CARD14 alterations in Tunisian patients with psoriasis and further characterization in European cohorts.

BACKGROUND: Rare highly penetrant gain-of-function mutations in caspase recruitment domain family, member 14 (CARD14) can lead to psoriasis, a chronic inflammatory disease of the skin and other organs. OBJECTIVES: To investigate the contribution of rare CARD14 variants to psoriasis in the Tunisian population and to expand knowledge of CARD14 variants in the European population. METHODS: CARD14 coding exons were resequenced in patients with psoriasis and controls from Tunisia and Europe, including 16 European cases with generalized pustular psoriasis (GPP). Novel variants were evaluated for their effect on nuclear factor (NF)-κB signalling. RESULTS: Rare variants in CARD14 were significantly enriched in Tunisian cases compared with controls. Three were collectively found in 5% of Tunisian cases, and all affected the N-terminal region of the protein harbouring its caspase recruitment domain or coiled-coil domain. These variants were c.349G>A (p.Gly117Ser), c.205C>T (p.Arg69Trp) and c.589G>A (p.Glu197Lys). c.589G>A (p.Glu197Lys) led to upregulation of NF-κB activity in a similar manner to that of previously described psoriasis-associated mutations. p.Arg69Trp led to sevenfold downregulation of NF-κB activity. One Tunisian case harboured a c.1356+5G>A splice alteration that is predicted to lead to loss of exon 9, which encodes part of the coiled-coil domain. No cases of GPP harboured an interleukin-36RN mutation, but one of 16 cases of GPP with a family history of psoriasis vulgaris harboured a c.1805C>T (p.Ser602Leu) mutation in CARD14. CONCLUSIONS: These observations provide further insights into the genetic basis of psoriasis in the Tunisian population and provide functional information on novel CARD14 variants seen in cases from Tunisia and other populations.

Meta-analysis of the TNFAIP3 region in psoriasis reveals a risk haplotype that is distinct from other autoimmune diseases.

Tumor necrosis factor alpha-inducible protein 3 (TNFAIP3) encodes a ubiquitin-modifying protein, A20, that is a critical regulator of inflammatory responses. TNFAIP3 polymorphisms are associated with the susceptibility to multiple autoimmune diseases (AIDs) including psoriasis, systemic lupus erythematosus, rheumatoid arthritis, systemic sclerosis and celiac disease. In order to refine the TNFAIP3 association signal in psoriasis and identify candidate causal variants, we performed imputation and meta-analysis of the TNFAIP3 region in five European ancestry cohorts totaling 4704 psoriasis cases and 7805 controls. We identified 49 variants whose significance exceeded a corrected Bonferroni threshold, with the top variant being rs582757 (P = 6.07 × 10(-12), odds ratio (OR) = 1.23). Conditional analysis revealed a suggestive independent association at rs6918329 (P(cond) = 7.22 × 10(-5), OR = 1.15). Functional annotation of the top variants identified several with a strong evidence of regulatory potential and several within long noncoding RNAs. Analysis of TNFAIP3 haplotypes revealed that the psoriasis risk haplotype is distinct from other AIDs. Overall, our findings identify novel candidate causal variants of TNFAIP3 in psoriasis and highlight the complex genetic architecture of this locus in autoimmune susceptibility.

Combined PKC and MEK inhibition for treating metastatic uveal melanoma.

Uveal melanoma (UM) is the most common primary intraocular malignancy and the second most common form of melanoma. UM has a strong tendency for metastatic disease, and no effective treatments have yet been identified. Activating oncogenic mutations are commonly found in GNAQ and GNA11 in UM, and inhibiting key downstream effectors of the GNAQ/11 signaling pathway represents a rational therapeutic approach for treating metastatic UM. Chen et al., doi:10.1038/onc.2013.418, now confirm activation of the MAPK and PKC pathways as a result of GNAQ and GNA11 activating mutations in melanocytes, and they demonstrate that MAPK activation occurs downstream of PKC activation. PKC inhibitors disrupt MAPK signaling and block proliferation of GNAQ/11 mutant UM cell lines and slow the in vivo growth of xenografted UM tumors without inducing their shrinkage. However, a combination of PKC and MEK inhibition led to sustained MAPK pathway inhibition and tumor regression in vivo. Hence, the authors concluded that MEK and PKC inhibition is synergistic, with superior efficacy to treatment of GNAQ/GNA11 mutant UMs with either drug alone.

