Gene polymorphism in Netherton and common atopic disease

African Americans with asthma: genetic insights

It has been well established that genetic factors strongly affect susceptibility to asthma and its associated traits. It is less clear to what extent genetic variation contributes to the ethnic disparities observed for asthma morbidity and mortality. Individuals of African descent with asthma have more severe asthma, higher IgE levels, a higher degree of steroid dependency, and more severe clinical symptoms than individuals of European descent with asthma but relatively few studies have focused on this particularly vulnerable ethnic group. Similar underrepresentation exists for other minorities, including Hispanics. In this review, a summary of linkage and association studies in populations of African descent is presented, and the role of linkage disequilibrium in the dissection of a complex trait such as asthma is discussed. Consideration for the impact of population stratification in recently admixed populations (i.e., European, African) is essential in genetic association studies focusing on African ancestry groups. With the most recent update on the International HapMap Project, efficient selection of haplotype tagging single nucleotide polymorphisms (htSNPs) for African Americans has accelerated and efficiency of htSNPs chosen from one population to represent other continental groups (e.g., African) has been demonstrated. Cutting-edge approaches, such as genomewide association studies, admixture mapping, and phylogenetic analyses, offer new opportunities for dissecting the genetic basis for asthma in populations of African descent.

Fleshing out filaggrin phenotypes

The association of filaggrin null alleles with eczema has been replicated in several European populations. Three large, well-conducted studies confirm this association and offer insights into the phenotypic nature of eczema associated with these alleles. Early data suggest that FLG-associated eczema may be more persistent, more likely to have palmar hyperlinearity, and more likely to be associated with asthma. These initial hints will require further confirmation in cohort studies.

Filaggrin mutations in children with severe atopic dermatitis

Atopic dermatitis (AD) results from strong genetic and environmental interactions. AD shows genetic linkage to Chromosome 1q21. This region contains the epidermal differentiation complex (EDC), which consists of genes that form essential components of epidermal surfaces. Filaggrin (FLG) is one of these. Mutations in FLG/(R501X and 2282del4) are reported to be strongly associated with AD and to influence asthma accompanying AD. We investigated these effects in families recruited through a child with severe AD. We genotyped two panels of families, totalling 426, containing 990 affected and unaffected children. We found significant associations with AD (P=0.0001), asthma (P=0.006), and atopy (P=0.002). The FLG mutations were present in 26.7% of patients with AD, but were also present in 14.4% of children without AD. They were weakly associated with disease severity. The variants were not independently associated with asthma. The overall LOD score for genetic linkage of markers to the region was 3.57. This fell to 2.03 after accounting for the FLG mutations, indicating the presence of other genetic variants influencing AD at this locus. Our results provide further confirmation of the importance of mutations in FLG and the skin barrier in AD pathogenesis. The results indicate that investigations of other genes within the EDC should be undertaken.

Serine proteases, their inhibitors and allergy

This paper reviews four serine protease inhibitors and three protease gene defects that are associated with allergic conditions, suggesting an important role for these genes and their products in the development of allergy. Serine protease inhibitors may have a therapeutic potential in the treatment of allergy.

Advances in understanding the genetic basis of inherited single gene skin barrier disorders: new clues to key genes that may be involved in the pathogenesis of atopic dermatitis

Increasing knowledge of genomic DNA sequences and genetic databases has led to the characterization of the molecular basis of several inherited skin disorders. In this review we summarize some of the major recent discoveries that have been made in defining the pathogenic mutations that cause inherited disorders of the skin barrier leading to skin scaling or increased transepidermal water loss in either rare disorders (Netherton’s syndrome or harlequin ichthyosis) or more common genodermatoses (ichthyosis vulgaris). These molecular breakthroughs have led to more accurate diagnoses, better genetic counselling and, where appropriate, the feasibility of DNA-based prenatal diagnosis, as well as the possibility of developing newer forms of treatment, including gene or protein therapy. Identifying the molecular basis of these conditions, especially ichthyosis vulgaris, has also provided dramatic new insight into the genetic abnormalities in the common disorder, atopic dermatitis. Thus research on the relatively rare single gene inherited skin disorders not only has benefits for patients and their families with these uncommon conditions but also has the potential to yield fresh and significant new information about very common skin diseases.

Quantitative linkage genome scan for atopy in a large collection of Caucasian families

Quantitative phenotypes correlated with a complex disorder offer increased power to detect linkage in comparison to affected-unaffected classifications. Asthma is a complex disorder characterized by periods of bronchial obstruction and increased bronchial hyper reactivity. In childhood and early adulthood, asthma is frequently associated also with quantitative measures of atopy. Genome wide quantitative multipoint linkage analysis was conducted for serum IgE levels and percentage of positive skin prick test (SPT(per)) using three large groups of families originally ascertained for asthma. In this report, 438 and 429 asthma families were informative for linkage using IgE and SPT(per) which represents 690 independent families. Suggestive linkage (LOD > or = 2) was found on chromosomes 1, 3, and 8q with maximum LODs of 2.34 (IgE), 2.03 (SPT(per)), and 2.25 (IgE) near markers D1S1653, D3S2322-D3S1764, and D8S2324, respectively. The results from chromosomes 1 and 3 replicate previous reports of linkage. We also replicate linkage to 5q with peak LODs of 1.96 (SPT(per)) and 1.77 (IgE) at or near marker D5S1480. Our results provide further evidence implicating chromosomes 1, 3, and 5q. The current report represents one of the biggest genome scans so far reported for asthma related phenotypes. This study also demonstrates the utility of increased sample sizes and quantitative phenotypes in linkage analysis of complex disorders.

Pharmacogenomics of beta2-agonist: key focus on signaling pathways

Asthma is one of the most common respiratory diseases, where inhalation and exhalation are obstructed due to narrowing of the airways by broncho-constriction or by inflammation. Among all the available anti-asthma therapies, beta2-agonists are the most effective bronchodilators available, and give rapid relief of asthma symptoms. Evidence suggests that the degree of beta2-agonist response varies greatly between patients and genetic factors have a major role in it. Despite several studies on the beta2-agonist pharmacogenetics, significant gaps in knowledge still remain and need to be resolved before the pharmacotyping of beta2-agonist responsiveness comes to clinical practice. As we know, beta2-agonists show their influence by targeting beta2-adrenergic receptors, leading to the activation of beta2-adrenergic receptors and its downstream cascade. Signaling through beta2-adrenergic receptors mediates numerous airway functions by regulating broncho-constriction and dilation pathways. Therefore, it is an important prerequisite to understand these pathways, which will assist in defining the variability in therapeutic responses for beta2-agonists. Owing to the complexity of the action of a beta2-agonist and its therapeutic response, a broader genomics approach will help in optimizing therapy for the individual patient. This might be achieved by considering and focusing on receptor/s at which the drug binds directly, signal transduction cascades or downstream proteins and proteins involved in the relaxation and constriction of the airway smooth muscle. Considering that a drug response may involve a large number of proteins, it seems unlikely that a single polymorphism or haplotype in a single gene would explain a high degree of drug response variability in a consistent fashion. Thus, it shows that a polygenic approach will be more appropriate. In order to follow this, the mode of action of the beta2-agonist and its downstream signaling cascade should essentially be assessed to resolve the beta2-agonist enigma.

