Guohua Yang

Oligodendrocytes (OLs) are the myelinating cells of the central nervous system (CNS). The PLP1 gene, predominantly expressed in OLs, encodes proteolipid protein (PLP), a major structural component of CNS myelin that also regulates oligodendrocyte precursor cell (OPC) proliferation, differentiation, and maturation. Pelizaeus–Merzbacher disease (PMD) is a rare X-linked leukodystrophy caused by PLP1 mutations and characterized by defective myelination. Clinical manifestations range from severe connatal PMD to classic PMD and the milder spastic paraplegia type 2 (SPG2), reflecting substantial phenotypic heterogeneity. Beyond disrupting myelin structure, PLP1 mutations impair oligodendrocyte development and function. Increasing evidence indicates that PMD is fundamentally a proteostasis disorder, in which misfolded PLP accumulates within the endoplasmic reticulum (ER), overwhelms ER quality control mechanisms, and triggers chronic unfolded protein response (UPR) activation. Persistent ER stress and maladaptive UPR signaling ultimately promote oligodendrocyte dysfunction and degeneration. Using PMD as a representative model, this review summarizes the relationships between PLP1 mutations and disease phenotypes and discusses the cellular mechanisms by which ER stress and UPR signaling contribute to oligodendrocyte pathology.

Arrhythmogenic right ventricular cardiomyopathy (ARVC; OMIM #609040) is an inherited cardiomyopathy characterized by juvenile sudden cardiac death (SCD), with > 40% of familial cases driven by PLAKOPHILIN 2 (PKP2; OMIM #602861) mutations. This study reports a Chinese ARVC family with neonatal severe early-onset phenotype caused by novel compound heterozygous PKP2 mutations that exhibiting cosegregation with biallelic mutations (while heterozygous carriers remained asymptomatic), and aims to elucidate the synergistic pathogenic mechanisms and clinical implications. Mutations were identified via whole-genome sequencing and familial cosegregation analysis. Pathogenicity was predicted using SpliceAI and MutationTaster. MiniGene splicing assays and RT-PCR validated aberrant splicing. We analyzed subcellular protein localization by immunofluorescence microscopy and assessed protein stability via cycloheximide chase (CHX). The proband carried a maternally inherited novel splice-site variant (PKP2: c.224–3 C > G) and a paternally inherited frameshift deletion (PKP2: c.1125_1132del). Functional validation demonstrated: (a) c.224–3 C > G caused exon 2 skipping (deletion rate > 90%), generating a truncated protein (p.Asn76Trpfs*7); (b) c.1125_1132del induced frameshift (p.Phe376Alafs*8) without altering splicing. The mutant protein exhibited unchanged half-life but aberrant nuclear aggregation (immunofluorescence-confirmed). This study first confirms that compound heterozygous PKP2 mutations cause severe early-onset ARVC through biallelic inactivation: the maternal splice variant (c.224–3 C > G) truncates the protein, ablating all functional domains, while the paternal frameshift mutation (c.1125_1132del) mislocalizes the protein to the nucleus. Both defects synergistically disrupt desmosomal integrity in cardiomyocytes. These findings expand the PKP2-associated genotype-phenotype spectrum and provide molecular basis for prenatal diagnosis and genetic counseling in high-risk families.

Background: We identified a novel variant in MBD5 located within intron 6: c.114‐13A>G (NM_018328.5) in a family with a patient presenting intellectual disability. This variant is hypothesized to be the etiological agent underlying the patient's condition.Methods: We conducted an analysis of mRNA splicing within the patient and their relatives' blood samples via reverse transcription polymerase chain reaction (RT‐PCR) to assess intronic mRNA splicing. Additionally, we employed a minigene vector construction approach to verify in vitro the splicing of mRNA containing the mutated fragment. Protein structure prediction analysis of the aberrant mRNA was performed using PyMOL software.Results: The patient harbors a novel mutation in the MBD5 gene: c.114‐13A>G. Analysis of the patient's blood sample revealed the presence of aberrantly sized mRNA molecules. Utilizing a minigene approach, we discovered that this mutation results in the generation of two types of abnormally sized mRNAs. The first type of abnormal splicing leads to a 12‐base pair retention at the 3′ end of intron 6, and the second type of abnormal splicing causes exon 7 skipping.Conclusion: In accordance with the “Standards and Guidelines for the Interpretation of Sequence Variants” established by the American College of Medical Genetics and Genomics (ACMG), the novel mutation c.114‐13A>G in the MBD5 gene meets the criteria for PS2 (the variant is de novo and not inherited from either parent) and PS3 (the variant affects mRNA splicing, resulting in aberrant transcripts). We propose that the c.114‐13A>G variant, located within intron 6 of the MBD5 gene, is pathogenic. This discovery not only expands the repository of pathogenic variants for MBD5 but also provides additional insights into intronic mutations of the MBD5 gene, thereby offering significant information for the genetic diagnosis of Autosomal Dominant Intellectual Disability Type 1.

