Homozygous and heterozygous disruptions of ANK3: at the crossroads of neurodevelopmental and psychiatric disorders

An Adaptable Spectrin/Ankyrin-Based Mechanism for Long-Range Organization of Plasma Membranes in Vertebrate Tissues

Ankyrins are membrane-associated proteins that together with their spectrin partners are responsible for micron-scale organization of vertebrate plasma membranes, including those of erythrocytes, excitable membranes of neurons and heart, lateral membrane domains of columnar epithelial cells, and striated muscle. Ankyrins coordinate functionally related membrane transporters and cell adhesion proteins (15 protein families identified so far) within plasma membrane compartments through independently evolved interactions of intrinsically disordered sequences with a highly conserved peptide-binding groove formed by the ANK repeat solenoid. Ankyrins are coupled to spectrins, which are elongated organelle-sized proteins that form mechanically resilient arrays through cross-linking by specialized actin filaments. In addition to protein interactions, cellular targeting and assembly of spectrin/ankyrin domains also critically depend on palmitoylation of ankyrin-G by aspartate-histidine-histidine-cysteine 5/8 palmitoyltransferases, as well as interaction of beta-2 spectrin with phosphoinositide lipids. These lipid-dependent spectrin/ankyrin domains are not static but are locally dynamic and determine membrane identity through opposing endocytosis of bulk lipids as well as specific proteins. A partnership between spectrin, ankyrin, and cell adhesion molecules first emerged in bilaterians over 500 million years ago. Ankyrin and spectrin may have been recruited to plasma membranes from more ancient roles in organelle transport. The basic bilaterian spectrin-ankyrin toolkit markedly expanded in vertebrates through gene duplications combined with variation in unstructured intramolecular regulatory sequences as well as independent evolution of ankyrin-binding activity by ion transporters involved in action potentials and calcium homeostasis. In addition, giant vertebrate ankyrins with specialized roles in axons acquired new coding sequences by exon shuffling. We speculate that early axon initial segments and epithelial lateral membranes initially were based on spectrin-ankyrin-cell adhesion molecule assemblies and subsequently served as "incubators," where ion transporters independently acquired ankyrin-binding activity through positive selection.

Sodium channel β subunits: emerging targets in channelopathies

Voltage-gated sodium channels (VGSCs) are responsible for the initiation and propagation of action potentials in excitable cells. VGSCs in mammalian brain are heterotrimeric complexes of α and β subunits. Although β subunits were originally termed auxiliary, we now know that they are multifunctional signaling molecules that play roles in both excitable and nonexcitable cell types and with or without the pore-forming α subunit present. β subunits function in VGSC and potassium channel modulation, cell adhesion, and gene regulation, with particularly important roles in brain development. Mutations in the genes encoding β subunits are linked to a number of diseases, including epilepsy, sudden death syndromes like SUDEP and SIDS, and cardiac arrhythmia. Although VGSC β subunit-specific drugs have not yet been developed, this protein family is an emerging therapeutic target.

Computational dissection of human episodic memory reveals mental process-specific genetic profiles

Episodic memory performance is the result of distinct mental processes, such as learning, memory maintenance, and emotional modulation of memory strength. Such processes can be effectively dissociated using computational models. Here we performed gene set enrichment analyses of model parameters estimated from the episodic memory performance of 1,765 healthy young adults. We report robust and replicated associations of the amine compound SLC (solute-carrier) transporters gene set with the learning rate, of the collagen formation and transmembrane receptor protein tyrosine kinase activity gene sets with the modulation of memory strength by negative emotional arousal, and of the L1 cell adhesion molecule (L1CAM) interactions gene set with the repetition-based memory improvement. Furthermore, in a large functional MRI sample of 795 subjects we found that the association between L1CAM interactions and memory maintenance revealed large clusters of differences in brain activity in frontal cortical areas. Our findings provide converging evidence that distinct genetic profiles underlie specific mental processes of human episodic memory. They also provide empirical support to previous theoretical and neurobiological studies linking specific neuromodulators to the learning rate and linking neural cell adhesion molecules to memory maintenance. Furthermore, our study suggests additional memory-related genetic pathways, which may contribute to a better understanding of the neurobiology of human memory.

