Genes, Brain and Behavior

Williams Syndrome is a rare neurodevelopmental disorder exhibiting cognitive and behavioral abnormalities, including increased social motivation, risk of anxiety and specific phobias along with perturbed motor function. Williams Syndrome is caused by a microdeletion of 26-28 genes on chromosome 7, including GTF2IRD1, which encodes a transcription factor suggested to play a role in the behavioral profile of Williams Syndrome. Duplications of the full region also lead to frequent autism diagnosis, social phobias, and language delay. Thus, genes in the region appear to regulate social motivation in a dose-sensitive manner. A Complete Deletion mouse, heterozygously eliminating the syntenic Williams Syndrome region, has been deeply characterized for cardiac phenotypes, but direct measures of social motivation have not been assessed. Furthermore, the role of Gtf2ird1 in these behaviors has not been addressed in a relevant genetic context. Here, we have generated a mouse overexpressing Gtf2ird1, which can be used both to model duplication of this gene alone and to rescue Gtf2ird1 expression in the Complete Deletion mice. Using a comprehensive behavioral pipeline and direct measures of social motivation, we provide evidence that the Williams Syndrome Critical Region regulates social motivation along with motor and anxiety phenotypes, but that Gtf2ird1 complementation is not sufficient to rescue most of these traits, and duplication does not decrease social motivation. However, Gtf2ird1 complementation does rescue light-aversive behavior and performance on select sensorimotor tasks, perhaps indicating a role for this gene in sensory processing or integration.

We identified two Collaborative Cross (CC) strains, CC004/TauUncJ (CC004) and CC041/TauUncJ (CC041), that differ significantly for locomotor response and self-administration of cocaine. In the current study, we crossed each of these strains to C57BL/6NJ (B6N) mice to produce two F2 populations and identify genetic loci that influence locomotor response to cocaine. We identified three significant loci on chromosomes 7, 11 and 14 in the CC041 F2 mapping cross that collectively explain 14% of the phenotypic variance for locomotor response to cocaine. We used a bioinformatic approach to identify high quality candidate genes that are genetically plausible, have functional relevance and are suitable for further exploration. Our study is the first to use CC strains to perform QTL mapping for addiction-related phenotypes and proposes several candidate genes for follow-up analyses.

Mllt11 (myeloid/lymphoid or mixed-lineage leukemia translocated to chromosome 11; also known as Af1q/TcF7c) has been identified as a novel regulator of neural development, playing a role in the migration and outgrowth of cortical projection neurons. We previously reported that the conditional inactivation of the Mllt11 gene in the mouse superficial cortex resulted in reduced connectivity of the corpus callosum and white matter fiber tracts, resulting in reduced cortical thickness. However, the behavioral consequences of Mllt11 loss are unknown. Callosal abnormalities are thought to be present in 3-5% of all neurodevelopmental disorders and reduced corpus callosum volume correlates with core symptoms of autism spectrum disorder (ASD) in humans. Cortical thickness dysregulation is likewise shared among various neurodevelopmental disorders including ASD. We therefore investigated the behavioral consequences of conditional knockout of Mllt11 in upper cortical layer 2/3 projection neurons using transgenic Cux2iresCre mice. Utilizing tasks designed to reflect core ASD symptoms, we examined the behaviors of both male and female conditional knockout animals. These tests included olfaction habituation/dishabituation, three-chambered social approach, marble burying, and nestlet shredding. We found sex-dependent disruptions in social preference and nestlet shredding in animals lacking Mllt11, with the female mice presenting with more disruptions than the males. Understanding the behavioral phenotype associated with genes of interest, specifically in the context of sex differences, is crucial to individualized treatment for neurodevelopmental disorders.

When next generation sequencing is performed in large batches, there are several stages at which samples can be swapped or mislabeled. It is therefore helpful, when possible, to integrate measures into analysis pipelines to confirm that samples match their assigned metadata. Here, we introduce RNA Strain-Match (GitHub: https://github.com/jon-willcox/RNA-strain-match), a quality control tool developed to match RNA data in the form of sequence alignment files (i.e. SAM or BAM files) to their corresponding genotype without the use of an RNA variant call format file. We successfully used RNA Strain-Match in tandem with assessment of markers for sex and transgene status to identify and correct sample mismatches in 50/379 samples (13%) from two distinct recombinant inbred mouse models (BXD and Collaborative Cross). We believe this tool will be beneficial to any research group working with similar data.