Background: Birt–Hogg–Dubé syndrome (BHD) was an autosomal dominant disorder caused by a mutation in the folliculin (FLCN) gene and characterized by benign cutaneous fibrofolliculomas in the head and neck, pulmonary cysts, spontaneous pneumothorax, and combined renal tumors.Methods: This study reported a familial case presenting multiple pulmonary bullae, recurrent spontaneous pneumothorax, diffuse cystic lesions in both lungs, and renal cysts. To further clarify the diagnosis, next‐generation sequencing (NGS) was performed in conjunction with the clinical diagnostic criteria for Birt–Hogg–Dubé. The eukaryotic recombinant expression vectors of pEGFP‐C1‐FLCN and knock‐in FLCN mutation by CRISPR/Cas9 were conducted in 293 T and BEAS‐2B cell lines. The mRNA and protein expression of the FLCN mutation were verified by fluorescence quantitative PCR and Western blot assay. Nonsense‐mediated mRNA decay (NMD) assays and immunohistochemical assays were conducted to elucidate the pathogenicity of the mutation and explore potential mechanisms.Results: A unique, novel, unspecified significance FLCN mutation NM_144997.7: c.21_22del (p. Cys8 Profs ^∗28) in Exon 4 was detected in both patients. The results demonstrated that the newly identified FLCN frameshift mutation significantly decreased FLCN mRNA and protein expression. The NMD complex recognized and degraded mRNAs containing a premature termination codon (PTC) in the open reading frame of the FLCN frameshift mutation, resulting in haploinsufficiency and ultimately contributing to the manifestation of BHD. Protein expression on the AMP‐activated protein kinase (AMPK), Wnt/β‐catenin, and mammalian target of rapamycin (mTOR) signaling pathways by immunohistochemistry indicated that FLCN frameshift mutations were responsible for BHD through the activation of AMPK, Wnt/β‐catenin, and mTOR signaling pathways.Conclusion: The study demonstrated that a novel FLCN frameshift mutation was responsible for the pathogenesis of BHD and preliminarily demonstrated that FLCN causes BHD through the AMPK, Wnt/β‐catenin, and mTOR signaling pathways.

Idiopathic congenital nystagmus (ICN) manifests as involuntary and periodic eye movements. To identify the genetic defect associated with X-linked ICN, Whole Exome Sequencing (WES) was conducted in two affected families. We identified two frameshift mutations in FRMD7, c.1492dupT/p.(Y498Lfs*15) and c.1616delG/p.(R539Kfs*2). Plasmids harboring the mutated genes and qPCR analysis revealed mRNA stability, evading degradation via the NMD pathway, and corroborated truncated protein production via Western-blot analysis. Notably, both truncated proteins were degraded through the proteasomal (ubiquitination) pathway, suggesting potential therapeutic avenues targeting this pathway for similar mutations. Moreover, we conducted a comprehensive analysis, summarizing 140 mutations within the FRMD7 gene. Our findings highlight the FERM and FA structural domains as mutation-prone regions. Interestingly, exons 9 and 12 are the most mutated regions, but 90% (28/31) mutations in exon 9 are missense while 84% (21/25) mutations in exon 12 are frameshift. A predominant occurrence of shift code mutations was observed in exons 11 and 12, possibly associated with the localization of premature termination codons (PTCs), leading to the generation of deleterious truncated proteins. Additionally, our conjecture suggests that the loss of FRMD7 protein function might not solely drive pathology; rather, the emergence of aberrant protein function could be pivotal in nystagmus etiology. We propose a dependence of FRMD7 protein normal function primarily on its anterior domain. Future investigations are warranted to validate this hypothesis.

Capsaicin (CAP) exerts significant anti-tumor effects on a variety of tumors, with low intrinsic toxicity. Cisplatin (DDP) is currently the first-line drug for the treatment of oral cancer; however, its clinical efficacy is impeded by chemoresistance and negligible side effects. Whether the combined use of CAP and DDP has a synergistic antitumor effect on tongue squamous cell carcinoma (TSCC) cells and its underlying mechanisms remains unclear. The present study revealed that CAP reduced the activity of TSCC cells in a dose- and time-dependent manner. We also observed changes in the mitochondrial functional structure of TSCC cells, along with the induction of mitochondrial apoptosis. Moreover, when CAP was combined with DDP, a synergistic cytotoxic effect on TSCC cells was observed, which had a significant impact on inducing apoptosis, inhibiting proliferation, and disrupting the mitochondrial membrane potential in TSCC cells compared to the single-drug treatment and control groups. These effects are associated with TRPV1, a high-affinity CAP receptor. The combined use of CAP and DDP can activate the TRPV1 receptor, resulting in intracellular Ca²⁺ overload and activation of the calpain pathway, ultimately leading to mitochondrial apoptosis. This potential mechanism was validated in TSCC xenograft models. In conclusion, our findings clearly demonstrate that CAP exerts synergistic pro-apoptotic effects with DDP in TSCC through the calpain pathway mediated by TRPV1. Thus, CAP can be considered an effective adjuvant drug for DDP in the treatment of TSCC.

