Novel genetic abnormalities in Bernard-Soulier syndrome in India

Lentiviral gene therapy reverts GPIX expression and phenotype in Bernard-Soulier syndrome type C

Bernard-Soulier syndrome (BSS) is a rare congenital disease characterized by macrothrombocytopenia and frequent bleeding. It is caused by pathogenic variants in three genes (GP1BA, GP1BB, or GP9) that encode for the GPIbα, GPIbβ, and GPIX subunits of the GPIb-V-IX complex, the main platelet surface receptor for von Willebrand factor, being essential for platelet adhesion and aggregation. According to the affected gene, we distinguish BSS type A1 (GP1BA), type B (GP1BB), or type C (GP9). Pathogenic variants in these genes cause absent, incomplete, or dysfunctional GPIb-V-IX receptor and, consequently, a hemorrhagic phenotype. Using gene-editing tools, we generated knockout (KO) human cellular models that helped us to better understand GPIb-V-IX complex assembly. Furthermore, we developed novel lentiviral vectors capable of correcting GPIX expression, localization, and functionality in human GP9-KO megakaryoblastic cell lines. Generated GP9-KO induced pluripotent stem cells produced platelets that recapitulated the BSS phenotype: absence of GPIX on the membrane surface and large size. Importantly, gene therapy tools reverted both characteristics. Finally, hematopoietic stem cells from two unrelated BSS type C patients were transduced with the gene therapy vectors and differentiated to produce GPIX-expressing megakaryocytes and platelets with a reduced size. These results demonstrate the potential of lentiviral-based gene therapy to rescue BSS type C.

Pathogenic Aspects of Inherited Platelet Disorders

Inherited platelet disorders (IPDs) constitute a large heterogeneous group of rare bleeding disorders. These are classified into: (1) quantitative defects, (2) qualitative disorders, or (3) altered platelet production rate disorders or increased platelet turnover. Classically, IPD diagnostic is based on clinical phenotype characterization, comprehensive laboratory analyses (platelet function analysis), and, in former times, candidate gene sequencing. Today, molecular genetic analysis is performed using next-generation sequencing, mostly by targeting enrichment of a gene panel or by whole-exome sequencing. Still, the biochemical and molecular genetic characterization of patients with congenital thrombocytopathias/thrombocytopenia is essential, since postoperative or posttraumatic bleeding often occurs due to undiagnosed platelet defects. Depending upon the kind of surgery or trauma, this bleeding may be life-threatening, e.g., after tonsillectomy or in brain surgery. Undiagnosed platelet defects may lead to additional surgery, hysterectomy, pulmonary bleeding, and even resuscitation. In addition, these increased bleeding symptoms can lead to wound healing problems. Only specialized laboratories can perform the special platelet function analyses (aggregometry, flow cytometry, or immunofluorescent microscopy of the platelets); therefore, many IPDs are still undetected.

Exploring Diagnostic Biomarkers and Comorbid Pathogenesis for Osteoarthritis and Metabolic Syndrome via Bioinformatics Approach

BACKGROUND

Metabolic syndrome (MS) has grown in recognition to contribute to the pathogenesis of osteoarthritis (OA), which is the most prevalent arthritis characterized by joint dysfunction. However, the specific mechanism between OA and MS remains unclear.

METHODS

The gene expression profiles and clinical information data of OA and MS were retrieved from the Gene Expression Omnibus (GEO) database. The genes in the key module of MS were identified by weighted gene co-expression network analysis (WGCNA), which intersected with the differentially expressed genes (DEGs) between control and MS samples to obtain hub genes for MS. The potential functions and pathways of hub genes were detected through the Gene Ontology (GO) and Kyoto Encyclopedia of Gene and Genome (KEGG) analyses. The genes involved in the different KEGG pathways between the control and OA samples overlapped with the DEGs between the two groups via the Venn analysis to gain the hub genes for OA affected by MS (MOHGs). Additionally, the least absolute shrinkage and selection operator (LASSO) was performed on the MOHGs to establish a diagnostic model for each disease.

RESULTS

A total of 61 hub genes for MS were identified that significantly enriched in platelet activation, complement and coagulation cascades, and hematopoietic cell lineage. Besides, 4 candidate genes (ELOVL7, F2RL3, GP9, and ITGA2B) were screened among the 6 MOHGs to construct a diagnostic model, showing good performance for distinguishing controls from patients with MS and OA. GSEA suggested that these diagnostic genes were closely associated with immune response, adipocytokine signaling, fatty acid metabolism, cell cycle, and platelet activation.

