LGI1 and LGI4 bind to ADAM22, ADAM23 and ADAM11

The transmembrane protein ADAM22 is expressed at high levels in the brain. From its molecular structure, ADAM22 is thought to be an adhesion molecule or a receptor because it has functional disintegrin-like and cysteine-rich sequences in its ectodomain. The phenotypic analysis of ADAM22-deficient mice has indicated the important roles played by ADAM22 in proper neuronal function and peripheral nerve development, however, the precise molecular function of ADAM22 is still unknown. To understand the function of ADAM22 on a molecular basis, we identified ADAM22 binding proteins by using immunoprecipitation and mass spectrometric analysis. This analysis revealed that Leucine-rich glioma inactivated 1 (LGI1) is the most potent ADAM22 binding protein in mouse brain. By our quantitative cell-ELISA system, we demonstrated the specific binding of LGI1 with ADAM22. Furthermore, we showed that LGI4, a putative ADAM22 ligand, also bound to ADAM22. Characterization of the binding specificity of LGI1 and LGI4 suggested that ADAM22 is not a sole receptor, because ADAM11 and ADAM23 had a significant binding ability to LGI1 or LGI4. Therefore, LGI-ADAM system seems to be regulated not only by the affinity but also by the cell-type-specific expression of each protein. Our findings provide new clues to understand the functions of LGI1 and LGI4 as an ADAMs ligand.     

LGI proteins in the nervous system

The development and function of the vertebrate nervous system depend on specific interactions between different cell types. Two examples of such interactions are synaptic transmission and myelination. LGI1-4 (leucine-rich glioma inactivated proteins) play important roles in these processes. They are secreted proteins consisting of an LRR (leucine-rich repeat) domain and a so-called epilepsy-associated or EPTP (epitempin) domain. Both domains are thought to function in protein–protein interactions. The first LGI gene to be identified, LGI1, was found at a chromosomal translocation breakpoint in a glioma cell line. It was subsequently found mutated in ADLTE (autosomal dominant lateral temporal (lobe) epilepsy) also referred to as ADPEAF (autosomal dominant partial epilepsy with auditory features). LGI1 protein appears to act at synapses and antibodies against LGI1 may cause the autoimmune disorder limbic encephalitis. A similar function in synaptic remodelling has been suggested for LGI2, which is mutated in canine Benign Familial Juvenile Epilepsy. LGI4 is required for proliferation of glia in the peripheral nervous system and binds to a neuronal receptor, ADAM22, to foster ensheathment and myelination of axons by Schwann cells. Thus, LGI proteins play crucial roles in nervous system development and function and their study is highly important, both to understand their biological functions and for their therapeutic potential. Here, we review our current knowledge about this important family of proteins, and the progress made towards understanding their functions.     

Using gene-history and expression analyses to assess the involvement of LGI genes in human disorders

Mutations in the leucine-rich, glioma-inactivated 1 gene, LGI1, cause autosomal-dominant lateral temporal lobe epilepsy via unknown mechanisms. LGI1 belongs to a subfamily of leucine-rich repeat genes comprising four members (LGI1-LGI4) in mammals. In this study, both comparative developmental as well as molecular evolutionary methods were applied to investigate the evolution of the LGI gene family and, subsequently, of the functional importance of its different gene members. Our phylogenetic studies suggest that LGI genes evolved early in the vertebrate lineage. Genetic and expression analyses of all five zebrafish lgi genes revealed duplications of lgi1 and lgi2, each resulting in two paralogous gene copies with mostly nonoverlapping expression patterns. Furthermore, all vertebrate LGI1 orthologs experience high levels of purifying selection that argue for an essential role of this gene in neural development or function. The approach of combining expression and selection data used here exemplarily demonstrates that in poorly characterized gene families a framework of evolutionary and expression analyses can identify those genes that are functionally most important and are therefore prime candidates for human disorders.     

