Significant but partial lipoprotein lipase functional loss caused by a novel occurrence of rare LPL biallelic variants.

BACKGROUND: Lipoprotein lipase (LPL) plays a crucial role in triglyceride hydrolysis. Rare biallelic variants in the LPL gene leading to complete or near-complete loss of function cause autosomal recessive familial chylomicronemia syndrome. However, rare biallelic LPL variants resulting in significant but partial loss of function are rarely documented. This study reports a novel occurrence of such rare biallelic LPL variants in a Chinese patient with hypertriglyceridemia-induced acute pancreatitis (HTG-AP) during pregnancy and provides an in-depth functional characterization. METHODS: The complete coding sequences and adjacent intronic regions of the LPL, APOC2, APOA5, LMF1, and GPIHBP1 genes were analyzed by Sanger sequencing. The aim was to identify rare variants, including nonsense, frameshift, missense, small in-frame deletions or insertions, and canonical splice site mutations. The functional impact of identified LPL missense variants on protein expression, secretion, and activity was assessed in HEK293T cells through single and co-transfection experiments, with and without heparin treatment. RESULTS: Two rare LPL missense variants were identified in the patient: the previously reported c.809G > A (p.Arg270His) and a novel c.331G > C (p.Val111Leu). Genetic testing confirmed these variants were inherited biallelically. Functional analysis showed that the p.Arg270His variant resulted in a near-complete loss of LPL function due to effects on protein synthesis/stability, secretion, and enzymatic activity. In contrast, the p.Val111Leu variant retained approximately 32.3% of wild-type activity, without impacting protein synthesis, stability, or secretion. Co-transfection experiments indicated a combined activity level of 20.7%, suggesting no dominant negative interaction between the variants. The patient's post-heparin plasma LPL activity was about 35% of control levels. CONCLUSIONS: This study presents a novel case of partial but significant loss-of-function biallelic LPL variants in a patient with HTG-AP during pregnancy. Our findings enhance the understanding of the nuanced relationship between LPL genotypes and clinical phenotypes, highlighting the importance of residual LPL function in disease manifestation and severity. Additionally, our study underscores the challenges in classifying partial loss-of-function variants in classical Mendelian disease genes according to the American College of Medical Genetics and Genomics (ACMG)'s variant classification guidelines.

Dynamic nomogram for predicting infected pancreatic necrosis in female patients of childbearing age with hypertriglyceridemia-induced acute pancreatitis.

BACKGROUND: Hypertriglyceridemia is a common cause of acute pancreatitis. Pregnant women are at risk of developing hypertriglyceridemia-induced acute pancreatitis (HTG-AP); however, whether pregnancy increases the risk of infected pancreatic necrosis (IPN) is unknown. AIM: We aimed to assess the association between pregnancy and IPN. METHODS: This 10-year retrospective cohort study was conducted at Jinling Hospital. Adult female patients of childbearing age with HTG-AP between January 2013 and September 2022 were screened. Logistic regression analyses were performed to assess the risk factors for IPN. Patients admitted within 7 days were assigned to the training and validation sets to develop a dynamic nomogram for IPN prediction. RESULTS: 489 patients were included, and 144 developed IPN. Logistic regression analyses revealed pregnancy (OR: 2.578 95% CI: 1.474-4.510) as an independent risk factor for IPN. Gestation weeks, ARDS, albumin level, and serum creatinine level were selected as the predictors of the dynamic nomogram for IPN prediction, with good discrimination in the training set (AUC 0.867 95% CI: 0.794-0.940) and validation set (AUC 0.957 95% CI: 0.885-1.000). CONCLUSION: Pregnancy increases the risk of IPN in adult patients of childbearing age with HTG-AP, and the dynamic nomogram may help risk stratification for IPN.

The East Asian-specific LPL p.Ala288Thr (c.862G > A) missense variant exerts a mild effect on protein function.

