A tyrosine-rich domain within homeodomain transcription factor Nkx2-5 is an essential element in the early cardiac transcriptional regulatory machinery

Molecular characterization of cell types in the squid Loligo vulgaris

Cephalopods are set apart from other mollusks by their advanced behavioral abilities and the complexity of their nervous systems. Because of the great evolutionary distance that separates vertebrates from cephalopods, it is evident that higher cognitive features have evolved separately in these clades despite the similarities that they share. Alongside their complex behavioral abilities, cephalopods have evolved specialized cells and tissues, such as the chromatophores for camouflage or suckers to grasp prey. Despite significant progress in genome and transcriptome sequencing, the molecular identities of cell types in cephalopods remain largely unknown. We here combine single-cell transcriptomics with in situ gene expression analysis to uncover cell type diversity in the European squid Loligo vulgaris. We describe cell types that are conserved with other phyla such as neurons, muscles, or connective tissues but also cephalopod-specific cells, such as chromatophores or sucker cells. Moreover, we investigate major components of the squid nervous system including progenitor and developing cells, differentiated cells of the brain and optic lobes, as well as sensory systems of the head. Our study provides a molecular assessment for conserved and novel cell types in cephalopods and a framework for mapping the nervous system of L. vulgaris.

Cell type diversity in a developing octopus brain

Octopuses are mollusks that have evolved intricate neural systems comparable with vertebrates in terms of cell number, complexity and size. The brain cell types that control their sophisticated behavioral repertoire are still unknown. Here, we profile the cell diversity of the paralarval Octopus vulgaris brain to build a cell type atlas that comprises mostly neural cells, but also multiple glial subtypes, endothelial cells and fibroblasts. We spatially map cell types to the vertical, subesophageal and optic lobes. Investigation of cell type conservation reveals a shared gene signature between glial cells of mouse, fly and octopus. Genes related to learning and memory are enriched in vertical lobe cells, which show molecular similarities with Kenyon cells in Drosophila. We construct a cell type taxonomy revealing transcriptionally related cell types, which tend to appear in the same brain region. Together, our data sheds light on cell type diversity and evolution in the octopus brain.

[Effect of dhfr gene overexpression on ethanol-induced abnormal cardiovascular development in zebrafish embryos]

OBJECTIVE

To study the effect of dhfr gene overexpression on ethanol-induced abnormal cardiac and vascular development in zebrafish embryos and underlying mechanisms.

METHODS

dhfr mRNA was transcribed in vitro and microinjected into zebrafish fertilized eggs to induce the overexpression of dhfr gene, and the efficiency of overexpression was verified. Wild-type zebrafish were divided into a control group, an ethanol group, and an ethanol+dhfr overexpression group (microinjection of 6 nL dhfr mRNA). The embryonic development was observed for each group. The transgenic zebrafish Tg (cmlc2:mcherry) with heart-specific red fluorescence was used to observe atrial and ventricular development. Fluorescence microscopy was performed to observe the development of cardiac outflow tract and blood vessels. Heart rate and ventricular shortening fraction were used to assess cardiac function. Gene probes were constructed, and embryo in situ hybridization and real-time PCR were used to measure the expression of nkx2.5, tbx1, and flk-1 in the embryo.

RESULTS

Compared with the ethanol group, the ethanol+dhfr overexpression group had a significant reduction in the percentage of abnormal embryonic development and a significant increase in the percentage of embryonic survival (P<0.05), with significant improvements in the abnormalities of the atrium, ventricle, outflow tract, and blood vessels and cardiac function. Compared with the control group, the ethanol group had significant reductions in the expression of nkx2.5, tbx1, and flk-1 (P<0.05), and compared with the ethanol group, the ethanol+dhfr overexpression group had significant increases in the expression of nkx2.5, tbx1, and flk-1 (P<0.05), which were still lower than their expression in the control group.

CONCLUSIONS

The overexpression of the dhfr gene can partially improve the abnormal development of embryonic heart and blood vessels induced by ethanol, possibly by upregulating the decreased expression of nkx2.5, tbx1, and flk-1 caused by ethanol.

An update on genetic variants of the NKX2-5

NKX2-5 is a homeodomain transcription factor that plays a crucial role in heart development. It is the first gene where a single genetic variant (GV) was found to be associated with congenital heart diseases in humans. In this study, we carried out a comprehensive survey of NKX2-5 GVs to build a unified, curated, and updated compilation of all available GVs. We retrieved a total of 1,380 unique GVs. From these, 970 had information on their frequency in the general population and 143 have been linked to pathogenic phenotypes in humans. In vitro effect was ascertained for 38 GVs. The homeodomain had the biggest cluster of pathogenic variants in the protein: 49 GVs in 60 residues, 23 in its third α-helix, where 11 missense variants may affect protein-DNA interaction or the hydrophobic core. We also pinpointed the likely location of pathogenic GVs in four linear motifs. These analyses allowed us to assign a putative explanation for the effect of 90 GVs. This study pointed to reliable pathogenicity for GVs in helix 3 of the homeodomain and may broaden the scope of functional and structural studies that can be done to better understand the effect of GVs in NKX2-5 function.

Analysis of NKX2-5 in 439 Chinese Patients with Sporadic Atrial Septal Defect

Background

The NKX2 gene family is made up of core transcription factors that are involved in the morphogenesis of the vertebrate heart. NKx2-5 plays a pivotal role in mouse cardiogenesis, and mutations in NKx2-5 result in an abnormal structure and function of the heart, including atrial septal defect and cardiac electrophysiological abnormalities.

Material/Methods

To investigate the genetic variation of NKX2-5 in Chinese patients with sporadic atrial septal defect, we sequenced the full length of the NKX2-5 gene in the participants of the study. Four hundred thirty-nine patients and 567 healthy unrelated individuals were recruited. Genomic DNA was extracted from the peripheral blood leukocytes of the participants. DNA samples from the participants were amplified by multiplex PCR and sequenced on an Illumina HiSeq platform. Variations were detected by comparison with a standard reference genome and annotation with a variant effect predictor.

Results

Thirty variations were detected in Chinese patients with sporadic atrial septal defect, and 6 single nucleotide polymorphisms (SNPs) had a frequency greater than 1%. Among the 30 variations, the SNPs rs2277923 and rs3729753 were extremely prominent, with a high frequency and odds ratio in patients.

Conclusions

Single nucleotide variations are the prominent genetic variations of NKX2-5 in Chinese patients with sporadic atrial septal defect. The SNPs rs2277923 and rs3729753 are prominent single nucleotide variations (SNVs) in Chinese patients with sporadic atrial septal defect.

Reversion to developmental pathways underlies rapid arm regeneration in juvenile European cuttlefish, Sepia officinalis (Linnaeus 1758)

Coleoid cephalopods, including the European cuttlefish (Sepia officinalis), possess the remarkable ability to fully regenerate an amputated arm with no apparent fibrosis or loss of function. In model organisms, regeneration usually occurs as the induction of proliferation in differentiated cells. In rare circumstances, regeneration can be the product of naïve progenitor cells proliferating and differentiating de novo . In any instance, the immune system is an important factor in the induction of the regenerative response. Although the wound response is well-characterized, little is known about the physiological pathways utilized by cuttlefish to reconstruct a lost arm. In this study, the regenerating arms of juvenile cuttlefish, with or without exposure at the time of injury to sterile bacterial lipopolysaccharide extract to provoke an antipathogenic immune response, were assessed for the transcription of early tissue lineage developmental genes, as well as histological and protein turnover analyses of the resulting regenerative process. The transient upregulation of tissue-specific developmental genes and histological characterization indicated that coleoid arm regeneration is a stepwise process with staged specification of tissues formed de novo, with immune activation potentially affecting the timing but not the result of this process. Together, the data suggest that rather than inducing proliferation of mature cells, developmental pathways are reinstated, and that a pool of naïve progenitors at the blastema site forms the basis for this regeneration.

Many ways to break a heart

A mutant transcription factor that has been linked to congenital heart disease has wider effects than previously thought.