LGI2 truncation causes a remitting focal epilepsy in dogs

One quadrillion synapses are laid in the first two years of postnatal construction of the human brain, which are then pruned until age 10 to 500 trillion synapses composing the final network. Genetic epilepsies are the most common neurological diseases with onset during pruning, affecting 0.5% of 2-10-year-old children, and these epilepsies are often characterized by spontaneous remission. We previously described a remitting epilepsy in the Lagotto romagnolo canine breed. Here, we identify the gene defect and affected neurochemical pathway. We reconstructed a large Lagotto pedigree of around 34 affected animals. Using genome-wide association in 11 discordant sib-pairs from this pedigree, we mapped the disease locus to a 1.7 Mb region of homozygosity in chromosome 3 where we identified a protein-truncating mutation in the Lgi2 gene, a homologue of the human epilepsy gene LGI1. We show that LGI2, like LGI1, is neuronally secreted and acts on metalloproteinase-lacking members of the ADAM family of neuronal receptors, which function in synapse remodeling, and that LGI2 truncation, like LGI1 truncations, prevents secretion and ADAM interaction. The resulting epilepsy onsets at around seven weeks (equivalent to human two years), and remits by four months (human eight years), versus onset after age eight in the majority of human patients with LGI1 mutations. Finally, we show that Lgi2 is expressed highly in the immediate post-natal period until halfway through pruning, unlike Lgi1, which is expressed in the latter part of pruning and beyond. LGI2 acts at least in part through the same ADAM receptors as LGI1, but earlier, ensuring electrical stability (absence of epilepsy) during pruning years, preceding this same function performed by LGI1 in later years. LGI2 should be considered a candidate gene for common remitting childhood epilepsies, and LGI2-to-LGI1 transition for mechanisms of childhood epilepsy remission.     

Selective inactivation of LGI1 in neuronal precursor cells leads to cortical dysplasia in mice

Constitutional mutations in Leucine‐rich glioma inactivated 1 (LGI1) predispose to an autosomal dominant epilepsy syndrome in humans and germline inactivation of LGI1 in mice leads to early onset seizures. LGI1 is highly expressed in the regions involved in neuronal stem cell generation and migration and detailed analysis of the brains in these mice reveals a subtle cortical dysplasia characterized by hypercellularity in the outer cortical layers. To investigate the cellular origin for this cortical dysplasia, we created mice that allow cell‐specific, conditional inactivation of LGI1. Exons 3–4, which contain critical motifs for LGI1 function, were targeted for deletion and, using a CMV‐cre mouse strain, global inactivation of LGI1 led to early onset seizures and the same cortical dysplasia seen in the constitutionally null mice. Similarly, inactivation of LGI1 in cells expressing Nestin, expressed primarily in neuronal precursor cells, led to early onset seizures and cortical dysplasia. In contrast, targeting inactivation of LGI1 in cells expressing Gfap, Camk2a, and parvalbumin, did not lead to cortical dysplasia. This strain of mouse, therefore, allows for a more refined investigation of the cell types involved in the cortical dysplasia seen following inactivation of LGI1 and potentially a better understanding of the molecular mechanisms behind LGI1‐induced epilepsy.     

Leucine-rich glioma inactivated 3 and tumor necrosis factor-α regulate mutually through NF-κB

Leucine-rich glioma inactivated 3 (LGI3) is a secreted protein member of LGI family. We previously reported that LGI3 increased in obese adipose tissues and suppressed adipogenesis through its receptor, ADAM23. We proposed that LGI3 may be a pro-inflammatory adipokine secreted predominantly by preadipocytes and macrophages. In this study, we showed that LGI3 and tumor necrosis factor-α (TNF-α) upregulated each other in 3T3-L1 cells. Treatment of 3T3-L1 preadipocytes with LGI3 protein increased TNF-α mRNA and protein. LGI3 treatment led to NF-κB activation and binding to an NF-κB binding site (−523 to −514) in TNF-α promoter. TNF-α treatment increased mRNA and protein expression of LGI3 and ADAM23. TNF-α increased NF-κB binding to a predicted binding site (−40 to −31) in LGI3 promoter. High fat diet-fed mice showed that LGI3 and TNF-α were increased and colocalized in adipose tissue inflammation. Taken together, these results suggested that mutual upregulation of LGI3 and TNF-α may play a role in adipose tissue inflammation in obesity.     

