Endothelin-converting enzyme-like 1 (ECEL1) is present both in the plasma membrane and in the endoplasmic reticulum

A novel compound heterozygous variant of ECEL1 induced joint dysfunction and cartilage degradation: a case report and literature review

Background

Distal arthrogryposis type 5D (DA5D) represents a subtype of distal arthrogryposis (DA) characterized by congenital joint contractures in the distal extremities. DA5D is inherited in a rare autosomal recessive manner and is associated with the ECEL1 gene. In this report, we describe a case of an infant with bilateral knee contractures and ptosis, caused by a novel compound heterozygous mutation of ECEL1.

Case presentation

We conducted DNA extraction, whole-exome sequencing analysis, and mutation analysis of ECEL1 to obtain genetic data on the patient. We subsequently analyzed the patient's clinical and genetic data. The proband was a 6 months-old male infant who presented with significant bilateral knee contracture disorders and bilateral ptosis. MRI demonstrated cartilage degradation in knee joint. Whole-exome sequencing of the patient's DNA revealed a compound heterozygous mutation of c.2152-15C>A and c.110_155del in ECEL1. Analysis with the MutationTaster application indicated that c.110_155del was pathogenic (probability = 1), causing frameshift mutations affecting 151 amino acids (p.F37Cfs*151). The truncated protein lost the substructure of a transmembranous site based on the predicted protein crystal structure AF-O95672-F1. The variant of c.2152-15C>A of ECEL1 was also predicted to be disease-causing (probability = 0.98) as it impaired the methylation of ECEL1 serving as an H3K27me3 modification site, which led to the dysfunction of the second topological domain. Therefore, we concluded that the compound heterozygous mutation caused the pathogenic phenotype of this proband.

Conclusion

The present case highlights the usefulness of molecular genetic screening in diagnosing unexpected joint disorder. Identification of novel mutations in the ECEL1 gene broadens the mutation spectrum of this gene and adds to the genotype-phenotype map of DA5D. Furthermore, rapid whole-exome sequencing analysis enabled timely diagnosis of this rare disease, facilitating appropriate treatment and scheduled follow-up to improve clinical outcomes.

A New Intronic Variant in ECEL1 in Two Patients with Distal Arthrogryposis Type 5D

Distal Arthrogryposis type 5D (DA5D) is characterized by congenital contractures involving the distal joints, short stature, scoliosis, ptosis, astigmatism, and dysmorphic features. It is inherited in an autosomal recessive manner, and it is a result of homozygous or compound heterozygous variants in the ECEL1 gene. Here, we report two patients of Sardinian origin harboring a new intronic homozygous variant in ECEL1 (c.1507-9G>A), which was predicted to affect mRNA splicing by activating a cryptic acceptor site. The frequency of the variant is very low in the general human population, and its presence in our families can be attributed to a founder effect. This study provides an updated review of the known causative mutations of the ECEL1 gene, enriching the allelic spectrum to include the noncoding sequence.

The Novel Compound Heterozygous Mutations of ECEL1 Identified in a Family with Distal Arthrogryposis Type 5D

Introduction

Distal arthrogryposis type 5D (DA5D) is an autosomal recessive disease. The clinical symptoms include contractures of the joints of limbs, especially camptodactyly of the hands and/or feet, unilateral ptosis, a round-shaped face, arched eyebrows, and micrognathia, without ophthalmoplegia. ECEL1 is a DA5D causative gene that encodes a membrane-bound metalloprotease. ECEL1 plays important roles in the final axonal arborization of motor nerves in limb skeletal muscles and neuromuscular junction formation during prenatal development.

Methods

A DA5D family with webbing of the elbows and fingers was recruited. We performed whole-exome sequencing (WES) and filtered mutations by disease-causing genes of arthrogryposis multiplex congenita (AMC). Mutational analysis and cosegregation confirmation were then performed.

Results

We identified novel compound heterozygous mutations of ECEL1 (NM_004826: c.69C>A, p.C23∗ and c.1810G>A, p.G604R) in the proband.

