Reelin functions beyond neuronal migration: from synaptogenesis to network activity modulation

The Reelin receptor ApoER2 is a cargo for the adaptor protein complex AP-4: Implications for Hereditary Spastic Paraplegia

Adaptor protein complex 4 (AP-4) is a heterotetrameric complex that promotes export of selected cargo proteins from the trans-Golgi network. Mutations in each of the AP-4 subunits cause a complicated form of Hereditary Spastic Paraplegia (HSP). Herein, we report that ApoER2, a receptor in the Reelin signaling pathway, is a cargo of the AP-4 complex. We identify the motif ISSF/Y within the ApoER2 cytosolic domain as necessary for interaction with the canonical signal-binding pocket of the µ4 (AP4M1) subunit of AP-4. AP4E1- knock-out (KO) HeLa cells and hippocampal neurons from Ap4e1-KO mice display increased co-localization of ApoER2 with Golgi markers. Furthermore, hippocampal neurons from Ap4e1-KO mice and AP4M1-KO human iPSC-derived cortical i3Neurons exhibit reduced ApoER2 protein expression. Analyses of biosynthetic transport of ApoER2 reveal differential post-Golgi trafficking of the receptor, with lower axonal distribution in KO compared to wild-type neurons, indicating a role of AP-4 and the ISSF/Y motif in the axonal localization of ApoER2. Finally, analyses of Reelin signaling in mouse hippocampal and human cortical KO neurons show that AP4 deficiency causes no changes in Reelin-dependent activation of the AKT pathway and only mild changes in Reelin-induced dendritic arborization, but reduces Reelin-induced ERK phosphorylation, CREB activation, and Golgi deployment. This work thus establishes ApoER2 as a novel cargo of the AP-4 complex, suggesting that defects in the trafficking of this receptor and in the Reelin signaling pathway could contribute to the pathogenesis of HSP caused by mutations in AP-4 subunits.

Cellular origin and molecular mechanisms of lung metastases in patients with aggressive hepatoblastoma

BACKGROUND AND AIMS

Lung metastases are the most threatening signs for patients with aggressive hepatoblastoma (HBL). Despite intensive studies, the cellular origin and molecular mechanisms of lung metastases in patients with aggressive HBL are not known. The aims of these studies were to identify metastasis-initiating cells in primary liver tumors and to determine if these cells are secreted in the blood, reach the lung, and form lung metastases.

APPROACH

We have examined mechanisms of activation of key oncogenes in primary liver tumors and lung metastases and the role of these mechanisms in the appearance of metastasis-initiating cells in patients with aggressive HBL by RNA-Seq, immunostaining, chromatin immunoprecipitation, Real-Time Quantitative Reverse Transcription PCR and western blot approaches. Using a protocol that mimics the exit of metastasis-initiating cells from tumors, we generated 16 cell lines from liver tumors and 2 lines from lung metastases of patients with HBL.

RESULTS

We found that primary HBL liver tumors have a dramatic elevation of neuron-like cells and cancer-associated fibroblasts and that these cells are released into the bloodstream of patients with HBL and found in lung metastases. In the primary liver tumors, the ph-S675-β-catenin pathway activates the expression of markers of cancer-associated fibroblasts; while the ZBTB3-SRCAP pathway activates the expression of markers of neurons via cancer-enhancing genomic regions/aggressive liver cancer domains leading to a dramatic increase of cancer-associated fibroblasts and neuron-like cells. Studies of generated metastasis-initiating cells showed that these cells proliferate rapidly, engage in intense cell-cell interactions, and form tumor clusters. The inhibition of β-catenin in HBL/lung metastases-released cells suppresses the formation of tumor clusters.

CONCLUSIONS

The inhibition of the β-catenin-cancer-enhancing genomic regions/aggressive liver cancer domains axis could be considered as a therapeutic approach to treat/prevent lung metastases in patients with HBL.

