A novel IGHMBP2 variant and clinical diversity in Vietnamese SMARD1 and CMT2S patients

Background

Pathogenic variants in the IGHMBP2 gene are associated with two distinct autosomal recessive neuromuscular disorders: spinal muscular atrophy with respiratory distress type 1 (SMARD1; OMIM #604320) and Charcot-Marie-Tooth type 2S (CMT2S; OMIM #616155). SMARD1 is a severe and fatal condition characterized by infantile-onset respiratory distress, diaphragmatic palsy, and distal muscular weakness, while CMT2S follows a milder clinical course, with slowly progressive distal muscle weakness and sensory loss, without manifestations of respiratory disorder.

Methods

Whole-exome sequencing of the IGHMBP2 gene was performed for eight Vietnamese patients with IGHMBP2-related neuromuscular disorders including five patients with SMARD1 and the others with CMT2S.

Results

We identified one novel IGHMBP2 variant c.1574T > C (p.Leu525Pro) in a SMARD1 patient. Besides that, two patients shared the same pathogenic variants (c.1235 + 3A > G/c.1334A > C) but presented completely different clinical courses: one with SMARD1 who deceased at 8 months of age, the other with CMT2S was alive at 3 years old without any respiratory distress.

Conclusion

This study is the first to report IGHMBP-2-related neuromuscular disorders in Vietnam. A novel IGHMBP2 variant c.1574T > C (p.Leu525Pro) expressing SMARD1 phenotype was detected. The presence of three patients with the same genotype but distinct clinical outcomes suggested the interaction of variants and other factors including relating modified genes in the mechanism of various phenotypes.

In silico validation revealed the role of SCN5A mutations and their genotype-phenotype correlations in Brugada syndrome

BACKGROUND

Brugada syndrome (BrS) is a rare genetic disease that causes sudden cardiac death (SCD) and arrhythmia. SCN5A pathogenic variants (about 30% of diagnosed patients) are responsible for BrS.

AIMS

Lack of knowledge regarding molecular characteristics and the correlation between genotype and phenotype interfere with the risk stratification and finding the optimal treatment in Vietnam. Therefore, we identified SCN5A variants and evaluated the genotype-phenotype correlation of BrS on 117 Vietnamese probands.

MATERIALS AND METHODS

The clinical characteristics and blood samples of BrS patients were collected. To determine SCN5A variants, Sanger sequencing was conducted, and subsequently, these variants were analyzed by bioinformatic tools.

RESULTS

In this cohort, the overall rate of detected variants in SCN5A was 25.6%, which could include both pathogenic and benign variants. In genetic testing, 21 SCN5A variants were identified, including eight novels and 15 published variants. Multiple bioinformatic tools were used to predict variant effect with c.551A>G, c.1890+14G>A, c.3338C>T, c.3578G>A, and c.5484C>T as benign, while other variants were predicted as disease-causing. The family history of SCD (risk ratio [RR] = 4.324, 95% CI: 2.290-8.269, p < 0.001), syncope (RR = 3.147, 95% CI: 1.668-5.982, p = 0.0004), and ventricular tachycardia/ventricular fibrillation (RR = 3.406, 95% CI: 1.722-5.400, p = 0.0035) presented a significantly higher risk in the SCN5A (+) group, consisting of individuals carrying any variant in the SCN5A gene, compared to SCN5A (-) individuals.

CONCLUSION

The results contribute to clarifying the impact of SCN5A variants on these phenotypes. Further follow-up studies need to be carried out to understand the functional effects of these SCN5A variants on the severity of BrS.

Merosin-deficient congenital muscular dystrophy type 1a: detection of LAMA2 variants in Vietnamese patients

Background: Merosin-deficient congenital muscular dystrophy type 1A (MDC1A), also known as laminin-α2 chain-deficient congenital muscular dystrophy (LAMA2-MD), is an autosomal recessive disease caused by biallelic variants in the LAMA2 gene. In MDC1A, laminin- α2 chain expression is absent or significantly reduced, leading to some early-onset clinical symptoms including severe hypotonia, muscle weakness, skeletal deformity, non-ambulation, and respiratory insufficiency. Methods: Six patients from five unrelated Vietnamese families presenting with congenital muscular dystrophy were investigated. Targeted sequencing was performed in the five probands. Sanger sequencing was carried out in their families. Multiplex ligation-dependent probe amplification was performed in one family to examine an exon deletion. Results: Seven variants of the LAMA2 (NM_000426) gene were identified and classified as pathogenic/likely pathogenic variants using American College of Medical Genetics and Genomics criteria. Two of these variants were not reported in the literature, including c.7156-5_7157delinsT and c.8974_8975insTGAT. Sanger sequencing indicated their parents as carriers. The mothers of family 4 and family 5 were pregnant and a prenatal testing was performed. The results showed that the fetus of the family 4 only carries c.4717 + 5G>A in the heterozygous form, while the fetus of the family 5 carries compound heterozygous variants, including a deletion of exon 3 and c.4644C>A. Conclusion: Our findings not only identified the underlying genetic etiology for the patients, but also provided genetic counseling for the parents whenever they have an offspring.

