Intracellular ISG15 is an interferon (IFN)-α/β-inducible ubiquitin-like modifier which can covalently bind other proteins in a process called ISGylation; it is an effector of IFN-α/β-dependent antiviral immunity in mice1–4. We previously published a study describing humans with inherited ISG15 deficiency but without unusually severe viral diseases5. We showed that these patients were prone to mycobacterial disease and that human ISG15 was non-redundant as an extracellular IFN-γ-inducing molecule. We show here that ISG15-deficient patients also display unanticipated cellular, immunological and clinical signs of enhanced IFN-α/β immunity, reminiscent of the Mendelian autoinflammatory interferonopathies Aicardi–Goutières syndrome and spondyloenchondrodysplasia6–9.We further show that an absence of intracellular ISG15 in the patients’ cells prevents the accumulation of USP1810,11, a potent negative regulator of IFN-α/β signalling, resulting in the enhancement and amplification of IFN-α/β responses. Human ISG15, therefore, is not only redundant for antiviral immunity, but is a key negative regulator of IFN-α/β immunity. In humans, intracellular ISG15 is IFN-α/β-inducible not to serve as a substrate for ISGylation-dependent antiviral immunity, but to ensure USP18-dependent regulation of IFN-α/β and prevention of IFN-α/β-dependent autoinflammation.

Age-related macular degeneration (AMD), the most common cause of irreversible vision loss in individuals aged older than 50 years, is classified as either wet (neovascular) or dry (nonneovascular). Inherited variation in the complement factor H gene is a major risk factor for drusen in dry AMD. Here we report that a single-nucleotide polymorphism in the promoter region of HTRA1, a serine protease gene on chromosome 10q26, is a major genetic risk factor for wet AMD. A whole-genome association mapping strategy was applied to a Chinese population, yielding a P value of <10(-11). Individuals with the risk-associated genotype were estimated to have a likelihood of developing wet AMD 10 times that of individuals with the wild-type genotype.

Familial idiopathic basal ganglia calcification (IBGC) is a genetic condition with a wide spectrum of neuropsychiatric symptoms, including parkinsonism and dementia. Here, we identified mutations in SLC20A2, encoding the type III sodium-dependent phosphate transporter 2 (PiT2), in IBGC-affected families of varied ancestry, and we observed significantly impaired phosphate transport activity for all assayed PiT2 mutants in Xenopus laevis oocytes. Our results implicate altered phosphate homeostasis in the etiology of IBGC.

Angiogenic factors are critical to the initiation of angiogenesis and maintenance of the vascular network. Here we use human genetics as an approach to identify an angiogenic factor, VG5Q, and further define two genetic defects of VG5Q in patients with the vascular disease Klippel-Trenaunay syndrome (KTS). One mutation is chromosomal translocation t(5;11), which increases VG5Q transcription. The second is mutation E133K identified in five KTS patients, but not in 200 matched controls. VG5Q protein acts as a potent angiogenic factor in promoting angiogenesis, and suppression of VG5Q expression inhibits vessel formation. E133K is a functional mutation that substantially enhances the angiogenic effect of VG5Q. VG5Q shows strong expression in blood vessels and is secreted as vessel formation is initiated. VG5Q can bind to endothelial cells and promote cell proliferation, suggesting that it may act in an autocrine fashion. We also demonstrate a direct interaction of VG5Q with another secreted angiogenic factor, TWEAK (also known as TNFSF12). These results define VG5Q as an angiogenic factor, establish VG5Q as a susceptibility gene for KTS, and show that increased angiogenesis is a molecular pathogenic mechanism of KTS.

TBX5 is a T-box transcription factor that plays a critical role in organogenesis. Seven missense mutations in TBX5 have been identified in patients with Holt-Oram syndrome characterized by congenital heart defects and upper limb abnormalities. However, the functional significance and molecular pathogenic mechanisms of these mutations are not clear. In this study we describe functional defects in DNA binding, transcriptional activity, protein-protein interaction, and cellular localization of mutant TBX5 with these missense mutations (Q49K, I54T, G80R, G169R, R237Q, R237W, and S252I). Mutations G80R, R237Q, and R237W represent a group of mutations that dramatically reduce DNA-binding activity of TBX5, leading to reduced transcription activation by TBX5 and the loss of synergy in transcriptional activation between TBX5 and NKX2.5. The second group of mutations includes Q49K, I54T, G169R, and S252I, which have no or moderate effect on DNA-binding activity and the function of transcription activation of TBX5 but cause the complete loss of synergistic transcription activity between TBX5 and NKX2.5. All seven missense mutations greatly reduced the interaction of TBX5 with NKX2.5 in vivo and in vitro. Immunofluorescent staining showed that wild type TBX5 was localized completely into the nucleus, but mutants were localized in both nucleus and cytoplasm. These results demonstrate that all seven missense mutations studied here are functional mutations with a spectrum of defects ranging from decreases in DNA-binding activity and transcriptional activation to the dramatic reduction of interaction between TBX5 and NKX2.5, and loss of synergy in transcriptional activation between these two proteins, as well as impairment in the nuclear localization of TBX5. These defects are likely central to the pathogenesis of Holt-Oram syndrome.