The Reelin Receptor ApoER2 is a Cargo for the Adaptor Protein Complex AP-4: Implications for Hereditary Spastic Paraplegia

Adaptor protein complex 4 (AP-4) is a heterotetrameric complex that promotes protein export from the trans -Golgi network. Mutations in each of the AP-4 subunits cause a complicated form of Hereditary Spastic Paraplegia (HSP). Herein, we report that ApoER2, a receptor in the Reelin signaling pathway, is a cargo of the AP-4 complex. We identify the motif ISSF/Y within the ApoER2 cytosolic domain as necessary for interaction with the canonical signal-binding pocket of the µ4 (AP4M1) subunit of AP-4. AP4E1 -knock-out (KO) HeLa cells and hippocampal neurons from Ap4e1 -KO mice display increased Golgi localization of ApoER2. Furthermore, hippocampal neurons from Ap4e1 -KO mice and AP4M1 -KO human iPSC-derived cortical i3Neurons exhibit reduced ApoER2 protein expression. Analyses of biosynthetic transport of ApoER2 reveal differential post-Golgi trafficking of the receptor, with lower axonal distribution in KO compared to wild-type neurons, indicating a role of AP-4 and the ISSF/Y motif in the axonal localization of ApoER2. Finally, analyses of Reelin signaling in mouse hippocampal and human cortical KO neurons show that AP4 deficiency causes no changes in Reelin-dependent activation of the AKT pathway and only mild changes in Reelin-induced dendritic arborization, but reduces Reelin-induced ERK phosphorylation, CREB activation, and Golgi deployment. Altogether, this work establishes ApoER2 as a novel cargo of the AP-4 complex, suggesting that defects in the trafficking of this receptor and in the Reelin signaling pathway could contribute to the pathogenesis of HSP caused by mutations in AP-4 subunits.

Fate tracking reveals differences between Reelin+ hepatic stellate cells (HSCs) and Desmin+ HSCs in activation, migration and proliferation

The activation of hepatic stellate cells (HSCs) is the main cause of liver fibrogenesis in response to different etiologies of chronic liver injuries. HSCs are heterogeneous, but the lack of specific markers to distinguish different HSC subset hinders the development of targeted therapy for liver fibrosis. In this study, we aim to reveal new HSC subsets by cell fate tracking. We constructed a novel ReelinCreERT2 transgenic mouse model to track the fate of cells expressing Reelin and their progeny (Reelin+ cells). And we investigated the property of Reelin+ cells, such as differentiation and proliferation, in hepatotoxic (carbon tetrachloride; CCl4 ) or cholestatic (bile duct ligation; BDL) liver injury models by immunohistochemistry. Our study revealed that Reelin+ cells were a new HSC subset. In terms of activation, migration, and proliferation, Reelin+ HSCs displayed different properties from Desmin+ HSCs (total HSCs) in cholestatic liver injury model but shared similar properties to total HSCs in hepatotoxic liver injury model. Besides, we did not find evidence that Reelin+ HSCs transdifferentiated into hepatocytes or cholangiocytes through mesenchymal-epithelial transition (MET). In this study, our genetic cell fate tracking data reveal that ReelinCreERT2-labelled cells are a new HSC subset, which provides new insights into targeted therapy for liver fibrosis.

Co-cultures of cerebellar slices from mice with different reelin genetic backgrounds as a model to study cortical lamination