Genomic imprinting in the brain is theorized to provide parental control over offspring social behaviors. Noncanonical genomic imprinting is a form of epigenetic regulation in which one of a genes alleles, either that of maternal or paternal inheritance, exhibits a bias towards higher expression of one parental allele compared to the other. This bias can differ depending on tissue type, and the degree of the parental allele expression bias can even vary across anatomical domains within the same tissue. Dopa decarboxylase (Ddc) and tyrosine hydroxylase (Th) are both noncanonically imprinted genes that preferentially express their maternal alleles in the brain and Ddc also has a paternal allele expression bias in the periphery. These two genes encode catecholamine synthesis enzymes for the production of dopamine (DA), norepinephrine (NE), and epinephrine (E), and Ddc is also in the serotonin (5-HT) synthesis pathway. These four neurotransmitters are critical regulators of social behavior and disruptions to them are implicated in human mental illnesses. Here we investigated the functional effects of noncanonical imprinting of Ddc and Th on social behavior in mice. By using reciprocal heterozygous mutant mice, we tested the impacts of Ddc and/or Th maternally and paternally inherited alleles on aggression, social recognition, dominance, and social preference behaviors. We found that Ddc paternal-null alleles affect aggression and social recognition behavior, Th maternal-null alleles affect sociability preferences, and compound inheritance of Th and Ddc maternal-null alleles influence preferences for social novelty. These results are consistent with Th and Ddc maternal allele biased expression in central monoaminergic systems regulating sociability, and Ddc paternal allele biased expression in peripheral monoaminergic systems regulating aggression and social recognition.

Cocaine use disorders (CUD) are devastating for affected individuals and impose a significant burden on society, but there are currently no FDA-approved therapies. The development of novel and effective treatments has been hindered by substantial gaps in our knowledge about the etiology of these disorders. The risk for developing a CUD is influenced by genetics, the environment and complex interactions between the two. Identifying specific genes and environmental risk factors that increase CUD risk would provide an avenue for the development of novel treatments. Rodent models of addiction-relevant behaviors have been a valuable tool for studying the genetics of response to drugs of abuse. Traditional genetic mapping using genetically and phenotypically divergent inbred mice has been successful in identifying numerous chromosomal regions that influence addiction-relevant behaviors, but these strategies rarely result in identification of the causal gene or genetic variant. To overcome this challenge, reduced complexity crosses (RCC) between closely related inbred mouse substrains have been proposed as a method for rapidly identifying and validating functional variants. The RCC approach is dependent on identifying phenotypic differences between substrains. To date, however, the study of addiction-relevant behaviors has been limited to very few sets of substrains, mostly comprising the C57BL/6 lineage. The present study expands upon the current literature to assess cocaine-induced locomotor activation in 20 inbred mouse substrains representing six inbred strain lineages (A/J, BALB/c, FVB/N, C3H/He, DBA/2 and NOD) that were either bred in-house or supplied directly by a commercial vendor. To our knowledge, we are the first to identify significant differences in cocaine-induced locomotor response in several of these inbred substrains. The identification of substrain differences allows for the initiation of RCC populations to more rapidly identify specific genetic variants associated with acute cocaine response. The observation of behavioral profiles that differ between mice generated in-house and those that are vendor-supplied also presents an opportunity to investigate the influence of environmental factors on cocaine-induced locomotor activity.

Studies have shown that substance use liability is associated with novelty seeking, anxiety-like behavior, and pain sensitivity. We examined whether common genetic variation in outbred Sprague-Dawley rats explained variation in behavioral measures from three assays with established links to substance use: locomotor response to a novel environment, elevated plus maze, and tail flick. We estimated single-nucleotide polymorphism heritability and performed genome-wide association analyses using permutation-derived significance thresholds (N=534-654 rats across traits). Heritability estimates ranged from 0.14-0.38 across eleven traits. Three independent loci were identified: chromosome 1 for elevated plus maze open-arm behavior (=0.05), chromosome 14 for elevated plus maze immobility (=0.10), and chromosome 17 for tail flick latency (=0.05). Candidate genes included Slc18a2, Gfra1, and Pdzd8 (chromosome 1); Rel and Bcl11a (chromosome 14); and Eci2 and Eci3 (chromosome 17). We compared these loci with our genome wide association study of a F2 intercross of selectively bred high- and low-responder rats, originally derived from Sprague-Dawleys, that model individual differences in externalizing and internalizing behavior. The current loci are distinct from the ones identified in the bred lines. This difference likely reflects selection history in the high- and low-responder F2s, which focused on facets of exploratory locomotion, while loci for anxiety and pain sensitivity traits were identified in the outbreds. This highlights the benefit of using both outbred and selectively bred rats to probe causal variants contributing to individual differences in substance use liability. The current outbred findings implicate monoaminergic signaling, transcriptional control, and lipid metabolism as testable mechanisms for addiction-relevant behaviors.

