial RPE specification and that BHLHE40 plays a role in separation of the early OV domains by maintaining OTX2 expression and antagonizing an NR developmental program.

LIM homeodomain proteins and associated partners: Then and now.

The field of molecular embryology started around 1990 by identifying new genes and analyzing their functions in early vertebrate embryogenesis. Those genes encode transcription factors, signaling molecules, their regulators, etc. Most of those genes are relatively highly expressed in specific regions or exhibit dramatic phenotypes when ectopically expressed or mutated. This review focuses on one of those genes, Lim1/Lhx1, which encodes a transcription factor. Lim1/Lhx1 is a member of the LIM homeodomain (LIM-HD) protein family, and its intimate partner, Ldb1/NLI, binds to two tandem LIM domains of LIM-HDs. The most ancient LIM-HD protein and its partnership with Ldb1 were innovated in the metazoan ancestor by gene fusion combining LIM domains and a homeodomain and by creating the LIM domain-interacting domain (LID) in ancestral Ldb, respectively. The LIM domain has multiple interacting interphases, and Ldb1 has a dimerization domain (DD), the LID, and other interacting domains that bind to Ssbp2/3/4 and the boundary factor, CTCF. By means of these domains, LIM-HD-Ldb1 functions as a hub protein complex, enabling more intricate and elaborate gene regulation. The common, ancestral role of LIM-HD proteins is neuron cell-type specification. Additionally, Lim1/Lhx1 serves crucial roles in the gastrula organizer and in kidney development. Recent studies using Xenopus embryos have revealed Lim1/Lhx1 functions and regulatory mechanisms during development and regeneration, providing insight into evolutionary developmental biology, functional genomics, gene regulatory networks, and regenerative medicine. In this review, we also discuss recent progress at unraveling participation of Ldb1, Ssbp, and CTCF in enhanceosomes, long-distance enhancer-promoter interactions, and trans-interactions between chromosomes.

Neuronal Lhx1 expression is regulated by DNMT1-dependent modulation of histone marks.

Apart from the conventional view of repressive promoter methylation, the DNA methyltransferase 1 (DNMT1) was recently described to modulate gene expression through a variety of interactions with diverse epigenetic key players. We here investigated the DNMT1-dependent transcriptional control of the homeobox transcription factor LHX1, which we previously identified as an important regulator in cortical interneuron development. We found that LHX1 expression in embryonic interneurons originating in the embryonic pre-optic area (POA) is regulated by non-canonic DNMT1 function. Analysis of histone methylation and acetylation revealed that both epigenetic modifications seem to be implicated in the control of Lhx1 gene activity and that DNMT1 contributes to their proper establishment. This study sheds further light on the regulatory network of cortical interneuron development including the complex interplay of epigenetic mechanisms.