[Genetic methods for analysis of autoinflammatory diseases]. / Genetische Methoden für die Analyse autoinflammatorischer Erkrankungen.

Over the past years the phenotypic and genetic spectrum of autoinflammatory diseases has continuously increased. Moreover, several monogenic autoinflammatory disorders have now been identified where febrile episodes are not among the leading symptoms and which can be accompanied by autoimmune phenomena and susceptibility to infections. Autoinflammatory conditions that are characterized by uncontrolled activity of cytokines, such as interleukin-1 beta (IL1ß), tumor necrosis factor alpha (TNF-α) and type 1 interferons (1-IFN), are amenable to specific therapeutic interventions. Thus, identification of the underlying genetic cause is important. During diagnostic work-up, genetic testing of a patient with autoinflammation should be carried out depending on the clinical presentation. If a distinct disorder is suspected, sequencing of the causative gene should be performed. Genetic tests using next generation sequencing (NGS), such as panel sequencing, exome sequencing and array comparative genomic hybridization (CGH) can be carried out if symptoms cannot be assigned to a specific disease entity.

[Type I interferonopathies. Systemic inflammatory diseases triggered by type I interferons]. / Typ-I-Interferonopathien. Durch Typ-1-Interferone bedingte entzündliche Systemerkrankungen.

Type I interferons mediate immune defense against viral infections. The induction of type I interferons has stimulating and modulating effects on the innate and adaptive immune systems thereby reducing tolerance against self-antigens. Genetic defects that result in an inadequate activation of the type I interferon system can cause a group of inflammatory disorders, which are collectively referred to as type I interferonopathies. While the clinical spectrum of type I interferonopathies is broad and heterogeneous, neurological and cutaneous symptoms are the most frequent manifestations. Some clinical and genetic features of type I interferonopathies are shared by multifactorial diseases, such as systemic lupus erythematosus and systemic vasculitis. Advances in understanding the disease mechanisms underlying type I interferonopathies have pinpointed novel targets for therapeutic interventions.

Aicardi-Goutières syndrome: a model disease for systemic autoimmunity.

Systemic autoimmunity is a complex disease process that results from a loss of immunological tolerance characterized by the inability of the immune system to discriminate self from non-self. In patients with the prototypic autoimmune disease systemic lupus erythematosus (SLE), formation of autoantibodies targeting ubiquitous nuclear antigens and subsequent deposition of immune complexes in the vascular bed induces inflammatory tissue injury that can affect virtually any organ system. Given the extraordinary genetic and phenotypic heterogeneity of SLE, one approach to the genetic dissection of complex SLE is to study monogenic diseases, for which a single gene defect is responsible. Considerable success has been achieved from the analysis of the rare monogenic disorder Aicardi-Goutières syndrome (AGS), an inflammatory encephalopathy that clinically resembles in-utero-acquired viral infection and that also shares features with SLE. Progress in understanding the cellular and molecular functions of the AGS causing genes has revealed novel pathways of the metabolism of intracellular nucleic acids, the major targets of the autoimmune attack in patients with SLE. Induction of autoimmunity initiated by immune recognition of endogenous nucleic acids originating from processes such as DNA replication/repair or endogenous retro-elements represents novel paradigms of SLE pathogenesis. These findings illustrate how investigating rare monogenic diseases can also fuel discoveries that advance our understanding of complex disease. This will not only aid the development of improved tools for SLE diagnosis and disease classification, but also the development of novel targeted therapeutic approaches.

Platelet function in obese children and adolescents.

UNLABELLED: Platelet hyperaggregability contributes to thromboembolic events of obesity in adulthood. In obese children hyperaggregability was described in platelet rich plasma. We investigated platelet aggregation in children with obesity and lipometabolic disorders in whole blood. PATIENTS, MATERIAL, METHODS: Specimens from patients with overweight (n = 35), hypercholesterolaemia and normal weight (n = 5), overweight plus combined lipometabolic disorder (n = 5) and healthy controls (n = 20) were investigated. Aggregation and ATP release were induced by ADP (20 µmol/l), collagen (1 µg/ml) and thrombin (0.5 U/ml) using a lumiaggregometer. RESULTS: Overweight children and normal weight patients with hypercholesterolaemia exhibited no significant differences in platelet aggregation compared to controls. Contrastingly, in patients with obesity plus lipometabolic disorder the aggregation rate was significantly higher (p < 0.05) suggesting a hyperaggregable state. CONCLUSION: Obviously in obese children a hypercoagulable state exists and the slight hyperaggregability observed in whole blood in this cohort might contribute to that. Any effort should be undertaken to avoid obesity in children especially in those countries where the prevalence of obesity in childhood is continuously increasing.

Familial chilblain lupus--a monogenic form of cutaneous lupus erythematosus due to a heterozygous mutation in TREX1.

Chilblain lupus erythematosus is a rare form of cutaneous lupus erythematosus characterized by bluish red infiltrates in acral locations of the body mostly affecting middle-aged women. We recently described a familial form of chilblain lupus manifesting in early childhood caused by a heterozygous mutation in the TREX1 gene, which encodes a 3'-5' DNA exonuclease. Thus, familial chilblain lupus represents the first monogenic form of cutaneous lupus erythematosus. Here we describe the unusual clinical course of this newly defined genodermatosis in an 18-year-old female member of the family in which familial chilblain lupus was originally described.

Three-generational alkaptonuria in a non-consanguineous family.

OBJECTIVE: Alkaptonuria (AKU) is a rare inborn error of metabolism of aromatic amino acids and considered to be an autosomal recessive trait caused by mutations in the homogentisate 1,2-dioxygenase (HGD) gene. A dominant pattern of inheritance has been reported but was attributed to extended consanguinity in many cases. However, we have observed a non-consanguineous family segregating AKU in a dominant manner over three generations. RESULTS: All affected individuals presented with typical features of AKU including darkening of the urine, ochronosis, arthropathy, and elevated urinary excretion of homogentisic acid. Sequence analysis of the HGD gene from genomic DNA of two affected individuals, uncle and niece, revealed a heterozygous missense mutation (M368V) in the uncle that was not present in his niece. Microsatellite genotyping demonstrated that both were heterozygous at the HGD locus and shared one haplotype. This haplotype did not contain a detectable HGD mutation. The haplotype was also found in a healthy son of the niece, making a dominant HGD mutation unlikely. Moreover, sequencing of cDNA from lymphoblastoid cells of the niece did not reveal an HGD mRNA with a potentially dominant-negative effect. CONCLUSION: Rare causes of the uncommon AKU inheritance in this family have to be considered, ranging from the coincidence of undetectable HGD mutations to a dominant mutation of a second, hitherto unknown AKU gene.

Altered structure, regulation, and function of the gene encoding the atrial natriuretic peptide in the stroke-prone spontaneously hypertensive rat.

Through the genotype/phenotype cosegregation analysis of an F(2) intercross, from the crossbreeding of stroke-prone spontaneously hypertensive rats (SHRSP) and stroke-resistant spontaneously hypertensive rats (SHR), we previously identified a quantitative trait locus for stroke on rat chromosome 5 (STR2) that colocalized with the genes encoding atrial and brain natriuretic peptides (ANP and BNP) and conferred a stroke-delaying effect. To further characterize ANP and BNP as candidates for stroke, we performed additional studies. Comparative sequence analysis revealed point mutations in both the coding and regulatory regions of ANP, whereas no interstrain differences were found for BNP. In in vitro studies in COS-7 and AtT-20 cells that were performed to test the relevance of a G-->A substitution at position 1125, a Gly-->Ser transposition in the SHRSP pro-ANP peptide resulted in different posttranslational processing of the SHRSP ANP gene product that was also associated with higher cGMP production (P<0.05). Furthermore, an analysis of a 5' end mutation affecting a PEA2 regulatory binding site in the 5' untranslated regulatory sequence of SHRSP ANP demonstrated a significantly lower ANP promoter activation in endothelial cells (P<0.05 versus the SHR ANP). In addition, the expression of ANP was significantly reduced in the brain, but not in the atria, of SHRSP compared with SHR (P<0.0001). No differences were detected with regard to BNP expression. The present results reveal substantial differences in ANP, but not BNP, structure and product among SHR and SHRSP, which supports a role of ANP in the pathogenesis of stroke in the SHRSP animal model.

Distinct renin isoforms generated by tissue-specific transcription initiation and alternative splicing.

The aspartyl protease renin catalyzes the initial and rate-limiting step in the formation of the biologically active peptide angiotensin II. It is mainly synthesized in the kidney as a preprohormone and secreted via constitutive and regulated pathways. We identified a novel transcript of the rat renin gene, renin b, characterized by the presence of an alternative first exon (exon 1b) that is spliced to exon 2 of the known transcript, termed renin a. We demonstrated that renin b is exclusively expressed in the brain. In contrast, renin a was not expressed in the brain. Using primer extension assays, we mapped the transcriptional start site of this novel mRNA within intron 1 of the rat genomic sequence, suggesting the presence of a brain-specific promoter within intron 1. The presence of a brain-specific renin isoform is evolutionally conserved, as demonstrated by the finding of renin b isoforms in mice and humans. The predicted protein renin b lacks the prefragment as well as a significant portion of the profragment and is therefore predicted not to be a secreted protein, unlike the classically described isoform renin a. As shown by in vitro translation of full-length renin b mRNA in the presence of microsomal membranes, renin b was not targeted into the endoplasmatic reticulum and remained intracellularly in transiently transfected AtT-20 cells. These findings provide evidence for a novel pathway of intracellular angiotensin generation that occurs exclusively in the brain.