Genomic studies of autism and other neurodevelopmental disorders have identified several relevant protein-coding and noncoding variants. One gene with an excess of protein-coding de novo variants is EBF3 that also is the gene underlying the Hypotonia, Ataxia, and Delayed Development Syndrome (HADDS). In previous work, we have identified noncoding de novo variants in an enhancer of EBF3 called hs737 and further showed that there was an enrichment of deletions of this enhancer in individuals with neurodevelopmental disorders. In this present study, we generated a novel mouse line that deletes the highly conserved, orthologous mouse region of hs737 within the Rr169617 regulatory region, and characterized the molecular and phenotypic aspects of this mouse model. This line contains a 1,160 bp deletion within Rr169617 and through heterozygous crosses we found a deviation from Mendelian expectation (p = 0.02) with a significant depletion of the deletion allele (p = 5.8 x 10-4). Rr169617+/- mice had a reduction of Ebf3 expression by 10% and Rr169617-/- mice had a reduction of Ebf3 expression by 20%. Differential expression analyses in E12.5 forebrain, midbrain, and hindbrain in Rr169617+/+versus Rr169617-/- mice identified dysregulated genes including histone genes (i.e., Hist1h1e, Hist1h2bk, Hist1h3i, Hist1h2ao) and other brain development related genes (e.g., Chd5, Ntng1). A priori phenotyping analysis (open field, hole board and light/dark transition) identified sex-specific differences in behavioral traits when comparing Rr169617-/- males versus females; whereby, males were observed to be less mobile, move slower, and spend more time in the dark. Furthermore, both sexes when homozygous for the enhancer deletion displayed body composition differences when compared to wild-type mice. Overall, we show that deletion within Rr169617 reduces the expression of Ebf3 and results in phenotypic outcomes consistent with potential sex specific behavioral differences. This enhancer deletion line provides a valuable resource for others interested in noncoding regions in neurodevelopmental disorders and/or those interested in the gene regulatory network downstream of Ebf3.

Many personality traits are influenced by genetic factors. Rodents models provide an efficient system for analyzing genetic contribution to these traits. Using 1,246 adolescent heterogeneous stock (HS) male and female rats, we conducted a genome-wide association study (GWAS) of behaviors measured in an open field, including locomotion, novel object interaction, and social interaction. We identified 30 genome-wide significant quantitative trait loci (QTL). Using multiple criteria, including the presence of high impact genomic variants and co-localization of cis-eQTL, we identified 13 candidate genes (Adarb2, Ankrd26, Cacna1c, Clock, Crhr1, Ctu2, Cyp26b1, Eva1a, Fam114a1, Kcnj9, Mlf2, Rab27b, Sec11a) for these traits. Most of these genes have been implicated by human GWAS of various psychiatric traits. For example, Cacna1c, a gene known to be critical for social behavior in rodents and implicated in human schizophrenia and bipolar disorder, is a candidate gene for distance to the social zone. In addition, the QTL region for total distance to the novel object zone, on Chr1 at 144 Mb, is syntenic to a hotspot on human Chr15 (82.5-90.8 Mb) that contains 14 genes associated with psychiatric or substance abuse traits. Although some of the genes identified by this study appear to replicate findings from prior human GWAS, others likely represent novel findings that can be the catalyst for future molecular and genetic insights into human psychiatric diseases. Together, these findings provide strong support for the use of the HS population to study psychiatric disorders.