BACKGROUND: Lipoprotein lipase (LPL) is the key enzyme responsible for the hydrolysis of triglycerides. Loss-of-function variants in the LPL gene are associated with hypertriglyceridemia (HTG) and HTG-related diseases. Unlike nonsense, frameshift and canonical GT-AG splice site variants, a pathogenic role for clinically identified LPL missense variants should generally be confirmed by functional analysis. Herein, we describe the clinical and functional analysis of a rare LPL missense variant. METHODS: Chinese patients with HTG-associated acute pancreatitis (HTG-AP) were screened for rare nonsense, frameshift, missense or canonical GT-AG splice site variants in LPL and four other lipid metabolism-related genes (APOC2, APOA5, GPIHBP1 and LMF1) by Sanger sequencing. The functional consequences of the LPL missense variant of interest were characterized by in vitro expression in HEK-293T and COS-7 cells followed by Western blot and LPL activity assays. RESULTS: Five unrelated HTG-AP patients were found to be heterozygous for a rare East Asian-specific LPL missense variant, c.862G > A (p.Ala288Thr). All five patients were adult males, and all were overweight and had a long history of alcohol consumption. Transfection of LPL wild-type and c.862G > A expression vectors into two cell lines followed by Western blot analysis served to exclude the possibility that the p.Ala288Thr missense variant either impaired protein synthesis or increased protein degradation. Contrary to a previous functional study that claimed that p.Ala288Thr had a severe impact on LPL function (reportedly having 36% normal activity), our experiments consistently demonstrated that the variant had a comparatively mild effect on LPL functional activity, which was mediated through its impact upon LPL protein secretion (~ 20% reduced secretion compared to wild-type). CONCLUSIONS: In this study, we identified the East Asian-specific LPL c.862G > A (p.Ala288Thr) missense variant in five unrelated HTG-AP patients. We demonstrated that this variant exerted only a relatively mild effect on LPL function in two cell lines. Heterozygosity for this LPL variant may have combined with alcohol consumption to trigger HTG-AP in these patients.

Classification of PRSS1 variants responsible for chronic pancreatitis: An expert perspective from the Franco-Chinese GREPAN study group.

BACKGROUND: PRSS1 was the first reported chronic pancreatitis (CP) gene. The existence of both gain-of-function (GoF) and gain-of-proteotoxicity (GoP) pathological PRSS1 variants, together with the fact that PRSS1 variants have been identified in CP subtypes spanning the range from monogenic to multifactorial, has made the classification of PRSS1 variants very challenging. METHODS: All currently reported PRSS1 variants (derived primarily from two databases) were manually reviewed with respect to their clinical genetics, functional analysis and population allele frequency. They were classified by variant type and pathological mechanism within the framework of our recently proposed ACMG/AMP guidelines-based seven-category system. RESULTS: The total number of distinct germline PRSS1 variants included for analysis was 100, comprising 3 copy number variants (CNVs), 12 5' and 3' variants, 19 intronic variants, 5 nonsense variants, 1 frameshift deletion variant, 6 synonymous variants, 1 in-frame duplication, 3 gene conversions and 50 missense variants. Based upon a combination of clinical genetic and functional analysis, population data and in silico analysis, we classified 26 variants (all 3 CNVs, the in-frame duplication, all 3 gene conversions and 19 missense) as "pathogenic", 3 variants (missense) as "likely pathogenic", 5 variants (four missense and one promoter) as "predisposing", 13 variants (all missense) as "unknown significance", 2 variants (missense) as "likely benign", and all remaining 51 variants as "benign". CONCLUSIONS: We describe an expert classification of the 100 PRSS1 variants reported to date. The results have immediate implications for reclassifying many ClinVar-registered PRSS1 variants as well as providing optimal guidelines/standards for reporting PRSS1 variants.

Frameshift coding sequence variants in the LPL gene: identification of two novel events and exploration of the genotype-phenotype relationship for variants reported to date.