Netherton syndrome: report of identical twins presenting with severe atopic dermatitis

We report the cases of 4-year-old identical twin sisters who presented with severe atopic dermatitis with intractable skin manifestations and multiple food allergies. Netherton syndrome (NS) (OMIM 256500) was suspected due to very high serum IgE levels, growth retardation, severe food allergies and typical hair finding (trichorrhexis invaginata). A definite diagnosis was made by genetic analysis. Our cases are unique in being the first identical twins with NS diagnosed by a novel mutation in the SPINK5 gene. NS should be considered in differential diagnosis in children who have generalized erythema with intractable eczematous lesions and elevated levels of IgE.

Epidermal barrier formation and recovery in skin disorders

Skin is at the interface between the complex physiology of the body and the external, often hostile, environment, and the semipermeable epidermal barrier prevents both the escape of moisture and the entry of infectious or toxic substances. Newborns with rare congenital barrier defects underscore the skin's essential role in a terrestrial environment and demonstrate the compensatory responses evoked ex utero to reestablish a barrier. Common inflammatory skin disorders such as atopic dermatitis and psoriasis exhibit decreased barrier function, and recent studies suggest that the complex response of epidermal cells to barrier disruption may aggravate, maintain, or even initiate such conditions. Either aiding barrier reestablishment or dampening the epidermal stress response may improve the treatment of these disorders. This Review discusses the molecular regulation of the epidermal barrier as well as causes and potential treatments for defects of barrier formation and proposes that medical management of barrier disruption may positively affect the course of common skin disorders.

Connexin 26 regulates epidermal barrier and wound remodeling and promotes psoriasiform response

Inflammatory skin disorders result in significant epidermal changes, including keratinocyte hyperproliferation, incomplete differentiation, and impaired barrier. Here we test whether, conversely, an impaired epidermal barrier can promote an inflammatory response. Mice lacking the transcription factor Kruppel-like factor 4 (Klf4) have a severe defect in epidermal barrier acquisition. Transcription profiling of Klf4(-/-) newborn skin revealed similar changes in gene expression to involved psoriatic plaques, including a significant upregulation of the gap junction protein connexin 26 (Cx26). Ectopic expression of Cx26 from the epidermis-specific involucrin (INV) promoter (INV-Cx26) demonstrated that downregulation of Cx26 is required for barrier acquisition during development. In juvenile and adult mice, persistent Cx26 expression kept wounded epidermis in a hyperproliferative state, blocked the transition to remodeling, and led to an infiltration of immune cells. Mechanistically, ectopic expression of Cx26 in keratinocytes resulted in increased ATP release, which delayed epidermal barrier recovery and promoted an inflammatory response in resident immune cells. These results provide a molecular link between barrier acquisition in utero and epidermal remodeling after wounding. More generally, these studies suggest that the most effective treatments for inflammatory skin disorders might concomitantly suppress the immune response and enhance epidermal differentiation to restore the barrier.

Proceedings of the 4th Georg Rajka International Symposium on Atopic Dermatitis, Arcachon, France, September 15-17, 2005

The 4th Georg Rajka International Symposium on Atopic Dermatitis presented a comprehensive view of our current understanding and management of atopic dermatitis (AD). These proceedings highlight contributions related to the history of AD doctrines; genetic and epigenetic background; epidemiology; maturation of the immune system; infection and innate-adaptive immunity; epidermal inflammation, including neurogenic inflammation and pruritus; animal models; skin barrier; evidence-based therapy and education programs; prognostic and severity markers; and allergy testing. Several studies in animal models and human subjects point to impaired skin barrier function as a primary defect that facilitates the effect of environmental factors and immune dysregulation found in AD. The new frontier in AD therapy should, in the near future, reflect our better understanding of the skin barrier. The influence of environmental factors on the skin and other epithelial barriers in the perinatal period needs to be better understood to implement appropriate prevention programs.

Analysis of polymorphisms in 16 genes in type 1 diabetes that have been associated with other immune-mediated diseases

BACKGROUND

The identification of the HLA class II, insulin (INS), CTLA-4 and PTPN22 genes as determinants of type 1 diabetes (T1D) susceptibility indicates that fine tuning of the immune system is centrally involved in disease development. Some genes have been shown to affect several immune-mediated diseases. Therefore, we tested the hypothesis that alleles of susceptibility genes previously associated with other immune-mediated diseases might perturb immune homeostasis, and hence also associate with predisposition to T1D.

METHODS

We resequenced and genotyped tag single nucleotide polymorphisms (SNPs) from two genes, CRP and FCER1B, and genotyped 27 disease-associated polymorphisms from thirteen gene regions, namely FCRL3, CFH, SLC9A3R1, PADI4, RUNX1, SPINK5, IL1RN, IL1RA, CARD15, IBD5-locus (including SLC22A4), LAG3, ADAM33 and NFKB1. These genes have been associated previously with susceptibility to a range of immune-mediated diseases including rheumatoid arthritis (RA), systemic lupus erythematosus (SLE), Graves' disease (GD), psoriasis, psoriatic arthritis (PA), atopy, asthma, Crohn disease and multiple sclerosis (MS). Our T1D collections are divided into three sample subsets, consisting of set 1 families (up to 754 families), set 2 families (up to 743 families), and a case-control collection (ranging from 1,500 to 4,400 cases and 1,500 to 4,600 controls). Each SNP was genotyped in one or more of these subsets. Our study typically had approximately 80% statistical power for a minor allele frequency (MAF) >5% and odds ratios (OR) of 1.5 with the type 1 error rate, alpha = 0.05.

RESULTS

We found no evidence of association with T1D at most of the loci studied 0.02

CONCLUSION

Polymorphisms in a variety of genes previously associated with immune-mediated disease susceptibility and/or having effects on gene function and the immune system, are unlikely to be affecting T1D susceptibility in a major way, even though some of the genes tested encode proteins of immune pathways that are believed to be central to the development of T1D. We cannot, however, rule out effect sizes smaller than OR 1.5.