Genome-wide linkage scan for psoriasis susceptibility loci in multiplex Tunisian families.

BACKGROUND: Psoriasis is a relapsing chronic inflammatory skin disease affecting all population groups, with a peak prevalence of 3% in northern European and Scandinavian caucasians. Epidemiological studies have implicated a genetic component to psoriasis. In the past 12 years multiple genome-wide linkage analyses have identified putative susceptibility loci on several chromosomes, with a major locus in the major histocompatibility complex region. OBJECTIVES: To investigate the genetic basis of familial psoriasis in the Tunisian population using a genome-wide linkage scan in seven ultiplex psoriatic families from Tunisia. METHODS: Following single nucleotide polymorphism (SNP) genotyping on the Affymetrix 10K SNP array, we performed nonparametric linkage (NPL) multipoint analyses to identify genotypes and obtain evidence for linkage with psoriasis across the genome. RESULTS: No chromosomal region gave consistent evidence for linkage, providing evidence for genetic heterogeneity in Tunisian psoriasis families. Significant evidence for linkage of psoriasis to chromosome 2p12 was seen in one family. We also identified several regions of tentative psoriasis linkage on chromosomes 2q, 4q, 6p, 11q, 12q, 9q and 13q. One family exhibiting suggestive evidence for linkage to 17q25 (PSORS2) was identified and all affected members harboured a p.Gly117Ser mutation in CARD14 (caspase recruitment domain family, member 14), recently reported to lead to psoriasis in a large family from the U.S.A. CONCLUSIONS: Our results support the genetic heterogeneity of psoriasis in the Tunisian population, provide confirmatory evidence for a novel psoriasis locus at chromosome 2p12 and reveal a psoriasis family with a mutation at PSORS2.

Psoriasis: genetic associations and immune system changes.

Psoriasis is a common inflammatory skin disease characterized by infiltration of inflammatory cells into the epidermis and altered keratinocyte differentiation. Psoriasis is currently thought of as a T-cell mediated 'Type-1' autoimmune disease. Gene expression changes in psoriasis lesions have been well documented, and strongly support an important role for tumor necrosis factor and interferon gamma signal pathways in its pathogenesis. The strongest genetic determinant of psoriasis identified to date lies within the class I region of the multiple histocompatibility locus antigen cluster, although its low penetrance implicates a requirement for other genetic risk factors. Multiple genome-wide linkage and an increasing number of association studies have been carried out, leading to multiple linkage peaks, and the identification of potential low risk variants. A number of these variants lie within genes encoding components of the immune system. However, the functional relationships between predisposing genetic variation is unclear, and presumably involves genetic susceptibility factors affecting both immune cell activation and keratinocyte differentiation. The interaction of environmental trigger factors with genetic effects is also not understood, but provide further evidence for the complex basis of this disease.

Psoriasis pathophysiology: current concepts of pathogenesis.

Psoriasis vulgaris is a common skin disorder characterised by focal formation of inflamed, raised plaques that constantly shed scales derived from excessive growth of skin epithelial cells. The disease is defined by a series of linked cellular changes in the skin: hyperplasia of epidermal keratinocytes, vascular hyperplasia and ectasia, and infiltration of T lymphocytes, neutrophils, and other types of leucocyte in affected skin. In a relatively short period, psoriasis vulgaris has been conceptualised as a T lymphocyte mediated autoimmune disease and new biological therapies that target T cells have just entered routine clinical practice. Similarly, rapid progress has been made towards dissecting cellular and molecular pathways of inflammation that contribute to disease pathogenesis. This short review presents current pathogenic concepts that have emerged from genetic, genomic, and cellular information obtained in basic studies and from clinical studies of selective immune targeting drugs.

Inactivation of human SRBC, located within the 11p15.5-p15.4 tumor suppressor region, in breast and lung cancers.