Atrial fibrillation (AF) is the most common arrhythmia in the clinical setting and an independent risk factor for stroke. Approximately 10 million Chinese people are affected by AF, but the genetic basis is largely unknown. A recent genome-wide association study in Iceland identified association between SNP rs2200733 on 4q25 and AF; however, many independent replication studies are essential to unequivocally validate this association. To assess the association between rs2200733 and AF as well as that between rs2200733 and ischemic stroke in a mainland Chinese Han population, we carried out case-control association studies with 383 AF patients versus 851 non-AF controls and 811 ischemic stroke patients versus 688 non-stroke controls. Highly significant association was detected between rs2200733 and AF in a Chinese Han population (allelic P = 3.7 × 10(-11) with OR = 1.81; genotypic P = 4.1 × 10(-12) with a dominant model). When the AF cases were divided into lone AF (32.6%) and other types of AF (67.4%), significantly stronger association was found with lone AF (OR = 2.40, P = 1.3 × 10(-9) compared to OR = 1.59, P = 6.2 × 10(-7) for other types of AF; P = 0.02 for two ORs). No significant association was found between rs2200733 and ischemic stroke. Our results suggest that SNP rs2200733 confers a highly significant risk of AF, but not ischemic stroke, in a more representative Chinese Han population in the mainland China.

Dyschromatosis universalis hereditaria (DUH) is a pigmentary genodermatosis characterized by a mixture of hyperpigmented and hypopigmented macules distributed randomly over the body. No causative genes have been reported to date. In this study, we investigated a large five-generation Chinese family with DUH. After excluding the two known DUH loci, we performed genome-wide linkage analysis and identified a DUH locus on chromosome 2q33.3-q36.1 with a maximum LOD score of 3.49 with marker D2S2382. Exome sequencing identified a c.1067T>C (p.Leu356Pro) mutation in exon 3 of ABCB6 (ATP-binding cassette subfamily B, member 6) in the DUH family. Two additional missense mutations, c.508A>G (p.Ser170Gly) in exon 1 and c.1736G>A (p.Gly579Glu) in exon 12 of ABCB6, were found in two out of six patients by mutational screening using sporadic DUH patients. Immunohistologic examination in biopsy specimens showed that ABCB6 is expressed in the epidermis and had a diffuse cytoplasmic distribution. Examination of subcellular localization of wild-type ABCB6 in a B16 mouse melanoma cell line revealed that it is localized to the endosome-like compartment and dendrite tips, whereas disease-causing mutations of ABCB6 resulted in its retention in the Golgi apparatus. Our studies identified ABCB6 as the first pathogenic gene associated with DUH. These findings suggest that ABCB6 may be a physiological factor for skin pigmentation.

Atrial fibrillation (AF) is the most common cardiac rhythm disorder at the clinical setting and accounts for up to 15% of all strokes. Recent genome-wide association studies (GWAS) identified two single nucleotide polymorphisms (SNPs), rs2106261 and rs7193343 in ZFHX3 (zinc finger homeobox 3 gene) and rs13376333 in KCNN3 (encoding a potassium intermediate/small conductance calcium-activated channel, subfamily N, member 3) that showed significant association with AF in multiple populations of European ancestry. Here, we studied a Chinese Han, GeneID cohort consisting of 650 AF patients and 1,447 non-AF controls to test whether the GWAS findings on ZFHX3/KCNN3 and AF can be expanded to a different ethnic population. No significant association was detected for rs7193343 in ZFHX3 and rs13376333 in KCNN3. However, significant association was identified between rs2106261 in ZFHX3 and AF in the GeneID population for both allelic frequencies (P = 0.001 after adjusting for covariates of age, gender, hypertension, coronary artery disease, and diabetes mellitus; OR = 1.32), and genotypic frequencies assuming either an additive or recessive model (OR = 1.29, P = 0.001 and OR = 1.77, P = 0.00018, respectively). When only lone AF cases were analyzed, the association remained significant (OR = 1.50, P = 0.001 for allelic association; OR = 1.45, P = 0.001 for an additive model; OR = 2.24, P = 0.000043 for a recessive model). Our results indicate that rs2106261 in ZFHX3 confers a significant risk of AF in a Chinese Han population. The study expands the association between ZFHX3 and AF to a non-European ancestry population and provides the first evidence of a cross-race susceptibility of the 16q22 AF locus.