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Key Words Collapse

MESH Headings

• ADAM Proteins/genetics
• Case-Control Studies
• Diabetes Mellitus, Type 1/genetics
• Genetic Predisposition to Disease
• Humans
• Immune System Diseases/genetics
• Polymorphism, Single Nucleotide

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Grants

• Wellcome Trust
• G0000934 Medical Research Council
• 068545/Z/02 Wellcome Trust

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Affiliation(s)

Deborah J Smyth Juvenile Diabetes Research Foundation/Wellcome Trust Diabetes and Inflammation Laboratory, Cambridge Institute for Medical Research, Wellcome Trust/MRC Building, Addenbrooke's Hospital, Hills Rd, Cambridge, CB2 2XY, UK
Joanna MM Howson Juvenile Diabetes Research Foundation/Wellcome Trust Diabetes and Inflammation Laboratory, Cambridge Institute for Medical Research, Wellcome Trust/MRC Building, Addenbrooke's Hospital, Hills Rd, Cambridge, CB2 2XY, UK
Felicity Payne Juvenile Diabetes Research Foundation/Wellcome Trust Diabetes and Inflammation Laboratory, Cambridge Institute for Medical Research, Wellcome Trust/MRC Building, Addenbrooke's Hospital, Hills Rd, Cambridge, CB2 2XY, UK
Lisa M Maier Juvenile Diabetes Research Foundation/Wellcome Trust Diabetes and Inflammation Laboratory, Cambridge Institute for Medical Research, Wellcome Trust/MRC Building, Addenbrooke's Hospital, Hills Rd, Cambridge, CB2 2XY, UK
Rebecca Bailey Juvenile Diabetes Research Foundation/Wellcome Trust Diabetes and Inflammation Laboratory, Cambridge Institute for Medical Research, Wellcome Trust/MRC Building, Addenbrooke's Hospital, Hills Rd, Cambridge, CB2 2XY, UK
Kieran Holland Juvenile Diabetes Research Foundation/Wellcome Trust Diabetes and Inflammation Laboratory, Cambridge Institute for Medical Research, Wellcome Trust/MRC Building, Addenbrooke's Hospital, Hills Rd, Cambridge, CB2 2XY, UK
Christopher E Lowe Juvenile Diabetes Research Foundation/Wellcome Trust Diabetes and Inflammation Laboratory, Cambridge Institute for Medical Research, Wellcome Trust/MRC Building, Addenbrooke's Hospital, Hills Rd, Cambridge, CB2 2XY, UK
Jason D Cooper Juvenile Diabetes Research Foundation/Wellcome Trust Diabetes and Inflammation Laboratory, Cambridge Institute for Medical Research, Wellcome Trust/MRC Building, Addenbrooke's Hospital, Hills Rd, Cambridge, CB2 2XY, UK
John S Hulme Juvenile Diabetes Research Foundation/Wellcome Trust Diabetes and Inflammation Laboratory, Cambridge Institute for Medical Research, Wellcome Trust/MRC Building, Addenbrooke's Hospital, Hills Rd, Cambridge, CB2 2XY, UK
Adrian Vella Juvenile Diabetes Research Foundation/Wellcome Trust Diabetes and Inflammation Laboratory, Cambridge Institute for Medical Research, Wellcome Trust/MRC Building, Addenbrooke's Hospital, Hills Rd, Cambridge, CB2 2XY, UK
Ingrid Dahlman Juvenile Diabetes Research Foundation/Wellcome Trust Diabetes and Inflammation Laboratory, Cambridge Institute for Medical Research, Wellcome Trust/MRC Building, Addenbrooke's Hospital, Hills Rd, Cambridge, CB2 2XY, UK
Alex C Lam Juvenile Diabetes Research Foundation/Wellcome Trust Diabetes and Inflammation Laboratory, Cambridge Institute for Medical Research, Wellcome Trust/MRC Building, Addenbrooke's Hospital, Hills Rd, Cambridge, CB2 2XY, UK
Sarah Nutland Juvenile Diabetes Research Foundation/Wellcome Trust Diabetes and Inflammation Laboratory, Cambridge Institute for Medical Research, Wellcome Trust/MRC Building, Addenbrooke's Hospital, Hills Rd, Cambridge, CB2 2XY, UK
Neil M Walker Juvenile Diabetes Research Foundation/Wellcome Trust Diabetes and Inflammation Laboratory, Cambridge Institute for Medical Research, Wellcome Trust/MRC Building, Addenbrooke's Hospital, Hills Rd, Cambridge, CB2 2XY, UK
Rebecca CJ Twells Juvenile Diabetes Research Foundation/Wellcome Trust Diabetes and Inflammation Laboratory, Cambridge Institute for Medical Research, Wellcome Trust/MRC Building, Addenbrooke's Hospital, Hills Rd, Cambridge, CB2 2XY, UK
John A Todd Juvenile Diabetes Research Foundation/Wellcome Trust Diabetes and Inflammation Laboratory, Cambridge Institute for Medical Research, Wellcome Trust/MRC Building, Addenbrooke's Hospital, Hills Rd, Cambridge, CB2 2XY, UK

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Candidate gene association studies and evidence for gene-by-gene interactions

Candidate gene studies in asthma are a powerful and valuable tool in asthma genetics. Although the quality of small-scale, freely associating studies has been questionable, increasingly serious efforts are made to establish, replicate, and verify association results. Association studies may help us to better understand the mechanisms underlying asthma. They may create hypotheses and help to direct functional studies to targets that are likely to give valuable results. However, they should not be over-interpreted; only biologic proof can verify associations between genetic variations and a certain disease outcome. The insight that gene-by-gene and gene-by-environment interactions may be crucial for understanding and pinpoint the complex mechanisms of genetic regulation of multifactorial diseases has gained momentum in the last years when technical improvement allowed for the effective genotyping and analysis of great numbers of polymorphisms in large populations. It can be expected that from this area of research new and exciting results will follow soon.

Atopic dermatitis

Atopic dermatitis (AD) is an eczematous, highly pruritic chronic inflammatory skin disease. It usually begins early in life and often occurs in people with a personal or family history of asthma and allergic rhinitis. The prevalence is high, especially in children,and it has been rising in recent decades, in parallel with asthma prevalence. Although AD is often described as an "allergic" dis-ease, allergic causation is difficult to document, and AD is increasingly viewed as a skin disease that predisposes to allergies. This interpretation, based on clinical, epidemiologic, and animal stu-dies, may greatly influence our approach to therapy and prevention of atopic diseases in the coming years.

hK5 and hK7, two serine proteinases abundant in human skin, are inhibited by LEKTI domain 6

BACKGROUND

Several skin diseases and atopic disorders including Netherton syndrome and atopic dermatitis have been associated with mutations and deviations of expression of SPINK5, the gene encoding the human 15-domain serine proteinase inhibitor LEKTI. The biochemical mechanisms underlying this phenomenon have not yet been fully clarified.