Idiopathic congenital nystagmus (ICN) is a condition characterized by involuntary and periodic eye movements. To identify the genetic defect associated with X-linked ICN, we performed WES in two families. We identified two novel frameshift mutations in FRMD7, c.1492dupT/p.Y498Lfs15 and c.1616delG/p.R539Kfs2. Plasmids containing the mutated genes were constructed and qPCR analysis showed that both mutations produce mRNAs that are not degraded by the NMD pathway. Western-blot analysis corroborated the production of truncated proteins. Further experiments found that both truncated proteins were degraded through the proteasomal (ubiquitination) pathway. This information may indicates that targeting the proteasomal pathway may be a potential therapeutic strategy for the types of mutation. Moreover, we summarized 140 mutations that have occurred on the FRMD7 gene to date and found that the FERM and FA structural domains are mutation-prone regions. Interestingly, exons 9 and 12 are the most mutated regions, but 90% (28/31) mutations in exon 9 are missense while 84% (21/25) mutations in exon 12 are frameshift. And almost all of the shift code mutations occurred on exons 11 and 12. We believe that this is related to the location of the premature termination codons (PTCs), leading to the production of harmful truncated proteins. Additionally, we have speculated that the loss of FRMD7 protein function is not all pathological, and the production of abnormal protein function is the cause of nystagmus. The normal function of FRMD7 depends mainly on the front half of the protein. Further research is needed to confirm this hypothesis.

Apoptosis and autophagy have been shown to act cooperatively and antagonistically in self-elimination process. On the one side, apoptosis and autophagy can act as partners to induce cell death in a coordinated or cooperative manner; on the flip side, autophagy acts as an antagonist to block apoptotic cell death by promoting cell survival. Our previous research indicated that trillin could induce apoptosis of PLC/PRF/5 cells, but the effects of trillin on autophagy as well as its functional relationship to apoptosis have not been elucidated. Here, the running study aims to investigate the function and molecular mechanism of trillin on autophagy with hepatocellular carcinoma (HCC) cells. The objective of this study is to investigate the molecular mechanism of trillin on autophagy in HCC cells. Protein levels of autophagy markers beclin1, LC3B, and p62 were detected by western blotting. 6-Hydroxyflavone and stattic were used to test the role of trillin regulation of autophagy via serine threonine kinase (AKT)/extracellular-regulated protein kinases (ERK) 1/2/mammalian target of rapamycin (mTOR)/signal transducer and activator of transcription 3 (STAT3) signaling pathway. Flow cytometry was used to detect caspase 3 activity and apoptosis in PLC/PRF/5 cells treated with trillin for 24 h with or without rapamycin, stattic, and 6-hydroxyflavone. The protein level of autophagy marker beclin1 was decreased, whilst the protein level of p62 was significantly increased by trillin treatment, indicating trillin treatment led to inhibition of autophagy in HCC cells. Trillin treatment could reduce the protein levels of p-AKT and p-ERK1/2, but enhance the protein levels of mTOR and p-mTOR, suggesting that trillin could inhibit AKT/ERK rather than mTOR. The AKT/ERK activator 6-hydroxyflavone could reverse the loss of AKT and ERK1/2 phosphorylation induced by trillin, implying that trillin impairs autophagy through activated mTOR rather than AKT/ERK. STAT3 and p-STAT3 were significantly upregulated by the trillin treatment with an increase in dose from 0 to 50 μM, suggesting that autophagy inhibition is mediated by trillin via activation of STAT3 signaling. The STAT3 inhibitor stattic significantly reversed the increased STAT3 phosphorylation at tyrosine 705 induced by trillin. The mTOR signaling inhibitor rapamycin reversed the trillin-induced mTOR phosphorylation enhancement but exerted no effects on total mTOR levels, suggesting trillin treatment led to inhibition of autophagy in HCC cells through activating mTOR/STAT3 pathway. Furthermore, caspase 3 activities and the total rate of apoptosis were increased by trillin treatment, which was reversed by rapamycin, stattic, and 6-hydroxyflavone, proving that trillin promotes apoptosis via activation of mTOR/STAT3 signaling. Trillin induced autophagy inhibition and promoted apoptosis in PLC/PRF/5 cells via the activation of mTOR/STAT3 signaling. Trillin has the potential to be a viable therapeutic option for HCC treatment.