Conclusions

We detected causative mutations in a DA5D family, expanding the spectrum of known ECEL1 mutations and contributing to the clinical diagnosis of DA5D.

New Insights of a Neuronal Peptidase DINE/ECEL1: Nerve Development, Nerve Regeneration and Neurogenic Pathogenesis

Our understanding of the physiological relevance of unique Damage-induced neuronal endopeptidase (DINE) [also termed Endothelin-converting enzyme-like 1 (ECEL1)] has recently expanded. DINE/ECEL1 is a type II membrane-bound metalloprotease, belonging to a family including the neprilysin (NEP) and endothelin-converting enzyme (ECE). The family members degrade and/or process peptides such as amyloid β and big-endothelins, which are closely associated with pathological conditions. Similar to NEP and ECE, DINE has been expected to play an important role in injured neurons as well as in developing neurons, because of its remarkable transcriptional response to neuronal insults and predominant neuronal expression from the embryonic stage. However, the physiological significance of DINE has long remained elusive. In the last decade, a series of genetically manipulated mice have driven research progress to elucidate the physiological aspects of DINE. The mice ablating Dine fail to arborize the embryonic motor axons in some subsets of muscles, including the respiratory muscles, and die immediately after birth. The abnormal phenotype of motor axons is also caused by one amino acid exchanges of DINE/ECEL1, which are responsible for distal arthrogryposis type 5 in a group of human congenital movement disorders. Furthermore, the mature Dine-deficient mice in which the lethality is rescued by genetic manipulation have shown the involvement of DINE in central nervous system regeneration. Here we describe recent research advances that DINE-mediated proteolytic processes are critical for nerve development, regeneration and pathogenesis, and discuss the future potential for DINE as a therapeutic target for axonal degeneration/disorder.

Ecel1 Knockdown With an AAV2-Mediated CRISPR/Cas9 System Promotes Optic Nerve Damage-Induced RGC Death in the Mouse Retina

Purpose

To assess the therapeutic potential of endothelin-converting enzyme-like 1 (Ecel1) in a mouse model of optic nerve crush.

Methods

Ecel1 expression was evaluated with real time quantitative (qRT)-PCR, Western blotting, and immunohistochemistry in mouse retinas after optic nerve crush. Vinblastine administration to the optic nerve and the intravitreal injection of N-methyl-d-aspartate (NMDA) were used to assess Ecel1 gene expression. Ecel1 was deleted with an adeno-associated viral (AAV) clustered regulatory interspaced short palindromic repeat (CRISPR)/Cas9 system, and retinal ganglion cell (RGC) survival was investigated with retrograde labeling, qRT-PCR, and visual evoked potential.

Results

Optic nerve crush induced Ecel1 expression specifically in the RGCs, peaking on day 4 after optic nerve crush. Ecel1 gene expression was induced by the vinblastine-induced inhibition of axonal flow, but not by NMDA-induced excitotoxicity, even though both are triggers of RGC death. Knockdown of Ecel1 promoted the loss of RGCs after optic nerve crush.

Conclusions

Our data suggest that Ecel1 induction is part of the retinal neuroprotective response to axonal injury in mice. These findings might provide insight into novel therapeutic targets for the attenuation of RGC damage, such as occurs in traumatic optic neuropathy.

ECEL1 gene related contractural syndrome: Long-term follow-up and update on clinical and pathological aspects

Autosomal recessive mutations in the ECEL1 gene have recently been associated with a wide phenotypic spectrum including severe congenital contractural syndromes and distal arthrogryposis type 5D (DA5D). Here, we describe four novel families with ECEL1 gene mutations, reporting 15 years of follow-up for four patients and detailed muscle pathological description for three individuals. In particular, we observed mild myopathic features, prominent core-like areas in one individual, and presence of nCAM positive fibres in three patients from 2 unrelated families suggesting a possible problem with innervation. Our findings expand current knowledge concerning the phenotypic and pathological spectrum associated with ECEL1 gene mutations and may suggest novel insights regarding the underlying pathomechanism of the disease.