NKX2-5 mutations causative for congenital heart disease retain functionality and are directed to hundreds of targets

We take a functional genomics approach to congenital heart disease mechanism. We used DamID to establish a robust set of target genes for NKX2-5 wild type and disease associated NKX2-5 mutations to model loss-of-function in gene regulatory networks. NKX2-5 mutants, including those with a crippled homeodomain, bound hundreds of targets including NKX2-5 wild type targets and a unique set of "off-targets", and retained partial functionality. NKXΔHD, which lacks the homeodomain completely, could heterodimerize with NKX2-5 wild type and its cofactors, including E26 transformation-specific (ETS) family members, through a tyrosine-rich homophilic interaction domain (YRD). Off-targets of NKX2-5 mutants, but not those of an NKX2-5 YRD mutant, showed overrepresentation of ETS binding sites and were occupied by ETS proteins, as determined by DamID. Analysis of kernel transcription factor and ETS targets show that ETS proteins are highly embedded within the cardiac gene regulatory network. Our study reveals binding and activities of NKX2-5 mutations on WT target and off-targets, guided by interactions with their normal cardiac and general cofactors, and suggest a novel type of gain-of-function in congenital heart disease.

NKX2-5 mutations in an inbred consanguineous population: genetic and phenotypic diversity

NKX2-5 mutations are associated with different forms of congenital heart disease. Despite the knowledge gained from molecular and animal studies, genotype-phenotype correlations in humans are limited by the lack of large cohorts and the incomplete assessment of family members. We hypothesized that studying the role of NKX2-5 in inbred populations with homogeneous genetic backgrounds and high consanguinity rates such as Lebanon could help closing this gap. We sequenced NKX2-5 in 188 index CHD cases (25 with ASD). Five variants (three segregated in families) were detected in eleven families including the previously documented p.R25C variant, which was found in seven patients from different families, and in one healthy individual. In 3/5 familial dominant ASD cases, we identified an NKX2-5 mutation. In addition to the heterogeneity of NKX2-5 mutations, a diversity of phenotypes occurred within the families with predominant ASD and AV block. We did in fact identify a large prevalence of Sudden Cardiac Death (SCD) in families with truncating mutations, and two patients with coronary sinus disease. NKX2-5 is thus responsible for dominant familial ASD even in consanguineous populations, and a wide genetic and phenotypic diversity is characteristic of NKX2-5 mutations in the Lebanese population.

Proper development of the outer longitudinal smooth muscle of the mouse pylorus requires Nkx2-5 and Gata3

BACKGROUND & AIMS

Infantile hypertrophic pyloric stenosis is a common birth anomaly characterized by obstruction of the pyloric lumen. A genome-wide association study implicated NKX2-5, which encodes a transcription factor that is expressed in embryonic heart and pylorus, in the pathogenesis of infantile hypertrophic pyloric stenosis. However, the function of the NKX2-5 in pyloric smooth muscle development has not been examined directly. We investigated the pattern of Nkx2-5 during the course of murine pyloric sphincter development and examined coexpression of Nkx2-5 with Gata3 and Sox9-other transcription factors with pyloric-specific mesenchymal expression. We also assessed pyloric sphincter development in mice with disruption of Nkx2-5 or Gata3.

METHODS

We used immunofluorescence analysis to compare levels of NKX2-5, GATA3, and SOX9 in different regions of smooth muscle cells. Pyloric development was assessed in mice with conditional or germline deletion of Nkx2-5 or Gata3, respectively.

RESULTS

Gata3, Nkx2-5, and Sox9 are coexpressed in differentiating smooth muscle cells of a distinct fascicle of the pyloric outer longitudinal muscle. Expansion of this fascicle coincides with development of the pyloric sphincter. Disruption of Nkx2-5 or Gata3 causes severe hypoplasia of this fascicle and alters pyloric muscle shape. Although expression of Sox9 requires Nkx2-5 and Gata3, there is no apparent hierarchical relationship between Nkx2-5 and Gata3 during pyloric outer longitudinal muscle development.

CONCLUSIONS

Nkx2-5 and Gata3 are independently required for the development of a pyloric outer longitudinal muscle fascicle, which is required for pyloric sphincter morphogenesis in mice. These data indicate that regulatory changes that alter Nkx2-5 or Gata3 expression could contribute to pathogenesis of infantile hypertrophic pyloric stenosis.

NK4 antagonizes Tbx1/10 to promote cardiac versus pharyngeal muscle fate in the ascidian second heart field

Cross inhibition between NK4 and TBX1 transcription factors specifies heart versus pharyngeal muscle fates by promoting the activation of tissue-specific regulators in distinct precursors within the cardiopharyngeal lineage of the ascidian, Ciona intestinalis.