BACKGROUND: Lipoprotein lipase (LPL) is the rate-limiting enzyme for triglyceride hydrolysis. Homozygous or compound heterozygous LPL variants cause autosomal recessive familial chylomicronemia syndrome (FCS), whereas simple heterozygous LPL variants are associated with hypertriglyceridemia (HTG) and HTG-related disorders. LPL frameshift coding sequence variants usually cause complete functional loss of the affected allele, thereby allowing exploration of the impact of different levels of LPL function in human disease. METHODS: All exons and flanking intronic regions of LPL were Sanger sequenced in patients with HTG-related acute pancreatitis (HTG-AP) or HTG-AP in pregnancy. Previously reported LPL frameshift coding sequence variants were collated from the Human Gene Mutation Database and through PubMed keyword searching. Original reports were manually evaluated for the following information: zygosity status of the variant, plasma LPL activity of the variant carrier, disease referred for genetic analysis, patient's age at genetic analysis, and patient's disease history. SpliceAI was employed to predict the potential impact of collated variants on splicing. RESULTS: Two novel rare variants were identified, and 53 known LPL frameshift coding sequence variants were collated. Of the 51 variants informative for zygosity, 30 were simple heterozygotes, 12 were homozygotes, and 9 were compound heterozygotes. Careful evaluation of the 55 variants with respect to their clinical and genetic data generated several interesting findings. First, we conclude that 6-7% residual LPL function could significantly delay the age of onset of FCS and reduce the prevalence of FCS-associated syndromes. Second, whereas a large majority of LPL frameshift coding sequence variants completely disrupt gene function through their "frameshift" nature, a small fraction of these variants may act wholly or partly as "in-frame" variants, leading to the generation of protein products with some residual LPL function. Third, we identified two candidate LPL frameshift coding sequence variants that may retain residual function based on genotype-phenotype correlation or SpliceAI-predicted data. CONCLUSIONS: This study reported two novel LPL variants and yielded new insights into the genotype-phenotype relationship as it pertains to LPL frameshift coding sequence variants.

Small Auxin Up RNA 56 (SAUR56) regulates heading date in rice.

Heading date is a critical agronomic trait that determines crop yield. Although numerous genes associated with heading date have been identified in rice, the mechanisms involving Small Auxin Up RNA (SAUR) family have not been elucidated. In this study, the biological function of several SAUR genes was initially investigated using the CRISPR-Cas9 technology in the Japonica cultivar Zhonghua11 (ZH11) background. Further analysis revealed that the loss-of-function of OsSAUR56 affected heading date in both NLD (natural long-day) and ASD (artificial short-day). OsSAUR56 exhibited predominant expression in the anther, with its protein localized in both the cytoplasm and nucleus. OsSAUR56 regulated flowering time and heading date by modulating the expression of the clock gene OsGI, as well as two repressors Ghd7 and DTH8. Furthermore, haplotype-phenotype association analysis revealed a strong correlation between OsSAUR56 and heading date, suggesting its role in selection during the domestication of rice. In summary, these findings highlights the importance of OsSAUR56 in the regulation of heading date for further potential facilitating genetic engineering for flowering time during rice breeding. Supplementary Information: The online version contains supplementary material available at 10.1007/s11032-023-01409-w.

Antimicrobial and anti-biofilm activity of Polygonum chinense L.aqueous extract against Staphylococcus aureus.

