2D organic–inorganic lead iodide perovskites have recently received tremendous attention as promising light absorbers for solar cells, due to their excellent optoelectronic properties, structural tunability, and environmental stability. However, although great efforts have been made, no 2D lead iodide perovskites have been discovered as ferroelectrics, in which the ferroelectricity may improve the photovoltaic performance. Here, by incorporating homochiral cations, 2D lead iodide perovskite ferroelectrics [R‐1‐(4‐chlorophenyl)ethylammonium]2PbI4 and [S‐1‐(4‐chlorophenyl)ethylammonium]2PbI4 are successfully obtained. The vibrational circular dichroism spectra and crystal structural analysis reveal their homochirality. They both crystalize in a polar space group P1 at room temperature, and undergo a 422F1 type ferroelectric phase transition with transition temperature as high as 483 and 473.2 K, respectively, showing a multiaxial ferroelectric nature. They also possess semiconductor characteristics with a direct bandgap of 2.34 eV. Nevertheless, their racemic analogue adopts a centrosymmetric space group P21/c at room temperature, exhibiting no high‐temperature phase transition. The homochirality in 2D lead iodide perovskites facilitates crystallization in polar space groups. This finding indicates an effective way to design high‐performance 2D lead iodide perovskite ferroelectrics with great application prospects.

Quasi-spherical molecules have recently been developed as promising building blocks for constructing high-performance molecular ferroelectrics. However, although the modification of spherical molecules into quasi-spherical ones can efficiently lower the crystal symmetry, it is still a challenge to precisely arouse a low-symmetric polar crystal structure. Here, by introducing directional hydrogen-bonding interactions in the molecular modification, we successfully reduced the cubic centrosymmetric Pm3̅m space group of [quinuclidinium]­ClO4 at room temperature to the orthorhombic polar Pna21 space group of [3-oxoquinuclidinium]­ClO4. Different from the substituent groups of −OH, −CH3, and CH2, the addition of a O group with H-acceptor to [quinuclidinium]+ forms directionally N–H···OC hydrogen-bonded chains, which plays a critical role in the generation of polar structure in [3-oxoquinuclidinium]­ClO4. Systematic characterization indicates that [3-oxoquinuclidinium]­ClO4 is an excellent molecular ferroelectric with a high Curie temperature of 457 K, a large saturate polarization of 6.7 μC/cm2, and a multiaxial feature of 6 equiv ferroelectric axes. This work demonstrates that the strategy of combining quasi-spherical molecule building blocks with directional intermolecular interactions provides an efficient route to precisely design new eminent molecular ferroelectrics.

Neuregulin 1 (Nrg1) encodes a neurotrophic factor and is genetically associated with schizophrenia, bipolar disorder and major depression. NRG1 has been shown to play important roles in neurodevelopment and neurotransmission. However, the knowledge about the cellular expression pattern of Nrg1 in mouse forebrain remains controversial and inconclusive. Here we used CRISPR/Cas9 techniques to generate Nrg1Cre/+ knockin mice which express the Cre recombinase immediately before the stop codon of Nrg1 gene. By crossing the Nrg1Cre/+ mice with Ai14 reporter mice which express fluorescent protein tdTomato in a Cre-dependent manner, we generated Nrg1 reporter mice which express tdTomato in cells where Nrg1 gene is actively transcribed. Using fluorescence imaging and unbiased stereology, we revealed the cellular expression pattern of Nrg1 in mouse forebrain regions including the olfactory bulb, cerebral cortex, striatum and hippocampus. We further performed stereotaxic injection of adeno-associated virus (AAV) which express tdTomato in a Cre-dependent way into different forebrain regions of adult Nrg1Cre/+ mice, and thus explored the distribution and axon projection of Nrg1-positive cells. These results provide fundamental information needed for the study of Nrg1 function in mouse forebrain. Moreover, the Nrg1Cre/+ mice generated here may represent a useful tool to study the function of neuronal populations expressing Nrg1.

Background Where the gene is expressed determines the function of the gene. Neuregulin 1 (Nrg1) encodes a tropic factor and is genetically linked with several neuropsychiatry diseases such as schizophrenia, bipolar disorder and depression. Nrg1 has broad functions ranging from regulating neurodevelopment to neurotransmission in the nervous system. However, the expression pattern of Nrg1 at the cellular and circuit levels in rodent brain is not full addressed. Methods Here we used CRISPR/Cas9 techniques to generate a knockin mouse line (Nrg1Cre/+) that expresses a P2A-Cre cassette right before the stop codon of Nrg1 gene. Since Cre recombinase and Nrg1 are expressed in the same types of cells in Nrg1Cre/+ mice, the Nrg1 expression pattern can be revealed through the Cre-reporting mice or adeno-associated virus (AAV) that express fluorescent proteins in a Cre-dependent way. Using unbiased stereology and fluorescence imaging, the cellular expression pattern of Nrg1 and axon projections of Nrg1-positive neurons were investigated. Results In the olfactory bulb (OB), Nrg1 is expressed in GABAergic interneurons including periglomerular (PG) and granule cells. In the cerebral cortex, Nrg1 is mainly expressed in the pyramidal neurons of superficial layers that mediate intercortical communications. In the striatum, Nrg1 is highly expressed in the Drd1-positive medium spiny neurons (MSNs) in the shell of nucleus accumbens (NAc) that project to substantia nigra pars reticulata (SNr). In the hippocampus, Nrg1 is mainly expressed in granule neurons in the dentate gyrus and pyramidal neurons in the subiculum. The Nrg1-expressing neurons in the subiculum project to retrosplenial granular cortex (RSG) and mammillary nucleus (MM). Nrg1 is highly expressed in the median eminence (ME) of hypothalamus and Purkinje cells in the cerebellum. Conclusions Nrg1 is broadly expressed in mouse brain, mainly in neurons, but has unique expression patterns in different brain regions.