Haploinsufficiency of Shank3 in Mice Selectively Impairs Target Odor Recognition in Novel Background Odors.

Individuals with mutations in a single copy of the SHANK3 gene present with social interaction deficits. Although social behavior in mice depends on olfaction, mice with mutations in a single copy of the Shank3 gene do not have olfactory deficits in simple odor identification tasks (Drapeau et al., 2018). Here, we tested olfaction in mice with mutations in a single copy of the Shank3 gene (Peça et al., 2011) using a complex odor task and imaging in awake mice. Average glomerular responses in the olfactory bulb of Shank3B +/- were correlated with WT mice. However, there was increased trial-to-trial variability in the odor responses for Shank3B +/- mice. Simulations demonstrated that this increased variability could affect odor detection in novel environments. To test whether performance was affected by the increased variability, we tested target odor recognition in the presence of novel background odors using a recently developed task (Li et al., 2023). Head-fixed mice were trained to detect target odors in the presence of known background odors. Performance was tested using catch trials where the known background odors were replaced by novel background odors. We compared the performance of eight Shank3B +/- mice (five males, three females) on this task with six WT mice (three males, three females). Performance for known background odors and learning rates were similar between Shank3B +/- and WT mice. However, when tested with novel background odors, the performance of Shank3B +/- mice dropped to almost chance levels. Thus, haploinsufficiency of the Shank3 gene causes a specific deficit in odor detection in novel environments. Our results are discussed in the context of other Shank3 mouse models and have implications for understanding olfactory function in neurodevelopmental disorders.SIGNIFICANCE STATEMENT People and mice with mutations in a single copy in the synaptic gene Shank3 show features seen in autism spectrum disorders, including social interaction deficits. Although mice social behavior uses olfaction, mice with mutations in a single copy of Shank3 have so far not shown olfactory deficits when tested using simple tasks. Here, we used a recently developed task to show that these mice could identify odors in the presence of known background odors as well as wild-type mice. However, their performance fell below that of wild-type mice when challenged with novel background odors. This deficit was also previously reported in the Cntnap2 mouse model of autism, suggesting that odor detection in novel backgrounds is a general deficit across mouse models of autism.

Knockout of the intellectual disability-linked gene Hs6st2 in mice decreases heparan sulfate 6-O-sulfation, impairs dendritic spines of hippocampal neurons, and affects memory.

Heparan sulfate (HS) is a linear polysaccharide that plays a key role in cellular signaling networks. HS functions are regulated by its 6-O-sulfation, which is catalyzed by three HS 6-O-sulfotransferases (HS6STs). Notably, HS6ST2 is mainly expressed in the brain and HS6ST2 mutations are linked to brain disorders, but the underlying mechanisms remain poorly understood. To determine the role of Hs6st2 in the brain, we carried out a series of molecular and behavioral assessments on Hs6st2 knockout mice. We first carried out strong anion exchange-high performance liquid chromatography and found that knockout of Hs6st2 moderately decreases HS 6-O-sulfation levels in the brain. We then assessed body weights and found that Hs6st2 knockout mice exhibit increased body weight, which is associated with abnormal metabolic pathways. We also performed behavioral tests and found that Hs6st2 knockout mice showed memory deficits, which recapitulate patient clinical symptoms. To determine the molecular mechanisms underlying the memory deficits, we used RNA sequencing to examine transcriptomes in two memory-related brain regions, the hippocampus and cerebral cortex. We found that knockout of Hs6st2 impairs transcriptome in the hippocampus, but only mildly in the cerebral cortex. Furthermore, the transcriptome changes in the hippocampus are enriched in dendrite and synapse pathways. We also found that knockout of Hs6st2 decreases HS levels and impairs dendritic spines in hippocampal CA1 pyramidal neurons. Taken together, our study provides novel molecular and behavioral insights into the role of Hs6st2 in the brain, which facilitates a better understanding of HS6ST2 and HS-linked brain disorders.

Undergraduate Participation in the Society for Neuroscience.

Undergraduate neuroscience education has grown substantially in the US as well as participation in outreach and research activities by undergraduates. In line with these observations, undergraduates may also be seeking membership in the Society for Neuroscience (SfN) as well as attending the SfN annual meeting. Data in the present report show that undergraduate membership in SfN has increased between 2013 and 2019 as well as annual undergraduate SfN meeting attendance and abstract submissions for research presentations. Increases were observed for both US and international undergraduates. These data are discussed in the context of motivations of undergraduates to pursue future academic training and/or careers in neuroscience. These data are important to faculty and administrators at institutions that currently have or seek to establish new undergraduate neuroscience programs given membership in a professional society and attendance at a major conference can positively impact academic and professional development.