A cDNA clone encoding human SRBC [serum deprivation response factor (sdr)-related gene product that binds to c-kinase] was isolated in a yeast two-hybrid screening, with amino acids 1-304 of BRCA1 as the probe. The human SRBC gene (hSRBC) was mapped to chromosome region 11p15.5-p15.4, close to marker D11S1323, at which frequent loss of heterozygosity (LOH) has been observed in sporadic breast, lung, ovarian, and other types of adult cancers as well as childhood tumors. hSRBC-coding region mutations including frame shift and truncation mutations were detected in a few ovarian and lung cancer cell lines. More significantly, the expression of hSRBC protein was down-regulated in a large fraction [30 (70%) of 43] of breast, lung, and ovarian cancer cell lines, whereas strong expression of hSRBC protein was detected in normal mammary and lung epithelial cells. The down-regulation of hSRBC expression in cancer cells was associated with hypermethylation of CpG dinucleotides in its promoter region, and 3 (60%) of 5 primary breast tumors and 11 (79%) of 14 primary lung tumors were also found to be hypermethylated. Treatment of breast cancer MCF7 cells with 5'azacytidine and Trichostatin A resulted in expression of hSRBC, confirming DNA methylation as the mode of inactivation. Our results suggest that epigenetic or mutational inactivation of hSRBC may contribute to the pathogenesis of several types of human cancers, marking hSRBC as a candidate tumor suppressor gene.

Insights into psoriasis and other inflammatory diseases from large-scale gene expression studies.

Approximately 2% of the Caucasian population is affected by psoriasis (PS); a chronic inflammatory skin disease triggered by both genetic and environmental risk factors. In addition to a major contribution from the HLA class I region, PS susceptibility loci have been mapped to a number of regions including 1q21, 3q21, 4qter, 14q31-q32, 17q24-q25, 19p13.3 and 20p. Some of these overlap with loci implicated in other autoimmune/inflammatory diseases. Global gene expression studies are beginning to provide insights into the etiology of these and other complex diseases. We used Affymetrix oligonucleotide arrays comprising approximately 12 000 known genes to initiate a more comprehensive analysis of the transcriptional changes that occur in involved and uninvolved skin of 15 psoriatic patients versus six normal controls. Expression levels of the transcripts detected on the arrays were first used to determine the relationship of samples to each other using hierarchical clustering. This analysis clearly differentiated involved psoriatic skin from uninvolved and normal skin. Clusters of differentially expressed genes with similar expression patterns in the same samples were then identified. Six out of 32 clusters contained a total of 177 transcripts that were differentially expressed in involved psoriatic skin versus normal skin. These differences were independent of the gender, age, skin site and HLA class I status of the patient. Ten of the 177 genes were also differentially expressed in uninvolved skin, and several mapped to regions previously shown to harbor psoriasis susceptibility loci.

Phenotypic heterogeneity in patients with familial partial lipodystrophy (dunnigan variety) related to the site of missense mutations in lamin a/c gene.

The lamin A/C (LMNA) gene has recently been reported to be mutated in familial partial lipodystrophy, Dunnigan variety (FPLD). We found mutations within exon 8 of LMNA (R482Q, R482W, and G465D) in 12 families with typical FPLD and in exon 11 (R582H) in 1 atypical family. To investigate phenotypic heterogeneity, we compared body fat distribution, using anthropometry and whole body magnetic resonance imaging, and metabolic parameters in women with atypical and typical FPLD. Compared with women with typical FPLD, the two sisters with atypical FPLD had less severe loss of sc fat from all the extremities and trunk and particularly from the gluteal region and medial parts of proximal thighs. Both types had similar excess of fat deposition in the neck, face, intraabdominal, and intermuscular regions. Women with atypical FPLD tended to have lower serum triglyceride and higher high density lipoprotein cholesterol concentrations. As exon 11 of LMNA does not comprise part of the lamin C-coding region, the R582H mutation affects only lamin A protein. Therefore, a unique phenotype of atypical FPLD may result from disrupted interaction of lamin A with other proteins and chromatin compared with typical FPLD, in which interaction of both lamins A and C may be disrupted.

JM2, encoding a fork head-related protein, is mutated in X-linked autoimmunity-allergic disregulation syndrome.

X-linked autoimmunity-allergic disregulation syndrome (XLAAD) is an X-linked recessive immunological disorder characterized by multisystem autoimmunity, particularly early-onset type 1 diabetes mellitus, associated with manifestations of severe atopy including eczema, food allergy, and eosinophilic inflammation. Consistent with the allergic phenotype, analysis of two kindreds with XLAAD revealed marked skewing of patient T lymphocytes toward the Th2 phenotype. Using a positional-candidate approach, we have identified in both kindreds mutations in JM2, a gene on Xp11.23 that encodes a fork head domain-containing protein. One point mutation at a splice junction site results in transcripts that encode a truncated protein lacking the fork head homology domain. The other mutation involves an in-frame, 3-bp deletion that is predicted to impair the function of a leucine zipper dimerization domain. Our results point to a critical role for JM2 in self tolerance and Th cell differentiation.