Distinct functional consequences of ECEL1/DINE missense mutations in the pathogenesis of congenital contracture disorders

Endothelin-converting enzyme-like 1 (ECEL1, also termed DINE in rodents), a membrane-bound metalloprotease, has been identified as a gene responsible for distal arthrogryposis (DA). ECEL1-mutated DA is generally characterized by ocular phenotypes in addition to the congenital limb contractures that are common to all DA subtypes. Until now, the consequences of the identified pathogenic mutations have remained incompletely understood because of a lack of detailed phenotypic analyses in relevant mouse models. In this study, we generated a new knock-in mouse strain that carries an ECEL1/DINE pathogenic G607S missense mutation, based on a previous study reporting atypical DA hindlimb phenotypes in two siblings with the mutation. We compared the morphological phenotypes of G607S knock-in mice with C760R knock-in mice that we previously established. Both C760R and G607S knock-in mouse embryos showed similar axonal arborization defects with normal trajectory patterns from the spinal cord to the target hindlimb muscles, as well as axon guidance defects of the abducens nerves. Intriguingly, distinct phenotypes in DINE protein localization and mRNA expression were identified in these knock-in mouse lines. For G607S, DINE mRNA and protein expression was decreased or almost absent in motor neurons. In the C760R mutant mice DINE was expressed and localized in the somata of motor neurons but not in axons. Our mutant mouse data suggest that ECEL1/DINE G607S and C760R mutations both lead to motor innervation defects as primary causes in ECEL1-mutated congenital contracture disorders. However, the functional consequences of the two mutations are distinct, with loss of axonal transport of ECEL1/DINE in C760R mutants and mRNA expression deficits in G607S mutants.

ECEL1 mutation implicates impaired axonal arborization of motor nerves in the pathogenesis of distal arthrogryposis

The membrane-bound metalloprotease endothelin-converting enzyme-like 1 (ECEL1) has been newly identified as a causal gene of a specific type of distal arthrogryposis (DA). In contrast to most causal genes of DA, ECEL1 is predominantly expressed in neuronal cells, suggesting a unique neurogenic pathogenesis in a subset of DA patients with ECEL1 mutation. The present study analyzed developmental motor innervation and neuromuscular junction formation in limbs of the rodent homologue damage-induced neuronal endopeptidase (DINE)-deficient mouse. Whole-mount immunostaining was performed in DINE-deficient limbs expressing motoneuron-specific GFP to visualize motor innervation throughout the limb. Although DINE-deficient motor nerves displayed normal trajectory patterns from the spinal cord to skeletal muscles, they indicated impaired axonal arborization in skeletal muscles in the forelimbs and hindlimbs. Systematic examination of motor innervation in over 10 different hindlimb muscles provided evidence that DINE gene disruption leads to insufficient arborization of motor nerves after arriving at the skeletal muscle. Interestingly, the axonal arborization defect in foot muscles appeared more severe than in other hindlimb muscles, which was partially consistent with the proximal-distal phenotypic discordance observed in DA patients. Additionally, the number of innervated neuromuscular junction was significantly reduced in the severely affected DINE-deficient muscle. Furthermore, we generated a DINE knock-in (KI) mouse model with a pathogenic mutation, which was recently identified in DA patients. Axonal arborization defects were clearly detected in motor nerves of the DINE KI limb, which was identical to the DINE-deficient limb. Given that the encoded sequences, as well as ECEL1 and DINE expression profiles, are highly conserved between mouse and human, abnormal arborization of motor axons and subsequent failure of NMJ formation could be a primary cause of DA with ECEL1 mutation.