A computational model of the LGI1 protein suggests a common binding site for ADAM proteins

Mutations of human leucine-rich glioma inactivated (LGI1) gene encoding the epitempin protein cause autosomal dominant temporal lateral epilepsy (ADTLE), a rare familial partial epileptic syndrome. The LGI1 gene seems to have a role on the transmission of neuronal messages but the exact molecular mechanism remains unclear. In contrast to other genes involved in epileptic disorders, epitempin shows no homology with known ion channel genes but contains two domains, composed of repeated structural units, known to mediate protein-protein interactions.A three dimensional in silico model of the two epitempin domains was built to predict the structure-function relationship and propose a functional model integrating previous experimental findings. Conserved and electrostatic charged regions of the model surface suggest a possible arrangement between the two domains and identifies a possible ADAM protein binding site in the β-propeller domain and another protein binding site in the leucine-rich repeat domain. The functional model indicates that epitempin could mediate the interaction between proteins localized to different synaptic sides in a static way, by forming a dimer, or in a dynamic way, by binding proteins at different times.The model was also used to predict effects of known disease-causing missense mutations. Most of the variants are predicted to alter protein folding while several other map to functional surface regions. In agreement with experimental evidence, this suggests that non-secreted LGI1 mutants could be retained within the cell by quality control mechanisms or by altering interactions required for the secretion process.     

富亮氨酸胶质瘤失活1蛋白抗体脑炎的病理特征及临床分析（附1 例案例报道）

目的:探索富亮氨酸胶质瘤失活1蛋白(LGI1)抗体相关自身免疫性脑炎的临床特点及治疗。方法:报道l例LG I1抗体阳性相关自身免疫性脑炎的临床资料,并结合相关文献讨论该病的临床病理特点。结果:老年男性,亚急性起病,反复多次发作并进行性加重,以近记忆下降、癫痫、认知和睡眠障碍为主要表现;头颅MRI示脑萎缩;LGI1抗体阳性。结论:本病患者具有认知功能、睡眠障碍及癫痫等,血清和脑脊液中抗LGI1抗体阳性,但无低钠血症,头颅影像学检查正常;急性发作期给予免疫抑制剂治疗后可获良好效果。     

The LGI1/epitempin gene encodes two protein isoforms differentially expressed in human brain

The leucine-rich, glioma inactivated 1 (LGI1)/Epitempin gene has been linked to two phenotypes as different as gliomagenesis and autosomal dominant lateral temporal epilepsy. Its function and the biochemical features of the encoded protein are unknown. We characterized the LGI1/Epitempin protein product by western blot analysis of mouse and human brain tissues. Two proteins of about 60 and 65 kDa were detected by an anti-LGI1 antibody within the expected molecular mass range. The two proteins appeared to reside in different subcellular compartments, as they were fractionated by differential centrifugation. The specificity of both polypeptides was validated by cell transfection assay and mass spectrometry analysis. Immunoblot analysis of protein distribution in various zones of the human brain revealed variable amounts of both proteins. Notably, these proteins were more abundant in the temporal neocortex than in the hippocampus, the difference in abundance of the 65-kDa product being particularly pronounced. These results suggest that the two protein isoforms encoded by LGI1/Epitempin are differentially expressed in the human brain, and that higher expression levels of these proteins in the lateral temporal cortex may underlie the susceptibility of this brain region to the epileptogenic effects of LGI1/Epitempin mutations.     

Ccz1p/Aut11p/Cvt16p is essential for autophagy and the cvt pathway

Recently mutations in the LGI1 (leucine-rich, glioma-inactivated 1) gene have been found in human temporal lobe epilepsy. We have now identified three formerly unknown LGI-like genes. Hydropathy plots and pattern analysis showed that LGI genes encode proteins with large extra- and intracellular domains connected by a single transmembrane region. Sequence analysis demonstrated that LGI1, LGI2, LGI3, and LGI4 form a distinct subfamily when compared to other leucine-rich repeat-containing proteins. In silico mapping and radiation hybrid experiments assigned LGI2, LGI3, and LGI4 to different chromosomal regions (4p15.2, 8p21.3, 19q13.11), some of which have been implicated in epileptogenesis and/or tumorigenesis.     