Background: Reelin has fundamental functions in the developing and mature brain. Its absence gives rise to the Reeler phenotype in mice, the first described cerebellar mutation. In homozygous mutants missing the Reelin gene ( reln -/-), neurons are incapable of correctly positioning themselves in layered brain areas such as the cerebral and cerebellar cortices. We here demonstrate that by employing ex vivo cultured cerebellar slices one can reduce the number of animals and use a non-recovery procedure to analyze the effects of Reelin on the migration of Purkinje neurons (PNs). Methods: We generated mouse hybrids (L7-GFP relnF1/) with green fluorescent protein (GFP)-tagged PNs, directly visible under fluorescence microscopy. We then cultured the slices obtained from mice with different reln genotypes and demonstrated that when the slices from reln -/- mutants were co-cultured with those from reln +/- mice, the Reelin produced by the latter induced migration of the PNs to partially rescue the normal layered cortical histology. We have confirmed this observation with Voronoi tessellation to analyze PN dispersion. Results: In images of the co-cultured slices from reln -/- mice, Voronoi polygons were larger than in single-cultured slices of the same genetic background but smaller than those generated from slices of reln +/- animals. The mean roundness factor, area disorder, and roundness factor homogeneity were different when slices from reln -/- mice were cultivated singularly or co-cultivated, supporting mathematically the transition from the clustered organization of the PNs in the absence of Reelin to a layered structure when the protein is supplied ex vivo. Conclusions: Neurobiologists are the primary target users of this 3Rs approach. They should adopt it for the possibility to study and manipulate ex vivo the activity of a brain-secreted or genetically engineered protein (scientific perspective), the potential reduction (up to 20%) of the animals used, and the total avoidance of severe surgery (3Rs perspective).

Co-cultures of cerebellar slices from mice with different reelin genetic backgrounds as a model to study cortical lamination

Background: Reelin has fundamental functions in the developing and mature brain. Its absence gives rise to the Reeler phenotype in mice, the first described cerebellar mutation. In homozygous mutants missing the Reelin gene ( reln -/-), neurons are incapable of correctly positioning themselves in layered brain areas such as the cerebral and cerebellar cortices. We here demonstrate that by employing ex vivo cultured cerebellar slices one can reduce the number of animals and use a non-recovery procedure to analyze the effects of Reelin on the migration of Purkinje neurons (PNs). Methods: We generated mouse hybrids (L7-GFP relnF1/) with green fluorescent protein (GFP)-tagged PNs, directly visible under fluorescence microscopy. We then cultured the slices obtained from mice with different reln genotypes and demonstrated that when the slices from reln -/- mutants were co-cultured with those from reln +/- mice, the Reelin produced by the latter induced migration of the PNs to partially rescue the normal layered cortical histology. We have confirmed this observation with Voronoi tessellation to analyze PN dispersion. Results: In images of the co-cultured slices from reln -/- mice, Voronoi polygons were larger than in single-cultured slices of the same genetic background but smaller than those generated from slices of reln +/- animals. The mean roundness factor, area disorder, and roundness factor homogeneity were different when slices from reln -/- mice were cultivated singularly or co-cultivated, supporting mathematically the transition from the clustered organization of the PNs in the absence of Reelin to a layered structure when the protein is supplied ex vivo. Conclusions: Neurobiologists are the primary target users of this 3Rs approach. They should adopt it for the possibility to study and manipulate ex vivo the activity of a brain-secreted or genetically engineered protein (scientific perspective), the potential reduction (up to 20%) of the animals used, and the total avoidance of severe surgery (3Rs perspective).

Critical functions of extracellular matrix in brain metastasis seeding

Human brain is characterized by extremely sparse extracellular matrix (ECM). Despite its low abundance, the significance of brain ECM in both physiological and pathological conditions should not be underestimated. Brain metastasis is a serious complication of cancer, and recent findings highlighted the contribution of ECM in brain metastasis development. In this review, we provide a comprehensive outlook on how ECM proteins promote brain metastasis seeding. In particular, we discuss (1) disruption of the blood-brain barrier in brain metastasis; (2) role of ECM in modulating brain metastasis dormancy; (3) regulation of brain metastasis seeding by ECM-activated integrin signaling; (4) functions of brain-specific ECM protein reelin in brain metastasis. Lastly, we consider the possibility of targeting ECM for brain metastasis management.