The neuronal endopeptidase ECEL1 is associated with a distinct form of recessive distal arthrogryposis

Distal arthrogryposis (DA) is a heterogeneous subgroup of arthrogryposis multiplex congenita (AMC), a large family of disorders characterized by multiple congenital joint limitations due to reduced fetal movements. DA is mainly characterized by contractures afflicting especially the distal extremities without overt muscular or neurological signs. Although a limited number of genes mostly implicated in the contractile apparatus have been identified in DA, most patients failed to show mutations in currently known genes. Using a pangenomic approach, we demonstrated linkage of DA to chromosome 2q37 in two consanguineous families and the endothelin-converting enzyme like 1 (ECEL1) gene present in this region was associated with DA. Screening of a panel of 20 families with non-specific DA identified seven homozygous or compound heterozygous mutations of ECEL1 in a total of six families. Mutations resulted mostly in the absence of protein. ECEL1 is a neuronal endopeptidase predominantly expressed in the central nervous system and brain structures during fetal life in mice and human. ECEL1 plays a major role in intramuscular axonal branching of motor neurons in skeletal muscle during embryogenesis. A detailed review of clinical findings of DA patients with ECEL1 mutations revealed a homogeneous and recognizable phenotype characterized by limited knee flexion, flexed third to fifth fingers and severe muscle atrophy predominant on lower limbs and tongue that suggested a common pathogenic mechanism. We described a new and homogenous phenotype of DA associated with ECEL1 that resulted in symptoms involving rather the peripheral than the central nervous system and suggesting a developmental dysfunction.

Gene expression signatures differentiate uterine endometrial stromal sarcoma from leiomyosarcoma

OBJECTIVE

Endometrial stromal sarcoma (ESS) and leiomyosarcoma (LMS) are the two most common uterine sarcomas, but both are rare tumors. The aim of the present study was to compare the global gene expression patterns of ESS and LMS.

METHODS

Gene expression profiles of 7 ESS and 13 LMS were analyzed using the HumanRef-8 BeadChip from Illumina. Differentially expressed candidate genes were validated using quantitative real-time PCR and immunohistochemistry.

RESULTS

Unsupervised hierarchical clustering using all 54,675 genes in the array separated ESS from LMS samples. We identified 549 unique probes that were significantly differentially expressed in the two malignancies by greater than 2-fold with 1% FDR cutoff using one-way ANOVA with Benjamini-Hochberg correction, of which 336 and 213 were overexpressed in ESS and LMS, respectively. Genes overexpressed in ESS included SLC7A10, EFNB3, CCND2, ECEL1, ITM2A, NPW, PLAG1 and GCGR. Genes overexpressed in LMS included CDKN2A, FABP3, TAGLN, JPH2, GEM, NAV2 and RAB23. The top 100 genes overexpressed in LMS included those coding for myosin light chain and caldesmon, but not the genes coding for desmin or actin. CD10 was not overexpressed in ESS. Results for selected genes were validated by quantitative real-time PCR and immunohistochemistry.

CONCLUSIONS

We present the first study in which gene expression profiling was shown to distinguish between ESS and LMS. The molecular signatures unique to each of these malignancies may aid in expanding the diagnostic battery for their differentiation, and may provide a molecular basis for prognostic studies and therapeutic target discovery.

Dynamic changes in the secondary structure of ECE-1 and XCE account for their different substrate specificities

Background

X-converting enzyme (XCE) involved in nervous control of respiration, is a member of the M13 family of zinc peptidases, for which no natural substrate has been identified yet. In contrast, it’s well characterized homologue endothelin-converting enzyme-1 (ECE-1) showed broad substrate specificity and acts as endopeptidase as well as dipeptidase. To explore the structural differences between XCE and ECE-1, homology model of XCE was built using the complex structure of ECE-1 with phosphoramidon (pdb-id: 3DWB) as template. Phosphoramidon was docked into the binding site of XCE whereas phosphate oxygen of the inhibitor was used as water molecule to design the apo forms of both enzymes. Molecular dynamics simulation of both enzymes was performed to analyze the dynamic nature of their active site residues in the absence and presence of the inhibitor.

Results

Homology model of XCE explained the role of non-conserved residues of its S2’ subsite. Molecular dynamics (MD) simulations identified the flexible transitions of F149/I150, N566/N571, W714/W719, and R145/R723 residues of ECE-1/XCE for the strong binding of the inhibitor. Secondary structure calculations using DSSP method reveals the folding of R145/R723 residue of ECE-1/XCE into β-sheet structure while unfolding of the S2’ subsite residues in aECE-1 and sustained compact folding of that of aXCE. The results evaluated are in good agreement with available experimental data, thus providing detailed molecular models which can explain the structural and specificities differences between both zinc peptidases.