OBJECTIVES

To identify target proteinases of LEKTI important for processes of desquamation and inflammation of the skin which will enable the development of specific drugs.

METHODS

The inhibitory activities of LEKTI domains 6 and 15 were tested on a number of commercially available serine proteinases and also on the purified kallikreins hK5 and hK7. In addition, recombinant hK5 was used.

RESULTS

LEKTI domain 6 is a potent inhibitor of hK5 and hK7, whereas LEKTI domain 15 exhibits inhibitory activity on plasmin. hK5 and hK7 in particular are relevant to skin disorders.

CONCLUSIONS

The inhibition of hK5 and hK7 by LEKTI domain 6 indicates an important regulatory role of LEKTI in processes of skin desquamation and inflammation, which may explain the severe pathological symptoms associated with abnormalities of SPINK5 and/or its expression. Thus, LEKTI represents a potential drug for the treatment of these disorders.

Inhibition of human kallikreins 5 and 7 by the serine protease inhibitor lympho-epithelial Kazal-type inhibitor (LEKTI)

LEKTI is a 120-kDa protein that plays an important role in skin development, as mutations affecting LEKTI synthesis underlie Netherton syndrome, an inherited skin disorder producing severe scaling. Its primary sequence indicates that the protein consists of 15 domains, all resembling a Kazal-type serine protease inhibitor. LEKTI and two serine proteases belonging to the human tissue kallikrein (hK) family (hK5 and hK7) are expressed in the granular layer of skin. In this study, we characterize the interaction of two recombinant LEKTI fragments containing three or four intact Kazal domains (domains 6–8 and 9–12) with recombinant rhK5, a trypsin-like protease, and recombinant rhK7, a chymotrypsin-like protease. Both fragments inhibited rhK5 similarly in binding and kinetic studies performed at pH 8.0, as well as pH 5.0, the pH of the stratum corneum where both LEKTI and proteases may function. Inhibition equilibrium constants (Ki) measured either directly in concentration-dependent studies or calculated from measured association (kass) and dissociation (kdis) rate constants were 1.2–5.5 nM at pH 8.0 and 10–20 nM at pH 5.0. At pH 8.0,kassandkdisvalues were 4.7×105 M−1s−1and 5.5×10−4 s−1, and at pH 5.0 they were 4.0×104 M−1 s−1and 4.3×10−4 s−1, respectively. The lowKiandkdisvalues (t1/2of 20–25 min) indicate tight and specific association. Only fragment 6–9′ was a good inhibitor of rhK7, demonstrating aKiof 11 nM at pH 8.0 in a reaction that was rapidly reversible. These results show that LEKTI, at least in fragment form, is a potent inhibitor of rhK5 and that this protease may be a target of LEKTI in human skin.

Rethinking genetic models of asthma: the role of environmental modifiers

Asthma is a common, chronic disease with a complex etiology. To date, more than 35 genes have been associated with asthma or related phenotypes in multiple populations, but none of them has been shown to contribute to risk in all populations studied. We suggest that genetic susceptibility is both context dependent and developmentally regulated, and that ignoring the environmental context will miss many important associations and clues to pathogenesis. We define 'environment' broadly to include the in utero environment, maternal affection status and sex, and propose that epigenetic mechanisms are the link between our genes and our environment.

Le syndrome de Netherton : une ectodermatose du petit nourrisson avec retard de croissance, déficit immunitaire et rachitisme. À propos de 3 cas

We report the cases of 2 boys and 1 girl suffering from Netherton syndrome. Both boys presented with a non-bullous congenital erythroderma and were diagnosed early as Netherton syndrome with hair biopsies. Both had severe failure to thrive, signs of atopy, several episodes of bacterial infection, and rickets (with a high blood level of vitamin D in the first boy, and vitamin D deficiency in the second). In the third case, the pilar abnormality appeared at the age of 3 years. The girl had ichtyosis linearis circumflexa, failure to thrive and severe constipation. Netherton syndrome is a rare disorder characterized by severe ichtyosis, signs of atopy, immune deficiency and failure to thrive. The disease is severe and comprises many complications in early infancy. It is due to a genetic disorder of recessive autosomal transmission, and the gene, SPINK5, is located in the chromosome 5. Prenatal diagnosis is possible. Two of our patients had rickets, which has never been described in such patients population.

Rapid detection of the SPINK5 polymorphism Glu420Lys by real-time PCR technology

BACKGROUND

The SPINK5 gene, encoding the serine protease inhibitor LEKTI maps to chromosome 5q32, and has been suggested to be a locus predisposing to atopic diseases in general. The Glu420Lys variant showed significant association with atopy, asthma and atopic dermatitis in recent studies.

AIMS OF THE STUDY

Development of a high throughput assay to analyse the polymorphism G1258A (Glu420Lys) in exon 14 of the SPINK5 gene followed by the validation using samples of 235 latex-allergic health care workers (HCWs) with (N=63) and without asthma (N=172), and 80 non-atopic controls.

METHODS

Twenty DNA samples were first analysed by a polymerase chain restriction fragment analysis (RFLP) using Hph I to generate defined control DNAs which were used for the development of the assay suitable for the detection of the Glu420Lys variant by LightCycler technology.

RESULTS AND CONCLUSIONS

315 samples were successfully screened with this new assay. The temperatures in the melting analysis of the SPINK5 exon 14 PCR product were characteristic to the probes hybridised to the mutant (AA) at 51.5 degrees C and to the wild-type (GG) at 59.5 degrees C. The fast and reliable mutation detection in the tested samples makes this high-speed method suitable for larger epidemiological studies.

A Japanese infant with localized ichthyosis linearis circumflexa on the palms and soles harbouring a compound heterozygous mutation in the SPINK5 gene

We report a 6-month-old Japanese boy showing ichthyosis linearis circumflexa localized on the palms and soles. He showed bamboo hairs and aminoaciduria, and was positive for cow's milk and egg IgE antibodies by radioallergosorbent tests. Trypsin-like hydrolytic activity in the patient's lesional stratum corneum showed an activity seven times higher than that in age-matched controls. DNA analysis showed that the patient harboured the compound heterozygous mutations R790X and 1220+1 G-->C in the SPINK5 gene, compatible with the diagnosis of Netherton syndrome (NS). As the genotype/phenotype correlations in NS have not yet been fully clarified, the position of the premature termination codon in the SPINK5 gene may contribute to explain such a mild form of NS in our patient.