The heart and head muscles share common developmental origins and genetic underpinnings in vertebrates, including humans. Parts of the heart and cranio-facial musculature derive from common mesodermal progenitors that express NKX2-5, ISL1, and TBX1. This ontogenetic kinship is dramatically reflected in the DiGeorge/Cardio-Velo-Facial syndrome (DGS/CVFS), where mutations of TBX1 cause malformations in the pharyngeal apparatus and cardiac outflow tract. Cardiac progenitors of the first heart field (FHF) do not require TBX1 and segregate precociously from common progenitors of the second heart field (SHF) and pharyngeal muscles. However, the cellular and molecular mechanisms that govern heart versus pharyngeal muscle specification within this lineage remain elusive. Here, we harness the simplicity of the ascidian larva to show that, following asymmetric cell division of common progenitors, NK4/NKX2-5 promotes GATAa/GATA4/5/6 expression and cardiac specification in the second heart precursors by antagonizing Tbx1/10-mediated inhibition of GATAa and activation of Collier/Olf/EBF (COE), the determinant of atrial siphon muscle (ASM) specification. Our results uncover essential regulatory connections between the conserved cardio-pharyngeal factor Tbx1/10 and muscle determinant COE, as well as a mutual antagonism between NK4 and Tbx1/10 activities upstream of GATAa and COE. The latter cross-antagonism underlies a fundamental heart versus pharyngeal muscle fate choice that occurs in a conserved lineage of cardio-pharyngeal progenitors. We propose that this basic ontogenetic motif underlies cardiac and pharyngeal muscle development and evolution in chordates.

Mutations in the regulatory genes encoding the transcription factors NKX2-5 and TBX1, which govern heart and head muscle development, cause prevalent congenital defects. Recent studies using vertebrate models have shown that the heart and pharyngeal head muscle cells derive from common progenitors in the early embryo. To better understand the genetic mechanisms by which these progenitors select one of the two developmental trajectories, we studied the activity of these transcription factors in a simple invertebrate chordate model, the sea squirt Ciona intestinalis. We show that the sea squirt homolog of NKX2-5 promotes early heart specification by inhibiting the formation of pharyngeal muscles. Conversely, the TBX1 homolog determines pharyngeal muscle fate by inhibiting GATAa and thereby the heart program it instructs, as well as promoting the pharyngeal muscle program through activation of COE (Collier/Olf-1/EBF), a recently identified regulator of skeletal muscle differentiation. Finally, we show that the NKX2-5 homolog protein directly binds to the COE gene to repress its activity. Notably, these antagonistic interactions occur in heart and pharyngeal precursors immediately following the division of their pluripotent mother cells, thus contributing to their respective fate choice. These mechanistic insights into the process of early heart versus head muscle specification in this simple chordate provide the grounds for establishing the etiology of human congenital cardio-craniofacial defects.

Congenital asplenia in mice and humans with mutations in a Pbx/Nkx2-5/p15 module

The molecular determinants of spleen organogenesis and the etiology of isolated congenital asplenia (ICA), a life-threatening human condition, are unknown. We previously reported that Pbx1 deficiency causes organ growth defects including asplenia. Here, we show that mice with splenic mesenchyme-specific Pbx1 inactivation exhibit hyposplenia. Moreover, the loss of Pbx causes downregulation of Nkx2-5 and derepression of p15Ink4b in spleen mesenchymal progenitors, perturbing the cell cycle. Removal of p15Ink4b in Pbx1 spleen-specific mutants partially rescues spleen growth. By whole-exome sequencing of a multiplex kindred with ICA, we identify a heterozygous missense mutation (P236H) in NKX2-5 showing reduced transactivation in vitro. This study establishes that a Pbx/Nkx2-5/p15 regulatory module is essential for spleen development.

