RNASEH2C c.194G>A is a Chinese-specific founder mutation in three unrelated patients with Aicardi-Goutières syndrome 3

Biallelic pathogenic variants in RNASEH2C cause Aicardi-Goutières syndrome 3 (AGS3, MIM #610329), a rare early-onset encephalopathy characterized by intermittent unexplained fever, chilblains, irritability, progressive microcephaly, dystonia, spasticity, severe psychomotor retardation and abnormal brain imaging. Currently, approximately 50 individuals with AGS3 and 19 variants in RNASEH2C have been revealed. Here, we reported the novel clinical manifestations and genotypic information of three unrelated Chinese patients with AGS3 caused by pathogenic variants in RNASEH2C. In addition to three novel missense variants (c.101G>A, p.Cys34Tyr; c.401T>A, p.Leu134Gln and c.434G>T, p.Arg145Leu), one missense variant (c.194G>A, p.Gly65Asp) reoccurred in all patients but was completely absent in South Asian and other ethnicities. Our study expanded the variant spectrum of RNASEH2C and identified RNASEH2C c.194G>A as a Chinese-specific founder mutation. The novel phenotypes, including mouth ulcers, hip dysplasia, retarded dentition and hypogonadism, observed in our patients greatly enriched the clinical characteristics of AGS3.     

Protective role of potentially lethal damage repair in the neoplastic transformation of Balb/c 3T3 cells treated with N-methyl-N′-nitro-N-nitrosoguanidine

To determine the role of repair of potentially lethal damage (PLD) in the initiation process of neoplastic transformation, BALB/c 3T3 cells treated with N-methyl-N′-nitro-N-nitrosoguanidine (MNNG) were temporarily exposed to conditioned medium obtained from density-inhibited Chinese hamster cell cultures, as a post-treatment for the induction of PLD repair. With or without this exposure, cell survival and transformation frequencies were simultaneously determined by colony-formation and focus-formation assays, respectively. Temporary exposure to conditioned medium resulted in a 20–30% increase in cell survival compared with no exposure. Post-treatment with conditioned medium resulted in a 60–65% reduction in transformation frequencies. At the molecular level, the repair of MNNG-induced single-strand breaks of DNA occurred much more rapidly in condition medium. These data suggest that PLD repair DNA replication. Thus, PLD repair appears to be preventive against neoplastic fixation in initiation of neoplastic development.     

Identification of a novel cathepsin C mutation (p.W185X) in a Brazilian kindred with Papillon-Lefèvre syndrome

Papillon-Lefèvre syndrome (PLS) is an autosomal recessive palmoplantar keratoderma caused by cathepsin C (CTSC) gene mutations. This study reports CTSC mutational and enzyme analyses in a consanguineous Brazilian family with PLS, representing the first enzymatic analysis of a Brazilian kinship with PLS. This family segregates a novel PLS-related mutation, p.W185X, that is associated with a complete loss of enzymatic activity.     

Suppression of a mitochondrial point mutation in a tRNA gene can cast light on the mechanisms of 3′ end-processing

We used a genetic approach to study the nuclear factors involved in the biogenesis of mitochondrial tRNAs. A point mutation in the mitochondrial tRNA^Asp gene of Saccharomyces cerevisiae had previously been shown to result in a temperature-sensitive respiratory-deficient phenotype as a result of the absence of 3 end-processing of the tRNA^Asp. Analysis of mitochondrial revertants has shown that all revertants sequenced have a G-A compensatory change at position 53, which restores the hydrogen-bond with the mutated nucleotide. We then searched for nuclear suppressors to identify the nuclear gene(s) involved in mitochondrial tRNA 3 end-processing. One such suppressor mutation was further characterized: it restores tRNA^Asp maturation and growth at 36°C on glycerol medium in heterozygous diploids, but leads to a defective growth phenotype in haploids.     

Identification of a novel 2026G→C mutation of the MRP2 gene in a Japanese patient with Dubin-Johnson syndrome

Dubin-Johnson syndrome is a recessive inherited disorder with conjugated hyperbilirubinemia caused by a dysfunction of multidrug resistance protein 2 (MRP2) on the canalicular membrane of hepatocytes. A mutational analysis of the MRP2 gene was carried out in three Japanese patients and their family members. In two patients, the homozygous mutations c.1901del67 and c,2272del168 were found. In the third patient, a –24CT polymorphism and the two mutations c.1901del67 and 2026GC were detected. The 2026GC mutation was a novel mutation in exon 16 affecting the conversion of Gly⁶⁷⁶ to Arg⁶⁷⁶ (G676R) in the MRP2 protein, and was not detected in fifty healthy volunteers. The G676R mutation was located in the Walker A motif of the first nucleotide binding domain in the MRP2 protein, and it was suggested that the mutation induced the dysfunction of the MRP2 protein. It was concluded that the compound heterozygosity of the two mutations of the MRP2 gene in the third patient contributed to the induction of hyperbilirubinemia in this case.     