A functional mutation in the terminal exon of elastin in severe, early-onset chronic obstructive pulmonary disease

We describe a novel variant in the terminal exon of human elastin, c.2318 G > A, resulting in an amino acid substitution of glycine 773 to aspartate (G773D) in a pedigree with severe early-onset chronic obstructive pulmonary disease (COPD). Transfection studies with elastin cDNAs demonstrate that the glycine to aspartate change compromises the ability of the mutant protein to undergo normal elastin assembly. Other functional consequences of this amino acid substitution include altered proteolytic susceptibility of the C-terminal region of elastin and reduced interaction of the exon 36 sequence with matrix receptors on cells. These results suggest that the G773D variant confers structural and functional consequences relevant to the pathogenesis of COPD.

The genetics of atopic dermatitis: recent findings and future options

Atopic dermatitis (AD) is a chronic pruritic skin disease affecting up to 15% of children in industrialized countries. AD belongs to the group of allergic disorders that include food allergy, allergic rhinitis, and asthma. A multifactorial background for AD has been suggested, with genetic as well as environmental factors influencing disease development. Genome-wide screens for AD have been completed in four different populations to date. Interestingly, the susceptibility regions identified for AD show little overlap with asthma susceptibility regions, suggesting that, at least in part, separate genes might be involved in the pathogenesis of the different atopic disorders. Instead, some of the identified regions overlap with susceptibility regions for psoriasis, another chronic skin disease. Thus, genes expressed in the skin might play an important role in AD pathogenesis, in addition to genes influencing atopic diatheses. Although no veritable "AD gene" has been identified by positional cloning to date, examples from other complex genetic disorders such as asthma show that this goal is likely to be reached in the near future. Candidate gene studies, on the other hand, have identified 19 genes that were shown to be associated with AD in at least one study. The results of genome-wide screens as well as candidate gene studies are evaluated here in detail.

Exploiting natural peptide diversity: novel research tools and drug leads

During the course of evolution, nature has developed a vast number of peptides in all living and past species that display an exceeding diversity of structure and biological effects, such as hormonal and enzyme-controlling activity, communication between cells, and participation in host defence. Sensitive mass spectrometric technologies have been introduced and facilitate access to new natural peptides, even in trace amounts, and allow the quantitative determination of the peptide status of cells, organs and whole organisms (peptidomics). Among the large number of new biologically active peptides identified from an increasing variety of natural sources, regulators of ion channels, chemoattractants, protease inhibitors, metabolism-related hormones, cytotoxins, and antimicrobials have been found. These novel peptides serve as research tools and have potential as diagnostic biomarkers and for the development of peptide and peptidometic drugs.

Characterization and expression analysis of the Spink5 gene, the mouse ortholog of the defective gene in Netherton syndrome

The human SPINK5 gene, encoding the putative 15-domain serine protease inhibitor LEKTI, was identified as the defective gene in the severe autosomal recessive ichthyosiform skin disorder known as Netherton syndrome and as a candidate susceptibility gene for atopic disease. Here we report mapping of the murine Spink5 gene to chromosome 18 and its characterization. We show that, unlike in humans, transcription of the mouse Spink5 gene generates two mRNAs that differ in the 3' untranslated region. The encoded protein, which is detected in differentiated primary cultured keratinocytes and mouse skin as an approximately 130-kDa glycosylated precursor, displays approximately 60% identity with its human counterpart but lacks the human LEKTI domain 6. As in the human, mouse Lekti represents a marker of epithelial differentiation, strongly expressed in the granular layer of the epidermis, in suprabasal layers of stratified epithelia, and in thymic Hassall's bodies. Our data indicate that mouse Spink5/Lekti, like its human counterpart, is involved in the control of epithelial tissue homeostasis, but also highlight specific features of the murine gene and protein.

Molecular genetics of the ichthyoses

The ichthyoses are a large, clinically, genetically, and etiologically heterogeneous group of disorders of cornification due to abnormal differentiation and desquamation of the epidermis. Although they differ in clinical features, inheritance, and structural and biochemical abnormalities of the epidermis, they often pose a diagnostic challenge. For each of the 12 ichthyoses and related disorders described here, the major disease genes have been identified and genotype-phenotype correlation have begun to emerge. The molecular findings reveal the functional importance and interactions of many different epidermal proteins and metabolic pathways, including major structural proteins (keratins, loricrin), enzymes involved in lipid metabolism (transglutaminase 1, lipoxygenases, fatty aldehyde dehydrogenase, steroid sulfatase, glucocerebrosidase, Delta8-Delta7 sterol isomerase, 3beta-hydroxysteroid dehydrogenase), and protein catabolism (LEKTI), peroxisomal transport and processing (Peroxin 7 receptor, Phytanoyl-CoA hydroxylase) and DNA repair (proteins of the transcription repair complex). This review highlights the spectacular advances in the molecular genetics and biology of heritable ichthyoses over the past decade. It illustrates the power of molecular diagnostics for refining disease classification, providing prenatal diagnosis, improving genetic counseling, and clinical management.

The immunogenetics of asthma and eczema: a new focus on the epithelium

Asthma and eczema (atopic dermatitis) are the most common chronic diseases of childhood. These diseases are characterized by the production of high levels of immunoglobulin E in response to common allergens. Their development depends on both genetic and environmental factors. Over the past few years, several genes and genetic loci that are associated with increased susceptibility to asthma and atopic dermatitis have been described. Many of these genes are expressed in the mucosa and epidermis, indicating that events at epithelial-cell surfaces might be driving disease processes. This review describes the mechanisms of innate epithelial immunity and the role of microbial factors in providing protection from disease development. Understanding events at the epithelial-cell surface might provide new insights for the development of new treatments for inflammatory epithelial disease.

Lethal, neonatal ichthyosis with increased proteolytic processing of filaggrin in a mouse model of Netherton syndrome

Netherton syndrome is an autosomal recessive multisystemic disorder characterized by congenital ichthyosiform erythroderma, hair shaft defects and atopy, caused by mutations within the human SPINK5 gene. To investigate the development of this disease, we have cloned mouse spink5 and created mice with a mutated premature stop codon at amino acid R820X, to produce an allele that closely mimics a point mutation (E827X) in human SPINK5. Newborn spink5(R820X/R820X) mice develop a lethal, severe ichthyosis with a loss of skin barrier function and dehydration, resulting in death within a few hours of birth, similar to that observed in patients with severe Netherton syndrome. Epidermal barrier function is compromised because of the stratum corneum becoming spontaneously detached in the newborn mice, and this is probably compounded by the reduced mechanical strength detected in the cornified envelopes. Biochemical analysis of skin from newborn wild-type and spink5(R820X/R820X) mice revealed a substantial increase in the proteolytic processing of profilaggrin into its constituent filaggrin monomers. Filaggrin functions to organize keratin filaments into highly ordered macrofibrils that crisscross the cornified cells of the stratum corneum imparting structural integrity, and defects in filaggrin processing occur in a number of forms of congenital ichthyosis. These data suggest that in the absence of the serine protease inhibitor spink5, there is an abnormal increase in the processing of profilaggrin, resulting in an overabundance of filaggrin monomers, and that this may play a direct role in the observed deficit in the adhesion of the stratum corneum and the severely compromised epidermal barrier function.

