Activation of feedforward wiring in adult hippocampal neurons by the basic-helix-loop-helix transcription factor Ascl4.

Although evidence indicates that the adult brain retains a considerable capacity for circuit formation, adult wiring has not been broadly considered and remains poorly understood. In this study, we investigate wiring activation in adult neurons. We show that the basic-helix-loop-helix transcription factor Ascl4 can induce wiring in different types of hippocampal neurons of adult mice. The new axons are mainly feedforward and reconfigure synaptic weights in the circuit. Mice with the Ascl4-induced circuits do not display signs of pathology and solve spatial problems equally well as controls. Our results demonstrate reprogrammed connectivity by a single transcriptional factor and provide insights into the regulation of brain wiring in adults.

Gephyrin phosphorylation facilitates sexually dimorphic development and function of parvalbumin interneurons in the mouse hippocampus.

The precise function of specialized GABAergic interneuron subtypes is required to provide appropriate synaptic inhibition for regulating principal neuron excitability and synchronization within brain circuits. Of these, parvalbumin-type (PV neuron) dysfunction is a feature of several sex-biased psychiatric and brain disorders, although, the underlying developmental mechanisms are unclear. While the transcriptional action of sex hormones generates sexual dimorphism during brain development, whether kinase signaling contributes to sex differences in PV neuron function remains unexplored. In the hippocampus, we report that gephyrin, the main inhibitory post-synaptic scaffolding protein, is phosphorylated at serine S268 and S270 in a developmentally-dependent manner in both males and females. When examining GphnS268A/S270A mice in which site-specific phosphorylation is constitutively blocked, we found that sex differences in PV neuron density in the hippocampal CA1 present in WT mice were abolished, coincident with a female-specific increase in PV neuron-derived terminals and increased inhibitory input onto principal cells. Electrophysiological analysis of CA1 PV neurons indicated that gephyrin phosphorylation is required for sexually dimorphic function. Moreover, while male and female WT mice showed no difference in hippocampus-dependent memory tasks, GphnS268A/S270A mice exhibited sex- and task-specific deficits, indicating that gephyrin phosphorylation is differentially required by males and females for convergent cognitive function. In fate mapping experiments, we uncovered that gephyrin phosphorylation at S268 and S270 establishes sex differences in putative PV neuron density during early postnatal development. Furthermore, patch-sequencing of putative PV neurons at postnatal day 4 revealed that gephyrin phosphorylation contributes to sex differences in the transcriptomic profile of developing interneurons. Therefore, these early shifts in male-female interneuron development may drive adult sex differences in PV neuron function and connectivity. Our results identify gephyrin phosphorylation as a new substrate organizing PV neuron development at the anatomical, functional, and transcriptional levels in a sex-dependent manner, thus implicating kinase signaling disruption as a new mechanism contributing to the sex-dependent etiology of brain disorders.

Controlled Construction of Core-Shell Structured Prussian Blue Analogues towards Enhanced Oxygen Reduction.

Metal-organic frameworks-based electrocatalysts have been developed as highly desirable and promising candidates for catalyzing oxygen reduction reaction (ORR), which, however, usually need to be prepared at elevated temperatures and may suffer from the framework collapse in water environments, largely preventing its industrial application. Herein, this work demonstrates a facile low-temperature ion exchange method to synthesize Mn and Fe co-loaded Prussian blue analogues possessing core-shell structured frameworks and favorable water-tolerance. Among the catalysts prepared, the optimal HMPB-2.6Mn shows a high ORR electrocatalytic performance featuring a half-wave potential of 0.86 V and zinc-air battery power density of 119 mW cm-2 , as well as negligible degradation up to 60 h, which are comparable to commercial Pt/C. Such an excellent electrocatalytic performance is attributed to the special core-shell-like structure with Mn concentrated in outer shell, and the synergetic interactions between Mn and Fe, endowing HMPB-Mn with outstanding ORR activity and good stability.

Short-Term Dendritic Dynamics of Neonatal Cortical Neurons Revealed by In Vivo Imaging with Improved Spatiotemporal Resolution.

Individual neurons in sensory cortices exhibit specific receptive fields based on their dendritic patterns. These dendritic morphologies are established and refined during the neonatal period through activity-dependent plasticity. This process can be visualized using two-photon in vivo time-lapse imaging, but sufficient spatiotemporal resolution is essential. We previously examined dendritic patterning from spiny stellate (SS) neurons, the major type of layer 4 (L4) neurons, in the mouse primary somatosensory cortex (barrel cortex), where mature dendrites display a strong orientation bias toward the barrel center. Longitudinal imaging at 8 h intervals revealed the long-term dynamics by which SS neurons acquire this unique dendritic pattern. However, the spatiotemporal resolution was insufficient to detect the more rapid changes in SS neuron dendrite morphology during the critical neonatal period. In the current study, we imaged neonatal L4 neurons hourly for 8 h and improved the spatial resolution by uniform cell surface labeling. The improved spatiotemporal resolution allowed detection of precise changes in dendrite morphology and revealed aspects of short-term dendritic dynamics unique to the neonatal period. Basal dendrites of barrel cortex L4 neurons were highly dynamic. In particular, both barrel-inner and barrel-outer dendrites (trees and branches) emerged/elongated and disappeared/retracted at similarly high frequencies, suggesting that SS neurons acquire biased dendrite patterns through rapid trial-and-error emergence, elongation, elimination, and retraction of dendritic trees and branches. We also found correlations between morphology and behavior (elongation/retraction) of dendritic tips. Thus, the current study revealed short-term dynamics and related features of cortical neuron dendrites during refinement.

Adsorption Site Regulations of [W-O]-Doped CoP Boosting the Hydrazine Oxidation-Coupled Hydrogen Evolution at Elevated Current Density.

Hydrazine oxidation reaction (HzOR) assisted hydrogen evolution reaction (HER) offers a feasible path for low power consumption to hydrogen production. Unfortunately however, the total electrooxidation of hydrazine in anode and the dissociation kinetics of water in cathode are critically depend on the interaction between the reaction intermediates and surface of catalysts, which are still challenging due to the totally different catalytic mechanisms. Herein, the [W-O] group with strong adsorption capacity is introduced into CoP nanoflakes to fabricate bifunctional catalyst, which possesses excellent catalytic performances towards both HER (185.60 mV at 1000 mA cm-2) and HzOR (78.99 mV at 10,00 mA cm-2) with the overall electrolyzer potential of 1.634 V lower than that of the water splitting system at 100 mA cm-2. The introduction of [W-O] groups, working as the adsorption sites for H2O dissociation and N2H4 dehydrogenation, leads to the formation of porous structure on CoP nanoflakes and regulates the electronic structure of Co through the linked O in [W-O] group as well, resultantly boosting the hydrogen production and HzOR. Moreover, a proof-of-concept direct hydrazine fuel cell-powered H2 production system has been assembled, realizing H2 evolution at a rate of 3.53 mmol cm-2 h-1 at room temperature without external electricity supply.

Consistent functional abnormalities in patients with postpartum depression.

Postpartum depression (PPD) is a common public health concern. A wide range of functional abnormalities in various brain regions have been reported in fMRI studies on PPD, however, a consistent functional changing pattern is still lacking. Herein, we obtained functional Magnetic Resonance Imaging (fMRI) data from 52 patients with PPD and 24 healthy postpartum women (HPW). Functional indexes (low-frequency fluctuation, degree centrality, and regional homogeneity) were calculated and compared among these groups to explore the functional changing patterns of PPD. Then, correlation analyses were performed to investigate the relationship between changed functional indexes and clinical measurements in the PPD. Finally, support vector machine (SVM) was performed to test whether these abnormal features can be used to distinguish PPD from HPW. As a result, we identified significantly and consistently functional changing pattern characterizing by increased functional activity in the left inferior occipital gyrus and decreased functional activity right anterior cingulate cortex in the PPD as compared to HPW. These functional values in the right anterior cingulate cortex were significantly correlated with depression symptoms in the PPD, and can be used as features to distinguish PPD from HPW. In conclusion, our results suggested that the right anterior cingulate cortex could be served as a functional neuro-imaging biomarker for PPD, which might be used as a potential target for neuro-modulation.

Commissural dentate granule cell projections and their rapid formation in the adult brain.

Dentate granule cells (GCs) have been characterized as unilaterally projecting neurons within each hippocampus. Here, we describe a unique class, the commissural GCs, which atypically project to the contralateral hippocampus in mice. Although commissural GCs are rare in the healthy brain, their number and contralateral axon density rapidly increase in a rodent model of temporal lobe epilepsies. In this model, commissural GC axon growth appears together with the well-studied hippocampal mossy fiber sprouting and may be important for the pathomechanisms of epilepsy. Our results augment the current view on hippocampal GC diversity and demonstrate powerful activation of a commissural wiring program in the adult brain.

