Clustering of CaV 1.3 L-type calcium channels by Shank3.

Clustering of L-type voltage-gated Ca2+ channels (LTCCs) in the plasma membrane is increasingly implicated in creating highly localized Ca2+ signaling nanodomains. For example, neuronal LTCC activation can increase phosphorylation of the nuclear CREB transcription factor by increasing Ca2+ concentrations within a nanodomain close to the channel, without requiring bulk Ca2+ increases in the cytosol or nucleus. However, the molecular basis for LTCC clustering is poorly understood. The postsynaptic scaffolding protein Shank3 specifically associates with one of the major neuronal LTCCs, the CaV 1.3 calcium channel, and is required for optimal LTCC-dependent excitation-transcription coupling. Here, we co-expressed CaV 1.3 α1 subunits with two distinct epitope-tags with or without Shank3 in HEK cells. Co-immunoprecipitation studies using the cell lysates revealed that Shank3 can assemble complexes containing multiple CaV 1.3 α1 subunits under basal conditions. Moreover, CaV 1.3 LTCC complex formation was facilitated by CaV ß subunits (ß3 and ß2a), which also interact with Shank3. Shank3 interactions with CaV 1.3 LTCCs and multimeric CaV 1.3 LTCC complex assembly were disrupted following the addition of Ca2+ to cell lysates, perhaps simulating conditions within an activated CaV 1.3 LTCC nanodomain. In intact HEK293T cells, co-expression of Shank3 enhanced the intensity of membrane-localized CaV 1.3 LTCC clusters under basal conditions, but not after Ca2+ channel activation. Live cell imaging studies also revealed that Ca2+ influx through LTCCs disassociated Shank3 from CaV 1.3 LTCCs clusters and reduced the CaV 1.3 cluster intensity. Deletion of the Shank3 PDZ domain prevented both binding to CaV 1.3 and the changes in multimeric CaV 1.3 LTCC complex assembly in vitro and in HEK293 cells. Finally, we found that shRNA knock-down of Shank3 expression in cultured rat primary hippocampal neurons reduced the intensity of surface-localized CaV 1.3 LTCC clusters in dendrites. Taken together, our findings reveal a novel molecular mechanism contributing to neuronal LTCC clustering under basal conditions.

Modeling intrahippocampal effects of anterior hippocampal hyperactivity relevant to schizophrenia using chemogenetic excitation of long axis-projecting mossy cells in the mouse dentate gyrus.

BACKGROUND: The anterior hippocampus of individuals with early psychosis or schizophrenia is hyperactive, as is the ventral hippocampus in many rodent models for schizophrenia risk. Mossy cells (MCs) of the ventral dentate gyrus (DG) densely project in the hippocampal long axis, targeting both dorsal DG granule cells and inhibitory interneurons. Mossy cells are responsive to stimulation throughout hippocampal subfields, and thus may be suited to detect hyperactivity in areas where it originates such as CA1. Here we tested the hypothesis that hyperactivation of ventral MCs activates dorsal DG granule cells to influence dorsal hippocampal function. METHODS: In CD-1 mice, we targeted dorsal DG-projecting ventral MCs using an adeno-associated virus intersectional strategy. In vivo fiber photometry recording of ventral MCs was performed during exploratory behaviors. We used excitatory chemogenetic constructs to test the effects of ventral MC hyperactivation on long-term spatial memory during an object location memory task. RESULTS: Photometry revealed ventral MCs were activated during exploratory rearing. Ventral MCs made functional monosynaptic inputs to dorsal DG granule cells, and chemogenetic activation of ventral MCs modestly increased activity of dorsal DG granule cells measured by c-Fos. Finally, chemogenetic activation of ventral MCs during the training phase of an object location memory task impaired test performance 24 hours later, without effects on locomotion or object exploration. CONCLUSIONS: These data suggest that ventral MC activation can directly excite dorsal granule cells and interfere with dorsal DG function, supporting future study of their in vivo activity in animal models for schizophrenia featuring ventral hyperactivity.

Anterior thalamic dysfunction underlies cognitive deficits in a subset of neuropsychiatric disease models.

Neuropsychiatric disorders are often accompanied by cognitive impairments/intellectual disability (ID). It is not clear whether there are converging mechanisms underlying these debilitating impairments. We found that many autism and schizophrenia risk genes are expressed in the anterodorsal subdivision (AD) of anterior thalamic nuclei, which has reciprocal connectivity with learning and memory structures. CRISPR-Cas9 knockdown of multiple risk genes selectively in AD thalamus led to memory deficits. While the AD is necessary for contextual memory encoding, the neighboring anteroventral subdivision (AV) regulates memory specificity. These distinct functions of AD and AV are mediated through their projections to retrosplenial cortex, using differential mechanisms. Furthermore, knockdown of autism and schizophrenia risk genes PTCHD1, YWHAG, or HERC1 from AD led to neuronal hyperexcitability, and normalization of hyperexcitability rescued memory deficits in these models. This study identifies converging cellular to circuit mechanisms underlying cognitive deficits in a subset of neuropsychiatric disease models.

Women's perceptions of antenatal care: are we following guideline recommended care?

BACKGROUND: Detection and management of antenatal risk factors is critical for improved maternal and infant outcomes. This study describes the proportion of pregnant women who self-reported being screened for and offered advice to manage antenatal risk factors in line with antenatal care recommendations; and the characteristics associated with rates of screening. METHODS: A survey was undertaken with 223 (64 % of eligible) pregnant women recruited from an outpatient obstetrics clinic at a public hospital. Participants self-reported whether they were: (i) screened for 23 guideline-recommended risk factors during their antenatal visit; (ii) offered assistance to manage identified risk factor(s); and (iii) received assistance that was of benefit. Association between rate of screening and participant characteristics was examined using multivariate quantile regression. RESULTS: Overall, 23 % of women reported that they were asked about every risk factor. Weight gain (48 %), diet (60 %) and oral health (31 %) were least frequently screened risk factors. The number of women who reported they were offered advice to manage identified risks and the value of that advice was perceived by women as suboptimal. Those women receiving shared care between a midwife and general practitioner, of Aboriginal or Torres Strait Islander descent, and without private health insurance reported being screened for a greater number of risk factors. CONCLUSIONS: Pregnant women report suboptimal rates of screening and management of antenatal risk factors. Initiatives to improve consistency in detection of antenatal risk factors and the application of appropriate interventions to manage those risk factors that are detected are required.