LEKTI demonstrable by immunohistochemistry of the skin: a potential diagnostic skin test for Netherton syndrome

BACKGROUND

Netherton syndrome (NS) is a rare autosomal recessive condition characterized by ichthyosiform erythroderma, trichorrhexis invaginata and atopic manifestations. Confirming the diagnosis may be difficult in the early stages. Mutations in the SPINK5 gene which encodes for the serine protease inhibitor LEKTI are associated with NS. These mutations create premature termination codons which result in absent or abnormal expression of LEKTI in patients with NS.

OBJECTIVES

To investigate the expression of LEKTI in the skin of patients with NS in comparison with normal controls and patients with other skin conditions, namely atopic dermatitis, psoriasis and nonbullous ichthyosiform erythroderma.

METHODS

Immunohistochemistry was performed on skin sections from four patients with NS, four normal controls, four with atopic dermatitis, two with psoriasis and two with nonbullous ichthyosiform erythroderma, using a primary rabbit polyclonal antibody against LEKTI.

RESULTS

LEKTI was localized to the stratum granulosum in normal skin. All four skin sections from patients with NS showed absent or very reduced staining for LEKTI. Staining in the other disorders showed positive LEKTI expression in varying patterns.

CONCLUSIONS

NS can be difficult to diagnose especially in the early stage, which can lead to inappropriate treatments particularly if it is misdiagnosed as atopic dermatitis. Immunohistochemistry of skin with an antibody against LEKTI is a potentially useful diagnostic test for NS.

Epidermal detachment, desmosomal dissociation, and destabilization of corneodesmosin in Spink5-/- mice

Netherton syndrome (NS) is a human autosomal recessive skin disease caused by mutations in the SPINK5 gene, which encodes the putative proteinase inhibitor LEKTI. We have generated a transgenic mouse line with an insertional mutation that inactivated the mouse SPINK5 ortholog. Mutant mice exhibit fragile stratum corneum and perinatal death due to dehydration. Our analysis suggests that the phenotype is a consequence of desmosomal fragility associated with premature proteolysis of corneodesmosin, an extracellular desmosomal component. Our mouse mutant provides a model system for molecular studies of desmosomal stability and keratinocyte adhesion, and for designing therapeutic strategies to treat NS.

DNA microarray analysis of chromosomal susceptibility regions to identify candidate genes for allergic disease: a pilot study

OBJECTIVE

To examine whether DNA microarray analysis of chromosomal susceptibility regions for allergy can help to identify candidate genes.

MATERIAL AND METHODS

Nasal biopsies were obtained from 23 patients with allergic rhinitis and 12 healthy controls. RNA was extracted from the biopsies and pooled into three patient and three control pools. These were then analysed in duplicate with DNA microarrays containing 12626 genes. Candidate genes were further examined in nasal biopsies (real-time polymerase chain reaction) and blood samples (single nucleotide polymorphisms) from other patients with allergic rhinitis and from controls.

RESULTS

A total of 37 differentially expressed genes were identified according to criteria involving both the size and consistency of the gene expression levels. The chromosomal location of these genes was compared with the chromosomal susceptibility regions for allergic disease. Using a statistical method, five genes were identified in these regions, including serine protease inhibitor, Kazal type, 5 (SPINK5) and HLA-DRB2. The relevance of these genes was examined in other patients with allergic rhinitis and in controls; none of the genes were differentially expressed in nasal biopsies. Moreover, no association between allergic rhinitis and SPINK5 polymorphisms was found, at either the genotype or haplotype level.

CONCLUSIONS

DNA microarray analysis of chromosomal susceptibility regions did not lead to identification of candidate genes that could be validated in a new material. However, because gene polymorphisms may cause differential gene expression, further studies, including validation data, are needed to examine this approach.

The Solution Structure of a Chimeric LEKTI Domain Reveals a Chameleon Sequence

The conversion of an alpha-helical to a beta-strand conformation and the presence of chameleon sequences are fascinating from the perspective that such structural features are implicated in the induction of amyloid-related fatal diseases. In this study, we have determined the solution structure of a chimeric domain (Dom1PI) from the multidomain Kazal-type serine proteinase inhibitor LEKTI using multidimensional NMR spectroscopy. This chimeric protein was constructed to investigate the reasons for differences in the folds of the homologous LEKTI domains 1 and 6 [Lauber, T., et al. (2003) J. Mol. Biol. 328, 205-219]. In Dom1PI, two adjacent phenylalanine residues (F28 and F29) of domain 1 were substituted with proline and isoleucine, respectively, as found in the corresponding P4' and P5' positions of domain 6. The three-dimensional structure of Dom1PI is significantly different from the structure of domain 1 and closely resembles the structure of domain 6, despite the sequence being identical to that of domain 1 except for the two substituted phenylalanine residues and being only 31% identical to the sequence of domain 6. The mutation converted a short 3(10)-helix into an extended loop conformation and parts of the long COOH-terminal alpha-helix of domain 1 into a beta-hairpin structure. The latter conformational change occurs in a sequence stretch distinct from the region containing the substituted residues. Therefore, this switch from an alpha-helical structure to a beta-hairpin structure indicates a chameleon sequence of seven residues. We conclude that the secondary structure of Dom1PI is determined not only by the local protein sequence but also by nonlocal interactions.