Nutritional Status, Refeeding Syndrome and Some Associated Factors of Patients at COVID-19 Hospital in Vietnam

Multisystem inflammatory syndrome is associated with COVID-19 and can result in reduced food intake, increased muscle catabolism, and electrolyte imbalance. Therefore COVID-19 patients are at high risk of being malnourished and of refeeding syndrome. The present study aimed to determine the prevalence and correlates of malnutrition and refeeding syndrome (RS) among COVID-19 patients in Hanoi, Vietnam. This prospective cohort study analyzed data from 1207 patients who were treated at the COVID-19 hospital of Hanoi Medical University (HMUH COVID-19) between September 2021 and March 2022. Nutritional status was evaluated by the Global Leadership Initiative on Malnutrition (GLIM) and laboratory markers. GLIM-defined malnutrition was found in 614 (50.9%) patients. Among those with malnutrition, 380 (31.5%) and 234 (19.4%) had moderate and severe malnutrition, respectively. The prevalence of risk of RS was 346 (28.7%). Those with severe and critical COVID symptoms are more likely to be at risk of RS compared to those with mild or moderate COVID, and having severe and critical COVID-19 infection increased the incidence of RS by 2.47 times, compared to mild and moderate disease. There was an association between levels of COVID-19, older ages, comorbidities, the inability of eating independently, hypoalbuminemia and hyponatremia with malnutrition. The proportion of COVID-19 patients who suffered from malnutrition was high. These results underscore the importance of early nutritional screening and assessment in COVID-19 patients, especially those with severe and critical infection.

Targeted next‐generation sequencing determined a novel SGCG variant that is associated with limb‐girdle muscular dystrophy type 2C: A case report

Limb‐girdle muscular dystrophy‐type 2C (LGMD2C) is caused by mutations in the SGCG gene. Here, we report a case of a 26‐year‐old male who had inactive walking due to proximal muscle weakness. Targeted next‐generation sequencing found a novel variant c.412C > T (Q138*) in the SGCG gene.

Case Report: Novel rare mutation c.6353C > G in the ABCA12 gene causing harlequin ichthyosis identified by whole exome sequencing

BACKGROUND

Harlequin ichthyosis (HI) is a severe rare genetic disease that mainly affects the skin. Neonates with this disease are born with thick skin and large diamond-shaped plates covering most of their bodies. Affected neonates lose the ability to control dehydration and regulate temperature and are more susceptible to infections. They also face respiratory failure and feeding problems. These clinical symptoms are factors associated with high mortality rates of neonates with HI. Until now, there are still no effective treatments for HI patients and most patients die in the newborn period. Mutation in the ABCA12 gene, which encodes an adenosine triphosphate-binding cassette (ABC) transporter, has been demonstrated as the major cause of HI.

CASE PRESENTATION

In this study, we report the case who is one infant that was born prematurely at 32 gestational weeks with the whole body covered with thick plate-like scales of skin. The infant was severely infected with mild edema, multiple cracked skins full of the body, yellow discharge, and necrosis of fingers and toes. The infant was suspected to be affected by HI. Whole exome sequencing (WES) was performed as a tool for detecting the novel mutation in one prematurely born Vietnam infant with HI phenotype. And after that, the mutation was confirmed by the Sanger sequencing method in the patient and the members of his family. In this case, one novel mutation c.6353C > G (p.S2118X, Hom) in the ABCA12 gene, was detected in the patient. The mutation has not been reported in any HI patients previously. This mutation was also found in a heterozygous state in the members of the patient's family, including his parents, an older brother, and an older sister who are no symptoms.

CONCLUSIONS

In this study, we identified a novel mutation in a Vietnamese patient with HI by whole exome sequencing. The results for the patient and the members of his family will be helpful in understanding the etiology of the disease, diagnosing carriers, assisting in genetic counseling, and emphasizing the need for DNA-based prenatal screening for families with a history of the disease.