Conclusions

Secondary structure changes of both enzymes during the simulation time revealed the importance of β-sheet structure of R145/R723 for its binding with the terminal carboxylate group of the inhibitor. Unfolding of the α-helix comprising the S2’ subsite residues in aECE-1 correlate well with its endopeptidase activity while their compact folding in aXCE may account for the inactivity of the enzyme towards large C-terminal containing substrates.

Methylcap-seq reveals novel DNA methylation markers for the diagnosis and recurrence prediction of bladder cancer in a Chinese population

PURPOSE

There is a need to supplement or supplant the conventional diagnostic tools, namely, cystoscopy and B-type ultrasound, for bladder cancer (BC). We aimed to identify novel DNA methylation markers for BC through genome-wide profiling of BC cell lines and subsequent methylation-specific PCR (MSP) screening of clinical urine samples.

EXPERIMENTAL DESIGN

The methyl-DNA binding domain (MBD) capture technique, methylCap/seq, was performed to screen for specific hypermethylated CpG islands in two BC cell lines (5637 and T24). The top one hundred hypermethylated targets were sequentially screened by MSP in urine samples to gradually narrow the target number and optimize the composition of the diagnostic panel. The diagnostic performance of the obtained panel was evaluated in different clinical scenarios.

RESULTS

A total of 1,627 hypermethylated promoter targets in the BC cell lines was identified by Illumina sequencing. The top 104 hypermethylated targets were reduced to eight genes (VAX1, KCNV1, ECEL1, TMEM26, TAL1, PROX1, SLC6A20, and LMX1A) after the urine DNA screening in a small sample size of 8 normal control and 18 BC subjects. Validation in an independent sample of 212 BC patients enabled the optimization of five methylation targets, including VAX1, KCNV1, TAL1, PPOX1, and CFTR, which was obtained in our previous study, for BC diagnosis with a sensitivity and specificity of 88.68% and 87.25%, respectively. In addition, the methylation of VAX1 and LMX1A was found to be associated with BC recurrence.

CONCLUSIONS

We identified a promising diagnostic marker panel for early non-invasive detection and subsequent BC surveillance.

Novel Kv3 glycoforms differentially expressed in adult mammalian brain contain sialylated N-glycans

The N-glycan pool of mammalian brain contains remarkably high levels of sialylated N-glycans. This study provides the first evidence that voltage-gated K+ channels Kv3.1, Kv3.3, and Kv3.4, possess distinct sialylated N-glycan structures throughout the central nervous system of the adult rat. Electrophoretic migration patterns of Kv3.1, Kv3.3, and Kv3.4 glycoproteins from spinal cord, hypothalamus, thalamus, cerebral cortex, hippocampus, and cerebellum membranes digested with glycosidases were used to identify the various glycoforms. Differences in the migration of Kv3 proteins were attributed to the desialylated N-glycans. Expression levels of the Kv3 proteins were highest in cerebellum, whereas those of Kv3.1 and Kv3.3 were much lower in the other 5 regions. The lowest level of Kv3.1 was expressed in the hypothalamus, whereas the lowest levels of Kv3.3 were expressed in both thalamus and hypothalamus. The other regions expressed intermediate levels of Kv3.3, with spinal cord expressing the highest. The expression level of Kv3.4 in the hippocampus was slightly lower than that in cerebellum, and was closely followed by the other 4 regions, with spinal cord expressing the lowest level. We suggest that novel Kv3 glycoforms may endow differences in channel function and expression among regions throughout the central nervous system.