Aggression is an evolutionarily conserved, adaptive component of social behavior. Studies in male mice illustrate that aggression is influenced by numerous factors including the degree to which an individual finds aggression rewarding and will work for access to attack and subordinate mice. While such studies have expanded our understanding of the molecular and circuit mechanisms of male aggression very little is known about female aggression, owed in part to limited availability of valid mouse models in females. Here we use an ethologically relevant model of male vs. female aggression by pair housing adult male and female outbred CFW mice with opposite sex cage mates. We assess reactive (defensive) aggression in the resident intruder (RI) test and appetitive (rewarding) aggression in the aggression conditioned place preference (CPP) and operant self-administration (SA) tests. Our results show dramatic sex differences in both qualitative and quantitative aspects of reactive vs. appetitive aggression. Males exhibit more wrestling and less investigative behavior during RI, find aggression rewarding and will work for access to a subordinate to attack. Females exhibit more bites, alternate between aggressive behaviors and investigative behaviors more readily during RI, however, they do not find aggression to be rewarding or reinforcing. These results establish sex differences in aggression in mice, providing an important resource for the field to better understand the circuit and molecular mechanisms of aggression in both sexes.

The fundamental skills for motor coordination and motor control emerge through development, from infancy to late childhood years. Neurodevelopmental disorders such as Developmental Coordination Disorder (DCD) lead to impaired acquisition of motor skills. This study investigated motor behaviors that reflect the core symptoms of human DCD through the use of BXD recombinant inbred lines of mice that are known to have divergent phenotypes in many behavioral traits, including motor activity. We sought to correlate behavior in basic motor control tasks with the known genotypes of these reference populations of mice using quantitative trait locus (QTL) mapping. We used twelve BXD lines with an average of 16 mice per group to assess the onset of reflexes during the early neonatal stage of life and differences in motor coordination using the open field, rotarod, and gait analyses during the adolescent/young adulthood period. Results indicated significant variability between lines in as to when neonatal reflexes appeared as well as significant line differences for all measures of motor coordination. Five lines (BXD15, BXD27, BXD28, BXD75, and BXD86) struggled with sensorimotor coordination as seen in gait analysis, rotarod, and open field, similar to human presentation of DCD. We identified three significant quantitative trait loci for gait on proximal Chr 3, Chr 4 and distal Chr 6. Based on expression, function, and polymorphism within the mapped QTL intervals, 7 candidate genes (Gpr63, Spata5, Trpc3, Cntn6, Chl1, Grm7 and Ogg1) emerged. This study offers new insights into mouse motor behavior which promises to be a first murine model to explore the genetics and neural correlates of DCD.

Disorders of creatine (Cr) synthesis and transport cause moderate to severe intellectual disability, epilepsy, and a lack of speech development. Mutations of the X-linked Cr transporter (CrT; SLC6A8) gene are the most frequent cause of Cr deficiency and one of the leading causes of X-linked intellectual disability. There are no treatments for CrT deficiency (CTD) and there are many unanswered questions related to this disorder. Rodent models of CTD have deficits in spatial learning and memory, object recognition memory, fear conditioning, and working memory, making them high-fidelity models of CTD. While these cognitive deficits provide important information related to CTD, they lack some translational relevance and do not address important aspects of executive function like attention and impulsivity. To address this gap in knowledge, we tested brain specific Slc6a8 knockout (bKO) mice in the 5-choice serial reaction time test (5CSRTT), a correlate of the continuous performance task in humans. Following 5CSRTT training, mice were then tested for 3 sessions using trials with a variable stimulus duration followed by 3 sessions using a fixed stimulus duration and variable intertrial interval. During both the testing phases the bKO mice had reduced accuracy along with increased omissions and correct latencies compared with controls. There were no increases in premature responses during the vITI, suggesting that these mice do not have an impulsive phenotype. The results of this study expand the known phenotype of Slc6a8 deficient mice and add a translationally relevant behavioral output to test potential therapies. SynopsisThis study shows that a mouse model of human creatine transporter deficiency, a devastating human condition, has an attention-deficit disorder-like phenotype without an increase in impulsivity.

Courtship behaviors consist of two phases, namely the appetitive and consummatory states. Despite the long history of the concept, few studies have been done regarding the genetic contribution on those two different phases. Male mice are known to produce distinct ultrasonic vocalizations (USVs) as they progress through courtship states1-14, and these courtship sounds also show strain-specific differences15-18. Here, we delved into USV syllable patterns emitted during specific courtship actions using inbred mouse strains and their progeny: C57BL/6J (B6) mice, 129S4/SvJae (129) mice, and their second filial generation (F2) offspring of mixed genetic backgrounds. B6, 129, and F2 mice generated similar USV syllables during mounting behavior. In contrast, B6 and 129 mice showed different USV syllable patterns during body and anogenital sniffing behavior, and the USV syllable usage of F2 mice in this courtship state diverged according to the degree of genetic similarity with B6 or 129 mice. From these results, we propose that differential selection pressures19-20 favored diversity in appetitive behavior but conservation in consummatory behaviors.