Polygonum chinense Linn. (Polygonum chinense L.) is one of the main raw materials of Chinese patent medicines such as Guangdong herbal tea. The increasing antibiotic resistance of S. aureus and the biofilm poses a serious health threat to humans, and there is an urgent need to provide new antimicrobial agents. As a traditional Chinese medicine, the antibacterial effect of Polygonum chinense L. has been reported, but the antibacterial mechanism of Polygonum chinense L.aqueous extract and its effect on biofilm have not been studied in great detail, which hinders its application as an effective antibacterial agent. In this study, the mechanism of action of Polygonum chinense L.aqueous extract on Staphylococcus aureus (S. aureus) and its biofilm was mainly evaluated by morphological observation, flow cytometry and laser confocal experiments. Our findings demonstrate that Polygonum chinense L.aqueous extract has a significant bacteriostatic effect on S. aureus. The result of growth curve exhibits that Polygonum chinense L.aqueous extract presents a significant inhibitory effect against S. aureus. Transmission electron microscopy (TEM) and scanning electron microscopy (SEM) reveals that Polygonum chinense L.aqueous extract exerts a potent destruction of the cell wall of S. aureus and a significant inhibitory effect on the formation of S. aureus biofilm. In addition, flow cytometry showed the ability of Polygonum chinense L.aqueous extract to promote apoptosis by disrupting cell membranes of S. aureus. Notably, confocal laser scanning microscopy (CLSM) images illustrated the ability of Polygonum chinense L.aqueous to inhibit the formation of S. aureus biofilms in a dose-dependent manner. These results suggested that Polygonum chinense L.aqueous is a promising alternative antibacterial and anti-biofilm agent for combating infections caused by planktonic and biofilm cells of S. aureus.

GPIHBP1 autoantibody is an independent risk factor for the recurrence of hypertriglyceridemia-induced acute pancreatitis.

BACKGROUND: GPIHBP1, a glycolipid-anchored protein of capillary endothelial cells, is a crucial partner for lipoprotein lipase (LPL) in plasma triglyceride metabolism. GPIHBP1 autoantibodies block LPL binding to GPIHBP1 and lead to severe hypertriglyceridemia (HTG) and HTG-induced acute pancreatitis (HTG-AP). We sought to define the incidence of GPIHBP1 autoantibodies in patients with HTG-AP. OBJECTIVE: We determined the incidence of GPIHBP1 autoantibody in HTG-AP patients, and compared the clinical features and long-term outcomes between GPIHBP1 autoantibody-positive and negative groups. METHODS: An enzyme-linked immunosorbent assay was used to screen for GPIHBP1 autoantibody in 116 HTG-AP patients hospitalized from Jan 1, 2015 to Aug 31, 2019. All patients were followed up for 24 months. The primary outcome was the recurrence rate of HTG-AP during the two-year follow-up period. The incidence of recurrent episodes was analyzed by the Kaplan-Meier method and multivariable Cox regression was used to identify risk factors. RESULTS: GPIHBP1 autoantibodies were present in 17 of 116 study patients (14.66%). The 2-year recurrence rate of HTG-AP was much higher in the GPIHBP1 autoantibody-positive group (35%, 6 in 17) than in the negative group (4%, 4 in 99). The multivariable Cox regression analysis showed that GPIHBP1 autoantibody was an independent risk factor for HTG-AP recurrence in two years. CONCLUSIONS: The presence of GPIHBP1 autoantibody is common in patients with HTG-AP, and is an independent risk factor for two-year recurrence of HTG-AP.

Expanding ACMG variant classification guidelines into a general framework.

BACKGROUND: The American College of Medical Genetics and Genomics (ACMG)-recommended five variant classification categories (pathogenic, likely pathogenic, uncertain significance, likely benign, and benign) have been widely used in medical genetics. However, these guidelines are fundamentally constrained in practice owing to their focus upon Mendelian disease genes and their dichotomous classification of variants as being either causal or not. Herein, we attempt to expand the ACMG guidelines into a general variant classification framework that takes into account not only the continuum of clinical phenotypes, but also the continuum of the variants' genetic effects, and the different pathological roles of the implicated genes. MAIN BODY: As a disease model, we employed chronic pancreatitis (CP), which manifests clinically as a spectrum from monogenic to multifactorial. Bearing in mind that any general conceptual proposal should be based upon sound data, we focused our analysis on the four most extensively studied CP genes, PRSS1, CFTR, SPINK1 and CTRC. Based upon several cross-gene and cross-variant comparisons, we first assigned the different genes to two distinct categories in terms of disease causation: CP-causing (PRSS1 and SPINK1) and CP-predisposing (CFTR and CTRC). We then employed two new classificatory categories, "predisposing" and "likely predisposing", to replace ACMG's "pathogenic" and "likely pathogenic" categories in the context of CP-predisposing genes, thereby classifying all pathologically relevant variants in these genes as "predisposing". In the case of CP-causing genes, the two new classificatory categories served to extend the five ACMG categories whilst two thresholds (allele frequency and functional) were introduced to discriminate "pathogenic" from "predisposing" variants. CONCLUSION: Employing CP as a disease model, we expand ACMG guidelines into a five-category classification system (predisposing, likely predisposing, uncertain significance, likely benign, and benign) and a seven-category classification system (pathogenic, likely pathogenic, predisposing, likely predisposing, uncertain significance, likely benign, and benign) in the context of disease-predisposing and disease-causing genes, respectively. Taken together, the two systems constitute a general variant classification framework that, in principle, should span the entire spectrum of variants in any disease-related gene. The maximal compliance of our five-category and seven-category classification systems with the ACMG guidelines ought to facilitate their practical application.