Complex oligosaccharides are N-linked to Kv3 voltage-gated K+ channels in rat brain

Neuronal Kv3 voltage-gated K(+) channels have two absolutely conserved N-glycosylation sites. Here, it is shown that Kv3.1, 3.3, and 3.4 channels are N-glycosylated in rat brain. Digestion of total brain membranes with peptide N glycosidase F (PNGase F) produced faster migrating immunobands than those of undigested membranes. Additionally, partial PNGase F digests showed that both sites are occupied by oligosaccharides. Neuraminidase treatment produced a smaller immunoband shift relative to PNGase F treatment. These results indicate that both sites are highly available and occupied by N-linked oligosaccharides for Kv3.1, 3.3, and 3.4 in rat brain, and furthermore that at least one oligosaccharide is of complex type. Additionally, these results point to an extracytoplasmic S1-S2 linker in Kv3 proteins expressed in native membranes. We suggest that N-glycosylation processing of Kv3 channels is critical for the expression of K(+) currents at the surface of neurons, and perhaps contributes to the pathophysiology of congenital disorders of glycosylation.

Identification and functional analysis of damage-induced neuronal endopeptidase (DINE), a nerve injury associated molecule

Nerve regeneration is a complex process associated with the expression of hundreds of genes. To elucidate the molecular mechanism responsible for nerve regeneration, hundreds of nerve regeneration-associated genes have been hunted using differential display polymerase chain reaction (DD-PCR), random cloning, microarray and proteomics. Damage-induced neuronal endopeptidase (DINE) is a newly identified nerve regeneration-related molecule derived from normal and axotomized hypoglosssal nuclei using DD-PCR. After full-length cloning, we have found that DINE is a neuron-specific membrane-bound metalloprotease. Damage-induced neuronal endopeptidase shares homology with neprilysin and endothelin-converting enzyme, which degrade or process neuropeptides. Although DINE has some neuroprotective effects, the physiological function of, as well as the substrate for, DINE remains obscure. The most intriguing property of DINE is its extreme transcriptional response against various types of nerve injuries, including that of the peripheral and central nervous systems. Thus, a more detailed expression profile of DINE mRNA was investigated using the dorsal root ganglion (DRG) after sciatic nerve injury. In the DRG, DINE mRNA was observed in small-sized DRG neurons after axotomy. This expression profile was similar to that of the neuropeptide galanin. Both in vitro and in vivo studies revealed that leukemia inhibitory factor and nerve growth factor withdrawal additively enhanced the expression of DINE, as well as that of galanin. Damage-induced neuronal endopeptidase and galanin may use common transcriptional regulation machinery. Although functional correlation of these molecules remains unclear, their simultaneous induction may provide more successful protection for injured neurons.

Localization and ontogeny of damage-induced neuronal endopeptidase mRNA-expressing neurons in the rat nervous system

Neuropeptides are crucial mediators in nervous and endocrine systems. Processing and degradation, the major regulatory mechanisms, of enzymes are essential for the control of these peptidergic intercellular signaling systems. Damage-induced neuronal endopeptidase (or endothelin converting enzyme-like1), a member of the neprilysin family, has recently been identified as an M13 zinc metalloprotease. Damage-induced neuronal endopeptidase mRNA expression is strikingly restricted to neurons, and is remarkably induced in response to various types of neuronal injuries, although its function and substrate remain unknown. To clarify the role of damage-induced neuronal endopeptidase, we examined the localization and ontogeny of damage-induced neuronal endopeptidase mRNA expression in the rat nervous system using in situ hybridization. Damage-induced neuronal endopeptidase mRNA was detected at embryonic day 12, and its expression restricted to the ventral region of the neural tube. Subsequently, expression was also apparent in primordia of the striatum, hypothalamus, and cranial motor nuclei during neural development. This specific distribution was relatively maintained in the adult brain, although expression levels became weaker. Expression of damage-induced neuronal endopeptidase was absent in the cerebral cortex, hippocampus, and cerebellum. In addition to prominent expression in CNS, intestinal and sensory ganglia and retina demonstrated transient intense damage-induced neuronal endopeptidase mRNA expression during the embryonic period that then declined, and disappeared after birth. The results indicated that damage-induced neuronal endopeptidase might play an important role in embryonic neural development, in particular in peripheral ganglia derived from the neural crest, and in some neurons originating from the basal plate such as the hypothalamus and cranial motor neurons.