Primary Literature In Clinical Neuroscience for In-Person Or Remote Instruction.

Structure and function relationships in the nervous system are a major component of neuroscience education. Readings and/or discussion of lesion studies in animal models are often used to demonstrate how brain injury/damage affects specific behaviors or cognitive processes. In contrast, primary literature in clinical neuroscience is less often used to teach brain structure and function relationships and this literature often describes remarkable stories of preserved brain function despite major brain injury/lesion. Here we describe a series of published articles in clinical neuroscience that we used in an undergraduate neuroscience course that challenge the simplistic views of brain localization of function and demonstrate the dynamic and plastic properties of the brain. Discussion of these primary articles can take place in-person or remote via video conferencing platforms.

Methamphetamine Impairs IgG1-Mediated Phagocytosis and Killing of Cryptococcus neoformans by J774.16 Macrophage- and NR-9640 Microglia-Like Cells.

The prevalence of methamphetamine (METH) use is estimated at ∼35 million people worldwide, with over 10 million users in the United States. Chronic METH abuse and dependence predispose the users to participate in risky behaviors that may result in the acquisition of HIV and AIDS-related infections. Cryptococcus neoformans is an encapsulated fungus that causes cryptococcosis, an opportunistic infection that has recently been associated with drug users. METH enhances C. neoformans pulmonary infection, facilitating its dissemination and penetration into the central nervous system in mice. C. neoformans is a facultative intracellular microorganism and an excellent model to study host-pathogen interactions. METH compromises phagocyte effector functions, which might have deleterious consequences on infection control. In this study, we investigated the role of METH in phagocytosis and antigen processing by J774.16 macrophage- and NR-9460 microglia-like cells in the presence of a specific IgG1 to C. neoformans capsular polysaccharide. METH inhibits antibody-mediated phagocytosis of cryptococci by macrophages and microglia, likely due to reduced expression of membrane-bound Fcγ receptors. METH interferes with phagocytic cells' phagosomal maturation, resulting in impaired fungal control. Phagocytic cell reduction in nitric oxide production during interactions with cryptococci was associated with decreased levels of tumor necrosis factor alpha (TNF-α) and lowered expression of Fcγ receptors. Importantly, pharmacological levels of METH in human blood and organs are cytotoxic to ∼20% of the phagocytes. Our findings suggest that METH abrogates immune cellular and molecular functions and may be deadly to phagocytic cells, which may result in increased susceptibility of users to acquire infectious diseases.

Quantitative Indicators of Continued Growth in Undergraduate Neuroscience Education in the US.

There is both anecdotal and quantitative evidence that undergraduate neuroscience education has grown substantially in the US. Therefore, efforts to continue to track changes in undergraduate neuroscience education are important. Here we provide quantitative data that both public and private institutions are creating new undergraduate neuroscience programs. In addition, we demonstrate that the number of graduates from undergraduate neuroscience programs continues to increase compared to graduates from other life sciences programs. These data are important to faculty and administrators at institutions that currently have or seek to establish new undergraduate neuroscience programs.

Malformation of the Posterior Cerebellar Vermis Is a Common Neuroanatomical Phenotype of Genetically Engineered Mice on the C57BL/6 Background.

C57BL/6 mice exhibit spontaneous cerebellar malformations consisting of heterotopic neurons and glia in the molecular layer of the posterior vermis, indicative of neuronal migration defect during cerebellar development. Recognizing that many genetically engineered (GE) mouse lines are produced from C57BL/6 ES cells or backcrossed to this strain, we performed histological analyses and found that cerebellar heterotopia were a common feature present in the majority of GE lines on this background. Furthermore, we identify GE mouse lines that will be valuable in the study of cerebellar malformations including diverse driver, reporter, and optogenetic lines. Finally, we discuss the implications that these data have on the use of C57BL/6 mice and GE mice on this background in studies of cerebellar development or as models of disease.

Diversity of Graduates from Bachelor's, Master's and Doctoral Degree Neuroscience Programs in the United States.