Dihydrofolate reductase is required for the development of heart and outflow tract in zebrafish

Folic acid is very important for embryonic development and folic acid inhibition can cause congenital heart defects in vertebrates. Dihydrofolate reductase (DHFR) is a key enzyme in folate-mediated metabolism. The dysfunction of DHFR disrupts the key biological processes which folic acid participates in. DHFR gene is conserved during vertebrate evolution. It is important to investigate the roles of DHFR in cardiac developments. In this study, we showed that DHFR knockdown resulted in the abnormal developments of zebrafish embryos in the early stages. Obvious malformations in heart and outflow tract (OFT) were also observed in DHFR knockdown embryos. DHFR overexpression rescued the abnormal phenotypes in the DHFR knockdown group. DHFR knockdown had negative impacts on the expressions of NKX2.5 (NK2 transcription factor-related 5), MEF2C (myocyte-specific enhancer factor 2C), TBX20 (T-box 20), and TBX1 (T-box 1) which are important transcriptional factors during cardiac development process, while DHFR overexpression had positive effects. DHFR was required for Hedgehog pathway. DHFR knockdown caused reduced cell proliferation and increased apoptosis, while its overexpression promoted cell proliferation and inhibited apoptosis. Taken together, our study suggested that DHFR plays crucial roles in the development of heart and OFT in zebrafish by regulating gene transcriptions and affecting cell proliferation and apoptosis.

Mutational spectrum in the cardiac transcription factor gene NKX2.5 (CSX) associated with congenital heart disease

Heterozygous mutations in the human transcription factor gene NKX2.5 are associated with either isolated or combined congenital heart disease (CHD), primarily secundum atrial septal defect-II (ASD-II), ventricular septal defect (VSD) or tetralogy of Fallot (TOF). Thus, NKX2.5 has an important role at different stages of cardiac development. The frequency of NKX2.5 mutations in a broader phenotypic spectrum of CHD is not completely determined. Here, we report the identification of two novel mutations in the NKX2.5 gene in a screening of 121 patients with a broad spectrum of CHDs. However, mutations were only associated with familial ASD-II and in both, patients also showed atrioventricular (AV) block. We found one missense mutation (R190L) in two siblings with ASD-II and a frame-shift mutation (A255fsX38) at the C-terminus in a mother and daughter. In addition, a single patient with hypoplastic left heart syndrome (HLHS) had the reported sequence variant R25C. Importantly, sporadic cases of CHD that share phenotypic aspects of NKX2.5 mutation carriers were negative for genetic analysis. Thus, even important for cardiac development, germline mutations in NKX2.5 are rare in patients with sporadic CHD and genetic and/or pathophysiologic heterogeneity is likely for sporadic forms of CHD.

From molecular mechanisms of cardiac development to genetic substrate of congenital heart diseases

Congenital heart disease is one of the most important chapters in medicine because its incidence is increasing and nowadays it is close to 1.2%. Most congenital heart disorders are the result of defects during embryogenesis, which implies that they are due to alterations in genes involved in cardiac development. This review summarizes current knowledge regarding the molecular mechanisms involved in cardiac development in order to clarify the genetic basis of congenital heart disease.

Somatic muscle development in Sepia officinalis (cephalopoda - mollusca): a new role for NK4

Cephalopods are emerging as new developmental models. These lophotrochozoans exhibit numerous morphological peculiarities among molluscs, not only regarding their nervous system but also regarding their circulatory system, which is closed and includes three hearts. However, the molecular control of cardiac myogenesis in lophotrochozoans is largely unknown. In other groups, cardiac development depends on numerous different genes, among them NK4 seems to have a well-conserved function throughout evolution. In this study, we assessed the expression pattern of SoNK4, the Sepia officinalis NK4 homologue, during Sepia officinalis development by whole-mount in situ hybridization. SoNK4 expression begins before morphogenesis, is not restricted to prospective cardiac muscles but above all concerns mesodermal structures potentially rich in muscles such as arms and mantle. These results suggest an important role of SoNK4 in locomotory (somatic) muscles development of Sepia officinalis, and thus a new role for NK4.

RNA toxicity in myotonic muscular dystrophy induces NKX2-5 expression

Myotonic muscular dystrophy (DM1) is the most common inherited neuromuscular disorder in adults and is considered the first example of a disease caused by RNA toxicity. Using a reversible transgenic mouse model of RNA toxicity in DM1, we provide evidence that DM1 is associated with induced NKX2-5 expression. Transgene expression resulted in cardiac conduction defects, increased expression of the cardiac-specific transcription factor NKX2-5 and profound disturbances in connexin 40 and connexin 43. Notably, overexpression of the DMPK 3' UTR mRNA in mouse skeletal muscle also induced transcriptional activation of Nkx2-5 and its targets. In human muscles, these changes were specific to DM1 and were not present in other muscular dystrophies. The effects on NKX2-5 and its downstream targets were reversed by silencing toxic RNA expression. Furthermore, using Nkx2-5+/- mice, we show that NKX2-5 is the first genetic modifier of DM1-associated RNA toxicity in the heart.