Trypsinogen (PRSS1 and PRSS2) gene dosage correlates with pancreatitis risk across genetic and transgenic studies: a systematic review and re-analysis.

Trypsinogen (PRSS1, PRSS2) copy number gains and regulatory variants have both been proposed to elevate pancreatitis risk through a gene dosage effect (i.e., by increasing the expression of wild-type protein). However, to date, their impact on pancreatitis risk has not been thoroughly evaluated whilst the underlying pathogenic mechanisms remain to be explicitly investigated in mouse models. Genetic studies of the rare trypsinogen duplication and triplication copy number variants (CNVs), and the common rs10273639C variant, were collated from PubMed and/or ClinVar. Mouse studies that analyzed the influence of a transgenically expressed wild-type human PRSS1 or PRSS2 gene on the development of pancreatitis were identified from PubMed. The genetic effects of the different risk genotypes, in terms of odds ratios, were calculated wherever appropriate. The genetic effects of the rare trypsinogen duplication and triplication CNVs were also evaluated by reference to their associated disease subtypes. We demonstrate a positive correlation between increased trypsinogen gene dosage and pancreatitis risk in the context of the rare duplication and triplication CNVs, and between the level of trypsinogen expression and disease risk in the context of the heterozygous and homozygous rs10273639C-tagged genotypes. We retrospectively identify three mouse transgenic studies that are informative in relation to the pathogenic mechanism underlying the trypsinogen gene dosage effect in pancreatitis. Trypsinogen gene dosage correlates with pancreatitis risk across genetic and transgenic studies, highlighting the fundamental role of dysregulated expression of wild-type trypsinogen in the etiology of pancreatitis. Specifically downregulating trypsinogen expression in the pancreas may serve as a potential therapeutic and/or prevention strategy for pancreatitis.

Risk Factors for Fetal Death and Maternal AP Severity in Acute Pancreatitis in Pregnancy.

Background: Acute pancreatitis in pregnancy is a rare but highly life-threatening gestational and perinatal disease. Objective: This study aimed to identify the risk factors for fetal death and acute pancreatitis severity. Methods: This retrospective cohort study enrolled patients with acute pancreatitis in pregnancy in our center from January 1, 2012, to August 1, 2020, and classified them according to two clinical endpoints, fetal outcome and disease severity. The groups were examined and compared according to gestational week, etiology, gravidity and parity, complications in pre- and post-delivery, and medical history. Logistic regression analysis was performed to identify the independent risk factors for fetal death and acute pancreatitis severity. Results: Of the 90 enrolled patients, 28 (31.1%) had fetal death and 43 (47.8%) had severe acute pancreatitis. Logistic regression analysis showed that pre-delivery acute respiratory distress syndrome (OR, 5.8; 95% CI, 1.5-22.4; p = 0.010) and gestational week (OR, 0.9; 95% CI, 0.8-1.0; p = 0.011) were risk factors for fetal death. Gestation week (OR, 1.2; 95% CI, 1.1-1.3; p = 0.003) and fetal intrauterine death (OR, 5.9; 95% CI, 1.8-19.4; p = 0.003) were risk factors for severe acute pancreatitis. Conclusions: Pre-delivery acute respiratory distress syndrome and gestational week were independent risk factors for fetal death. Fetal intrauterine death and gestational week were independent risk factors for severe acute pancreatitis.