Feasibility of combining short tandem repeats (STRs) haplotyping with preimplantation genetic diagnosis (PGD) in screening for beta thalassemia

β-thalassemia is an autosomal recessive disease with the reduction or absence in the production of β-globin chain in the hemoglobin, which is caused by mutations in the Hemoglobin subunit beta (HBB) gene. In Vietnam, the number of β-thalassemia carriers range from 1.5 to 25.0%, depending on ethnic and geographical areas, which is much higher than WHO's data worldwide (1.5%). Hence, preimplantation genetic diagnosis (PGD) plays a crucial role in reducing the rate of β-thalassemia affected patients/carriers. In this research, we report the feasibility and reliability of conducting PGD in combination with the use of short tandem repeat (STR) markers in facilitating the birth of healthy children. Six STRs, which were reported to closely linked with the HBB gene, were used on 15 couples of β-thalassemia carriers. With 231 embryos, 168 blastocysts were formed (formation rate of 72.73%), and 88 were biopsied and examined with STRs haplotyping and pedigree analysis. Thus, the results were verified by Sanger sequencing, as a definitive diagnosis. Consequently, 11 over 15 couples have achieved pregnancy of healthy or at least asymptomatic offspring. Only three couples failed to detect any signs of pregnancy such as increased Human Chorionic Gonadotropin (HCG) level, foetal sac, or heart; and one couple has not reached embryo transfer as they were proposed to continue with HLA-matching to screen for a potential umbilical cord blood donor sibling. Thus, these results have indicated that the combination of PGD with STRs analysis confirmed by Sanger sequencing has demonstrated to be a well-grounded and practical clinical strategy to improve the detection of β-thalassemia in the pregnancies of couples at-risk before embryo transfer, thus reducing β-thalassemia rate in the population.

A Case Series of Hypertrophic Cardiomyopathy Conducted in Vietnam Revealing a Novel Pathogenic Variant of the TNNT2 Gene

Background:

Hypertrophic Cardiomyopathy (HCM) is one of the leading causes of sudden cardiac death in adults.HCM is inherited in an autosomal dominant manner; however, the genetic etiology of the disease is not fully explained and studies on the hereditary characteristics in family trees are still underway.

Methods:

Ten HCM patients and 31 of their relatives were recruited. Targeted sequencing for 4 HCM related-genes, including MYH7, MYBPC3, TNNT2, and TNNI3, using targeted next-generation sequencing (NGS) was carried out. Demographic, clinical, electrocardiography, and echocardiography characteristics were also characterized.

Results:

Among the 10 HCM patients, 5 were identified with the HCM pathogenic variants in MYH7 (3 patients), MYBPC3 (1 patient), and TNNT2 (1 patient) genes. Eleven out of 31 relatives from these 5 genotype-positive patients carried the same pathogenic variants. We found the novel c.822-2 A>G variant in the splicing site of the TNNT2 gene responsible for HCM disease in a family with 7 subjects genotype positive and 3 others who suffered from sudden cardiac death.

Conclusion:

This case series highlighted the importance of genetic testing for clinically confirmed HCM patients and family members. The genetic information can be used as a molecular marker to complement the clinical presentation in the diagnosis of HCM, as well as a prognostic tool for the patients and their family members.

Whole exome sequencing analysis in a couple with three children who died prematurely due to carnitine-acylcarnitine translocase deficiency

OBJECTIVE

We investigated a strategy of exome sequencing DNA from the unaffected parents and applied a set of filtering criteria to identify genes where both partners are heterozygous for a potentially pathogenic variant.

CASE REPORT

We report a non-consanguineous couple who had three daughters, all spontaneous preterm birth at 36 weeks gestation and died in the first period after birth, suspected inborn errors of metabolism. Two days after birth, the first daughter presented with difficulty breathing, cyanosis and died; the second died at 33 days old; the third daughter was isolated under special care and was taken to the mother's room, developed the same symptoms and died after 5 days. Dried blood spot testing screen of 55 congenital metabolic disorders was negative.

CONCLUSION

Heterogenous variant in SLC25A20 gene was found in both parents, contributing to the delineations of the neonatal phenotypes related to SLC25A20 mutation in CACTD.