Pcdh11x controls target specification of mossy fiber sprouting.

Circuit formation is a defining characteristic of the developing brain. However, multiple lines of evidence suggest that circuit formation can also take place in adults, the mechanisms of which remain poorly understood. Here, we investigated the epilepsy-associated mossy fiber (MF) sprouting in the adult hippocampus and asked which cell surface molecules define its target specificity. Using single-cell RNAseq data, we found lack and expression of Pcdh11x in non-sprouting and sprouting neurons respectively. Subsequently, we used CRISPR/Cas9 genome editing to disrupt the Pcdh11x gene and characterized its consequences on sprouting. Although MF sprouting still developed, its target specificity was altered. New synapses were frequently formed on granule cell somata in addition to dendrites. Our findings shed light onto a key molecular determinant of target specificity in MF sprouting and contribute to understanding the molecular mechanism of adult brain rewiring.

Circuit formation in the adult brain.

Neurons in the mammalian central nervous system display an enormous capacity for circuit formation during development but not later in life. In principle, new circuits could be also formed in adult brain, but the absence of the developmental milieu and the presence of growth inhibition and hundreds of working circuits are generally viewed as unsupportive for such a process. Here, we bring together evidence from different areas of neuroscience-such as neurological disorders, adult-brain neurogenesis, innate behaviours, cell grafting, and in vivo cell reprogramming-which demonstrates robust circuit formation in adult brain. In some cases, adult-brain rewiring is ongoing and required for certain types of behaviour and memory, while other cases show significant promise for brain repair in disease models. Together, these examples highlight that the adult brain has higher capacity for structural plasticity than previously recognized. Understanding the underlying mechanisms behind this retained plasticity has the potential to advance basic knowledge regarding the molecular organization of synaptic circuits and could herald a new era of neural circuit engineering for therapeutic repair.

Recurrent rewiring of the adult hippocampal mossy fiber system by a single transcriptional regulator, Id2.

Circuit formation in the central nervous system has been historically studied during development, after which cell-autonomous and nonautonomous wiring factors inactivate. In principle, balanced reactivation of such factors could enable further wiring in adults, but their relative contributions may be circuit dependent and are largely unknown. Here, we investigated hippocampal mossy fiber sprouting to gain insight into wiring mechanisms in mature circuits. We found that sole ectopic expression of Id2 in granule cells is capable of driving mossy fiber sprouting in healthy adult mouse and rat. Mice with the new mossy fiber circuit solved spatial problems equally well as controls but appeared to rely on local rather than global spatial cues. Our results demonstrate reprogrammed connectivity in mature neurons by one defined factor and an assembly of a new synaptic circuit in adult brain.

[Mild and moderate postpartum depression treated with acupuncture of Tiaoren Tongdu: a real world study].

OBJECTIVE: To observe the clinical therapeutic effect on mild and moderate postpartum depression treated with acupuncture of Tiaoren Tongdu (regulating the conception vessel and unblocking the governor vessel) on the base of real world. METHODS: A total of 116 patients with mild and moderate postpartum depression were divided into an acupuncture group (103 cases) and a non-acupuncture group (13 cases) according to treatment regimen provided. In the acupuncture group, acupuncture of Tiaoren Tongdu was applied to Baihui (GV 20), Yintang (GV 29), Zhongwan (CV 12), Qihai (CV 6), Guanyuan (CV 4), Neiguan (PC 6), Shenmen (HT 7), Hegu (LI 4), Zusanli (ST 36), Sanyinjiao (SP 6) and Taichong (LR 3). Needles were retained for 30 min each time, the treatment was given once every other day, 3 times a week. In the non-acupuncture group, psychotherapy was provided, once daily. The duration of treatment in the two groups was 8 weeks. According to the treatment times of acupuncture, the acupuncture group was subdivided into an acupuncture A group (60 cases with total treatments ≥ 6 times) and an acupuncture B group (43 cases with total treatments<6 times). Using propensity score matching method, the patients of the acupuncture A and B groups were matched each other. Finally, 31 pairs of cases were matched successfully. Before treatment, at 1st, 2nd, 4th and 8th weeks of treatment, as well as at 3-month follow-up, the scores of Hamilton depression scale (HAMD) were compared in patients among the three groups. Using Logistic regression, the impact of acupuncture frequencies on the therapeutic effect was analyzed and the clinical therapeutic effect was assessed. RESULTS: The total effective rate of the acupuncture A group was 100.0% (31/31), better than 76.9% (10/13) in the non-acupuncture group and 58.1% in the acupuncture B group (18/31) (P<0.05). HAMD score at each time point after treatment was lower than that before treatment in the patients of each group (P<0.05). But HAMD score at each time point after treatment in either the acupuncture A group or the acupuncture B group was lower than that in the non-acupuncture group separately (P<0.05), HAMD scores in the acupuncture A group at the 4th and 8th weeks of treatment and at follow-up were lower than those in the acupuncture B group (P<0.05). Logistic regression analysis showed that the total times of acupuncture treatment and the persistent days of treatment had a certain relation to therapeutic effect (P<0.05). CONCLUSION: Acupuncture of Tiaoren Tongdu effectively improves in mild and moderate postpartum depression and its therapeutic effect is closely related to treatment course.

Transcriptional and morphological profiling of parvalbumin interneuron subpopulations in the mouse hippocampus.

The diversity reflected by >100 different neural cell types fundamentally contributes to brain function and a central idea is that neuronal identity can be inferred from genetic information. Recent large-scale transcriptomic assays seem to confirm this hypothesis, but a lack of morphological information has limited the identification of several known cell types. In this study, we used single-cell RNA-seq in morphologically identified parvalbumin interneurons (PV-INs), and studied their transcriptomic states in the morphological, physiological, and developmental domains. Overall, we find high transcriptomic similarity among PV-INs, with few genes showing divergent expression between morphologically different types. Furthermore, PV-INs show a uniform synaptic cell adhesion molecule (CAM) profile, suggesting that CAM expression in mature PV cells does not reflect wiring specificity after development. Together, our results suggest that while PV-INs differ in anatomy and in vivo activity, their continuous transcriptomic and homogenous biophysical landscapes are not predictive of these distinct identities.

Interaction of tobacco smoking and alcohol consumption with obesity on cardiovascular disease in a Chinese cohort.

OBJECTIVE: We aimed to detect the synergistic effect between alcohol drinking, smoking and obesity on incident cardiovascular disease (CVD) in a Chinese population- based cohort. METHODS: We performed this study based on a prospective cohort based on a Chinese population in Jiangsu, China. Logistic regression was employed to detect the interaction of smoking, drinking with obesity on susceptibility to CVD, and calculate the odds ratio (OR) of CVD and corresponding 95% confidence interval (CI). RESULTS: A total of 3598 subjects (1451 males and 2147 females) were enrolled, including 82 CVD patients (36 males and 46 females) who new developed CVD at the follow-up. We found a significant abdominal obesity-current smoking interaction on CVD risk. Compared to never-smokers with normal waist circumference, OR (95% CI) of CVD were 2.44 (1.56-3.81), 1.58 (0.93-2.69), and 5.37 (3.08-9.34) for smokers with normal waist circumference, abdominal obese nonsmokers and abdominal obese smokers, respectively. Synergy index for this interaction was 2.35 (1.05-4.50). We also found a significant abdominal obesity-alcohol drinking interaction on CVD. Compared to never-drinkers with normal waist circumference, OR (95% CI) of CVD were 1.57 (1.01-2.45), 1.84 (1.08-3.12), and 4.44 (2.55-7.72) for drinkers with normal waist circumference, abdominal obese non- drinkers and abdominal obese drinkers, respectively. Synergy index for this interaction was 2.44 (1.04-5.72). CONCLUSION: We found significant interactions between alcohol drinking and abdominal obesity, smoking and abdominal obesity on CVD risk, suggested that the effect of alcohol drinking or smoking on CVD susceptibility seems to be modified by abdominal obesity.

Single-cell RNA-Seq characterization of anatomically identified OLM interneurons in different transgenic mouse lines.

Inhibitory GABAergic interneurons create different brain activity patterns that correlate with behavioural states. In this characterizing study, we used single-cell RNA-Seq to analyse anatomically- and electrophysiologically identified hippocampal oriens-lacunosum moleculare (OLM) interneurons. OLMs express somatostatin (Sst), generate feedback inhibition and play important roles in theta oscillations and fear encoding. Although an anatomically- and biophysically homogenous population, OLMs presumably comprise of two functionally distinct types with different developmental origins, inferred from the expression pattern of serotonin type-3a (5-HT3a, or Htr3a) receptor subunit and 5-HT excitability in a set of OLMs. To broadly characterize OLM cells, we used the Sst-Cre and the BAC transgenic Htr3a-Cre mouse lines and separately analysed SstCre-OLM and Htr3aCre-OLM types. We found a surprisingly consistent expression of Npy in OLMs, which was previously not associated with the identity of this type. Our analyses furthermore revealed uniform expression of developmental origin-related genes, including transcription factors and neurexin isoforms, without providing support for the current view that OLMs may originate from multiple neurogenic zones. Together, we found that OLMs constitute a highly homogenous transcriptomic population. Finally, our results revealed surprisingly infrequent expression of Htr3a in only ~10% of OLMs and an apparently specific expression of the 5-HT3b subunit-coding gene Htr3b in Htr3aCre-OLMs, but not in SstCre-OLMs. However, additional in situ hybridization experiments suggested that the differential expression of Htr3b may represent an unexpected consequence arising from the design of the Htr3a-Cre BAC transgenic line.

Single-Cell RNA-Seq Reveals Developmental Origins and Ontogenetic Stability of Neurexin Alternative Splicing Profiles.

Neurexins are key synaptic organizers that are expressed in thousands of alternatively spliced isoforms. Because transsynaptic neurexin interactions with different postsynaptic molecules are largely isoform dependent, a cell type-level census of different neurexin isoforms could predict molecular interactions relating to synapse identity and function. Using single-cell transcriptomics to study the origin of neurexin diversity in multiple murine mature and embryonic cell types, we have discovered shared neurexin expression patterns in developmentally related cells. By comparing neurexin profiles in immature embryonic neurons, we show that neurexin profiles are specified during early development and remain unchanged throughout neuronal maturation. Thus, our findings reveal ontogenetic stability and provide a cell type-level census of neurexin isoform expression in the cortex.

The Serum BDNF Level Offers Minimum Predictive Value for Motor Function Recovery After Stroke.

Brain-derived neurotrophic factor (BDNF) plays an important role in neuroplasticity and neurogenesis following ischemic and non-ischemic brain injury. The predictive value of BDNF for short-term outcome after stroke is controversial. The objective of this study was to investigate the relationship among serum BDNF level, fractional anisotropy (FA), and functional outcome during post-acute stroke rehabilitation. Serum BDNF levels were measured on admission to an acute inpatient rehabilitation hospital. The primary functional outcome was functional independence measure (FIM) motor subscore at discharge. The secondary outcome measures were FIM total score at discharge, FIM motor subscore on admission, length of stay in the hospital, and discharge destination. We investigated the relationship among the level of serum BDNF and FA as well as functional outcome measures. Three hundred forty-eight consecutive stroke subjects were included in the analysis. Serum BDNF levels on admission were statistically but not clinically correlated with FIM motor subscore at discharge (r = 0.173, P = 0.001) and FIM total score at discharge (r = 0.155, P = 0.004). Receiver operating characteristic (ROC) analysis of BDNF as a predictor for FIM motor subscore improvement showed low accuracy of prediction with an area under the curve (AUC) of 0.581 (P = 0.026). Serum BDNF significantly correlated with FA in the high FIM motor group (n = 10, r = 0.609, P = 0.031) but not in the low FIM motor group (n = 11, r = - 0.132, P = 0.349). The serum BDNF level alone offers minimum predictive value for recovery of motor function during post-acute rehabilitation. Our findings suggest that serum BDNF level may be correlated with FA.

Protocadherin-αC2 is required for diffuse projections of serotonergic axons.

Serotonergic axons extend diffuse projections throughout various brain areas, and serotonergic system disruption causes neuropsychiatric diseases. Loss of the cytoplasmic region of protocadherin-α (Pcdh-α) family proteins, products of the diverse clustered Pcdh genes, causes unbalanced distributions (densification and sparsification) of serotonergic axons in various target regions. However, which Pcdh-α member(s) are responsible for the phenotype is unknown. Here we demonstrated that Pcdh-αC2 (αC2), a Pcdh-α isoform, was highly expressed in serotonergic neurons, and was required for normal diffusion in single-axon-level analyses of serotonergic axons. The loss of αC2 from serotonergic neurons, but not from their target brain regions, led to unbalanced distributions of serotonergic axons. Our results suggest that αC2 expressed in serotonergic neurons is required for serotonergic axon diffusion in various brain areas. The αC2 extracellular domain displays homophilic binding activity, suggesting that its homophilic interaction between serotonergic axons regulates axonal density via αC2's cytoplasmic domain.

Supernova: A Versatile Vector System for Single-Cell Labeling and Gene Function Studies in vivo.

Here we describe "Supernova" series of vector systems that enable single-cell labeling and labeled cell-specific gene manipulation, when introduced by in utero electroporation (IUE) or adeno-associated virus (AAV)-mediated gene delivery. In Supernova, sparse labeling relies on low TRE leakage. In a small population of cells with over-threshold leakage, initial tTA-independent weak expression is enhanced by tTA/TRE-positive feedback along with a site-specific recombination system (e.g., Cre/loxP, Flpe/FRT). Sparse and bright labeling by Supernova with little background enables the visualization of the morphological details of individual neurons in densely packed brain areas such as the cortex and hippocampus, both during development and in adulthood. Sparseness levels are adjustable. Labeled cell-specific gene knockout was accomplished by introducing Cre/loxP-based Supernova vectors into floxed mice. Furthermore, by combining with RNAi, TALEN, and CRISPR/Cas9 technologies, IUE-based Supernova achieved labeled cell-specific gene knockdown and editing/knockout without requiring genetically altered mice. Thus, Supernova system is highly extensible and widely applicable for single-cell analyses in complex organs, such as the mammalian brain.

A population association study of PPAR δ gene rs2016520 and rs9794 polymorphisms and haplotypes with body mass index and waist circumference in a Chinese population.

BACKGROUND: Peroxisome proliferator-activated receptor (PPAR) gene plays an important role in obesity and PPAR δ protein is a potent inhibitor; however, few previous studies have focused on this gene. AIM: To investigate the association of haplotypes of PPAR δ gene rs2016520 and rs9794 with abnormal weight (BMI ≥ 24 kg/m(2)) and abdominal obesity (WC ≥ 90 cm for males and ≥ 80 cm for females) in a Chinese Han population. SUBJECTS AND METHODS: In total, 820 subjects (270 men, 550 women) were randomly selected from the PMMJS cohort population and no individuals were related. rs2016520 and rs9794 were detected by TaqMan fluorescence probe. Hardy-Weinberg equilibrium (HWE) was used to detect genotype typing errors by Fisher's exact test. Linkage disequilibrium (LD) between polymorphisms was estimated by using SHEsis. Two PPAR δ SNPs (rs2016520 and rs9794) were analysed by using the logistic regression model. RESULTS: After adjustment for covariates, the haplotype containing the rs1026520-C and rs9794-C alleles was associated with a statistically significant decreased risk of obesity (OR = 0.64; 95% CI = 0.48-0.84, p = 0.0015). Coincidentally, the haplotype containing the rs1026520-C and rs9794-C alleles was also associated with a statistically decreased risk of abdominal obesity after covariate adjustment (OR = 0.59, 95% CI = 0.45-0.77, p < 0.001). CONCLUSION: C-C haplotype, constructed from rs2016520 and rs9794 alleles, showed a significant protective effect for both abnormal weight and abdominal obesity.

Molecular cloning and partial characterization of a low-density lipoprotein receptor-related protein 13 (Lrp13) involved in vitellogenin uptake in the cutthroat trout (Oncorhynchus clarki).

Multiple ovarian membrane proteins that bind vitellogenin (Vtg) have been detected in teleosts. One of these Vtg receptors was recently identified as low-density lipoprotein receptor-related protein 13 (lrp13/Lrp13) in perciform species, but little is known about this Vtg receptor in salmonid fish. In this study, a cDNA encoding a putative Vtg receptor with 13+1 ligand binding repeats (lr13+1) was cloned from the ovary, and identified as an lrp13 ortholog for cutthroat trout (Oncorhynchus clarki). This lrp13 was predominantly expressed in the pre-vitellogenic stage ovary, and its expression decreased during vitellogenesis. Ovarian localization of Lrp13 was observed by immunohistochemistry using specific antiserum against recombinant Lrp13. Lrp13 immunoreactivity was observed at the oolemma, throughout the zona radiata, and within the perivitelline space between the zona radiata and granulosa cells in ovarian follicles at both the lipid-droplet and vitellogenic stages of growth-an expression pattern that mimics that of a lr8/LR8-type Vtg receptor in this species and of lrp13/Lrp13 in Morone species. Six discrete Vtg-binding proteins were detected in cutthroat trout ovarian membrane proteins when probing with a digoxygenin-labeled salmonid A-type Vtg (VtgAs) followed by chemiluminescent ligand detection. Western blotting using the anti-Lrp13 serum revealed a broad signal consisting of two proteins with masses ranging from ∼190 to ∼210 kDa, which corresponded with some of the VtgA-binding proteins. These findings suggest that, in addition to lr8/LR8, lrp13/Lrp13 acts as a VtgA receptor in trout.