In most mammals, mothers exhibit natural variations in care that propagate between generations of female offspring. However, there is limited information on genetic variation that influences this propagation. We assessed early-life maternal care received by individual female rat offspring in relation to genetic polymorphisms linked to dopaminergic activity, maternal care provisioning, and dopaminergic activity in the maternal brain. We also conducted a systematic analysis of other genetic variants potentially related to maternal behavior in our Long-Evans rat population. We found that dopamine receptor 2 (rs107017253) variation interacted with the relationship between early-life maternal care received and dopamine levels in the nucleus accumbens which, in turn, were associated with later-life maternal care provisioning. We also discovered and validated new variants that were predicted by our systematic analysis. Our findings suggest that genetic variation influences the relationship between maternal care received and maternal care provisioning, similar to findings in human populations.

Human genetic association studies have linked a single nucleotide polymorphism (SNP) of the alpha5 subunit of nicotinic acetylcholine receptors (nAChRs) to an increased risk of nicotine dependence, alcohol use disorders (AUDs) and schizophrenia. We used transgenic mice expressing either the SNP rs16969968 (termed 5SNP or 5KI) or a knockout of the Chrna5 gene (5KO) to investigate the role of 5-containing nAChRs (5*nAChRs) in emotion recognition and prosocial, rescuing-like behavioral tasks. We found that 5KO mice are impaired in the recognition of a negative affective state in a familiar peer, and displayed severely altered pro-social, altruistic behaviors, eventually assaulting peers in distress. In contrast, 5KI mice exhibited normal or improved emotion recognition and increased rescuing-like behavior. Importantly, effects of 5 mutations on emotion recognition were modulated by sex. These results demonstrate the critical implication of 5*nAChRs in emotion recognition and prosocial behaviors, revealing, sex-dependent patterns of these social emotional deficits in 5KI and 5KO mice. The current study also supports the view that 5KI and 5KO may provide a valuable preclinical model of Type I (female 5KI mice), and Type II (male 5KO mice) behavioral profiles of AUD.

Cocaine self-administration is complexly determined trait, and a substantial proportion of individual differences in cocaine use is determined by genetic variation. Cocaine intravenous self-administration (IVSA) procedures in laboratory animals provide opportunities to prospectively investigate neurogenetic influences on the acquisition of voluntary cocaine use. Large and genetically diverse mouse populations, including the Hybrid Mouse Diversity Panel (HMDP), have been developed for forward genetic approaches that can reveal genetic variants that influence traits like cocaine IVSA. This population enables high resolution and well-powered genome wide association studies, as well as the discovery of genetic correlations. Here, we provide information on cocaine (or saline - as a control) IVSA in 65 strains of the HMDP. We found cocaine IVSA to be substantially heritable in this population, with strain-level intake ranging for near zero to >25 mg/kg/session. Though saline IVSA was also found to be heritable, a very modest genetic correlation between cocaine and saline IVSA indicates that operant responding for the cocaine reinforcer was influenced by a substantial proportion of unique genetic variants. These data indicate that the HMDP is suitable for forward genetic approaches for the analysis of cocaine IVSA, and this project has also led to the discovery of reference strains with extreme cocaine IVSA phenotypes, revealing them as polygenic models of risk and resilience to cocaine reinforcement. This is part of an ongoing effort to characterize genetic and genomic variation that moderates cocaine IVSA, which may, in turn, provide a more comprehensive understanding of cocaine risk genetics and neurobiology.