Microcephaly primary hereditary (MCPH): Report of novel ASPM variants and prenatal diagnosis in a Vietnamese family

OBJECTIVE

MCPH (microcephaly primary hereditary) is a group of autosomal recessive developmental disorders with microcephaly present at birth and intellectual disability. Since a second trimester ultrasound is not able to detect subtypes with minimal prenatal presentations, only prenatal diagnosis by genetic testing can confirm these cases and allow for effective genetic counseling, especially a family with a previously affected child.

CASE REPORT

A 37-year-old women was pregnant for the third time and had two prior children with profound microcephaly and mental retardation. Targeted panel sequencing identified novel compound heterozygous ASPM pathogenic variants: c.1615_1616del (p. Glu539ArgfsTer15); c.∗293T > A (p. Leu98Ter), which confirmed the diagnosis of MCPH5 (#OMIM 608716). Genetic testing was conducted for family members and applied on prenatal diagnosis.

CONCLUSION

This is the first cases of MCPH5 to be reported in Vietnam and the genetic result aided in prenatal diagnosis of a high-risk pregnancy. The study highlights the importance of genetic testing in defining definitive diagnosis which allowed for timely prenatal diagnosis and genetic counseling for the family.

Association of the STAT4, CDKN1A, and IRF5 variants with risk of lupus nephritis and renal biopsy classification in patients in Vietnam

BACKGROUND

Lupus nephritis is a common complication of systemic lupus erythematosus (SLE, OMIM #15200) in the Asian population and a main contributor to mortality and morbidity. In this study, we evaluate the variants on three genes STAT4, CDKN1A, and IRF5 and their association with lupus nephritis.

METHOD

One hundred fifty-two SLE patients with confirmed lupus nephritis (through biopsy) and 76 healthy controls were recruited. Genotyping of SNPs on three gene STAT4, CDKN1A, and IRF5, phenotypic, and laboratory assessment were performed; renal biopsy and classification were carried out for the patient group.

RESULTS

Carriers of rs7582694 C alleles on STAT4 have higher risk of lupus nephritis (OR 2.0; 95% CI [1.14, 3.19]; p = 0.015), at higher risk of hematuria and higher serum level of dsDNA antibodies compared to controls (p < 0.05) and were more likely to have nephrotic histopathology grading of class III or higher. No association was observed for CDKN1A; and no variation was observed for the IRF5 gene in both the study and control group.

CONCLUSION

This study investigates the relationship between STAT4, CDKN1A, and IRF5 gene and SLE in a Vietnamese patient population. Patients with the C allele (STAT4) in rs7582694 were associated with a more severe disease phenotype.

A case of self-improving collodion ichthyosis in Vietnam

Autosomal recessive congenital ichthyosis is a heterogeneous group of congenital disorders characterized by aberrant skin cornification and diffuse skin scaling. Some patients with this condition are born encased in a collodion membrane which is later shed, revealing the underlying skin disorder. Self-healing collodion baby (SHCB) is a less common phenotype of this disorder, accounting for about 10% of the patients, in which the membrane peels after several weeks, leaving no underlying skin aberration. Here, we report and discuss the diagnosis and management of an infant with SHCB in Vietnam due to compound heterozygous pathogenic mutations in TGM1.

Acromesomelic dysplasia Maroteaux-type in patients from Vietnam

Acromesomelic dysplasias are rare skeletal disorders leading to severe short stature and abnormal skeletal morphology. Acromesomelic dysplasia Maroteaux-type is caused by homozygous or compound heterozygous pathogenic variants in NPR2 that encodes for natriuretic peptide receptor B. Here, we reported the first AMDM case in South East Asia and identified a novel pathogenic variant in NPR2 (c. 152T>C, p. (Leu51Pro)). Further analyses reveal the parents and two other family members were heterozygous for the variant. The clinical report highlights the importance of molecular genetic testing in diagnosing rare hereditable disease affecting skeletal abnormalities.

Mosaicism in carrier of Duchenne muscular dystrophy mutation - Implication for prenatal diagnosis

OBJECTIVE

Duchenne muscular dystrophy (DMD) is a severe disorder caused by mutation in the X-linked dystrophin gene, therefor carrier testing is required for all female family members. However, there are cases mutation analysis cannot detect any mutation due to a phenomenon called mosaicism. The case report describes a case of mosaicism in a DMD carrier and discusses the approach in diagnosis and counseling of familial disorder.