Mutations in cardiac T-box factor gene TBX20 are associated with diverse cardiac pathologies, including defects of septation and valvulogenesis and cardiomyopathy

The T-box family transcription factor gene TBX20 acts in a conserved regulatory network, guiding heart formation and patterning in diverse species. Mouse Tbx20 is expressed in cardiac progenitor cells, differentiating cardiomyocytes, and developing valvular tissue, and its deletion or RNA interference-mediated knockdown is catastrophic for heart development. TBX20 interacts physically, functionally, and genetically with other cardiac transcription factors, including NKX2-5, GATA4, and TBX5, mutations of which cause congenital heart disease (CHD). Here, we report nonsense (Q195X) and missense (I152M) germline mutations within the T-box DNA-binding domain of human TBX20 that were associated with a family history of CHD and a complex spectrum of developmental anomalies, including defects in septation, chamber growth, and valvulogenesis. Biophysical characterization of wild-type and mutant proteins indicated how the missense mutation disrupts the structure and function of the TBX20 T-box. Dilated cardiomyopathy was a feature of the TBX20 mutant phenotype in humans and mice, suggesting that mutations in developmental transcription factors can provide a sensitized template for adult-onset heart disease. Our findings are the first to link TBX20 mutations to human pathology. They provide insights into how mutation of different genes in an interactive regulatory circuit lead to diverse clinical phenotypes, with implications for diagnosis, genetic screening, and patient follow-up.

Activation of MEK-ERK by heregulin-beta1 promotes the development of cardiomyocytes derived from ES cells

We have previously shown that heregulin-beta1 (HRG-beta1) was involved in the development and survival of cardiomyocytes derived from embryonic stem (ES) cells. This study was conducted to investigate the intracellular signal mechanisms by which HRG-beta1 stimulates cardiogenesis in ES cells. The treatment with ErbB receptor inhibitor decreased the population of cardiomyocytes and transcripts levels of cardiac genes (Nkx2.5, beta-MHC, cTnI, and MLC2a). The phosphorylation of ERK and development of cardiomyocytes by treatment with HRG-beta1 was suppressed upon treatment with MEK1 inhibitor. Furthermore, cardiomyocytes and level of MHC protein were significantly increased by overexpression of wild type MEK1 or constitutive active MEK1, but not dominant negative MEK1. These results suggest that HRG-beta1 promotes the development of cardiomyocytes predominantly by activation of MEK-ERK.

An Nkx2-5/Bmp2/Smad1 negative feedback loop controls heart progenitor specification and proliferation

During heart development the second heart field (SHF) provides progenitor cells for most cardiomyocytes and expresses the homeodomain factor Nkx2-5. We now show that feedback repression of Bmp2/Smad1 signaling by Nkx2-5 critically regulates SHF proliferation and outflow tract (OFT) morphology. In the cardiac fields of Nkx2-5 mutants, genes controlling cardiac specification (including Bmp2) and maintenance of the progenitor state were upregulated, leading initially to progenitor overspecification, but subsequently to failed SHF proliferation and OFT truncation. In Smad1 mutants, SHF proliferation and deployment to the OFT were increased, while Smad1 deletion in Nkx2-5 mutants rescued SHF proliferation and OFT development. In Nkx2-5 hypomorphic mice, which recapitulate human congenital heart disease (CHD), OFT anomalies were also rescued by Smad1 deletion. Our findings demonstrate that Nkx2-5 orchestrates the transition between periods of cardiac induction, progenitor proliferation, and OFT morphogenesis via a Smad1-dependent negative feedback loop, which may be a frequent molecular target in CHD.

Ciona intestinalis as a model for cardiac development

The primitive chordate Ciona intestinalis has emerged as a significant model system for the study of heart development. The Ciona embryo employs a conserved heart gene network in the context of extremely low cell numbers and reduced genetic redundancy. Here, I review recent studies on the molecular genetics of Ciona cardiogenesis as well as classic work on heart anatomy and physiology. I also discuss the potential of employing Ciona to decipher a comprehensive chordate gene network and to determine how this network controls heart morphogenesis.