A novel phenotype in N-glycosylation disorders: Gillessen-Kaesbach-Nishimura skeletal dysplasia due to pathogenic variants in ALG9

A rare lethal autosomal recessive syndrome with skeletal dysplasia, polycystic kidneys and multiple malformations was first described by Gillessen-Kaesbach et al and subsequently by Nishimura et al. The skeletal features uniformly comprise a round pelvis, mesomelic shortening of the upper limbs and defective ossification of the cervical spine. We studied two unrelated families including three affected fetuses with Gillessen-Kaesbach-Nishimura syndrome using whole-exome and Sanger sequencing, comparative genome hybridization and homozygosity mapping. All affected patients were shown to have a novel homozygous splice variant NM_024740.2: c.1173+2T>A in the ALG9 gene, encoding alpha-1,2-mannosyltransferase, involved in the formation of the lipid-linked oligosaccharide precursor of N-glycosylation. RNA analysis demonstrated skipping of exon 10, leading to shorter RNA. Mass spectrometric analysis showed an increase in monoglycosylated transferrin as compared with control tissues, confirming that this is a congenital disorder of glycosylation (CDG). Only three liveborn children with ALG9-CDG have been previously reported, all with missense variants. All three suffered from intellectual disability, muscular hypotonia, microcephaly and renal cysts, but none had skeletal dysplasia. Our study shows that some pathogenic variants in ALG9 can present as a lethal skeletal dysplasia with visceral malformations as the most severe phenotype. The skeletal features overlap with that previously reported for ALG3- and ALG12-CDG, suggesting that this subset of glycosylation disorders constitutes a new diagnostic group of skeletal dysplasias.

Subcellular patterning: axonal domains with specialized structure and function

Myelinated axons are patterned into discrete and often-repeating domains responsible for the efficient and rapid transmission of electrical signals. These domains include nodes of Ranvier and axon initial segments. Disruption of axonal patterning leads to nervous system dysfunction. In this review, we introduce the concept of subcellular patterning as applied to axons and discuss how these patterning events depend on both intrinsic, cytoskeletal mechanisms and extrinsic, myelinating glia-dependent mechanisms.

Hierarchical microtubule organization controls axon caliber and transport and determines synaptic structure and stability

The dimensions of axons and synaptic terminals determine cell-intrinsic properties of neurons; however, the cellular mechanisms selectively controlling establishment and maintenance of neuronal compartments remain poorly understood. Here, we show that two giant Drosophila Ankyrin2 isoforms, Ank2-L and Ank2-XL, and the MAP1B homolog Futsch form a membrane-associated microtubule-organizing complex that determines axonal diameter, supports axonal transport, and provides independent control of synaptic dimensions and stability. Ank2-L controls microtubule and synaptic stability upstream of Ank2-XL that selectively controls microtubule organization. Synergistically with Futsch, Ank2-XL provides three-dimensional microtubule organization and is required to establish appropriate synaptic dimensions and release properties. In axons, the Ank2-XL/Futsch complex establishes evenly spaced, grid-like microtubule organization and determines axonal diameter in the absence of neurofilaments. Reduced microtubule spacing limits anterograde transport velocities of mitochondria and synaptic vesicles. Our data identify control of microtubule architecture as a central mechanism to selectively control neuronal dimensions, functional properties, and connectivity.