CASE REPORT

The proband was diagnosed with DMD at age six. Sequencing of Dystrophin gene identified a 2-nucleotide deletion c.2032_2033delCA, p.Q678DfsX41. Family investigation suggested that the mother was an obligate carrier of Dystrophin mutation. Sequencing of DNA sample from the mother's peripheral blood did not reveal any mutation, there for we take sample from hair follicle for analysis. The result indicated that the mother was a carrier but was masked from initial analysis by mosaicsism.

CONCLUSION

We suggested that more care need to be taken in identifying cases when no mutation was detected in probable or obligate carrier and prenatal diagnosis should remain an option.

Prenatal diagnosis of a case with SEA-HPFH deletion thalassemia with whole HBB gene deletion

OBJECTIVE

The thalassemias is a group of hereditary disorders with impaired production of functional hemoglobin. In this report we described a rare case of compound heterozygous mutation of South-East Asia type hereditary persistence of fetal hemoglobin (SEA-HPFH) and β -thalassemia that allowed prenatal diagnosis to be performed in a subsequent pregnancy in the family.

CASE REPORT

The father showed a SEA-HPFH thalassemia trait phenotype, while his genotype revealed that he was heterozygous for the SEA-HPFH deletion; The mother genotype was heterozygote for IVS-II-654 mutation; the second child had co-inherited both parental mutations and was, thus, a compound heterozygote for β-thalassemia (IVS-II-654)/SEA-HPFH deletion. His phenotype was intermediate β-thalassemia. Prenatal genotyping of a fetal sample during the third pregnancy confirmed the fetus was only heterozygote for SEA-HPFH deletion and the parents elected to continue the pregnancy.

CONCLUSION

We described the clinical and molecular characterization of the first detected case of compound β-Thalassemia/SEA-HPFH deletion in Northern Vietnam. The report also highlighted the accuracy and necessity of mutation screening for families with thalassemia to inform accurate genetic counseling and targeted prenatal diagnosis when desired.

Analysis of the cause of recurrent pregnancy loss in Vietnam: A cross-sectional study

Recurrent pregnancy loss (RPL) is a physical and mental burden for women. In Vietnam, exploring the cause of miscarriages is still a challenge to clinical physicians. We aimed to investigate the etiology of RPL in the National Hospital of Obstetrics and Gynecology in Vietnam from 2012 to 2014. The cross-sectional study included 301 pregnant women with a history of RPL. The patients were examined and offered medical testing to determine the cause(s). Based on the testing, we determined causation for (11.29%) patients who had positive scores on an antiphospholipid antibody test and who were subsequently successfully treated for their problem.

ID: 1048 A novel nonsense mutation in the CYP21A2 gene of a Vietnamese patient with congenital adrenal hyperplasia

Inactivating mutations in the CYP21A2 gene which encodes the protein involved in steroid synthesis have been reported in the patients with congenital adrenal hyperplasia (CAH). An infant who diagnosed with the severe phenotype of CAH such as increasing testicular volume, elevating of 17-hydroxyprogesteron, testosterone and progesterone and his family were subjected for genetic studies. Initially, we used PCR and direct sequencing to screen mutations in the CYP21 gene in the proband and his family. We identified a novel nonsense mutation c.374C>G predicts a substitution of serine for a stop codon at codon 125 (p.S125*) within exon 3 in the proband. However, the inheritance pattern of the mutation was not consistent with disease causation because of a heterozygous mutation carrier in father and sibling, wild-type alleles in mother but mutant alleles in proband. This inspired us to find deletions of exon using multiplex ligation-dependent probe amplification (MLPA) assay. In the profiles of MLPA electropherogram, the proband had a large deletion in exon 3, but his mother did not have. It means that the proband inherited a normal allele from his mother and a mutant allele from his father, but the deletion of a normal allele occurred in the proband. Therefore, mutation c.374C>G (p.S125*) in exon 3 in the proband is considered as a heterozygous deletion mutation. In addition, a large deletion in exon 1 in the maternal allele in the proband is observed. Taking together, the proband carried a nonsense mutation accompanied with two deletions in exon 1 and exon 3 in the CYP21A2 gene affect the CAH phenotype severity. These mutations also expand the CYP21A2 mutation spectrum in CAH disorder. This case also highlights the need of caution when interpreting results of molecular genetics and biochemical testing during genetic counseling.

Abstract P3-10-04: Prevalence of pain and barriers to pain management in breast cancer survivors in Vietnam

Introduction: Breast cancer-related pain significantly affects quality of life and is well-documented in developed countries. However, little is known about the extent of breast cancer-related pain in developing countries. A study at the National Cancer Institute of Vietnam reported that 44% of breast cancer patients experienced moderate to severe pain. However, this study did not include breast cancer survivors, and little is known about the prevalence of pain and its management in this patient population.