CD36 c.1264 T>G null mutation impairs acquisition of IgG antibodies to Plasmodium falciparum MSP1₁₉ antigen and is associated with higher malaria incidences in Tanzanian children

Polymorphisms in genes that encode crucial signalling molecules have been proposed as factors that influence susceptibility to, and outcome of malaria. We studied the role of a mutation, c.1264 T>G, that causes CD36 deficiency on IgG responses to MSP‐1₁₉ antigen and malaria incidence. Children were genotyped for the c.1264 T>G mutation at the beginning of the study using PCR‐RFLP. IgG levels [optical density (OD) readings] and per cent seropositivity to MSP‐1₁₉ were determined at baseline by ELISA. Children were followed for 12 months for acquisition of anti‐MSP‐1₁₉ IgG antibody and malaria incidence. We observed a significant increase in the production of anti‐MSP‐1₁₉ IgG antibody in normal and heterozygous children during the 12 months of follow‐up, but not in homozygous mutants. Normal children had a significantly lower malaria incidence rate compared to other genotypes (χ² = 115.59; P < 0.01). We conclude that the presence of the c.1264 T>G mutation that leads to CD36 deficiency is closely associated with reduced IgG production and higher malaria incidence. It is most likely that deficiency of CD36 which is known to modulate dendritic cell function suppresses the production of protective IgG antibodies directed to Plasmodium falciparum MSP‐1₁₉ antigen, which predisposes to the acquisition of clinical malaria in children.     

SOCS3 is a suppressor of γc cytokine signaling and constrains generation of murine Foxp3+ regulatory T cells

SOCS3 is a cytosolic inhibitor of cytokine signaling that suppresses the activation of cytokine receptor-associated JAK kinases. Mechanistically, SOCS3 is recruited to a site in the cytokine receptors known as the SOCS3-interaction motif, and then binds JAK molecules to inhibit their kinase activity. The SOCS3-interaction motif is found in receptors of the gp130 cytokine family but mostly absent from other cytokine receptors, including γc. Thus, SOCS3 has been considered a selective suppressor of gp130 family cytokines, but not γc cytokines. Considering that γc signaling induces SOCS3 expression in T cells, here we revisited the role of SOCS3 on γc signaling. Using SOCS3 transgenic mice, we found that increased abundance of SOCS3 not only suppressed signaling of the gp130 family cytokine IL-6, but also signaling of the γc family cytokine IL-7. Consequently, SOCS3 transgenic mice were impaired in IL-7-dependent T cell development in the thymus and the homeostasis of mature T cells in peripheral tissues. Moreover, enforced SOCS3 expression interfered with the generation of Foxp3⁺ regulatory T cells that requires signaling by the γc family cytokine IL-2. Collectively, we report an underappreciated role for SOCS3 in suppressing γc cytokine signaling, effectively expanding its scope of target cytokines in T cell immunity.     

Identification of the first deep intronic mutation in the RPS6KA3 gene in a patient with a severe form of Coffin–Lowry syndrome

Coffin–Lowry syndrome (CLS) is an X-linked disorder characterized by growth and psychomotor retardation, hypotonia and progressive skeletal changes. RPS6KA3 is the only gene known to be associated with CLS, and over 150 distinct inactivating mutations in this gene have so far been reported in CLS patients. However, no defect is found in about half of the CLS compatible patients by exon sequencing. We report here the first deep intronic mutation in RPS6KA3, which is associated with the retention of intronic sequences in the mRNAs. Indeed, this finding suggests that all the patients with a highly suggestive CLS clinical diagnosis, but in whom exon screening has failed to detect a mutation, should be reanalyzed at the RNA level.     

GSK3β inhibition and LEF1 upregulation in skeletal muscle following a bout of downhill running

Canonical Wnt signaling is important in skeletal muscle repair but has not been well characterized in response to physiological stimuli. The objective of this study was to assess the effect of downhill running (DHR) on components of Wnt signaling. Young, male C57BL/J6 mice were exposed to DHR. Muscle injury and repair (MCadherin) were measured in soleus. Gene and protein expression of Wnt3a, active β-catenin, GSK3β, and LEF1 were measured in gastrocnemius. Muscle injury increased 6 days post-DHR and MCadherin protein increased 5 days post-DHR. Total and active GSK3β protein decreased 3 days (9-fold and 3.6-fold, respectively) post-DHR. LEF1 protein increased 6 days (5-fold) post-DHR. DHR decreased GSK3β and increased LEF1 protein expression, but did not affect other components of Wnt signaling. Due to their applicability, using models of physiological stimuli such as DHR will provide significant insight into cellular mechanisms within muscle.     