Localization of a gene for familial recurrent arthritis.

OBJECTIVE: To localize the gene for familial recurrent arthritis via a genome-wide linkage scan in an extended kindred with the disease. METHODS: A 3-generation family in which 9 members were diagnosed with juvenile idiopathic arthritis (JIA) was ascertained. In this family the disease was of very early onset and included episodic inflammation leading to eventual destruction of joints, muscle, and skin. We treated this disorder as a distinct clinical entity that we have named "familial recurrent arthritis." A genome-wide linkage scan with polymorphic microsatellites at 10-15-cM resolution was initiated. RESULTS: The genome-wide scan generated a maximum 2-point logarithm of odds score with D15S211 (Zmax = 3.27 at thetamax = 0.0010). Haplotype reconstruction defined a candidate region of approximately 20 cM flanked proximally by D15S983 and distally by D15S127 on human chromosome 15. CONCLUSION: A gene for familial recurrent arthritis was localized to 15q22-24, as a result of a genome-wide linkage scan in a large, multiply affected kindred. Identification of the altered gene will provide insights into the pathogenesis of autoimmune joint destruction that is reminiscent of JIA.

Localization of susceptibility to familial idiopathic scoliosis.

STUDY DESIGN: Genome-wide linkage surveys in large multiplex families with apparent inherited idiopathic scoliosis. OBJECTIVE: To identify chromosomal loci encoding genes involved in susceptibility to idiopathic scoliosis by positional cloning. SUMMARY OF BACKGROUND DATA: Although the inheritance of idiopathic scoliosis most often exhibits a complex pattern, autosomal dominant inheritance can be identified in some families. Families exhibiting such an inheritance pattern present an opportunity to identify the predisposing gene(s) by positional cloning. METHODS: Probands having clinically relevant idiopathic scoliosis (50 degrees Cobb angle) from large multiplex families were identified. A curve of 15 degrees, made from standing posteroanterior radiographs, was required for a positive diagnosis. A genome-wide search in one large family (seven affected members) was conducted with 385 polymorphic microsatellite markers spaced at an approximate 10-cM resolution. Hot spots identified in this family were subsequently tested in a second large kindred. RESULTS: Maximum evidence of allele-sharing in affected individuals from the first family was detected for three loci on chromosomes 6p, distal 10q, and 18q with nonparametric lod scores of 1.42 (P = 0.020), 1.60 (P = 0.019), and 8.26 (P = 0.002), respectively. Evidence of allele-sharing was also detected in the second family at distal chromosome 10q (nonparametric lod score = 2.02; P = 0.033). CONCLUSIONS: These data indicate a limited number of genetic loci predisposing to idiopathic scoliosis.

Paroxysmal kinesigenic dyskinesia and infantile convulsions: clinical and linkage studies.

OBJECTIVE: To clinically characterize affected individuals in families with paroxysmal kinesigenic dyskinesia (PKD), examine the association with infantile convulsions, and confirm linkage to a pericentromeric chromosome 16 locus. BACKGROUND: PKD is characterized by frequent, recurrent attacks of involuntary movement or posturing in response to sudden movement, stress, or excitement. Recently, an autosomal dominant PKD locus on chromosome 16 was identified. METHODS: The authors studied 11 previously unreported families of diverse ethnic background with PKD with or without infantile convulsions and performed linkage analysis with markers spanning the chromosome 16 locus. Detailed clinical questionnaires and interviews were conducted with affected and unaffected family members. RESULTS: Clinical characterization and sampling of 95 individuals in 11 families revealed 44 individuals with paroxysmal dyskinesia, infantile convulsions, or both. Infantile convulsions were surprisingly common, occurring in 9 of 11 families. In only two individuals did generalized seizures occur in later childhood or adulthood. The authors defined a 26-cM region using linkage data in 11 families (maximum lod score 6.63 at theta = 0). Affected individuals in one family showed no evidence for a shared haplotype in this region, implying locus heterogeneity. CONCLUSIONS: Identification and characterization of the PKD/infantile convulsions gene will provide new insight into the pathophysiology of this disorder, which spans the phenotypic spectrum between epilepsy and movement disorder.

Human population expansion and microsatellite variation.