The demography of United States graduates from science, technology, engineering, and math (STEM) degree programs is well-understood; however, data particularly describing the gender and ethnic diversity of graduates of neuroscience programs has not been analyzed, limiting our knowledge of specific areas where diversity and fair representation are lacking. Using over 30 years of data from the National Center for Education Statistics, we documented the demography of neuroscience graduates from bachelor's, master's, and doctoral degree programs. Recent graduation trends indicate greater numbers of female graduates from bachelor's and graduate degree programs. White (non-Hispanic) males and females represent the largest group of graduates while Asian/Pacific Islanders represent the largest non-White group of graduates. Although the number of underrepresented minorities graduating from neuroscience degree programs at every level has increased in recent years, they still lag compared to White (non-Hispanic) and Asian/Pacific Islanders. These data provide valuable information that can be used to promote greater diversity among neuroscience graduates by higher education faculty and administrators and federal funding agencies.

Characterizing the Undergraduate Neuroscience Major in the U.S.: An Examination of Course Requirements and Institution-Program Associations.

Neuroscience is a rapidly expanding field, and many colleges and universities throughout the country are implementing new neuroscience degree programs. Despite the field's growth and popularity, little data exists on the structural character of current undergraduate neuroscience programs. We collected and examined comprehensive data on existing undergraduate neuroscience programs, including academic major requirements and institution characteristics such as size, financial resources, and research opportunities. Thirty-one variables covering information about course requirements, department characteristics, financial resources, and institution characteristics were collected from 118 colleges and universities in the United States that offer a major titled "neuroscience" or "neural sciences." Data was collected from publicly available sources (online databases, institutions' neuroscience program websites) and then analyzed to define the average curriculum and identify associations between institution and program characteristics. Our results suggest that the average undergraduate neuroscience major requires 3 chemistry, 3 biology, 3 laboratory, 2-3 neuroscience, 1 physics, 1 math, and 2 psychology courses, suggesting that most neuroscience programs emphasize the natural sciences over the social sciences. Additionally, while 98% of institutions in our database offer research opportunities, only 31% required majors to perform research. Of note, 70% of institutions offering a neuroscience major do not have a neuroscience department, suggesting that most institutions offer neuroscience as an interdisciplinary major spanning several departments. Finally, smaller liberal arts colleges account for the majority of institutions offering a neuroscience major. Overall, these findings may be useful for informing groups interested in undergraduate neuroscience training, including institutions looking to improve or establish programs, students wanting to major in neuroscience and employers hiring neuroscience graduates.

Perinatal exposure to benzyl butyl phthalate induces alterations in neuronal development/maturation protein expression, estrogen responses, and fear conditioning in rodents.

Phthalate exposure has recently been associated with behavioral actions that are linked to its endocrine-disrupting properties. The purpose of this study was to investigate the molecular, anatomical, and behavioral effects of indirect perinatal benzyl butyl phthalate (BBP) exposure in offspring of BBP-treated pregnant dams. In two separate experiments, we administered BBP (10.0 µg/ml) on food pellets to pregnant dams and examined the offspring. The first experiment revealed reproductive anatomical abnormalities linked to BBP's endocrine-disrupting properties, whereas histological analysis revealed preserved hippocampal neuronal migration. The second experiment demonstrated learning and memory impairments accompanied by molecular abnormalities in multiple brain regions. Offspring from BBP-treated dams had altered levels of several proteins important for neuronal circuitry formation, tissue development, and maturation. We suggest that BBP administration disrupts normal learning and that these effects could be related to alterations in brain development and result in a phenotype similar to that observed in neurodevelopmental disorders.

A Quantitative Examination of Undergraduate Neuroscience Majors Applying and Matriculating to Osteopathic Medical School.

Undergraduates choose to become neuroscience majors for a number of reasons including future career goals. Faculty and administration of undergraduate neuroscience programs understand that many neuroscience majors have aspirations of applying and matriculating to medical school (Prichard, 2015); however a quantitative understanding of this particular student population remains unknown, especially in the context of the national growth in undergraduate neuroscience education (Ramos et al., 2011). In the present report, we use medical school application data to establish a novel quantitative understanding of the number of neuroscience majors that apply and matriculate to osteopathic medical school. Our data indicate that a substantial number of neuroscience majors do indeed apply and matriculate to medical school compared to other majors in the life sciences, math and physical sciences, and humanities. These data are relevant to faculty and administration of undergraduate neuroscience programs and suggest that when programmatic, curricular, and training decisions are made, they should be made in the context of the diverse motivations and professional goals of neuroscience majors including careers in medicine. Finally, our novel quantitative approach of determining student motivation and professional goals based on application/matriculation data, can complement traditional methods such as surveys and questionnaires and can be used to determine the extent to which neuroscience majors apply to other professional and graduate degree programs.