Influence of a mutation in IFN-γ receptor 2 (IFNGR2) in human cells on the generation of Th17 cells in memory T cells

The T cell subsets involved in inflammatory reactions are mainly the IFN-γ secreting Th1 cells and IL17-producing Th17 cells. Although Th17 cells are primed in the thymus, there is evidence that Th17 cells can be generated from effector memory CD4⁺ T cells. Cytokines as IL-6, TGF-β, IL-21 and IL-23 involved in development of Th17 cells are well described. Here we analyzed the impact of a mutation in the IFN-γ receptor 2 (IFN-γR2) on the induction of Th17 cells. By isolation of T cells and monocytes of a patient with this mutation we could demonstrate an inhibitory role of IFN-γ signaling as IFN-γR2-deficient monocytes induce a higher percentage of IL-17⁺ cells from both healthy and IFN-γR2-deficient CD4⁺ T cells. This data confirm the interference of these two T helper subsets and points to a balance of Th1 and Th17 cells obtained by their own cytokine production and their interplay with APCs.     

The C9ORF72 expansion mutation is a common cause of ALS+/?FTD in Europe and has a single founder

A massive hexanucleotide repeat expansion mutation (HREM) in C9ORF72 has recently been linked to amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD). Here we describe the frequency, origin and stability of this mutation in ALS+/−FTD from five European cohorts (total n=1347). Single-nucleotide polymorphisms defining the risk haplotype in linked kindreds were genotyped in cases (n=434) and controls (n=856). Haplotypes were analysed using PLINK and aged using DMLE+. In a London clinic cohort, the HREM was the most common mutation in familial ALS+/−FTD: C9ORF72 29/112 (26%), SOD1 27/112 (24%), TARDBP 1/112 (1%) and FUS 4/112 (4%) and detected in 13/216 (6%) of unselected sporadic ALS cases but was rare in controls (3/856, 0.3%). HREM prevalence was high for familial ALS+/−FTD throughout Europe: Belgium 19/22 (86%), Sweden 30/41 (73%), the Netherlands 10/27 (37%) and Italy 4/20 (20%). The HREM did not affect the age at onset or survival of ALS patients. Haplotype analysis identified a common founder in all 137 HREM carriers that arose around 6300 years ago. The haplotype from which the HREM arose is intrinsically unstable with an increased number of repeats (average 8, compared with 2 for controls, P<10⁻⁸). We conclude that the HREM has a single founder and is the most common mutation in familial and sporadic ALS in Europe.     

Interplay between the effects of a Protein Kinase C phosphomimic (T204E) and a dilated cardiomyopathy mutation (K211Δ or R206W) in rat cardiac troponin T blunts the magnitude of muscle length-mediated crossbridge recruitment against the β-myosin heavy chain background

Failing hearts of dilated cardiomyopathy (DCM)-patients reveal systolic dysfunction and upregulation of several Protein Kinase C (PKC) isoforms. Recently, we demonstrated that the functional effects of T204E, a PKC phosphomimic of cardiac troponin T (TnT), were differently modulated by α- and β-myosin heavy chain (MHC) isoforms. Therefore, we hypothesized that the interplay between the effects of T204E and a DCM-linked mutation (K211Δ or R206W) in TnT would modulate contractile parameters linked-to systolic function in an MHC-dependent manner. To test our hypothesis, five TnT variants (wildtype, K211Δ, K211Δ + T204E, R206W, and R206W + T204E) were generated and individually reconstituted into demembranated cardiac muscle fibers from normal (α-MHC) and propylthiouracil-treated (β-MHC) rats. Steady-state and mechano-dynamic measurements were performed on reconstituted fibers. Myofilament Ca²⁺ sensitivity (pCa₅₀) was decreased by both K211Δ and R206W to a greater extent in α-MHC fibers (~0.15 pCa units) than in β-MHC fibers (~0.06 pCa units). However, T204E exacerbated the attenuating influence of both mutants on pCa₅₀ only in β-MHC fibers. Moreover, the magnitude of muscle length (ML)-mediated crossbridge (XB) recruitment was decreased by K211Δ + T204E (~47 %), R206W (~34 %), and R206W + T204E (~36 %) only in β-MHC fibers. In relevance to human hearts, which predominantly express β-MHC, our data suggest that the interplay between the effects of DCM mutations, PKC phosphomimic in TnT, and β-MHC lead to systolic dysfunction by attenuating pCa₅₀ and the magnitude of ML-mediated XB recruitment.     