Identification of a novel idiopathic epilepsy locus in Belgian Shepherd dogs

Epilepsy is the most common neurological disorder in dogs, with an incidence ranging from 0.5% to up to 20% in particular breeds. Canine epilepsy can be etiologically defined as idiopathic or symptomatic. Epileptic seizures may be classified as focal with or without secondary generalization, or as primary generalized. Nine genes have been identified for symptomatic (storage diseases) and one for idiopathic epilepsy in different breeds. However, the genetic background of common canine epilepsies remains unknown. We have studied the clinical and genetic background of epilepsy in Belgian Shepherds. We collected 159 cases and 148 controls and confirmed the presence of epilepsy through epilepsy questionnaires and clinical examinations. The MRI was normal while interictal EEG revealed abnormalities and variable foci in the clinically examined affected dogs. A genome-wide association study using Affymetrix 50K SNP arrays in 40 cases and 44 controls mapped the epilepsy locus on CFA37, which was replicated in an independent cohort (81 cases and 88 controls; combined p = 9.70×10⁻¹⁰, OR = 3.3). Fine mapping study defined a ∼1 Mb region including 12 genes of which none are known epilepsy genes or encode ion channels. Exonic sequencing was performed for two candidate genes, KLF7 and ADAM23. No variation was found in KLF7 but a highly-associated non-synonymous variant, G1203A (R387H) was present in the ADAM23 gene (p = 3.7×10⁻⁸, OR = 3.9 for homozygosity). Homozygosity for a two-SNP haplotype within the ADAM23 gene conferred the highest risk for epilepsy (p = 6.28×10⁻¹¹, OR = 7.4). ADAM23 interacts with known epilepsy proteins LGI1 and LGI2. However, our data suggests that the ADAM23 variant is a polymorphism and we have initiated a targeted re-sequencing study across the locus to identify the causative mutation. It would establish the affected breed as a novel therapeutic model, help to develop a DNA test for breeding purposes and introduce a novel candidate gene for human idiopathic epilepsies.     

Mutant LGI1 inhibits seizure-induced trafficking of Kv4.2 potassium channels

Activity-dependent redistribution of ion channels mediates neuronal circuit plasticity and homeostasis, and could provide pro-epileptic or compensatory anti-epileptic responses to a seizure. Thalamocortical neurons transmit sensory information to the cerebral cortex and through reciprocal corticothalamic connections are intensely activated during a seizure. Therefore, we assessed whether a seizure alters ion channel surface expression and consequent neurophysiologic function of thalamocortical neurons. We report a seizure triggers a rapid (<2h) decrease of excitatory postsynaptic current (EPSC)-like current-induced phasic firing associated with increased transient A-type K(+) current. Seizures also rapidly redistributed the A-type K(+) channel subunit Kv4.2 to the neuronal surface implicating a molecular substrate for the increased K(+) current. Glutamate applied in vitro mimicked the effect, suggesting a direct effect of glutamatergic transmission. Importantly, leucine-rich glioma-inactivated-1 (LGI1), a secreted synaptic protein mutated to cause human partial epilepsy, regulated this seizure-induced circuit response. Human epilepsy-associated dominant-negative-truncated mutant LGI1 inhibited the seizure-induced suppression of phasic firing, increase of A-type K(+) current, and recruitment of Kv4.2 surface expression (in vivo and in vitro). The results identify a response of thalamocortical neurons to seizures involving Kv4.2 surface recruitment associated with dampened phasic firing. The results also identify impaired seizure-induced increases of A-type K(+) current as an additional defect produced by the autosomal dominant lateral temporal lobe epilepsy gene mutant that might contribute to the seizure disorder.     

Leucine-rich glioma inactivated 3 regulates adipogenesis through ADAM23

Leucine-rich glioma inactivated 3 (LGI3) is a secreted protein and a member of LGI/epitempin family. We previously showed that LGI3 was highly expressed in brain and played regulatory roles in neuronal exocytosis and differentiation. Besides the nervous system, LGI3 was shown to be expressed in diverse tissues. In this study, we found that LGI3 and its receptor candidate ADAM23 were expressed in adipose tissues and 3T3-L1 cells. 3T3-L1 preadipocytes secreted a 60-kDa protein, a major secreted form of LGI3, which declined with adipocyte differentiation. LGI3 was also expressed in adipose tissue macrophages in the ob/ob mice and in macrophage cell line. The 60-kDa LGI3 protein was selectively increased in the ob/ob adipose tissues comparing with the lean mice. Pull-down experiments, coimmunoprecipitation and immunocytochemistry indicated that LGI3 associated with ADAM23 in adipose tissues and 3T3-L1 cells. Knockdown of LGI3 or ADAM23 by siRNA increased adipogenesis in 3T3-L1 cells. Treatment with LGI3 protein did not affect preadipocyte proliferation but attenuated adipogenesis and this effect was reversed by siRNA-mediated knockdown of ADAM23. Taken together, we propose that LGI3 may be a candidate adipokine that is perturbed in obesity and suppresses adipogenesis through its receptor, ADAM23.     