Chronic Pancreatitis: The True Pathogenic Culprit within the SPINK1 N34S-Containing Haplotype Is No Longer at Large.

A diverse range of loss-of-function variants in the SPINK1 gene (encoding pancreatic secretory trypsin inhibitor) has been identified in patients with chronic pancreatitis (CP). The haplotype harboring the SPINK1 c.101A>G (p.Asn34Ser or N34S) variant (rs17107315:T>C) is one of the most important heritable risk factors for CP as a consequence of its relatively high prevalence worldwide (population allele frequency ≈ 1%) and its considerable effect size (odds ratio ≈ 11). The causal variant responsible for this haplotype has been intensively investigated over the past two decades. The different hypotheses tested addressed whether the N34S missense variant has a direct impact on enzyme structure and function, whether c.101A>G could affect pre-mRNA splicing or mRNA stability, and whether another variant in linkage disequilibrium with c.101A>G might be responsible for the observed association with CP. Having reviewed the currently available genetic and experimental data, we conclude that c.-4141G>T (rs142703147:C>A), which disrupts a PTF1L-binding site within an evolutionarily conserved HNF1A-PTF1L cis-regulatory module located ∼4 kb upstream of the SPINK1 promoter, can be designated as the causal variant beyond reasonable doubt. This case illustrates the difficulties inherent in determining the identity of the causal variant underlying an initially identified disease association.

Digenic Inheritance and Gene-Environment Interaction in a Patient With Hypertriglyceridemia and Acute Pancreatitis.

The etiology of hypertriglyceridemia (HTG) and acute pancreatitis (AP) is complex. Herein, we dissected the underlying etiology in a patient with HTG and AP. The patient had a 20-year history of heavy alcohol consumption and an 8-year history of mild HTG. He was hospitalized for alcohol-triggered AP, with a plasma triglyceride (TG) level up to 21.4 mmol/L. A temporary rise in post-heparin LPL concentration (1.5-2.5 times of controls) was noted during the early days of AP whilst LPL activity was consistently low (50∼70% of controls). His TG level rapidly decreased to normal in response to treatment, and remained normal to borderline high during a ∼3-year follow-up period during which he had abstained completely from alcohol. Sequencing of the five primary HTG genes (i.e., LPL, APOC2, APOA5, GPIHBP1 and LMF1) identified two heterozygous variants. One was the common APOA5 c.553G > T (p.Gly185Cys) variant, which has been previously associated with altered TG levels as well as HTG-induced acute pancreatitis (HTG-AP). The other was a rare variant in the LPL gene, c.756T > G (p.Ile252Met), which was predicted to be likely pathogenic and found experimentally to cause a 40% loss of LPL activity without affecting either protein synthesis or secretion. We provide evidence that both a gene-gene interaction (between the common APOA5 variant and the rare LPL variant) and a gene-environment interaction (between alcohol and digenic inheritance) might have contributed to the development of mild HTG and alcohol-triggered AP in the patient, thereby improving our understanding of the complex etiology of HTG and HTG-AP.

Gene-environment interaction between APOA5 c.553G>T and pregnancy in hypertriglyceridemia-induced acute pancreatitis.

