A novel truncated variant in SPAST results in spastin accumulation and defects in microtubule dynamics

OBJECTIVE

Haploinsufficiency is widely accepted as the pathogenic mechanism of hereditary spastic paraplegias type 4 (SPG4). However, there are some cases that cannot be explained by reduced function of the spastin protein encoded by SPAST. The aim of this study was to identify the causative variant of SPG4 in a large Chinese family and explore its pathological mechanism.

MATERIALS AND METHODS

A five-generation family with 49 members including nine affected (4 males and 5 females) and 40 unaffected individuals in Mongolian nationality was recruited. Whole exome sequencing was employed to investigate the genetic etiology. Western blotting and immunofluorescence were used to analyze the effects of the mutant proteins in vitro.

RESULTS

A novel frameshift variant NM_014946.4: c.483_484delinsC (p.Val162Leufs*2) was identified in SPAST from a pedigree with SPG4. The variant segregated with the disease in the family and thus determined as the disease-causing variant. The c.483_484delinsC variant produced two truncated mutants (mutant M1 and M87 isoforms). They accumulated to a higher level and presented increased stability than their wild-type counterparts and may lost the microtubule severing activity.

CONCLUSION

SPAST mutations leading to premature stop codons do not always act through haploinsufficiency. The potential toxicity to the corticospinal tract caused by the intracellular accumulation of truncated spastin should be considered as the pathological mechanism of SPG4.

A meta-analysis of the risk factors for surgical site infection in patients with colorectal cancer

The purpose of the meta-analysis was to evaluate and compare the surgical site infection (SSI) risk factors in patients with colorectal cancer (CC). The results of this meta-analysis were analysed, and the odds ratio (OR) and mean difference (MD) with 95% confidence intervals (CIs) were calculated using dichotomous or contentious random or fixed-effect models. For the current meta-analysis, 23 examinations spanning from 2001 to 2023 were included, encompassing 89 859 cases of CC. Clean-contaminated surgical site wounds had significantly lower infections (OR, 0.36; 95% CI, 0.20-0.64, p < 0.001) compared to contaminated surgical site wounds in patients with CCs. Males had significantly higher SSIs (OR, 1.18; 95% CI, 1.12-1.24, p < 0.001) compared to females in patients with CC. American Society of Anesthesiology score ≥3 h had a significantly higher SSI (OR, 1.42; 95% CI, 1.18-1.71, p < 0.001) compared to <3 score in patients with CCs. Body mass index ≥25 had significantly higher SSIs (OR, 1.54; 95% CI, 1.11-2.14, p = 0.01) compared to <25 in patients with CCs. The presence of stoma creation had a significantly higher SSI rate (OR, 2.28; 95% CI, 1.37-3.79, p = 0.001) compared to its absence in patients with CC. Laparoscopic surgery had significantly lower SSIs (OR, 0.68; 95% CI, 0.59-0.78, p < 0.001) compared to open surgery in patients with CC. The presence of diabetes mellitus had a significantly higher SSI rate (OR, 1.24; 95% CI, 1.15-1.33, p < 0.001) compared to its absence in patients with CCs. No significant difference was found in SSI rate in patients with CCs between <3 and ≥3 h of operative time (OR, 1.07; 95% CI, 0.75-1.51, p = 0.72), between the presence and absence of blood transfusion (OR, 1.60; 95% CI, 0.69-3.66, p = 0.27) and between the presence and absence of previous laparotomies (OR, 1.47; 95% CI, 0.93-2.32, p = 0.10). The examined data revealed that contaminated wounds, male sex, an American Society of Anesthesiology score ≥3 h, a body mass index ≥25, stoma creation, open surgery and diabetes mellitus are all risk factors for SSIs in patients with CC. However, operative time, blood transfusion and previous laparotomies were not found to be risk factors for SSIs in patients with CC. However, given that several comparisons had a small number of chosen research, consideration should be given to their values.

METTL3 exerts synergistic effects on m6A methylation and histone modification to regulate the function of VGF in lung adenocarcinoma

BACKGROUND

Multiple genetic and epigenetic regulatory mechanisms play a vital role in tumorigenesis and development. Understanding the interplay between different epigenetic modifications and its contribution to transcriptional regulation in cancer is essential for precision medicine. Here, we aimed to investigate the interplay between N6-methyladenosine (m6A) modifications and histone modifications in lung adenocarcinoma (LUAD).

RESULTS

Based on the data from public databases, including chromatin property data (ATAC-seq, DNase-seq), methylated RNA immunoprecipitation sequencing (MeRIP-seq), and gene expression data (RNA-seq), a m6A-related differentially expressed gene nerve growth factor inducible (VGF) was identified between LUAD tissues and normal lung tissues. VGF was significantly highly expressed in LUAD tissues and cells, and was associated with a worse prognosis for LUAD, silencing of VGF inhibited the malignant phenotype of LUAD cells by inactivating the PI3K/AKT/mTOR pathway. Through the weighted correlation network analysis (WGCNA) and integration of TCGA-LUAD RNA-seq and m6A methyltransferase METTL3-knockdown RNA-seq data, a significant positive correlation between METTL3 and VGF was observed. By using the MeRIP-qPCR and dual-luciferase reporter assays, we demonstrated that METTL3 knockdown decreased m6A modification level of VGF coding sequences in LUAD cells, the colorimetric m6A quantification assay also showed that METTL3 knockdown significantly decreased global m6A modification level in LUAD cells. Interestingly, we found that METTL3 knockdown also reduced VGF expression by increasing H3K36me3 modification at the VGF promoter. Further research revealed that METTL3 knockdown upregulated the expression of histone methylase SETD2, the major H3K36me3 methyltransferase, by methylating the m6A site in the 3'UTR of SETD2 mRNA in LUAD cells.

CONCLUSIONS

Overall, our results reveal that the expression of VGF in LUAD cells is regulated spatio-temporally by METTL3 through both transcriptional (via histone modifications) and post-transcriptional (via m6A modifications) mechanisms. The synergistic effect of these multiple epigenetic mechanisms provides new opportunities for the diagnosis and precision treatment of tumors.