Identification of a common risk haplotype for canine idiopathic epilepsy in the ADAM23 gene

Background

Idiopathic epilepsy is a common neurological disease in human and domestic dogs but relatively few risk genes have been identified to date. The seizure characteristics, including focal and generalised seizures, are similar between the two species, with gene discovery facilitated by the reduced genetic heterogeneity of purebred dogs. We have recently identified a risk locus for idiopathic epilepsy in the Belgian Shepherd breed on a 4.4 megabase region on CFA37.

Results

We have expanded a previous study replicating the association with a combined analysis of 157 cases and 179 controls in three additional breeds: Schipperke, Finnish Spitz and Beagle (p_c = 2.9e–07, p_GWAS = 1.74E-02). A targeted resequencing of the 4.4 megabase region in twelve Belgian Shepherd cases and twelve controls with opposite haplotypes identified 37 case-specific variants within the ADAM23 gene. Twenty-seven variants were validated in 285 cases and 355 controls from four breeds, resulting in a strong replication of the ADAM23 locus (p_raw = 2.76e–15) and the identification of a common 28 kb-risk haplotype in all four breeds. Risk haplotype was present in frequencies of 0.49–0.7 in the breeds, suggesting that ADAM23 is a low penetrance risk gene for canine epilepsy.

Conclusions

These results implicate ADAM23 in common canine idiopathic epilepsy, although the causative variant remains yet to be identified. ADAM23 plays a role in synaptic transmission and interacts with known epilepsy genes, LGI1 and LGI2, and should be considered as a candidate gene for human epilepsies.

Electronic supplementary material

The online version of this article (doi:10.1186/s12864-015-1651-9) contains supplementary material, which is available to authorized users.     

When MT1-MMP meets ADAMs

MT1-MMP is a membrane-tethered enzyme capable of remodeling extracellular matrix. MT1-MMP-deficient mice exhibit systematic defects during development, especially in craniofacial development characterized by retarded calvarial bone formation. Recently, we identified MT1-MMP as a critical positive modulator of FGF signaling during intramembranous ossification. MT1-MMP cleaves ADAM9 to protect FGFR2 from ectodomain shedding. Depletion of ADAM9 in MT1-MMP-deficient mice significantly rescued the calvarial defects via restoring FGF signaling. Interestingly, this regulatory mechanism seems to be highly tissue-specific, as defective FGF2-induced corneal angiogenesis in Mmp14^?/? mice could not be rescued by removal of ADAM9. In addition, MT1-MMP also cleaves another ADAM family member, ADAM15. Our current findings not only present a novel regulatory mechanism for FGF signaling but also reveal a functional crosstalk between MMP and ADAM families. Better understanding of the interplay between ADAMs and MT1-MMP and its consequences for signaling pathways will provide new insights into therapeutic approaches for the management of developmental disorders and various diseases, such as cancer.     

Defining the expression pattern of the LGI1 gene in BAC transgenic mice

The LGI1 gene has been implicated in the development of epilepsy and the invasion phenotype of glial cells. Controversy over the specific tissue expression pattern of this gene has stemmed from conflicting reports generated using immunohistochemistry and the polymerase chain reaction. LGI1 is one of a four-member family of secreted proteins with high homology and here we demonstrate, using GFP-tagged constructs from the four LGI1family members, that commonly used antibodies against LGI1 cross-react with different family members. With the uncertainty surrounding the use of commercially available antibodies to truly establish the expression pattern of LGI1, we generated transgenic mice carrying the LGI1-containing BAC, RP23-127G7, which had been modified to express the GFP reporter gene under the control of the endogenous regulatory elements required for LGI1 expression. Three founder mice were generated, and immunohistochemistry was used to determine the tissue-specific pattern of expression. In the brain, distinct regions of glial and neuronal cell expression were identified, as well as the choriod plexus, which is largely pia-derived. In addition, strong expression levels were identified in glandular regions of the prostate, individual tubules in the kidney, sympathetic ganglia in the kidney, sebaceous glands in the skin, the islets of Langerhans, the endometrium, and the ovary and testes. All other major organs analyzed were negative. The pattern of reporter gene expression was identical in three individual founder mice, arguing against a position effect altering expression profile due to the integration site of the BAC.     