The role of microRNAs in neurobiology and pathophysiology of the hippocampus

MicroRNAs (miRNAs) are short non-coding and well-conserved RNAs that are linked to many aspects of development and disorders. MicroRNAs control the expression of genes related to different biological processes and play a prominent role in the harmonious expression of many genes. During neural development of the central nervous system, miRNAs are regulated in time and space. In the mature brain, the dynamic expression of miRNAs continues, highlighting their functional importance in neurons. The hippocampus, as one of the crucial brain structures, is a key component of major functional connections in brain. Gene expression abnormalities in the hippocampus lead to disturbance in neurogenesis, neural maturation and synaptic formation. These disturbances are at the root of several neurological disorders and behavioral deficits, including Alzheimer's disease, epilepsy and schizophrenia. There is strong evidence that abnormalities in miRNAs are contributed in neurodegenerative mechanisms in the hippocampus through imbalanced activity of ion channels, neuronal excitability, synaptic plasticity and neuronal apoptosis. Some miRNAs affect oxidative stress, inflammation, neural differentiation, migration and neurogenesis in the hippocampus. Furthermore, major signaling cascades in neurodegeneration, such as NF-Kβ signaling, PI3/Akt signaling and Notch pathway, are closely modulated by miRNAs. These observations, suggest that microRNAs are significant regulators in the complicated network of gene regulation in the hippocampus. In the current review, we focus on the miRNA functional role in the progression of normal development and neurogenesis of the hippocampus. We also consider how miRNAs in the hippocampus are crucial for gene expression mechanisms in pathophysiological pathways.

Neuroplasticity-Related Genes and Dopamine Receptors Associated with Regional Cortical Thickness Increase Following Electroconvulsive Therapy for Major Depressive Disorder

Electroconvulsive therapy (ECT) is an effective neuromodulatory therapy for major depressive disorder (MDD). Treatment is associated with regional changes in brain structure and function, indicating activation of neuroplastic processes. To investigate the underlying neurobiological mechanism of macroscopic reorganization following ECT, we longitudinally (before and after ECT in two centers) collected magnetic resonance images for 96 MDD patients. Similar patterns of cortical thickness (CT) changes following ECT were observed in two centers. These CT changes were spatially colocalized with a weighted combination of genes enriched for neuroplasticity-related ontology terms and pathways (e.g., synaptic pruning) as well as with a higher density of D2/3 dopamine receptors. A multiple linear regression model indicated that the region-specific gene expression and receptor density patterns explained 40% of the variance in CT changes after ECT. In conclusion, these findings suggested that dopamine signaling and neuroplasticity-related genes are associated with the ECT-induced morphological reorganization.

Characterization by Gene Expression Analysis of Two Groups of Dopaminergic Cells Isolated from the Mouse Olfactory Bulb

The olfactory bulb (OB) is one of two regions of the mammalian brain which undergo continuous neuronal replacement during adulthood. A significant fraction of the cells added in adulthood to the bulbar circuitry is constituted by dopaminergic (DA) neurons. We took advantage of a peculiar property of dopaminergic neurons in transgenic mice expressing eGFP under the tyrosine hydroxylase (TH) promoter: while DA neurons located in the glomerular layer (GL) display full electrophysiological maturation, eGFP+ cells in the mitral layer (ML) show characteristics of immature cells. In addition, they also display a lower fluorescence intensity, possibly reflecting different degrees of maturation. To investigate whether this difference in maturation might be confirmed at the gene expression level, we used a fluorescence-activated cell sorting technique on enzymatically dissociated cells of the OB. The cells were divided into two groups based on their level of fluorescence, possibly corresponding to immature ML cells and fully mature DA neurons from the GL. Semiquantitative real-time PCR was performed to detect the level of expression of genes linked to the degree of maturation of DA neurons. We showed that indeed the cells expressing low eGFP fluorescence are immature neurons. Our method can be further used to explore the differences between these two groups of DA neurons.