Ankyrin-G regulates neurogenesis and Wnt signaling by altering the subcellular localization of β-catenin

Ankyrin-G is a scaffolding protein required for the formation of the axon initial segment in neurons. Recent genome-wide association studies and whole-exome sequencing have identified ANK3, the gene coding for ankyrin-G, to be a risk gene for multiple neuropsychiatric disorders, such as bipolar disorder, schizophrenia and autism spectrum disorder. Here, we describe a novel role for ankyrin-G in neural progenitor proliferation in the developing cortex. We found that ankyrin-G regulates canonical Wnt signaling by altering the subcellular localization and availability of β-catenin in proliferating cells. Ankyrin-G loss-of-function increases β-catenin levels in the nucleus, thereby promoting neural progenitor proliferation. Importantly, abnormalities in proliferation can be rescued by reducing Wnt pathway signaling. Taken together, these results suggest that ankyrin-G is required for proper brain development.

Homozygous missense mutation in STYXL1 associated with moderate intellectual disability, epilepsy and behavioural complexities

The introduction of massive parallel sequencing has led to the identification of multiple novel genes for intellectual disability (ID) as well as epilepsy. Whereas dominant de novo mutations have been proven to be a leading cause for these disorders, they do not apply to families suggestive of an autosomal recessive inheritance pattern. In this study, we combined the use of linkage analysis with exome sequencing to elucidate the cause of moderate non-syndromic ID, epilepsy and behavioural problems in a consanguineous Asian family. A founder missense mutation was identified in STYXL1. We propose this as a novel candidate gene involved in ID, accompanied by seizures and behavioural problems. Our findings further confirm the genetic heterogeneity of cognitive disorders and genetic epilepsy.

Giant ankyrin-G: a critical innovation in vertebrate evolution of fast and integrated neuronal signaling

Axon initial segments (AISs) and nodes of Ranvier are sites of clustering of voltage-gated sodium channels (VGSCs) in nervous systems of jawed vertebrates that facilitate fast long-distance electrical signaling. We demonstrate that proximal axonal polarity as well as assembly of the AIS and normal morphogenesis of nodes of Ranvier all require a heretofore uncharacterized alternatively spliced giant exon of ankyrin-G (AnkG). This exon has sequence similarity to I-connectin/Titin and was acquired after the first round of whole-genome duplication by the ancestral ANK2/ANK3 gene in early vertebrates before development of myelin. The giant exon resulted in a new nervous system-specific 480-kDa polypeptide combining previously known features of ANK repeats and β-spectrin-binding activity with a fibrous domain nearly 150 nm in length. We elucidate previously undescribed functions for giant AnkG, including recruitment of β4 spectrin to the AIS that likely is regulated by phosphorylation, and demonstrate that 480-kDa AnkG is a major component of the AIS membrane "undercoat' imaged by platinum replica electron microscopy. Surprisingly, giant AnkG-knockout neurons completely lacking known AIS components still retain distal axonal polarity and generate action potentials (APs), although with abnormal frequency. Giant AnkG-deficient mice live to weaning and provide a rationale for survival of humans with severe cognitive dysfunction bearing a truncating mutation in the giant exon. The giant exon of AnkG is required for assembly of the AIS and nodes of Ranvier and was a transformative innovation in evolution of the vertebrate nervous system that now is a potential target in neurodevelopmental disorders.

Giant ankyrin-G stabilizes somatodendritic GABAergic synapses through opposing endocytosis of GABAA receptors

GABAA-receptor-based interneuron circuitry is essential for higher order function of the human nervous system and is implicated in schizophrenia, depression, anxiety disorders, and autism. Here we demonstrate that giant ankyrin-G (480-kDa ankyrin-G) promotes stability of somatodendritic GABAergic synapses in vitro and in vivo. Moreover, giant ankyrin-G forms developmentally regulated and cell-type-specific micron-scale domains within extrasynaptic somatodendritic plasma membranes of pyramidal neurons. We further find that giant ankyrin-G promotes GABAergic synapse stability through opposing endocytosis of GABAA receptors, and requires a newly described interaction with GABARAP, a GABAA receptor-associated protein. We thus present a new mechanism for stabilization of GABAergic interneuron synapses and micron-scale organization of extrasynaptic membrane that provides a rationale for studies linking ankyrin-G genetic variation with psychiatric disease and abnormal neurodevelopment.