BACKGROUND: The etiology of hypertriglyceridemia (HTG) and, consequently, HTG-induced acute pancreatitis (HTG-AP), is complex. OBJECTIVE: Herein, we explore a possible gene-environment interaction between APOA5 c.553G>T (p.185Gly>Cys, rs2075291), a common variant associated with altered triglyceride levels, and pregnancy in HTG-AP. METHODS: We enrolled 318 Chinese HTG-AP patients and divided them into 3 distinct groups: Group 1, male patients (n = 183); Group 2, female patients whose disease was unrelated to pregnancy (n = 105); and Group 3, female patients whose disease was related to pregnancy (n = 30). APOA5 rs2075291 genotype status was determined by Sanger sequencing. A total of 362 healthy Han Chinese subjects were used as controls. Data on body mass index, peak triglyceride level, age of disease onset, episode number, and clinical severity of HTG-AP were collected from each patient. Multiple comparisons, between patient groups, between patient groups and controls, or within each patient group, were performed. RESULTS: A robust association of APOA5 rs2075291 with HTG-AP in general, and HTG-AP during pregnancy in particular, was demonstrated. The minor T allele showed a stronger association with Group 3 patients than with either Group 1 or Group 2 patients. This stronger association was due mainly to the much higher frequency of TT genotype in Group 3 patients (20%) than that (<6%) in Group 1 and Group 2 patients. Moreover, the TT genotype was associated with a significantly higher peak triglyceride level in Group 3 patients compared with the GG genotype. CONCLUSION: Our findings provide evidence for an interaction between APOA5 rs2075291 and pregnancy in HTG-AP.

Identification of a novel LPL nonsense variant and further insights into the complex etiology and expression of hypertriglyceridemia-induced acute pancreatitis.

BACKGROUND: Hypertriglyceridemia (HTG) is a leading cause of acute pancreatitis. HTG can be caused by either primary (genetic) or secondary etiological factors, and there is increasing appreciation of the interplay between the two kinds of factors in causing severe HTG. OBJECTIVES: The main aim of this study was to identify the genetic basis of hypertriglyceridemia-induced acute pancreatitis (HTG-AP) in a Chinese family with three affected members (the proband, his mother and older sister). METHODS: The entire coding and flanking sequences of LPL, APOC2, APOA5, GPIHBP1 and LMF1 genes were analyzed by Sanger sequencing. The newly identified LPL nonsense variant was subjected to functional analysis by means of transfection into HEK-293 T cells followed by Western blot and activity assays. Previously reported pathogenic LPL nonsense variants were collated and compared with respect to genotype and phenotype relationship. RESULTS: We identified a novel nonsense variant, p.Gln118* (c.351C > T), in the LPL gene, which co-segregated with HTG-AP in the Chinese family. We provided in vitro evidence that this variant resulted in a complete functional loss of the affected LPL allele. We highlighted a role of alcohol abuse in modifying the clinical expression of the disease in the proband. Additionally, our survey of 12 previously reported pathogenic LPL nonsense variants (in 20 carriers) revealed that neither serum triglyceride levels nor occurrence of HTG-AP was distinguishable among the three carrier groups, namely, simple homozygotes, compound heterozygotes and simple heterozygotes. CONCLUSIONS: Our findings, taken together, generated new insights into the complex etiology and expression of HTG-AP.

Identification and functional characterization of a novel heterozygous missense variant in the LPL associated with recurrent hypertriglyceridemia-induced acute pancreatitis in pregnancy.

BACKGROUND: Acute pancreatitis in pregnancy (APIP) is a life-threatening disease for both mother and fetus. To date, only three patients with recurrent hypertriglyceridemia-induced APIP (HTG-APIP) have been reported to carry rare variants in the lipoprotein lipase (LPL) gene, which encodes the key enzyme responsible for triglyceride (TG) metabolism. Coincidently, all three patients harbored LPL variants on both alleles and presented with complete or severe LPL deficiency. METHODS: The entire coding regions and splice junctions of LPL and four other TG metabolism genes (APOC2, APOA5, GPIHBP1, and LMF1) were analyzed by Sanger sequencing in a Han Chinese patient who had experienced two episodes of HTG-APIP. The impact of a novel LPL missense variant on LPL protein expression and activity was analyzed by transient expression in HEK293T cells. RESULTS: A novel heterozygous LPL missense variant, p.His210Leu (c.629A > T), was identified in our patient. This variant did not affect protein synthesis but significantly impaired LPL secretion and completely abolished the enzymatic activity of the mutant protein. CONCLUSION: This report describes the first identification and functional characterization of a heterozygous variant in the LPL that predisposed to recurrent HTG-APIP. Our findings confirm a major genetic contribution to the etiology of individual predisposition to HTG-APIP.