Monoallelic and biallelic mutations in RELN underlie a graded series of neurodevelopmental disorders

Reelin, a large extracellular protein, plays several critical roles in brain development and function. It is encoded by RELN, first identified as the gene disrupted in the reeler mouse, a classic neurological mutant exhibiting ataxia, tremors and a 'reeling' gait. In humans, biallelic variants in RELN have been associated with a recessive lissencephaly variant with cerebellar hypoplasia, which matches well with the homozygous mouse mutant that has abnormal cortical structure, small hippocampi and severe cerebellar hypoplasia. Despite the large size of the gene, only 11 individuals with RELN-related lissencephaly with cerebellar hypoplasia from six families have previously been reported. Heterozygous carriers in these families were briefly reported as unaffected, although putative loss-of-function variants are practically absent in the population (probability of loss of function intolerance = 1). Here we present data on seven individuals from four families with biallelic and 13 individuals from seven families with monoallelic (heterozygous) variants of RELN and frontotemporal or temporal-predominant lissencephaly variant. Some individuals with monoallelic variants have moderate frontotemporal lissencephaly, but with normal cerebellar structure and intellectual disability with severe behavioural dysfunction. However, one adult had abnormal MRI with normal intelligence and neurological profile. Thorough literature analysis supports a causal role for monoallelic RELN variants in four seemingly distinct phenotypes including frontotemporal lissencephaly, epilepsy, autism and probably schizophrenia. Notably, we observed a significantly higher proportion of loss-of-function variants in the biallelic compared to the monoallelic cohort, where the variant spectrum included missense and splice-site variants. We assessed the impact of two canonical splice-site variants observed as biallelic or monoallelic variants in individuals with moderately affected or normal cerebellum and demonstrated exon skipping causing in-frame loss of 46 or 52 amino acids in the central RELN domain. Previously reported functional studies demonstrated severe reduction in overall RELN secretion caused by heterozygous missense variants p.Cys539Arg and p.Arg3207Cys associated with lissencephaly suggesting a dominant-negative effect. We conclude that biallelic variants resulting in complete absence of RELN expression are associated with a consistent and severe phenotype that includes cerebellar hypoplasia. However, reduced expression of RELN remains sufficient to maintain nearly normal cerebellar structure. Monoallelic variants are associated with incomplete penetrance and variable expressivity even within the same family and may have dominant-negative effects. Reduced RELN secretion in heterozygous individuals affects only cortical structure whereas the cerebellum remains intact. Our data expand the spectrum of RELN-related neurodevelopmental disorders ranging from lethal brain malformations to adult phenotypes with normal brain imaging.

Lipophorin receptors regulate mushroom body development and complex behaviors in Drosophila

BACKGROUND

Drosophila melanogaster lipophorin receptors (LpRs), LpR1 and LpR2, are members of the LDLR family known to mediate lipid uptake in a range of organisms from Drosophila to humans. The vertebrate orthologs of LpRs, ApoER2 and VLDL-R, function as receptors of a glycoprotein involved in development of the central nervous system, Reelin, which is not present in flies. ApoER2 and VLDL-R are associated with the development and function of the hippocampus and cerebral cortex, important association areas in the mammalian brain, as well as with neurodevelopmental and neurodegenerative disorders linked to those regions. It is currently unknown whether LpRs play similar roles in the Drosophila brain.

RESULTS

We report that LpR-deficient flies exhibit impaired olfactory memory and sleep patterns, which seem to reflect anatomical defects found in a critical brain association area, the mushroom bodies (MB). Moreover, cultured MB neurons respond to mammalian Reelin by increasing the complexity of their neurite arborization. This effect depends on LpRs and Dab, the Drosophila ortholog of the Reelin signaling adaptor protein Dab1. In vitro, two of the long isoforms of LpRs allow the internalization of Reelin, suggesting that Drosophila LpRs interact with human Reelin to induce downstream cellular events.