Glial ankyrins facilitate paranodal axoglial junction assembly

Neuron-glia interactions establish functional membrane domains along myelinated axons. These include nodes of Ranvier, paranodal axoglial junctions and juxtaparanodes. Paranodal junctions are the largest vertebrate junctional adhesion complex, and they are essential for rapid saltatory conduction and contribute to assembly and maintenance of nodes. However, the molecular mechanisms underlying paranodal junction assembly are poorly understood. Ankyrins are cytoskeletal scaffolds traditionally associated with Na(+) channel clustering in neurons and are important for membrane domain establishment and maintenance in many cell types. Here we show that ankyrin-B, expressed by Schwann cells, and ankyrin-G, expressed by oligodendrocytes, are highly enriched at the glial side of paranodal junctions where they interact with the essential glial junctional component neurofascin 155. Conditional knockout of ankyrins in oligodendrocytes disrupts paranodal junction assembly and delays nerve conduction during early development in mice. Thus, glial ankyrins function as major scaffolds that facilitate early and efficient paranodal junction assembly in the developing CNS.

Structural basis of diverse membrane target recognitions by ankyrins

Ankyrin adaptors together with their spectrin partners coordinate diverse ion channels and cell adhesion molecules within plasma membrane domains and thereby promote physiological activities including fast signaling in the heart and nervous system. Ankyrins specifically bind to numerous membrane targets through their 24 ankyrin repeats (ANK repeats), although the mechanism for the facile and independent evolution of these interactions has not been resolved. Here we report the structures of ANK repeats in complex with an inhibitory segment from the C-terminal regulatory domain and with a sodium channel Nav1.2 peptide, respectively, showing that the extended, extremely conserved inner groove spanning the entire ANK repeat solenoid contains multiple target binding sites capable of accommodating target proteins with very diverse sequences via combinatorial usage of these sites. These structures establish a framework for understanding the evolution of ankyrins' membrane targets, with implications for other proteins containing extended ANK repeat domains.

DOI:http://dx.doi.org/10.7554/eLife.04353.001

Proteins are made up of smaller building blocks called amino acids that are linked to form long chains that then fold into specific shapes. Each protein gets its unique identity from the number and order of the amino acids that it contains, but different proteins can contain similar arrangements of amino acids. These similar sequences, known as motifs, are usually short and typically mark the sites within proteins that bind to other molecules or proteins. A single protein can contain many motifs, including multiple repeats of the same motif.

One common motif is called the ankyrin (or ANK) repeat, which is found in 100s of proteins in different species, including bacteria and humans. Ankyrin proteins perform a range of important functions, such as connecting proteins in the cell surface membrane to a scaffold-like structure underneath the membrane.

Proteins containing ankyrin repeats are known to interact with a diverse range of other proteins (or targets) that are different in size and shape. The 24 repeats found in human ankyrin proteins appear to have essentially remained unchanged for the last 500 million years. As such, it remains unclear how the conserved ankyrin repeats can bind to such a wide variety of protein targets.

Now, Wang, Wei et al. have uncovered the three-dimensional structure of ankyrin repeats from a human ankyrin protein while it was bound either to a regulatory fragment from another ankyrin protein or to a region of a target protein (which transports sodium ions in and out of cells). The ankyrin repeats were shown to form an extended ‘left-handed helix’: a structure that has also been seen in other proteins with different repeating motifs. Wang, Wei et al. found that the ankyrin protein fragment bound to the inner surface of the part of the helix formed by the first 14 ankyrin repeats. The target protein region also bound to the helix's inner surface. Wang, Wei et al. show that this surface contains many binding sites that can be used, in different combinations, to allow ankyrins to interact with diverse proteins.

Other proteins with long sequences of repeats are widespread in nature, but uncovering the structures of these proteins is technically challenging. Wang, Wei et al.'s findings might reveal new insights into the functions of many of such proteins in a wide range of living species. Furthermore, the new structures could help explain why specific mutations in the genes that encode ankyrins (or their binding targets) can cause various diseases in humans—including heart diseases and psychiatric disorders.

DOI:http://dx.doi.org/10.7554/eLife.04353.002

Psychiatric risk factor ANK3/ankyrin-G nanodomains regulate the structure and function of glutamatergic synapses

Recent evidence implicates glutamatergic synapses as key pathogenic sites in psychiatric disorders. Common and rare variants in the ANK3 gene, encoding ankyrin-G, have been associated with bipolar disorder, schizophrenia, and autism. Here we demonstrate that ankyrin-G is integral to AMPAR-mediated synaptic transmission and maintenance of spine morphology. Using superresolution microscopy we find that ankyrin-G forms distinct nanodomain structures within the spine head and neck. At these sites, it modulates mushroom spine structure and function, probably as a perisynaptic scaffold and barrier within the spine neck. Neuronal activity promotes ankyrin-G accumulation in distinct spine subdomains, where it differentially regulates NMDA receptor-dependent plasticity. These data implicate subsynaptic nanodomains containing a major psychiatric risk molecule, ankyrin-G, as having location-specific functions and open directions for basic and translational investigation of psychiatric risk molecules.

The node of Ranvier in CNS pathology

Healthy nodes of Ranvier are crucial for action potential propagation along myelinated axons, both in the central and in the peripheral nervous system. Surprisingly, the node of Ranvier has often been neglected when describing CNS disorders, with most pathologies classified simply as being due to neuronal defects in the grey matter or due to oligodendrocyte damage in the white matter. However, recent studies have highlighted changes that occur in pathological conditions at the node of Ranvier, and at the associated paranodal and juxtaparanodal regions where neurons and myelinating glial cells interact. Lengthening of the node of Ranvier, failure of the electrically resistive seal between the myelin and the axon at the paranode, and retraction of myelin to expose voltage-gated K⁺ channels in the juxtaparanode, may contribute to altering the function of myelinated axons in a wide range of diseases, including stroke, spinal cord injury and multiple sclerosis. Here, we review the principles by which the node of Ranvier operates and its molecular structure, and thus explain how defects at the node and paranode contribute to neurological disorders.

Genetic modulation of working memory deficits by ankyrin 3 gene in schizophrenia

Neuropsychological endophenotype approach is an emerging strategy in schizophrenia research to understand and identify the functional importance of genetically transmitted, brain-based deficits present in this disorder. Accumulating evidence indicated that working memory deficit is a core neuropsychological dysfunction in schizophrenia and a primary endophenotype indexing the liability to develop schizophrenia. Genetic variation in ankyrin 3 gene (ANK3) is likely to have widespread cognitive effects. Our previous study has identified a significant association of ANK3 SNPs and schizophrenia. In this study, we aimed to examine whether the schizophrenia-risk SNPs within ANK3 may affect working memory deficits in schizophrenia patients. Herein, we assess the working memory performance in 163 patients with first-episode, antipsychotic-naïve schizophrenia and 42 sex, age-matched healthy subjects using N-back task. Two SNPs rs10761482 and rs10994336 were genotyped among the patients and 209 controls. Our results showed that schizophrenia patients showed significantly poorer performance than healthy controls on N-back task (ps<0.01). After adjusting for the scores of intelligence quotient, memory quotient and the demographic factors, there was a significant genotype effect of the rs10994336 on the accuracy rate and reaction time of 2-back item (p=0.048 and 0.024, respectively). Post-hoc analyses showed that patients with rs10994336T/T genotype had significantly lower accuracy rate and more reaction time at 2-back task than those with T/C and C/C genotypes. The association of SNP rs10994336 with schizophrenia was replicated in our sample (genotypic p=0.024 and allelic p=0.006). However, we did not find any significant association of rs10761482 with schizophrenia and parameters in N-back task. Our results indicated that genetic variation within ANK3 may exert gene-specific modulating effects on working memory deficits in schizophrenia.