Polymorphisms at di-, tri-, and tetranucleotide microsatellite loci have been analyzed in 14 worldwide populations. A statistical index of population expansion, denoted S(k), is introduced to detect historical changes in population size using the variation at the microsatellites. The index takes the value 0 at equilibrium with constant population size and is positive or negative according to whether the population is expanding or contracting, respectively. The use of S(k) requires estimation of properties of the mutation distribution for which we use both family data of Dib et al. for dinucleotide loci and our population data on tri- and tetranucleotide loci. Statistical estimates of the expansion index, as well as their confidence intervals from bootstrap resampling, are provided. In addition, a dynamical analysis of S(k) is presented under various assumptions on population growth or decline. The studied populations are classified as having high, intermediate, or low values of S(k) and genetic variation, and we use these to interpret the data in terms of possible population dynamics. Observed values of S(k) for samples of di-, tri-, and tetranucleotide data are compatible with population expansion earlier than 60,000 years ago in Africa, Asia, and Europe if the initial population size before the expansion was on the order of 500. Larger initial population sizes force the lower bound for the time since expansion to be much earlier. We find it unlikely that bottlenecks occurred in Central African, East Asian, or European populations, and the estimated expansion times are rather similar for all of these populations. This analysis presented here suggests that modern human populations departed from Africa long before they began to expand in size. Subsequently, the major groups (the African, East Asian, and European groups) started to grow at approximately same time. Populations of South America and Oceania show almost no growth. The Mbuti population from Zaire appears to have experienced a bottleneck during its expansion.

Mutational and haplotype analyses of families with familial partial lipodystrophy (Dunnigan variety) reveal recurrent missense mutations in the globular C-terminal domain of lamin A/C.

Familial partial lipodystrophy (FPLD), Dunnigan variety, is an autosomal dominant disorder characterized by marked loss of subcutaneous adipose tissue from the extremities and trunk but by excess fat deposition in the head and neck. The disease is frequently associated with profound insulin resistance, dyslipidemia, and diabetes. We have localized a gene for FPLD to chromosome 1q21-q23, and it has recently been proposed that nuclear lamin A/C is altered in FPLD, on the basis of a novel missense mutation (R482Q) in five Canadian probands. This gene had previously been shown to be altered in autosomal dominant Emery-Dreifuss muscular dystrophy (EDMD-AD) and in dilated cardiomyopathy and conduction-system disease. We examined 15 families with FPLD for mutations in lamin A/C. Five families harbored the R482Q alteration that segregated with the disease phenotype. Seven families harbored an R482W alteration, and one family harbored a G465D alteration. All these mutations lie within exon 8 of the lamin A/C gene-an exon that has also been shown to harbor different missense mutations that are responsible for EDMD-AD. Mutations could not be detected in lamin A/C in one FPLD family in which there was linkage to chromosome 1q21-q23. One family with atypical FPLD harbored an R582H alteration in exon 11 of lamin A. This exon does not comprise part of the lamin C coding region. All mutations in FPLD affect the globular C-terminal domain of the lamin A/C protein. In contrast, mutations responsible for dilated cardiomyopathy and conduction-system disease are observed in the rod domain of the protein. The FPLD mutations R482Q and R482W occurred on different haplotypes, indicating that they are likely to have arisen more than once.

A locus for paroxysmal kinesigenic dyskinesia maps to human chromosome 16.

OBJECTIVE: To use genetic linkage analysis to localize a gene for paroxysmal kinesigenic dyskinesia (PKD) in a three generation African-American kindred. BACKGROUND: PKD is a rare autosomal dominant disorder characterized by episodic choreiform or dystonic movements that are brought on or exacerbated by voluntary movement. There are individuals with the clinical features of PKD but with no family history of the disease, but whether these sporadic cases represent spontaneous mutations of PKD or have a distinct condition is unknown. METHODS: A genome-wide linkage scan of polymorphic microsatellites at 25 cM resolution was performed to localize a gene for PKD in one African-American kindred. Pairwise multipoint linkage analyses were performed at different penetrance estimates. RESULTS: Evidence for linkage of the kinesigenic form of paroxysmal dyskinesia to chromosome 16 was obtained. A maximum lod score of 4.40 at theta = 0 was obtained with D16S419. Critical recombinants place the PKD gene between D16S3100 and D16S771. CONCLUSIONS: A paroxysmal kinesigenic dyskinesia (PKD) locus lies within an 18 cM interval on 16p11.2-q11.2, between D16S3100 and D16S771. A gene for infantile convulsions with paroxysmal choreoathetosis has also been mapped to this region. These two regions overlap by approximately 6 cM. These two diseases could be caused by different mutations in the same gene or two distinct genes may lie within this region.