Expression of LEKTI domains 6-9' in the baculovirus expression system: recombinant LEKTI domains 6-9' inhibit trypsin and subtilisin A

The precursor lympho-epithelial Kazal-type-related inhibitor (LEKTI), containing two Kazal-type and 13 nonKazal-type domains, is an efficient inhibitor of multiple serine proteinases, among them plasmin, subtilisin A, cathepsin G, elastase, and trypsin. To gain insight into the structure and function of some of these domains, a portion of the cDNA coding for LEKTI domains 6-9' was cloned and expressed in Sf9 cells using the baculovirus expression vector system (BEVS). Through a single purification step using a Co2+ column, 3-4 mg of purified recombinant LEKTI-domains 6-9' (rLEKTI6-9') with the predicted molecular mass of 34.6 kDa was obtained from the cell pellet of a 1-L culture. Unlike full-length LEKTI, rLEKTI6-9' inhibited trypsin and subtilisin A but not plasmin, cathepsin G, or elastase. The inhibition of trypsin and subtilisin A by rLEKTI6-9' occurred through a noncompetitive mechanism, with inhibitory constants (Ki) of 356 +/- 12 and 193 +/- 10 nM, respectively. On the basis of the Ki values, rLEKTI6-9' was determined to be a more potent trypsin inhibitor and a less potent subtilisin A inhibitor than the full-length LEKTI. In contrast to LEKTI domains 6-9', recombinant LEKTI domain 6 does not inhibit subtilisin A but competitively inhibited trypsin with a Ki of 200 +/- 10 nM. Taking LEKTI6-9' as an example, the BEVS should facilitate the structure-function analysis of naturally occurring processed LEKTI forms that have physiological relevance.

Association between polymorphisms in the SPINK5 gene and atopic dermatitis in the Japanese

Atopy, which is characterized by increased levels of immunoglobulin E (IgE) against common environmental allergens, is considered the strongest predisposing factor for asthma and atopic dermatitis (AD). Mutations in the gene encoding serine protease inhibitor Kazal-type 5 (SPINK5) are responsible for Netherton syndrome, a rare skin disorder characterized by greatly elevated IgE levels with atopic manifestations. A recent study of Caucasian AD families showed that maternally derived alleles of the SPINK5 gene are associated with development of AD and asthma, suggesting the parent-of-origin effect for the development of atopic diseases in the SPINK5 gene. We studied the possible association of the SPINK5 gene for the development of atopic diseases by determining the genotypes of five polymorphisms in a Japanese population. Ttransmission disequilibrium tests revealed an association of SPINK5 polymorphisms with AD but not with asthma. Our data indicate that the SPINK5 gene is associated with AD across ethnicities.

Association between polymorphisms in serine protease inhibitor, kazal type 5 and asthma phenotypes in a large German population sample

BACKGROUND

Atopic diseases are characterized by immunoglobulin E (IgE)-mediated immune responses towards common allergens, many of which are proteases. Recently it has been suggested that a proteinase inhibitor gene, SPINK5, which is located on chromosome 5q31, may play a role in the pathogenesis of atopic diseases.

OBJECTIVE

We investigated the association between the polymorphism G1258A leading to a putative amino acid change (Glu420Lys) in serine protease inhibitor, kazal type 5 (SPINK5) and phenotypes of atopic diseases in a large general population sample of German children.

METHODS

Parental questionnaires were used and children underwent skin prick testing, pulmonary function testing and bronchial challenge. Blood was collected for serum IgE measurements and DNA extraction. In total, 1161 children were genotyped for the SPINK5 Glu420Lys polymorphism and association studies were performed.

RESULTS

A significant association between SPINK5 420Lys and the development of asthma was observed (OR 1.77; 95%CI: 1.02-3.06, P=0.041 for 420Lys homocygotes). Atopic carriers of SPINK5 420Lys showed an increased risk for asthma and asthma symptoms (OR 2.06; 95%CI: 1.01-4.20, P=0.047). When children with a combination of asthma and atopic dermatitis were compared with normal controls, the SPINK5 420Lys genotype was more prevalent in the disease group (OR 4.56; 95%CI: 1.370-15.12, P=0.007). No association between SPINK5 420Lys genotypes and total serum IgE levels, skin prick test (SPT) reactivity or atopic dermatitis was observed.

CONCLUSION

These results suggest that SPINK5 Glu420Lys polymorphism may be associated with certain asthma phenotypes characterized by the concomitant expression of asthma and atopic dermatitis or SPT reactivity.

Identification of a locus for type I punctate palmoplantar keratoderma on chromosome 15q22-q24

BACKGROUND

The identification of the molecular basis of disorders of keratinisation has significantly advanced our understanding of skin biology, revealing new information on key structures in the skin, such as the intermediate filaments, desmosomes, and gap junctions. Among these disorders, there is an extraordinarily heterogeneous group known as palmoplantar keratodermas (PPK), for which only a few molecular defects have been described. A particular form of PPK, known as punctate PPK, has been described in a few large autosomal dominant pedigrees, but its genetic basis has yet to be identified.

AIM

Identification of the gene for punctate PPK.

METHODS

Clinical examination and linkage analysis in three families with punctate PPK.

RESULTS

A genomewide scan was performed on an extended autosomal dominant pedigree, and linkage to chromosome 15q22-q24 was identified. With the addition of two new families with the same phenotype, we confirmed the mapping of the locus for punctate PPK to a 9.98 cM interval, flanked by markers D15S534 and D15S818 (maximum two point lod score of 4.93 at theta = 0 for marker D15S988).

CONCLUSIONS

We report the clinical and genetic findings in three pedigrees with the punctate form of PPK. We have mapped a genetic locus for this phenotype to chromosome 15q22-q24, which indicates the identification of a new gene involved in skin integrity.

Association studies for asthma and atopic diseases: a comprehensive review of the literature

Hundreds of genetic association studies on asthma-related phenotypes have been conducted in different populations. To date, variants in 64 genes have been reported to be associated with asthma or related traits in at least one study. Of these, 33 associations were replicated in a second study, 9 associations were not replicated either in a second study or a second sample in the same study, and 22 associations were reported in just a single published study. These results suggest the potential for a great amount of heterogeneity underlying asthma. However, many of these studies are methodologically limited and their interpretation hampered by small sample sizes.

LD mapping of maternally and non-maternally derived alleles and atopy in FcepsilonRI-beta

Polymorphisms in the beta chain of the high affinity receptor for IgE (Fc epsilon RI-beta, MS4A2) are consistently associated with traits underlying asthma and atopy (immunoglobulin E-mediated allergy). However, the causal variants and haplotypes underlying disease have not yet been identified. Maternal effects, with association confined to maternally derived alleles, have been shown in some studies but not in others. We have therefore extended the known sequence and systematically detected polymorphisms across an 18.1 Kb genomic region that includes Fc epsilon RI-beta. Association testing in two panels of subjects showed the presence of single-nucleotide polymorphisms (SNPs) affecting prick skin tests and specific IgE responses in several clusters. Stepwise analyses indicated that the clusters represent independent effects. Interferon regulatory factor 2 (IRF-2) sites were altered by significantly associated SNPs in two regions. Strong association to maternally derived alleles was seen in one panel of subjects and not in the other. Maternal and non-maternally derived associations tended to share the same SNP clusters, but associations were stronger in the presence of maternal effects. Two regions of increased CpG concentration were identified in Fc epsilon RI-beta. One of these approximated a SNP cluster that showed strong association and maternal effects, providing a potential substrate for epigenetic effects.

Barrier function of the skin: "la raison d'être" of the epidermis

The primary function of the epidermis is to produce the protective, semi-permeable stratum corneum that permits terrestrial life. The barrier function of the stratum corneum is provided by patterned lipid lamellae localized to the extracellular spaces between corneocytes. Anucleate corneocytes contain keratin filaments bound to a peripheral cornified envelope composed of cross-linked proteins. The many layers of these specialized cells in the stratum corneum provide a tough and resilient framework for the intercellular lipid lamellae. The lamellae are derived from disk-like lipid membranes extruded from lamellar granules into the intercellular spaces of the upper granular layer. Lysosomal and other enzymes present in the extracellular compartment are responsible for the lipid remodeling required to generate the barrier lamellae as well as for the reactions that result in desquamation. Lamellar granules likely originate from the Golgi apparatus and are currently thought to be elements of the tubulo-vesicular trans-Golgi network. The regulation of barrier lipid synthesis has been studied in a variety of models, with induction of several enzymes demonstrated during fetal development and keratinocyte differentiation, but an understanding of this process at the molecular genetic level awaits further study. Certain genetic defects in lipid metabolism or in the protein components of the stratum corneum produce scaly or ichthyotic skin with abnormal barrier lipid structure and function. The inflammatory skin diseases psoriasis and atopic dermatitis also show decreased barrier function, but the underlying mechanisms remain under investigation. Topically applied "moisturizers" work by acting as humectants or by providing an artificial barrier to trans-epidermal water loss; current work has focused on developing a more physiologic mix of lipids for topical application to skin. Recent studies in genetically engineered mice have suggested an unexpected role for tight junctions in epidermal barrier function and further developments in this area are expected. Ultimately, more sophisticated understanding of epidermal barrier function will lead to more rational therapy of a host of skin conditions in which the barrier is impaired.

Homologous proteins with different folds: the three-dimensional structures of domains 1 and 6 of the multiple Kazal-type inhibitor LEKTI

We have determined the solution structures of recombinant domain 1 and native domain 6 of the multi-domain Kazal-type serine proteinase inhibitor LEKTI using multi-dimensional NMR spectroscopy. While two of the 15 potential inhibitory LEKTI domains contain three disulfide bonds typical of Kazal-type inhibitors, the remaining 13 domains have only two of these disulfide bridges. Therefore, they may represent a novel type of serine proteinase inhibitor. The first and the sixth LEKTI domain, which have been isolated from human blood ultrafiltrate, belong to this group. In spite of sharing the same disulfide pattern and a sequence identity of about 35% from the first to the fourth cysteine, the two proteins show different structures in this region. The three-dimensional structure of domain 6 consists of two helices and a beta-hairpin structure, and closely resembles the three-dimensional fold of classical Kazal-type serine proteinase inhibitors including the inhibitory binding loop. Domain 6 has been shown to be an efficient, but non-permanent serine proteinase inhibitor. The backbone geometry of its canonical loop is not as well defined as the remaining structural elements, providing a possible explanation for its non-permanent inhibitory activity. We conclude that domain 6 belongs to a subfamily of classical Kazal-type inhibitors, as the third disulfide bond and a third beta-strand are missing. The three-dimensional structure of domain 1 shows three helices and a beta-hairpin, but the central part of the structure differs remarkably from that of domain 6. The sequence adopting hairpin structure in domain 6 exhibits helical conformation in domain 1, and none of the residues within the putative P3 to P3' stretch features backbone angles that resemble those of the canonical loop of known proteinase inhibitors. No proteinase has been found to be inhibited by domain 1. We conclude that domain 1 adopts a new protein fold and is no canonical serine proteinase inhibitor.

Association of SPINK5 gene polymorphisms with atopic dermatitis in the Japanese population

BACKGROUND

Netherton's syndrome (NS) is an autosomal recessive disorder characterized by trichorrhexis invaginata ('bamboo hair'), congenital ichthyosiform erythroderma and an atopic diathesis. NS has recently been shown to be due to a defect in the SPINK5 gene, encoding LEKTI, a 15-domain serine protease inhibitor. SPINK5 maps to chromosome 5q31-q32, and has been suggested to be a locus predisposing to atopy in general. Recently, coding polymorphisms in SPINK5 exons 13 and 14 have been reported to be associated with atopy, asthma and atopic dermatitis (AD).

OBJECTIVES

To examine whether these polymorphisms are also associated with AD in Japan.

METHODS

We characterized eight polymorphisms in SPINK5 exons 13 and 14 in 124 Japanese patients with AD and 110 healthy controls. The polymorphisms we examined were IVS12-26C-->T, IVS12-10A-->G, 1103A-->G (Asn368Ser, in exon 13), 1156G-->A (Asp386Asn, in exon 13), 1188T-->C (His396His, in exon 13), IVS13-50G-->A, 1258G-->A (Glu420Lys, in exon 14) and IVS14+19G-->A.

RESULTS

We found significant associations between seven of these polymorphisms and AD in Japanese patients.

CONCLUSIONS

This study confirms the previous suggestion of an association between SPINK5 and AD.

Association mapping of complex diseases in linked regions: estimation of genetic effects and feasibility of testing rare variants

Association mapping in linked regions is a current major approach for the identification of genes for complex diseases. Loci contributing to linkage, even with small values of sibling recurrence risk (lambda(s)), may be equivalent to substantial underlying genetic effects for association studies. For disease alleles with a frequency as low as 1%, highly reliable association studies (80% power for significance level alpha=10(-6)) require only 277, 781, and 1289 families or cases and controls for loci detected with lambda(s) of 1.5, 1.1, and 1.05, respectively, under a multiplicative genetic model. Under alternative models, provided epistatic effects are minor, larger achievable sample sizes will provide sufficient power to map almost any disease gene that may have initially contributed to linkage.

Progress in molecular genetics of heritable skin diseases: the paradigms of epidermolysis bullosa and pseudoxanthoma elasticum

The 42nd Annual Symposium on the Biology of the Skin, entitled "The Genetics of Skin Disease", was held in Snowmass Village, Colorado, in July 1993. That meeting presented the opportunity to discuss how modern approaches to molecular genetics and molecular biology could be applied to understanding the mechanisms of skin diseases. The published proceedings of this meeting stated that "It is an opportune time to examine the genetics of skin disease" (Norris et al, 1994). Indeed, this meeting just caught the wave of early pioneering studies that have helped us to understand the molecular basis of a large number of genodermatoses. This overview presented in the 50th Annual Symposium on the biology of the skin, highlights the progress made in the molecular genetics of heritable skin diseases over the past decade.