Axon initial segments: diverse and dynamic neuronal compartments

The axon initial segment (AIS) is a structurally and molecularly unique neuronal compartment of the proximal axon that functions as both a physiological and physical bridge between the somatodendritic and axonal domains. The AIS has two main functions: to initiate action potentials and to maintain neuronal polarity. The cytoskeletal scaffold ankyrinG is responsible for these functions and clusters ion channels at the AIS. Recent studies reveal how the AIS forms and remarkable diversity in its structure, function, and composition that may be modulated by neuronal activity and posttranslational modifications of AIS proteins. Furthermore, AIS proteins have been implicated in a variety of human diseases. Here, we discuss these findings and what they teach us about the dynamic AIS.

Cognitive effects of the ANK3 risk variants in patients with bipolar disorder and healthy individuals

BACKGROUND

Genetic variants within the ankyrin 3 gene (ANK3) have been identified as a risk factor for bipolar disorder. ANK3 influences action potential generation by clustering sodium gated channels and plays an integral role in neurotransmission. Thus, this gene may influence cognition, a process compromised in bipolar disorder. We investigated whether genetic variants of ANK3 would be associated with an array of cognitive functions in patients with bipolar disorder and healthy individuals.

METHODS

In a sample of 49 patients with bipolar disorder and 633 healthy subjects, we examined possible effects of 2 risk variants within ANK3, rs10994336 and rs10761482, on 7 neurocognitive domains.

RESULTS

Compared to healthy subjects, patients with bipolar disorder demonstrated significantly poorer performance on most of the cognitive domains examined. The risk C-allele of rs10761482 was significantly associated with worse performance on verbal comprehension, logical memory and processing speed in patients. This allele was significantly associated with worse performance on executive function and visual memory in healthy individuals. No significant association was observed between rs10994336 and cognition either in patients or healthy individuals.

LIMITATIONS

The sample size of patients with bipolar disorder was small, and most of the patients were on psychotropic medication.

CONCLUSIONS

These results indicate that a risk variant within ANK3 may have an impact on neurocognitive function, suggesting a mechanism by which ANK3 confers risk for bipolar disorder.

Drosophila models of early onset cognitive disorders and their clinical applications

The number of genes known to cause human monogenic diseases is increasing rapidly. For the extremely large, genetically and phenotypically heterogeneous group of intellectual disability (ID) disorders, more than 600 causative genes have been identified to date. However, knowledge about the molecular mechanisms and networks disrupted by these genetic aberrations is lagging behind. The fruit fly Drosophila has emerged as a powerful model organism to close this knowledge gap. This review summarizes recent achievements that have been made in this model and envisions its future contribution to our understanding of ID genetics and neuropathology. The available resources and efficiency of Drosophila place it in a position to tackle the main challenges in the field: mapping functional modules of ID genes to provide conceptually novel insights into the genetic control of cognition, tailored functional studies to improve 'next-generation' diagnostics, and identification of reversible ID phenotypes and medication. Drosophila's behavioral repertoire and powerful genetics also open up perspectives for modeling genetically complex forms of ID and neuropsychiatric disorders, which overlap in their genetic etiologies. In conclusion, Drosophila provides many opportunities to advance future medical genomics of early onset cognitive disorders.

Association of a risk allele of ANK3 with cognitive performance and cortical thickness in patients with first-episode psychosis

BACKGROUND

The gene ANK3 is implicated in bipolar disorder and schizophrenia. The present study investigated the influence of this gene on cognitive performance and brain structure among individuals with first-episode psychosis (FEP). The brief illness duration of an FEP sample makes it well suited for studying the effects of genetic variation.