Identification of a novel and heterozygous LMF1 nonsense mutation in an acute pancreatitis patient with severe hypertriglyceridemia, severe obesity and heavy smoking.

BACKGROUND: Hypertriglyceridemia (HTG) is one of the most common etiologies of acute pancreatitis (AP). Variants in five genes involved in the regulation of plasma lipid metabolism, namely LPL, APOA5, APOC2, GPIHBP1 and LMF1, have been frequently reported to cause or predispose to HTG. METHODS: A Han Chinese patient with HTG-induced AP was assessed for genetic variants by Sanger sequencing of the entire coding and flanking sequences of the above five genes. RESULTS: The patient was a 32-year-old man with severe obesity (Body Mass Index = 35) and heavy smoking (ten cigarettes per day for more than ten years). At the onset of AP, his serum triglyceride concentration was elevated to 1450.52 mg/dL. We sequenced the entire coding and flanking sequences of the LPL, APOC2, APOA5, GBIHBP1 and LMF1 genes in the patient. We found no putative deleterious variants, with the exception of a novel and heterozygous nonsense variant, c.1024C > T (p.Arg342*; rs776584760), in exon 7 of the LMF1 gene. CONCLUSIONS: This is the first time that a heterozygous LMF1 nonsense variant was found in a HTG-AP patient with severe obesity and heavy smoking, highlighting an important interplay between genetic and lifestyle factors in the etiology of HTG.

Compound but non-linked heterozygous p.W14X and p.L279 V LPL gene mutations in a Chinese patient with long-term severe hypertriglyceridemia and recurrent acute pancreatitis.

BACKGROUND: Variants in the lipoprotein lipase (LPL), apolipoprotein C-II (APOC2), apolipoprotein A-V (APOA5), GPIHBP1 and LMF1 genes may cause severe hypertriglyceridemia (HTG), which is now the second-leading aetiology of acute pancreatitis in China. METHODS: The patient and his family were assessed for gene variants by Sanger sequencing of exons and exon-intron junctions of the LPL, GPIHBP1, APOA5, APOC2, and LMF1 genes. Post-heparin blood was collected for LPL mass and activity detection. RESULTS: The patient had suffered from long-term severe hypertriglyceridemia and recurrent abdominal pain for over 30 years, since age 26, and 3 bouts of acute pancreatitis. Two heterozygous LPL single-nucleotide polymorphisms (SNPs) were compound but dislinked: a single-nucleotide substitution (c.42G > A) resulting in the substitution of tryptophan with a stop codon (p.W14X) in one allele, and a single-nucleotide substitution (c.835C > G) resulting in a leucine-to-valine substitution (p.L279 V) in another allele. Only one SNP, p.L279 V, was detected in his son. Post-heparin LPL activity and mass were also lower in the patient. CONCLUSION: Two heterozygous LPL SNPs, W14X and L279 V, were newly found to be compound but dislinked, which may cause long-term severe hypertriglyceridemia and recurrent acute pancreatitis.

Metal-silicene interaction studied by scanning tunneling microscopy.

Ag atoms have been deposited on 3 × 3 silicene and √3 × âˆš3 silicene films by molecular beam epitaxy method in ultrahigh vacuum. Using scanning tunneling microscopy and Raman spectroscopy, we found that Ag atoms do not form chemical bonds with both 3 × 3 silicene and √3 × âˆš3 silicene films, which is due to the chemically inert surface of silicene. On 3 × 3 silicene films, Ag atoms mostly form into stable flat-top Ag islands. In contrast, Ag atoms form nanoclusters and glide on silicene films, suggesting a more inert nature. Raman spectroscopy suggests that there is more sp (2) hybridization in √3 × âˆš3 than in √7 × âˆš7/3 × 3 silicene films.