CONCLUSIONS

These findings demonstrate that LpRs contribute to MB development and function, supporting the existence of a LpR-dependent signaling in Drosophila, and advance our understanding of the molecular factors functioning in neural systems to generate complex behaviors in this model. Our results further emphasize the importance of Drosophila as a model to investigate the alterations in specific genes contributing to neural disorders.

Uncovering the Underlying Mechanisms of Ketamine as a Novel Antidepressant

Major depressive disorder (MDD) is a devastating psychiatric disorder which exacts enormous personal and social-economic burdens. Ketamine, an N-methyl-D-aspartate receptor (NMDAR) antagonist, has been discovered to exert rapid and sustained antidepressant-like actions on MDD patients and animal models. However, the dissociation and psychotomimetic propensities of ketamine have limited its use for psychiatric indications. Here, we review recently proposed mechanistic hypotheses regarding how ketamine exerts antidepressant-like actions. Ketamine may potentiate α-amino-3-hydroxy-5-methyl-4-isoxazole-propionic acid receptor (AMPAR)-mediated transmission in pyramidal neurons by disinhibition and/or blockade of spontaneous NMDAR-mediated neurotransmission. Ketamine may also activate neuroplasticity- and synaptogenesis-relevant signaling pathways, which may converge on key components like brain-derived neurotrophic factor (BDNF)/tropomyosin receptor kinase B (TrkB) and mechanistic target of rapamycin (mTOR). These processes may subsequently rebalance the excitatory/inhibitory transmission and restore neural network integrity that is compromised in depression. Understanding the mechanisms underpinning ketamine’s antidepressant-like actions at cellular and neural circuit level will drive the development of safe and effective pharmacological interventions for the treatment of MDD.

Parvalbumin-Positive Interneurons Regulate Cortical Sensory Plasticity in Adulthood and Development Through Shared Mechanisms

Parvalbumin-positive neurons are the largest class of GABAergic, inhibitory neurons in the central nervous system. In the cortex, these fast-spiking cells provide feedforward and feedback synaptic inhibition onto a diverse set of cell types, including pyramidal cells, other inhibitory interneurons, and themselves. Cortical inhibitory networks broadly, and cortical parvalbumin-expressing interneurons (cPVins) specifically, are crucial for regulating sensory plasticity during both development and adulthood. Here we review the functional properties of cPVins that enable plasticity in the cortex of adult mammals and the influence of cPVins on sensory activity at four spatiotemporal scales. First, cPVins regulate developmental critical periods and adult plasticity through molecular and structural interactions with the extracellular matrix. Second, they activate in precise sequence following feedforward excitation to enforce strict temporal limits in response to the presentation of sensory stimuli. Third, they implement gain control to normalize sensory inputs and compress the dynamic range of output. Fourth, they synchronize broad network activity patterns in response to behavioral events and state changes. Much of the evidence for the contribution of cPVins to plasticity comes from classic models that rely on sensory deprivation methods to probe experience-dependent changes in the brain. We support investigating naturally occurring, adaptive cortical plasticity to study cPVin circuits in an ethologically relevant framework, and discuss recent insights from our work on maternal experience-induced auditory cortical plasticity.

Behavioral and Cognitive Consequences of Obesity in Parents and Offspring in Female and Male Rats: Implications of Neuroinflammation and Neuromodulation