CONCLUSION

Taken together, we identified 4 potential gene biomarkers for diagnosing MS and OA patients, providing a theoretical basis and reference for the diagnostics and treatment targets of MS and OA.

Identification of mutations in SLC4A1, GP1BA and HFE in a family with venous thrombosis of unknown cause by next-generation sequencing

Various risk factors, including high age, female gender, obesity and certain genetic defects have been linked to venous thrombosis. A Taiwanese family with venous thrombosis of unknown cause were enrolled in the present study. In this pedigree, two women without any specific underlying diseases suffered from venous thrombotic events at the same age. No specific risk factors or coagulation abnormalities were identified. The main proband's younger brother also had intestinal arterial thrombosis at 54 years of age. Therefore, it was hypothesized that familial genetic defects may be the cause of venous thrombosis within this family. Blood samples collected from certain members of this pedigree were subjected to whole-exome sequencing, and three genetic variants were identified, including a missense variant of solute carrier family 4 member 1 (SLC4A1) (c.388G>A), a deletion on glycoprotein Ib platelet α subunit (GP1BA) (c.1322_1344del23) and an insertion in the splice site of homeostatic iron regulator (HFE). To date, none of these three genetic variants have been reported to be associated with venous thrombosis, to the best of our knowledge. The present study suggests that these genetic variants of SLC4A1, GP1BA and HFE may be associated with venous thrombosis in an Asian pedigree.

Molecular pathology of rare bleeding disorders (RBDs) in India: a systematic review

Background

Though rare in occurrence, patients with rare bleeding disorders (RBDs) are highly heterogeneous and may manifest with severe bleeding diathesis. Due to the high rate of consanguinity in many caste groups, these autosomal recessive bleeding disorders which are of rare occurrence in populations across the world, may not be as rare in India.

Objectives

To comprehensively analyze the frequency and nature of mutations in Indian patients with RBDs.

Methods

Pubmed search was used (www.pubmed.com) to explore the published literature from India on RBDs using the key words “rare bleeding disorders”, “mutations”, “India”, “fibrinogen”, “afibrinogenemia”, “factor II deficiency”, “prothrombin” “factor VII deficiency”, “factor V deficiency”, “factor X deficiency”, “factor XI deficiency”, “combined factor V and VIII deficiency”, “factor XIII deficiency”, “Bernard Soulier syndrome” and “Glanzmanns thrombasthenia” in different combinations. A total of 60 relevant articles could be retrieved. The distribution of mutations from India was compared with that of the world literature by referring to the Human Gene Mutation Database (HGMD) (www.hgmd.org).

Results

Taken together, 181 mutations in 270 patients with different RBDs have been reported from India. Though the types of mutations reported from India and their percentage distribution with respect to the world data are largely similar, yet much higher percentage of small deletions, duplication mutations, insertions, indels were observed in this analysis. Besides the identification of novel mutations and polymorphisms, several common mutations have also been reported, which will allow to develop a strategy for mutation screening in Indian patients with RBDs.

Conclusion

There is a need for a consortium of Institutions working on the molecular pathology of RBDs in India. This will facilitate a quicker and cheaper diagnosis of RBDs besides its utility in first trimester prenatal diagnosis of the affected families.

Spectrum of the mutations in Bernard-Soulier syndrome

Bernard-Soulier syndrome (BSS) is a rare autosomal recessive bleeding disorder characterized by defects of the GPIb-IX-V complex, a platelet receptor for von Willebrand factor (VWF). Most of the mutations identified in the genes encoding for the GP1BA (GPIbα), GP1BB (GPIbβ), and GP9 (GPIX) subunits prevent expression of the complex at the platelet membrane or more rarely its interaction with VWF. As a consequence, platelets are unable to adhere to the vascular subendothelium and agglutinate in response to ristocetin. In order to collect information on BSS patients, we established an International Consortium for the study of BSS, allowing us to enrol and genotype 132 families (56 previously unreported). With 79 additional families for which molecular data were gleaned from the literature, the 211 families characterized so far have mutations in the GP1BA (28%), GP1BB (28%), or GP9 (44%) genes. There is a wide spectrum of mutations with 112 different variants, including 22 novel alterations. Consistent with the rarity of the disease, 85% of the probands carry homozygous mutations with evidence of founder effects in some geographical areas. This overview provides the first global picture of the molecular basis of BSS and will lead to improve patient diagnosis and management.