Differential localization and roles of splice variants of rat suppressor of cancer cell invasion (SCAI) in neuronal cells

A Single-Nucleus Transcriptome-Wide Association Study Implicates Novel Genes in Depression Pathogenesis

BACKGROUND

Depression, a common psychiatric illness and global public health problem, remains poorly understood across different life stages, which hampers the development of novel treatments.

METHODS

To identify new candidate genes for therapeutic development, we performed differential gene expression analysis of single-nucleus RNA sequencing data from the dorsolateral prefrontal cortex of older adults (n = 424) in relation to antemortem depressive symptoms. Additionally, we integrated genome-wide association study results for depression (n = 500,199) along with genetic tools for inferring the expression of 14,048 unique genes in 7 cell types and 52 cell subtypes to perform a transcriptome-wide association study of depression followed by Mendelian randomization.

RESULTS

Our single-nucleus transcriptome-wide association study analysis identified 68 candidate genes for depression and showed the greatest number being in excitatory and inhibitory neurons. Of the 68 genes, 53 were novel compared to previous studies. Notably, gene expression in different neuronal subtypes had varying effects on depression risk. Traits with high genetic correlations with depression, such as neuroticism, shared more transcriptome-wide association study genes than traits that were not highly correlated with depression. Complementing these analyses, differential gene expression analysis across 52 neocortical cell subtypes showed that genes such as KCNN2, SCAI, WASF3, and SOCS6 were associated with late-life depressive symptoms in specific cell subtypes.

CONCLUSIONS

These 2 sets of analyses illustrate the utility of large single-nucleus RNA sequencing data both to uncover genes whose expression is altered in specific cell subtypes in the context of depressive symptoms and to enhance the interpretation of well-powered genome-wide association studies so that we can prioritize specific susceptibility genes for further analysis and therapeutic development.

Brain-derived neurotrophic factor (BDNF) downregulates mRNA levels of suppressor of cancer cell invasion (SCAI) variants in cortical neurons

Suppressor of cancer cell invasion (SCAI) acts as a transcriptional repressor of serum response factor (SRF)-mediated gene expression by binding to megakaryoblastic leukemia (MKL)/myocardin-related transcription factor (MRTF), which is an SRF transcriptional coactivator. Growing evidence suggests that SCAI is a negative regulator of neuronal morphology, whereas MKL2/MRTFB is a positive regulator. The mRNA expression of SCAI is downregulated during brain development, suggesting that a reduction in SCAI contributes to the reduced suppression of SRF-mediated gene induction, thus increasing dendritic complexity and developing neuronal circuits. In the present study, we hypothesized that brain-derived neurotrophic factor (BDNF), which is important for neuronal plasticity and development, might alter SCAI mRNA levels. We therefore investigated the effects of BDNF on SCAI mRNA levels in primary cultured cortical neurons. Furthermore, because alternative splicing generates several SCAI variants in the brain, we measured SCAI variant mRNA after BDNF stimulation. Both SCAI variant 1 and total SCAI mRNA expression levels were downregulated by BDNF. Moreover, the extracellular signal-regulated protein kinase/mitogen-activated protein kinase (ERK/MAPK) pathway was involved in the BDNF-mediated decrease in SCAI mRNA expression. Our findings provide insights into the molecular mechanism underlying a neurotrophic factor switch for the repressive transcriptional complex that includes SCAI.

A review on the biological roles of LncRNA PTCSC3 in cancerous and non-cancerous disorders

Long non-coding RNA papillary thyroid carcinoma susceptibility candidate 3 (LncRNA PTCSC3) is located on human chromosome 14q13.3. PTCSC3 functions as a tumor suppressor lncRNA to regulate essential cellular processes such as apoptosis, cell proliferation, migration, invasion, angiogenesis, and epithelial-to-mesenchymal transition. PTCSC3 is also involved in the regulation of the Wnt/β-catenin signaling pathway, aerobic glycolysis, and p53 pathways. Downregulation of PTCSC3 has been associated with an increased risk of many tumors such as thyroid, gastric, laryngeal, breast, cervical, oral, lung, and glioma cancers. In addition, dysregulation of PTCSC3 has been reported in non-cancerous disorders notably osteoporosis and periodontitis. However, a number of single nucleotide polymorphisms at PTCSC3 have been linked to a higher risk of human diseases. This literature review summarizes the diagnostic, prognostic, and the clinical value of abnormal expression of PTCSC3 in cancerous and non-cancerous disorders and comprehensively analyzes potential molecular regulatory mechanism related to PTCSC3, which is expected to provide clear guidance for future PTCSC3 research.

Preventive effect of a Kampo medicine, kososan, on recurrent depression in a mouse model of repeated social defeat stress

Depression is deemed a mood disorder characterized by a high rate of relapse. Therefore, overcoming of the recurrent depression is globally expecting. Kososan, a traditional Japanese herbal medicine, has been clinically used for mild depressive mood, and our previous studies have shown some evidence for its antidepressive-like efficacy in experimental animal models of depression. However, it remains unclear whether kososan has beneficial effects on recurrent depression. Here, we examined its effect using a mouse model of modified repeated social defeat stress (SDS) paradigm. Male BALB/c mice were exposed to a 5-min SDS from unfamiliar aggressive CD-1 mice for 5 days. Kososan extract (1.0 kg/kg/day) or an antidepressant milnacipran (60 mg/kg/day) was administered orally for 26 days (days 7-32) to depression-like mice with social avoidant behaviors on day 6. Single 5 min of SDS was subjected to mice recovered from the social avoidance on day 31, and then the recurrence of depression-like behaviors was evaluated on day 32. Hippocampal gene expression patterns were also assayed by DNA microarray analysis. Water- or milnacipran-administered mice resulted in a recurrence of depression-like behaviors by re-exposure of single SDS, whereas kososan-administered mice did not recur depression-like behaviors. Distinct gene expression patterns were also found for treating kososan and milnacipran. Collectively, this finding suggests that kososan exerts a preventive effect on recurrent depression-like behaviors in mice. Pretreatment of kososan is more useful for recurrent depression than that of milnacipran.