METHODS

We genotyped 2 single nucleotide polymorphisms (SNPs; rs1938526 and rs10994336) in ANK3 in patients with FEP. Multivariate analysis of variance compared risk allele carriers and noncarriers on 6 domains of cognition consistent with MATRICS consensus. A subsample of 82 patients was assessed using magnetic resonance imaging. We compared brain structure between carriers and noncarriers using cortical thickness analysis and voxel-based morphometry on white matter.

RESULTS

In the 173 patients with FEP included in our study, rs1938526 and rs10994336 were in very high linkage disequilibrium (d' = 0.95), and analyses were therefore only carried out on the SNP (rs1938526) with the highest minor allele frequency (G). Allele G of rs1938526, was associated with lower cognitive performance across domains (F6,164 = 2.38, p = 0.030) and significantly lower scores on the domains of verbal memory (p = 0.015), working memory (p = 0.006) and attention (p = 0.019). The significant effects of this SNP on cognition were not maintained when controlling for IQ. Cortical thinning was observed in risk allele carriers at diverse sites across cortical lobes bilaterally at a threshold of p < 0.01, false discovery rate-corrected. Risk-allele carriers did not show any regions of reduced white matter volume.

LIMITATIONS

The sample size is modest given that a low-frequency variant was being examined.

CONCLUSION

The ANK3 risk allele rs1938526 appears to be associated with general cognitive impairment and widespread cortical thinning in patients with FEP.

Neurodevelopmental disorders: mechanisms and boundary definitions from genomes, interactomes and proteomes

Neurodevelopmental disorders such as intellectual disability, autism spectrum disorder and schizophrenia lack precise boundaries in their clinical definitions, epidemiology, genetics and protein-protein interactomes. This calls into question the appropriateness of current categorical disease concepts. Recently, there has been a rising tide to reformulate neurodevelopmental nosological entities from biology upward. To facilitate this developing trend, we propose that identification of unique proteomic signatures that can be strongly associated with patient's risk alleles and proteome-interactome-guided exploration of patient genomes could define biological mechanisms necessary to reformulate disorder definitions.

MeCP2 regulates the synaptic expression of a Dysbindin-BLOC-1 network component in mouse brain and human induced pluripotent stem cell-derived neurons

Clinical, epidemiological, and genetic evidence suggest overlapping pathogenic mechanisms between autism spectrum disorder (ASD) and schizophrenia. We tested this hypothesis by asking if mutations in the ASD gene MECP2 which cause Rett syndrome affect the expression of genes encoding the schizophrenia risk factor dysbindin, a subunit of the biogenesis of lysosome-related organelles complex-1 (BLOC-1), and associated interacting proteins. We measured mRNA and protein levels of key components of a dysbindin interaction network by, quantitative real time PCR and quantitative immunohistochemistry in hippocampal samples of wild-type and Mecp2 mutant mice. In addition, we confirmed results by performing immunohistochemistry of normal human hippocampus and quantitative qRT-PCR of human inducible pluripotent stem cells (iPSCs)-derived human neurons from Rett syndrome patients. We defined the distribution of the BLOC-1 subunit pallidin in human and mouse hippocampus and contrasted this distribution with that of symptomatic Mecp2 mutant mice. Neurons from mutant mice and Rett syndrome patients displayed selectively reduced levels of pallidin transcript. Pallidin immunoreactivity decreased in the hippocampus of symptomatic Mecp2 mutant mice, a feature most prominent at asymmetric synapses as determined by immunoelectron microcopy. Pallidin immunoreactivity decreased concomitantly with reduced BDNF content in the hippocampus of Mecp2 mice. Similarly, BDNF content was reduced in the hippocampus of BLOC-1 deficient mice suggesting that genetic defects in BLOC-1 are upstream of the BDNF phenotype in Mecp2 deficient mice. Our results demonstrate that the ASD-related gene Mecp2 regulates the expression of components belonging to the dysbindin interactome and these molecular differences may contribute to synaptic phenotypes that characterize Mecp2 deficiencies and ASD.