Selectively-bred High Responder (bHR) and Low Responder (bLR) rats model the extreme externalizing and internalizing behavior accompanying many psychiatric disorders. To elucidate gene expression underlying these heritable behavioral differences, bHRs and bLRs (generation 37) were used to produce a F0-F1-F2 cross. We measured exploratory locomotion, anxiety-like behavior, and reward cue sensitivity (Pavlovian Conditioned Approach), and performed hippocampal RNA-Seq in male and female F0s (n=24) and F2s (n=250). Behaviors that diverged during selective breeding remained correlated in F2s, implying a shared genetic basis. F0 bHR/bLR differential expression was robust, surpassing differences associated with sex, and predicted expression patterns associated with F2 behavior. With bHR-like behavior, gene sets related to growth/proliferation were upregulated, whereas with bLR-like behavior, gene sets related to mitochondrial function, oxidative stress, and microglial activation were upregulated. This differential expression could be successfully predicted based on F0 genotype using cis-expression quantitative trait loci (cis-eQTLs) identified in the F2s. Colocalization of these cis-eQTLs with behavioral Quantitative Trait Loci pinpointed 16 differentially expressed genes that were strong candidates for mediating the influence of genetic variation on behavioral temperament. Our findings implicate hippocampal bioenergetic regulation of oxidative stress, microglial activation, and growth-related processes in shaping behavioral temperament, modulating vulnerability to psychiatric disorders.

Gene-environment interactions in the postnatal period have a long-term impact on neurodevelopment. To effectively model neurodevelopment in the mouse, we incorporated several validated behavioural tests to develop a behavioural pipeline that measures translationally relevant milestones of development in mice. The behavioral phenotype of 1060 wild type and genetically-modified mice was examined in parallel with structural brain imaging. The influence of genetics, sex, and early life stress on behaviour and neuroanatomy was determined using traditional statistical and machine learning methods. The results demonstrated that neuroanatomical diversity was primarily associated with genotype whereas behavioural phenotypic diversity was observed to be more susceptible to gene-environment interactions.

Numerous mouse models have been engineered to carry alterations to the Disrupted in Schizophrenia 1 (Disc1) gene, thought to be involved in neurodevelopmental conditions. However, most Swiss and probably all 129 mouse substrains, which are widely used in biological research, naturally carry a 25 bp deletion in Disc1 exon 6. Despite the prevalence of these strains, little has been done to characterize the extent to which this natural mutation affects behavioral output and may unintentionally impact studies. Here, we report on experiments to test the effects of this deletion on social and exploratory behaviors. To model natural conditions, we designed a seminatural environment to house groups of mice (4 females and 1 male; 3 groups per strain) for prolonged periods and then employed this model to study social behaviors. First, we compared behavioral phenotypes in C57Bl/6Jrj (B6) mice and 129S4 (S4Disc1-/-) natural mutants to validate our setup. Then, to assess the contribution of the naturally mutated Disc1 to social behavior differences, the wild-type (WT) Disc1 allele was crossed into S4 mice (S4Disc1+/+). S4 and B6 lines were drastically different, with S4 mice being hypoactive, less explorative, and less social than B6 mice. However, S4 mice expressing WT Disc1 only marginally differed from S4Disc1-/- mice, showing little to no contribution of Disc1 to their behavioral phenotype. Thus, this mutation holds little significance for natural exploratory and social behaviors in the seminatural environment.

Latrophilin-3 (LPHN3) is a brain specific adhesion G-protein coupled receptor associated with elevated risk of attention deficit hyperactivity disorder (ADHD). We developed a global Lphn3 knock-out (gKO) rat using CRISPR/Cas9 to delete exon-3. Here we report the development of a floxed Lphn3 rat crossed with tyrosine hydroxylase (Th-Cre) rats to create a conditional Lphn3 KO rat specific for catecholaminergic- positive cells. The gKO rats are hyperactive and have egocentric and allocentric navigation deficits but showed sparing of conditioned contextual and novel object recognition memory. Here we compared gKO and cKO rats controlling for litter effects. Both gKO and cKO rats were hyperactive and were impaired in egocentric navigation in the Cincinnati water maze (CWM) with deficits greater in gKO rats. The gKO rats were impaired in allocentric navigation in the Morris water maze (MWM) whereas cKO rats were only slightly affected compared with WT, cre, and floxed rats. Striatal tyrosine hydroxylase and dopamine D1 receptors were not significantly different in either model, nor were NMDA-NR1 or NMDA-NR2 in the hippocampus. We previously showed, however, that dopamine is released more rapidly in the striatum of gKO rats by fast- scan cyclic voltammetry. The cKO model shows an important role of catecholamines in the phenotype of LPHN3 disruption and add evidence that this synaptic protein plays a role in neuroplasticity that are consistent with ADHD.