Obesity is a rapidly growing public health concern that can create a family-wise burden. This study was aimed to investigate behavioral, cognitive, neuroinflammatory, and neuromodulatory consequences of the diet and parental obesity. Female and male Wistar albino rats were fed on either an obesogenic or standard diet for 12 weeks, beginning with weaning. Thereafter, the animals were matched and allowed to mate. Pups born to obese or normal parents received either the diet or standard chow to the same age. The obesogenic diet and/or parental obesity increased the locomotor activity in both females and males. The diet exhibited anxiolytic-like and antidepressant-like properties, and impaired short-term object memory as well as spatial memory. Interestingly, the obesogenic diet resulted in neuroinflammation only in naïve animals, but not in the ones with parental obesity. BDNF, SIRT1, and p53 expressions were decreased, whereas RelN expression was increased in the brain with the diet, regardless of parental obesity. Multi-factor analyses demonstrated that the obesogenic diet is the prominent influencer of cognitive, neuroinflammatory, and neuromodulatory results while parental obesity has an effect on spatial memory, neuroinflammation, and hippocampal RelN and p53 expressions. Here, we provided supporting evidence for detrimental cognitive and neuroinflammatory consequences of early life consumption of the obesogenic diet which accompanies alterations in neuromodulatory factors. Surprisingly, the diet was found beneficial against anxiety-like and depression-like behaviors, and additionally, parental obesity was demonstrated to impair some aspects of cognitive performance which appears unrelated to neuroinflammation.

Keeping the Balance: GABAB Receptors in the Developing Brain and Beyond

The main neurotransmitter in the brain responsible for the inhibition of neuronal activity is γ-aminobutyric acid (GABA). It plays a crucial role in circuit formation during development, both via its primary effects as a neurotransmitter and also as a trophic factor. The GABA_B receptors (GABA_BRs) are G protein-coupled metabotropic receptors; on one hand, they can influence proliferation and migration; and, on the other, they can inhibit cells by modulating the function of K⁺ and Ca²⁺ channels, doing so on a slower time scale and with a longer-lasting effect compared to ionotropic GABA_A receptors. GABA_BRs are expressed pre- and post-synaptically, at both glutamatergic and GABAergic terminals, thus being able to shape neuronal activity, plasticity, and the balance between excitatory and inhibitory synaptic transmission in response to varying levels of extracellular GABA concentration. Furthermore, given their subunit composition and their ability to form complexes with several associated proteins, GABA_BRs display heterogeneity with regard to their function, which makes them a promising target for pharmacological interventions. This review will describe (i) the latest results concerning GABA_BRs/GABA_BR-complex structures, their function, and the developmental time course of their appearance and functional integration in the brain, (ii) their involvement in manifestation of various pathophysiological conditions, and (iii) the current status of preclinical and clinical studies involving GABA_BR-targeting drugs.

Molecular typing of familial temporal lobe epilepsy

The pathogenesis of temporal lobe epilepsy (TLE) was originally considered to be acquired. However, some reports showed that TLE was clustered in some families, indicating a genetic etiology. With the popularity of genetic testing technology, eleven different types of familial TLE (FTLE), including ETL1-ETL11, have been reported, of which ETL9-ETL11 had not yet been included in the OMIM database. These types of FTLE were caused by different genes/Loci and had distinct characteristics. ETL1, ETL7 and ETL10 were characterized by auditory, visual and aphasia seizures, leading to the diagnosis of familial lateral TLE. ETL2, ETL3 and ETL6 showed prominent autonomic symptom and automatism with or without hippocampal abnormalities, indicating a mesial temporal origin. Febrile seizures were common in FTLEs such as ETL2, ETL5, ETL6 and ETL11. ETL4 was diagnosed as occipitotemporal lobe epilepsy with a high incidence of migraine and visual aura. Considering the diversity and complexity of the symptoms of TLE, neurologists enquiring about the family history of epilepsy should ask whether the relatives of the proband had experienced unnoticeable seizures and whether there is a family history of other neurological diseases carefully. Most FTLE patients had a good prognosis with or without anti-seizure medication treatment, with the exception of patients with heterozygous mutations of the CPA6 gene. The pathogenic mechanism was diverse among these genes and spans disturbances of neuron development, differentiation and synaptic signaling. In this article, we describe the research progress on eleven different types of FTLE. The precise molecular typing of FTLE would facilitate the diagnosis and treatment of FTLE and genetic counseling for this disorder.