The interaction between ADAM22 and 14-3-3β

ADAM family consists of a number of transmembrane proteins that contain a disintegrin and metalloprotease domain. ADAMs are involved in a highly diverse set of biological processes, including fertilization, neurogenesis, myogenesis and inflammatory response. The ADAM proteins have both cell adhesion and protease activities.Adam22 is highly expressed in human brain. Theadam22-/- mice presented severe ataxia and died before weaning, but the function of ADAM22 is still unknown. 14-3-3 β interacting with ADAM22 was detected by using yeast two-hybrid assay. The specificity of interaction between ADAM22 and 14-3-3β was proved byin vitro binding assay and immunoprecipitation. The major 14-3-3β binding site was located in the last 28 amino acid residues of ADAM22 cytoplasmic tail. Protein 14-3-3β is abundant and plays an important role in mediating cell diffusion, migration and cell cycle control. The interaction of ADAM22 and 14-3-3β suggests that the ADAM22 may play a crucial role in neural function and development.     

The interaction between ADAM22 and 14-3-3β

ADAM family consists of a number of transmembrane proteins that contain a disintegrin and metalloprotease domain. ADAMs are involved in a highly diverse set of biological processes, including fertilization, neurogenesis, myogenesis and inflammatory response. The ADAM proteins have both cell adhesion and protease activities. Adam22 is highly expressed in human brain. The adam22-/- mice presented severe ataxia and died before weaning, but the function of ADAM22 is still unknown. 14-3-3β interacting with ADAM22 was detected by using yeast two-hybrid assay. The specificity of interaction between ADAM22 and 14-3-3β was proved by in vitro binding assay and immunoprecipitation. The major 14-3-3β binding site was located in the last 28 amino acid residues of ADAM22 cytoplasmic tail. Protein 14-3-3β is abundant and plays an important role in mediating cell diffusion, migration and cell cycle control. The interaction of ADAM22 and 14-3-3β suggests that the ADAM22 may play a crucial role in neural function and development.     

The novel EPTP repeat defines a superfamily of proteins implicated in epileptic disorders

Recent studies suggest that mutations in the LGI1/Epitempin gene cause autosomal dominant lateral temporal epilepsy. This gene encodes a protein of unknown function, which we postulate is secreted. The LGI1 protein has leucine-rich repeats in the N-terminal sequence and a tandem repeat (which we named EPTP) in its C-terminal region. A redefinition of the C-terminal repeat and the application of sensitive sequence analysis methods enabled us to define a new superfamily of proteins carrying varying numbers of the novel EPTP repeats in combination with various extracellular domains. Genes encoding proteins of this family are located in genomic regions associated with epilepsy and other neurological disorders.     

Molecular cloning and characterization of the family of feline leucine-rich glioma-inactivated (LGI) genes,and mutational analysis in familial spontaneous epileptic cats

Background

Leucine-rich glioma-inactivated (LGI) proteins play a critical role in synaptic transmission. Dysfunction of these genes and encoded proteins is associated with neurological disorders such as genetic epilepsy or autoimmune limbic encephalitis in animals and human. Familial spontaneous epileptic cats (FSECs) are the only feline strain and animal model of familial temporal lobe epilepsy. The seizure semiology of FSECs comprises recurrent limbic seizures with or without evolution into generalized epileptic seizures, while cats with antibodies against voltage-gated potassium channel complexed/LGI1 show limbic encephalitis and recurrent limbic seizures. However, it remains unclear whether the genetics underlying FSECs are associated with LGI family genes. In the present study, we cloned and characterized the feline LGI1–4 genes and examined their association with FSECs. Conventional PCR techniques were performed for cloning and mutational analysis. Characterization was predicted using bioinformatics software.

Results

The cDNAs of feline LGI1–4 contained 1674-bp, 1650-bp, 1647-bp, and 1617-bp open reading frames, respectively, and encoded proteins comprising 557, 549, 548, and 538 amino acid residues, respectively. The feline LGI1–4 putative protein sequences showed high homology with Homo sapiens, Canis familiaris, Bos taurus, Sus scrofa, and Equus caballus (92%–100%). Mutational analysis in 8 FSECs and 8 controls for LGI family genes revealed 3 non-synonymous and 14 synonymous single nucleotide polymorphisms in the coding region. Only one non-synonymous single nucleotide polymorphism in LGI4 was found in 3 out of 8 FSECs. Using three separate computational tools, this mutation was not predicted to be disease causing. No co-segregation of the disease was found with any variant.

Conclusions

We cloned the cDNAs of the four feline LGI genes, analyzed the amino acid sequences, and revealed that epilepsy in FSEC is not a monogenic disorder associated with LGI genes.