Undergraduate Neuroscience Education in the U.S.: Quantitative Comparisons of Programs and Graduates in the Broader Context of Undergraduate Life Sciences Education.

The impact of undergraduate neuroscience programs on the broader landscape of life sciences education has not been described. Using data from the National Center for Education Statistics, we found that the number of undergraduate neuroscience programs in the U.S. continues to grow. Within any given institution, neuroscience programs exist alongside a small number of other life sciences undergraduate programs, suggesting that neuroscience is one of few major options from which students can choose from at many institutions. Neuroscience majors constitute a substantial proportion of all life sciences graduates at many institutions, and in several cases, neuroscience majors were the majority of life sciences graduates. Thus, neuroscience programs contribute substantially to life sciences education, and neuroscience is a highly attractive major among undergraduate students where these programs are available. These data have implications for institutions with existing neuroscience programs as well as for institutions seeking to establish a new program.

Neurodevelopmental Malformations of the Cerebellar Vermis in Genetically Engineered Rats.

The cerebellar vermis is particularly vulnerable to neurodevelopmental malformations in humans and rodents. Sprague-Dawley, and Long-Evans rats exhibit spontaneous cerebellar malformations consisting of heterotopic neurons and glia in the molecular layer of the vermis. Malformations are almost exclusively found along the primary fissure and are indicative of deficits of neuronal migration during cerebellar development. In the present report, we test the prediction that genetically engineered rats on Sprague-Dawley or Long-Evans backgrounds will also exhibit the same cerebellar malformations. Consistent with our hypothesis, we found that three different transgenic lines on two different backgrounds had cerebellar malformations. Heterotopia in transgenic rats had identical cytoarchitecture as that observed in wild-type rats including altered morphology of Bergmann glia. In light of the possibility that heterotopia could affect results from behavioral studies, these data suggest that histological analyses be performed in studies of cerebellar function or development when using genetically engineered rats on these backgrounds in order to have more careful interpretation of experimental findings.

Cellular and axonal constituents of neocortical molecular layer heterotopia.

Human neocortical molecular layer heterotopia consist of aggregations of hundreds of neurons and glia in the molecular layer (layer I) and are indicative of neuronal migration defect. Despite having been associated with dyslexia, epilepsy, cobblestone lissencephaly, polymicrogyria, and Fukuyama muscular dystrophy, a complete understanding of the cellular and axonal constituents of molecular layer heterotopia is lacking. Using a mouse model, we identify diverse excitatory and inhibitory neurons as well as glia in heterotopia based on molecular profiles. Using immunocytochemistry, we identify diverse afferents in heterotopia from subcortical neuromodulatory centers. Finally, we document intracortical projections to/from heterotopia. These data are relevant toward understanding how heterotopia affect brain function in diverse neurodevelopmental disorders.

Intrinsic properties of and thalamocortical inputs onto identified corticothalamic-VPM neurons.

Corticothalamic (CT) feedback plays an important role in regulating the sensory information that the cortex receives. Within the somatosensory cortex layer VI originates the feedback to the ventral posterior medial (VPM) nucleus of the thalamus, which in turn receives sensory information from the contralateral whiskers. We examined the physiology and morphology of CT neurons in rat somatosensory cortex, focusing on the physiological characteristics of the monosynaptic inputs that they receive from the thalamus. To identify CT neurons, rhodamine microspheres were injected into VPM and allowed to retrogradely transport to the soma of CT neurons. Thalamocortical slices were prepared at least 3 days post injection. Whole-cell recordings from labeled CT cells in layer VI demonstrated that they are regular spiking neurons and exhibit little spike frequency adaption. Two anatomical classes were identified based on their apical dendrites that either terminated by layer V (compact cells) or layer IV (elaborate cells). Thalamic inputs onto identified CT-VPM neurons demonstrated paired pulse depression over a wide frequency range (2-20 Hz). Stimulus trains also resulted in significant synaptic depression above 10 Hz. Our results suggest that thalamic inputs differentially impact CT-VPM neurons in layer VI. This characteristic may allow them to differentiate a wide range of stimulation frequencies which in turn further tune the feedback signals to the thalamus.