Validation study of HLA-B*13:01 as a biomarker of dapsone hypersensitivity syndrome in leprosy patients in Indonesia.

Leprosy is a stigmatizing, chronic infection which degenerates the nervous system and often leads to incapacitation. Multi-drug therapy which consists of dapsone, rifampicin and clofazimine has been effective to combat this disease. In Indonesia, especially in Papua Island, leprosy is still a problem. Furthermore, there had been higher reports of Dapsone Hypersensitivity Syndrome (DHS) which also challenges leprosy elimination in certain aspects. Globally, DHS has a prevalence rate of 1.4% and a fatality rate up to 13%. The aim of this study is to validate HLA-B*13:01, a previously discovered biomarker for DHS in the Chinese population, as a biomarker for DHS in the Papua population.This is a case-control study of 34 leprosy patients who presented themselves with DHS (case subjects) and 52 leprosy patients without DHS (control subjects). Patients were recruited from 2 provinces: Papua and West Papua. DNA was extracted from 3 ml blood specimens. HLA-B alleles were typed using the gold-standard sequence based typing method. Results were then analysed using logistic regression and risk assessment was carried out. The results of HLA-typing showed that HLA-B*13:01 was the most significant allele associated with DHS, with odds ratio = 233.64 and P-value = 7.11×10-9, confirming the strong association of HLA-B*13:01 to DHS in the Papua population. The sensitivity of this biomarker is 91.2% and specificity is 96.2%, with an area under the curve of 0.95. HLA-B*13:01 is validated as a biomarker for DHS in leprosy patients in Papua, Indonesia, and can potentially be a good predictor of DHS to help prevent this condition in the future.

Genome-wide linkage, exome sequencing and functional analyses identify ABCB6 as the pathogenic gene of dyschromatosis universalis hereditaria.

BACKGROUND: As a genetic disorder of abnormal pigmentation, the molecular basis of dyschromatosis universalis hereditaria (DUH) had remained unclear until recently when ABCB6 was reported as a causative gene of DUH. METHODOLOGY: We performed genome-wide linkage scan using Illumina Human 660W-Quad BeadChip and exome sequencing analyses using Agilent SureSelect Human All Exon Kits in a multiplex Chinese DUH family to identify the pathogenic mutations and verified the candidate mutations using Sanger sequencing. Quantitative RT-PCR and Immunohistochemistry was performed to verify the expression of the pathogenic gene, Zebrafish was also used to confirm the functional role of ABCB6 in melanocytes and pigmentation. RESULTS: Genome-wide linkage (assuming autosomal dominant inheritance mode) and exome sequencing analyses identified ABCB6 as the disease candidate gene by discovering a coding mutation (c.1358C>T; p.Ala453Val) that co-segregates with the disease phenotype. Further mutation analysis of ABCB6 in four other DUH families and two sporadic cases by Sanger sequencing confirmed the mutation (c.1358C>T; p.Ala453Val) and discovered a second, co-segregating coding mutation (c.964A>C; p.Ser322Lys) in one of the four families. Both mutations were heterozygous in DUH patients and not present in the 1000 Genome Project and dbSNP database as well as 1,516 unrelated Chinese healthy controls. Expression analysis in human skin and mutagenesis interrogation in zebrafish confirmed the functional role of ABCB6 in melanocytes and pigmentation. Given the involvement of ABCB6 mutations in coloboma, we performed ophthalmological examination of the DUH carriers of ABCB6 mutations and found ocular abnormalities in them. CONCLUSION: Our study has advanced our understanding of DUH pathogenesis and revealed the shared pathological mechanism between pigmentary DUH and ocular coloboma.

Isthmin is a novel secreted angiogenesis inhibitor that inhibits tumour growth in mice.

Anti-angiogenesis represents a promising therapeutic strategy for the treatment of various malignancies. Isthmin (ISM) is a gene highly expressed in the isthmus of the midbrain-hindbrain organizer in Xenopus with no known functions. It encodes a secreted 60 kD protein containing a thrombospondin type 1 repeat domain in the central region and an adhesion-associated domain in MUC4 and other proteins (AMOP) domain at the C-terminal. In this work, we demonstrate that ISM is a novel angiogenesis inhibitor. Recombinant mouse ISM inhibited endothelial cell (EC) capillary network formation on Matrigel through its C-terminal AMOP domain. It also suppressed vascular endothelial growth factor (VEGF)-basic fibroblast growth factor (bFGF) induced in vivo angiogenesis in mouse. It mitigated VEGF-stimulated EC proliferation without affecting EC migration. Furthermore, ISM induced EC apoptosis in the presence of VEGF through a caspase-dependent pathway. ISM binds to αvß(5) integrin on EC surface and supports EC adhesion. Overexpression of ISM significantly suppressed mouse B16 melanoma tumour growth through inhibition of tumour angiogenesis without affecting tumour cell proliferation. Knockdown of isthmin in zebrafish embryos using morpholino antisense oligonucleotides led to disorganized intersegmental vessels in the trunk. Our results demonstrate that ISM is a novel endogenous angiogenesis inhibitor with functions likely in physiological as well as pathological angiogenesis.