Objectives: Determine the prevalence of pain, adequacy of pain management, and barriers to care in breast cancer survivors in Vietnam.

Methods: We administered previously validated and published symptom assessment tools (the BPI and MDASI) to 160 unselected Vietnamese women diagnosed and treated for breast cancer in 2007. Here we present a preliminary description of the results for the first 40 breast cancer survivors enrolled in this study.

Results: The most frequently reported symptoms were pain (62.5%, with 40% reporting the pain as severe), memory loss (50%), numbness/tingling (50%), sleep disturbance (45%), and appetite loss (32.5%). Only 23% reported adequate symptom management, with the costs of treatment and the false belief that no treatments existed for the pain being frequently cited as barriers to care.

Discussion: Cancer-related pain is highly prevalent in breast cancer survivors treated at the largest cancer hospital in Vietnam. The majority of patients report inadequate management of pain, often attributable to costs and false beliefs regarding pain management. Initiatives aimed at patient education and improving accessibility to pain management could significantly improve the quality of life in this patient population.

Citation Information: Cancer Res 2013;73(24 Suppl): Abstract nr P3-10-04.

High-yield expression and purification of human interferon alpha-1 in Pichia pastoris

For several years, interferon alpha-1, also known as interferon alpha-D, has been studied for treatment of various viral diseases, such as hepatic fibrosis caused by hepatitis B, herpes simplex virus keratitis, and bovine respiratory diseases in calves. Currently, recombinant human interferon alpha-D (rHuIFNalphaD) is expressed intracellularly in Escherichia coli or secreted by Bacillus subtilis and Saccharomyces cerevisiae. In this report, we describe the process of obtaining a relatively high-yield secretion of biologically active recombinant rHuIFNalphaD using the Pichia pastoris system. The process produced as high as 0.7 mg of purified protein per 20 ml of shake culture of rHuIFNalphaD with better bioactivity than the commercially available rHuIFNalphaD molecule produced in E. coli.

Fructose 1,6-bisphosphate aldolase is a heparin-binding protein

Proteins with affinity to heparin under physiological conditions were isolated from bovine cerebral cortex. First, the extract of cerebral cortex was applied to a chondroitin polysulfate column under physiological conditions. Then, the pass-through fraction was applied to a heparin column. Among the bands on SDS polyacrylamide gel electrophoresis of the fraction bound to the heparin column, the major one was identified as fructose 1,6-bisphosphate aldolase (FPA), a cytosolic enzyme involved in the glycolytic pathway. The results indicated that FPA is a heparin-binding protein which exhibits no affinity to chondroitin polysulfate. The results of affinity chromatographies revealed that FPA binds to intact heparin and modified heparins desulfated at C2 OH of the iduronic acid residue or at C6 OH or C2 NH2 of the glucosamine residue. When 6-O-desulfated heparin was employed as the affinity ligand, a single peak having FPA activity was isolated from the extract of bovine cerebral cortex. By further Mono Q chromatography and Superdex gel-filtration, five isoenzymes were purified with more than 50% recovery. These isoenzymes were identified as FPA A4, A3C1, A2C2, A1C3, and C4 by native electrophoresis with and without 4 M urea and subsequent amino acid sequence analysis. The use of 6-O-desulfated heparin affinity chromatography thus facilitated the purification of FPA.

Structural requirements of human tissue factor pathway inhibitor (TFPI) and heparin for TFPI-heparin interaction

Heparin affinity chromatography of synthetic peptide fragments mimicking tissue factor pathway inhibitor (TFPI) indicated that the minimal heparin binding sequence consists of 12 amino acid residues located at the C-terminal tail. Within this minimal sequence, Arg-257 and Arg-259 appeared to contribute most significantly to interaction with heparin. Affinity chromatography of TFPI using immobilized heparin derivatives regiospecifically desulfated at O-6 of the glucosamine residue, N-2 of the glucosamine residue, and/or O-2 of the iduronic acid residue indicated that all the sulfate groups in heparin appeared to be required for TFPI-heparin interaction. Among them, however, the 6-O-sulfate groups appeared to make the largest contribution to the interaction, while the 2-O-sulfate groups contributed the least. In vitro experiments on the inhibition of factor Xa by TFPI enhanced with native and chemically modified heparins afforded similar results.