Expanding the keratin mutation database: novel and recurrent mutations and genotype-phenotype correlations in 28 patients with epidermolytic ichthyosis.

BACKGROUND: Epidermolytic ichthyosis (EI) is a hereditary keratinization disorder caused by mutations in the keratin 1 (KRT1) or keratin 10 (KRT10) genes. In most cases of severe EI, heterozygous single point mutations are found at the highly conserved helix boundary motifs of KRT1 and KRT10 that play a critical role in filament formation. The presence of palmoplantar keratoderma suggests KRT1 mutations, whereas KRT10 mutations in most instances give rise to the nonpalmoplantar variants. OBJECTIVES: To identify the underlying mutations in patients with EI and to correlate genotype and phenotype. METHODS: Mutation analysis was performed in 28 patients with EI by direct sequencing of KRT1 and KRT10 genes. RESULTS: We identified 14 different mutations, of which four have not been published previously. CONCLUSIONS: Identification of novel mutations and genotype-phenotype correlations in EI allows improved understanding of disease pathogenesis as well as better patient management.

Identification of novel and known KRT5 and KRT14 mutations in 53 patients with epidermolysis bullosa simplex: correlation between genotype and phenotype.

BACKGROUND: Basal epidermolysis bullosa simplex (EBS) is a hereditary skin blistering disorder resulting in most cases from missense mutations in the keratin 5 (KRT5) or keratin 14 (KRT14) genes. OBJECTIVES: To identify the underlying mutations in different EBS subtypes and correlate genotype and phenotype. METHODS: Mutation analysis was performed in 53 patients with EBS and their families by direct sequencing of the KRT5 and KRT14 genes. RESULTS: We identified 39 different mutations, of which 15 have not been published previously. Three novel deletion/insertion mutations, among them one in-frame duplication, were associated with the rare phenotype of EBS with mottled pigmentation. We identified for the first time a patient with compound heterozygosity for KRT5 mutations causing Dowling-Degos disease and EBS. CONCLUSIONS: Identification of novel mutations and genotype-phenotype correlations in EBS allow improved understanding of disease pathogenesis as well as better patient management.

Focal activation of a mutant allele defines the role of stem cells in mosaic skin disorders.

Stem cells are crucial for the formation and maintenance of tissues and organs. The role of stem cells in the pathogenesis of mosaic skin disorders remains unclear. To study the molecular and cellular basis of mosaicism, we established a mouse model for the autosomal-dominant skin blistering disorder, epidermolytic hyperkeratosis (MIM 113800), which is caused by mutations in either keratin K1 or K10. This genetic model allows activation of a somatic K10 mutation in epidermal stem cells in a spatially and temporally controlled manner using an inducible Cre recombinase. Our results indicate that lack of selective pressure against certain mutations in epidermal stem cells leads to mosaic phenotypes. This finding has important implications for the development of new strategies for somatic gene therapy of dominant genodermatoses.

Determination of ellagic acid in oak leaves and in sheep ruminal fluid by ion-pair RP-HPLC.

An isocratic ion-pair high-performance liquid chromatography (IP-RP-HPLC) method with UV detection was developed to identify and quantify ellagic acid (EA). This phenolic compound is widely distributed in the plants and is often present in the diet of ruminants. The method was validated and validation parameters were: linearity range 5-100 mg/L; correlation coefficient, 0.9995; mean recoveries (99.94 and 101.07%) and detection limit 1.4 mg/L. Method was applied for the determination of ellagic acid in oak leaves and in ruminal fluid from to a vitro ruminal system. The proposed method proved to be rapid and accurate and can be successfully used in ruminant nutrition studies.

Disease model: heritable skin blistering.

Hereditary skin blistering disorders comprise a group of genodermatoses whose common primary feature is the formation of blisters following minor trauma. Examples of such conditions include epidermolysis bullosa and several bullous forms of ichthyosis. Distinct mutations in various genes encoding intra- and extra-cellular structural components of the skin reflect the clinical heterogeneity of these disorders. Several animal models are currently used to study the role of these molecules in the disease process. Some of these models will find their place in evaluating new therapeutic strategies for this devastating group of diseases.

A novel substitution in keratin 10 in epidermolytic hyperkeratosis.

Epidermolytic hyperkeratosis is characterized by tonofilament clumping, cytolysis, and blister formation in suprabasal keratinocytes. It has been shown that the tonofilament aggregates in these areas are composed of keratin 1 (K1) and keratin 10 (K10), and several K1 and K10 point mutations have been identified as the molecular basis of epidermolytic hyperkeratosis. In this report we identify a novel, single base pair substitution resulting in an amino acid exchange from tyrosine to serine at residue 14 within the conserved 1A region of K10 (Y14S). This A to C transversion in codon 160 was only present in the affected individual and was associated with a very severe disease phenotype. Our observations are in agreement with previous reports documenting that this tyrosine residue, located at the beginning of the rod domain of type I keratins, is particularly sensitive to amino acid substitutions, and that alterations in this residue can have deleterious effects on filament assembly and stability.

A novel mutation in the 1A domain of keratin 2e in ichthyosis bullosa of Siemens.

Ichthyosis bullosa of Siemens (IBS) is a rare autosomal dominant skin disorder with clinical features similar to epidermolytic hyperkeratosis (EHK). Both diseases have been linked to the type II keratin cluster on chromosome 12q. Hyperkeratosis and blister formation are relatively mild in IBS compared with EHK, and the lysis of keratinocytes is restricted to the upper spinous and granular layers of the epidermis of IBS patients, whereas in EHK lysis occurs in the lower spinous layer. Recently, mutations in the helix initiation and termination motifs of keratin 2e (K2e) have been described in IBS patients. The majority of the mutations reported to date lie in the 2B region. In this report, we have examined a large kindred in which the disease was originally diagnosed as EHK and mapped to the type II keratin cluster on chromosome 12q. