[PLXNA1 is highly expressed in hepatocellular carcinoma and affects patients' survival and immune microenvironment].

OBJECTIVE: To investigate PLXNA1 expression in hepatocellular carcinoma (HCC) and explore its biological function and impacts on patients' survival outcomes and immune microenvironment. METHODS: Bioinformatic analysis of highly expressed immune-related genes in HCC were performed using TCGA database and Immport website, and 7 genes associated with the survival outcomes of the patients were identified using univariate Cox regression analysis, Gene Expression Profiling Interactive Analysis, and Kaplan Meier plotter website. The expression profile of PLXNA1 in HCC was verified using GEO database. The impact of PLXNA1 expression on survival outcomes of HCC patients was analyzed using TCGA database, Kaplan Meier, and timeROC curve analyses, and its association with immune cell infiltration was explored using TIMER website, CIBERSORT, and ssGSEA. Immunohistochemmistry was used to detect PLXNA1 expression in clinical specimens of HCC and adjacent tissues, and the correlation of PLXNA1 expression level with the patients' survival was analyzed. RT-qPCR was used to examine PLXNA1 expressions in different HCC cell lines, and the effects of PLXNA1 knockdown on proliferation and migration of SMMC-7721 cells were evaluated using CCK-8 and Transwell assays. RESULTS: Bioinformatic analyses suggested that PLXNA1 was highly expressed in HCC, and its high expression was associated with poor survival outcomes of the patients. PLXNA1 expression level was significantly correlated with immune cell infiltration in HCC. Immunohistochemmistry showed that compared with the adjacent tissues, HCC tissues had significantly higher PLXNA1 expressions, which were associated with a poor patient survival and served also as a diagnostic indicator for HCC (AUC= 0.9346). In cultured HCC cell lines, SMMC-7721 cells showed a higher PLXNA1 expression than HL-7702 cells, and PLXNA1 knockdown significantly suppressed proliferation and migration of SMMC-7721 cells. CONCLUSION: PLXNA1 is highly expressed in HCC to promote tumor cell migration and proliferation and affect the patients' survival outcomes and immune microenvironment.

PlexinA1-deficient mice exhibit decreased cell density and augmented oxidative stress in parvalbumin-expressing interneurons in the medial prefrontal cortex.

PlexinA1 (PlxnA1) is a transmembrane receptor for semaphorins (Semas), a large family of axonal guidance cues vital during neural development. PlxnA1 is expressed in embryonic interneurons, and PlxnA1 deletion in mice leads to less interneurons in the developing cortex. In addition, PlxnA1 has been identified as a schizophrenia susceptibility gene. In our previous study, PlxnA1 knockout (KO) mice under a BALB/cAJ genetic background exhibited significantly increased self-grooming and reduced prepulse inhibition, a reliable phenotype for investigating the neurobiology of schizophrenia. However, the mechanism underlying the abnormal behavior of PlxnA1 KO mice remains unclear. We first confirmed PlxnA1 mRNA expression in parvalbumin-expressing interneurons (PV cells) in the medial prefrontal cortex (mPFC) of adult mice. Immunohistochemical analysis (IHC) showed significantly decreased densities of both GABAergic neurons and PV cells in the mPFC of PlxnA1 KO mice compared with wild type mice (WT). PV cells were found to express molecule interacting with CasL 1 (MICAL1), an effector involved in Sema-Plxn signaling for axon guidance, suggesting MICAL1 and PlxnA1 co-expression in PV cells. Furthermore, IHC analysis of 8-oxo-dG, an oxidative stress marker, revealed significantly increased oxidative stress in PlxnA1-deficient PV cells compared with WT. Thus, increased oxidative stress and decreased PV cell density in the mPFC may determine the onset of PlxnA1 KO mice's abnormal behavior. Accordingly, deficient PlxnA1-mediated signaling may increase oxidative stress in PV cells, thereby disrupting PV-cell networks in the mPFC and causing abnormal behavior related to neuropsychiatric diseases.

Rare variant screening and burden analysis of PLXNA1 in Parkinson's disease.

BACKGROUND AND PURPOSE: Recently, p.Glu1121Ter in PLXNA1 was identified as a potential cause of parkinsonism. However, no further replication has been conducted in a wider range of Parkinson's disease (PD) cohorts. We aimed to evaluate the genetic role of PLXNA1 in PD. METHODS: We systematically analyzed the rare protein-coding variants (minor allele frequency [MAF] < 0.01) in 1080 patients and 1051 healthy controls. Fisher's exact test was used to analyze the associations between each variant and risk of PD, while, at gene level, over-representation of rare variants in patients was examined using the optimized sequence kernel association test (SKAT-O). RESULTS: In total, 43 rare variants were identified in PD. No variant was significantly associated with risk of PD. Burden analysis showed enrichment of ultra-rare variants (MAF < 0.001) of PLXNA1 in PD. One patient carried a variant (p.E1121D) in the same amino acid as that in the original study. Both patients showed worsened motor symptoms, and developed dyskinesia during follow-up. CONCLUSIONS: Our study explored the rare variant of PLXNA1 in PD, and paves the way for future research on the genetic role of PLXNA1 in PD.

Analysis of PLXNA1, NRP1, and NRP2 variants in a cohort of patients with isolated hypogonadotropic hypogonadism.

BACKGROUND: Isolated hypogonadotropic hypogonadism (IHH) is a clinical syndrome described by failure of gonadal function secondary to defects on the synthesis, secretion, or action of the gonadotropin-releasing hormone (GnRH). The secreted glycoprotein SEMA3A binds its receptors NRP1 or NRP2 and PLXNA to participate in axonal projection, dendritic branching, synaptic formation, and neuronal migration. Deficiency in SEMA3A, NRP1, NRP2, and PLXNA1 have been related to abnormal GnRH neuron development in mice and IHH in humans. METHODS: The aim of this study was to examine the genotypic and phenotypic spectra of the NRP1, NRP2, and PLXNA1 genes in a large cohort of IHH probands from China. We screened NRP1, NRP2, and PLXNA1 variants in Chinese IHH patients by whole exome sequencing and pedigree analysis. RESULTS: We identified 10 heterozygous missense variants in PLXNA1, five heterozygous missense variants in NRP1, and two heterozygous missense variants in NRP2. NRP1 variants were found only in IHH patients with defective olfaction (i.e., Kallmann syndrome, KS). In addition, 85% (17/20) of patients harbored variants in other IHH-associated genes. CONCLUSION: Our study greatly enriched the genotypic and phenotypic spectra of PLXNA1, NRP1, and NRP2 in IHH. It may be conducive to the genetic counseling, diagnosis, and treatment of IHH with mutations in the PLXNA1, NRP1, and NRP2 genes. Furthermore, our results indicated that NRP1 were strongly linked to hearing loss.

A Spatiotemporal Sequence of Sensitization to Slits and Semaphorins Orchestrates Commissural Axon Navigation.

Accurate perception of guidance cues is crucial for cell and axon migration. During initial navigation in the spinal cord, commissural axons are kept insensitive to midline repellents. Upon midline crossing in the floor plate, they switch on responsiveness to Slit and Semaphorin repulsive signals and are thus propelled away and prevented from crossing back. Whether and how the different midline repellents control specific aspects of this navigation remain to be elucidated. We set up a paradigm for live-imaging and super-resolution analysis of PlexinA1, Neuropilin-2, and Robo1/2 receptor dynamics during commissural growth cone navigation in chick and mouse embryos. We uncovered a remarkable program of sensitization to midline cues achieved by unique spatiotemporal sequences of receptor allocation at the growth-cone surface that orchestrates receptor-specific growth-cone behavior changes. This reveals post-translational mechanisms whereby coincident guidance signals are temporally resolved to allow the generation of specific guidance responses.

MicroRNA-134 prevents the progression of esophageal squamous cell carcinoma via the PLXNA1-mediated MAPK signalling pathway.

BACKGROUND: MicroRNAs (miRNAs) are involved in oncogenesis of esophageal squamous cell carcinoma (ESCC). miR-134 is reported to have a tumour-suppressive role but its role in ESCC is not known. The present study was designed to examine whether miR-134 inhibits ESCC development and further explored relevant underlying mechanisms. METHODS: Differentially expressed genes related to ESCC were identified from microarray gene expression profiles. Immunohistochemical staining and RT-qRCR assays identified elevated PLXNA1 expression levels and low miR-134. The relationship between miR-134 and PLXNA1 was predicted and further verified by a dual-luciferase reporter assay. The expression levels of miR-134 and PLXNA1 in ESCC cells were modified by miR-134 mimic/inhibitor and siRNA against PLXNA1, respectively. Thereafter, the expression of MAPK signalling pathway-related proteins, as well as the viability, migration, invasion, cell cycle and cell apoptosis of ESCC cells was investigated. FINDINGS: The results showed that miR-134 could block the MAPK signalling pathway by downregulating PLXNA1. When miR-134 was overexpressed or PLXNA1 was silenced, cell apoptosis was enhanced, the cell cycle was retarded, and the cell proliferation, migration and invasion were suppressed. In vivo experiments confirmed that miR-134 overexpression or PLXNA1 silencing restrained tumour growth and lymph node metastasis. INTERPRETATION: These findings demonstrate that cancer cell proliferation, migration, invasion, and tumour metastasis of ESCC can be suppressed by overexpression of miR-134 through downregulating PLXNA1, which subsequently blocks the MAPK signalling pathway. These results provide new potential targets and strategies for the treatment of ESCC.

Prevalence and associated phenotypes of PLXNA1 variants in normosmic and anosmic idiopathic hypogonadotropic hypogonadism.

Idiopathic hypogonadotropic hypogonadism (IHH) can be divided into two major forms, normosmic IHH and Kallmann syndrome (KS). Genetic mutations are responsible for the majority of IHH. PLXNA1 has recently been implicated in the GnRH neuron migration and the etiology of KS. We aimed to investigate the prevalence and associated phenotypes of PLXNA1 variants in a large cohort of IHH patients. We screened the whole exome data of 215 IHH patients in a single center for causative PLXNA1 variants. Our studies showed eight novel (p.Arg836His, p.Lys1451Arg, p.Val287Met, p.Val536Ile, p.Ser1850Arg, p.Ile1701Val, p.Arg319Trp, and p.Pro485Leu) and two previously described (p.Arg528Trp and p.Gly720Glu) heterozygous PLXNA1 variants in nine affected individuals from seven unrelated families. Only three of nine patients were anosmic (KS) while the remaining patients showed normal olfactory function (nIHH). Seven of nine patients (77.7%) harbored additional one or two variants in other nIHH/KS-associated genes, including PROKR2, IGSF10, HS6ST1, SEMA3E, CCDC141, FGFR1, NRP1, POLR3A, and SRA1. Our findings indicate that PLXNA1 variants cause not only anosmic but also normosmic IHH with a relatively high prevalence (3.9%). Heterozygous missense PLXNA1 variants appear to be involved together with other IHH gene variants in bringing about the IHH disease phenotype.

PLXNA1 developmental encephalopathy with syndromic features: A case report and review of the literature.

Developmental encephalopathies constitute a broad and genetically heterogeneous spectrum of disorders associated with global developmental delay, intellectual disability, frequent epilepsy, and other neurofunctional abnormalities. Here, we report a male presenting with infantile onset epilepsy and syndromic features resembling Dubowitz syndrome identified to have a de novo PLXNA1 variant by whole exome sequencing. This constitutes the second report of PLXNA1 sequence variation associated with early onset epilepsy, and the first to expand on the clinical features of this emerging disorder. This reports suggests that nonsynonymous de novo sequence variations in PLXNA1 are associated with a novel human phenotype characterized by intractable early onset epilepsy, intellectual disability, and syndromic features.