The genes encoding for neuregulin1 (NRG1), a growth factor, and its receptor ErbB4 are both risk factors of major depression disorder and schizophrenia (SZ). They have been implicated in neural development and synaptic plasticity. However, exactly how NRG1 variations lead to SZ remains unclear. Indeed, NRG1 levels are increased in postmortem brain tissues of patients with brain disorders. Here, we studied the effects of high-level NRG1 on dendritic spine development and function. We showed that spine density in the prefrontal cortex and hippocampus was reduced in mice (ctoNrg1) that overexpressed NRG1 in neurons. The frequency of miniature excitatory postsynaptic currents (mEPSCs) was reduced in both brain regions of ctoNrg1 mice. High expression of NRG1 activated LIMK1 and increased cofilin phosphorylation in postsynaptic densities. Spine reduction was attenuated by inhibiting LIMK1 or blocking the NRG1–LIMK1 interaction, or by restoring NRG1 protein level. These results indicate that a normal NRG1 protein level is necessary for spine homeostasis and suggest a pathophysiological mechanism of abnormal spines in relevant brain disorders.

The precise control of the nervous system function under the vitality of synapses is extremely critical. Efforts have been taken to explore the underlying cellular and molecular mechanisms for synapse formation. Cell adhesion molecules have been found important for synapse assembly in the brain. Many trans-adhesion complexes have been identified to modulate excitatory synapse formation. However, little is known about the synaptogenic mechanisms for inhibitory synapses. ErbB4 is a receptor tyrosine kinase enriched in interneurons. Here, we showed that overexpressing ErbB4 in HEK293T cells induced gephyrin or GABAAR α1 puncta in co-cultured primary hippocampal neurons. This induction of ErbB4 was independent of its kinase activity. K751M, a kinase-dead mutant of ErbB4, can also induce gephyrin or GABAAR α1 puncta in the co-culture system. We further constructed K751M knock-in mice and found that the homozygous were viable at birth and fertile without changes in gross brain structure. The number of interneurons and inhibitory synapses onto pyramidal neurons (PyNs) were comparable between K751M and wild-type mice but decreased in ErbB4-Null mice. Moreover, ErbB4 can interact in trans with Slitrk3, a transmembrane postsynaptic protein at inhibitory synapses, through the extracellular RLD domain of ErbB4. The deletion of RLD diminished the induction of gephyrin or GABAAR α1 puncta by ErbB4. Finally, disruption of ErbB4–Slitrk3 interaction through neutralization of Slitrk3 by secretable RLD decreased inhibitory synapses onto PyNs and impaired GABAergic transmission. These results identify that ErbB4, as a cell adhesion molecule, promotes inhibitory synapse formation onto PyNs by interacting with Slitrk3 and in a kinase-independent manner, providing an unexpected mechanism of ErbB4 in inhibitory synapse formation.

Background Low-density lipoprotein receptor-related protein 4 (LRP4) plays a critical role in the central nervous system (CNS), including hippocampal synaptic plasticity, maintenance of excitatory synaptic transmission, fear regulation, as well as long-term potentiation (LTP). Results In this study, we found that Lrp4 was highly expressed in layer II of the piriform cortex. Both body weight and brain weight decreased in Lrp4ECD/ECD mice without TMD (Transmembrane domain) and ICD (intracellular domain) of LRP4. However, in the piriform cortical neurons of Lrp4ECD/ECD mice, the spine density increased, and the frequency of both mEPSC (miniature excitatory postsynaptic current) and sEPSC (spontaneous excitatory postsynaptic current) was enhanced. Intriguingly, finding food in the buried food-seeking test was prolonged in both Lrp4ECD/ECD mice and Lrp4 cKO (conditional knockout of Lrp4 in the piriform cortex) mice. Conclusions This study indicated that the full length of LRP4 in the piriform cortex was necessary for maintaining synaptic plasticity and the integrity of olfactory function.

ObjectiveTo systematically verify the accuracy of a four-step prenatal ultrasonography in diagnosing fetal total anomalous pulmonary venous connection (TAPVC).MethodsA total of 62 TAPVC fetuses received prenatal ultrasonography and were confirmed by postnatal echocardiography, surgery, or postabortion autopsy. The suspected TAPVC fetuses were further screened by a four-step prenatal ultrasonography for TAPVC classification, pulmonary venous obstruction, and the associated malformations, and followed postpartum. The sonographic features, clinical data, and prognosis of the TAPVC fetuses were retrospectively analyzed.ResultsOf the 62 TAPVC fetuses, supracardiac TAPVC was found in 20 cases, intracardiac TAPVC in 12, infracardiac TAPVC in 21, and mixed TAPVC in 9. A total of 30 cases with right atrium isomerism were correctly diagnosed. Of the 11 cases with other intracardiac and extracardiac malformations, 1 case was missed to be diagnosed. Of the 21 isolated TAPVC cases, 6 were missed prenatally and 1 case was prenatally diagnosed as intracardiac and postnatally proved to be mixed (intracardiac type + supracardiac type) by echocardiography. Of the 13 TAPVC live births, 4 infants died in the neonatal period without operation. Of the nine infants undergoing the operation, five recuperated and survived; one survived but had complications with superior vena cava obstruction and collateral circulation formation, and three died postoperatively.ConclusionThe four-step prenatal ultrasound procedure can comprehensively and systematically evaluate fetal TAPVC, detailing the classification, potential obstruction, and associated malformations. It provides substantial support for subsequent prenatal counseling and neonatal assessment. The retrospective analysis also reveals that isolated TAPVC is more prone to be missed in diagnosis.

Although itch and pain have many similarities, they are completely different in perceptual experience and behavioral response. In recent years, we have a deep understanding of the neural pathways of itch sensation transmission. However, there are few reports on the role of non‐neuronal cells in itch. Microglia are known to play a key role in chronic neuropathic pain and acute inflammatory pain. It is still unknown whether microglia are also involved in regulating the transmission of itch sensation. In the present study, we used several kinds of transgenic mice to specifically deplete CX3CR1+ microglia and peripheral macrophages together (whole depletion), or selectively deplete microglia alone (central depletion). We observed that the acute itch responses to histamine, compound 48/80 and chloroquine were all significantly reduced in mice with either whole or central depletion. Spinal c‐fos mRNA assay and further studies revealed that histamine and compound 48/80, but not chloroquine elicited primary itch signal transmission from DRG to spinal Npr1‐ and somatostatin‐positive neurons relied on microglial CX3CL1‐CX3CR1 pathway. Our results suggested that microglia were involved in multiple types of acute chemical itch transmission, while the underlying mechanisms for histamine‐dependent and non‐dependent itch transmission were different that the former required the CX3CL1‐CX3CR1 signal pathway.