Blockade of Tim-3 Pathway Ameliorates Interferon-γ Production from Hepatic CD8^＋ T Cells in a Mouse Model of Hepatitis B Virus Infection

T cell immunoglobulin- and mucin-domain-containing molecule-3 （Tim-3） has been reported to participate in the pathogenesis of inflammatory diseases. However, whether Tim-3 is involved in hepatitis B virus （HBV） infection remains unknown. Here, we studied the expression and function of Tim-3 in a hydrodynamics-based mouse model of HBV infection. A significant increase of Tim-3 expression on hepatic T lymphocytes, especially on CD8^＋ T cells, was demonstrated in HBV model mice from day 7 to day 18. After Tim-3 knockdown by specific shRNAs, significantly increased IFN-γ production from hepatic CD8^＋ T cells in HBV model mice was observed. Very interestingly, we found Tim-3 expression on CD8^＋ T cells was higher in HBV model mice with higher serum anti-HBs production. Moreover, Tim-3 knockdown influenced anti-HBs production in vivo. Collectively, our data suggested that Tim-3 might act as a potent regulator of antiviral T-cell responses in HBV infection. Cellular ＆ Molecular Immunology.     

Polymorphisms in the human CYP1A1 gene as susceptibility factors for lung cancer: exon-7 mutation (4889 A to G), and a T to C mutation in the 3′-flanking region

Genetic differences in the metabolism of carcinogens may codetermine individual predisposition to cancer. Cytochrome P-4501A1 (CYP1A1) metabolically activates precarcinogens in cigarette smoke, such as benzo(a)pyrene, which is also an inducer of CYP1A1. Two point mutations have been reported, m1 in the 3-flanking region (6235T to C), and m2 within exon 7 (4889A to G), the latter leading to an isoleucine to valine exchange. In the Japanese population ml and m2 are correlated with lung cancer, suggesting an increased susceptibility to cigarette smoking related lung cancer. We studied 142 lung cancer and 171 reference patients in an ethnically homogeneous German group for m1 and m2 mutations by restriction fragment length polymorphism and allele-specific polymerase chain reaction, respectively. No statistically significant difference was found in the distribution of m1 alleles between lung cancer and controls; the frequency was 8.5% and 7.3% of the alleles, respectively (odds ratio = 1.17). A trend to an overrepresentation of ml alleles was observed among 52 squamous cell carcinoma patients (odds ratio = 1.65). In contrast, the frequency of m2 alleles in lung cancer patients was twofold higher (6.7%) than in the reference group (3.2%; odds ratio = 2.16; 95% confidence limits 0.96–5.11, P = 0.033); the odds ratio of m2 alleles in squamous cell carcinoma was 2.51 (95% confidence limits 0.85–7.05, P = 0.05). There was a close genetic linkage of m2 to m1 (10 of 11 reference patients), but a significantly higher number of cancer patients showed no linkage compared to the controls (odds ratio = 8.89, 95% confidence limits 0.83–433, P = 0.04). Thus no association was found between presence of ml alleles and lung cancer, but, in contrast, m2 alleles proved as a hereditary risk factor, especially if not linked with m1 alleles.Abbreviations Ah aryl hydrocarbon - CYP1A1 cytochrome P4501A1 - CYP1A1 CYP1A1 gene - PCR polymerase chain reaction - PY pack years - RFLP restriction fragment length polymorphism Correspondence to: N. Drakoulis     

A common beta ig-h3 gene mutation (delta f540) in a large cohort of Sardinian Reis Bücklers corneal dystrophy patients. Mutations in brief no. 180. Online

Reis-Bücklers' corneal dystrophy (RBCD) is a relatively rare autosomal dominant disease originating in the Bowman's membrane, which causes severe visual impairment. Recently RBCD, together with lattice corneal dystrophy type I (LCDI), granular corneal dystrophy (CDGG1) and Avellino stromal dystrophy (ASD), all mapped on 5q31, were found to be associated to four different mutations in the beta ig-h3 gene which codify for kerato-epithelin. We identified several cases of RBCD in Sardinia. We reconstructed through genealogical search two eight generation-families, originating from the same village (Arbus), indicating a common ancestor for RBCD in Sardinia. Linkage studies on these families confirmed the association of the disease with the 5q31 region. Sequence analysis of beta ig-h3 gene revealed a trinucleotide deletion in exon 12, corresponding to the loss of F540 in the protein sequence (delta F540). Our data describe a new mutation in the beta ig-h3 gene causing RBCD. This dominant negative mutation is located in the fourth internal repeat of kerato-epithelin which is a protein domain highly conserved across species. This suggests the basic role of this domain in maintaining the proper kerato-epithelin structure which when altered can cause the typical precipitates in the RBCD cornea.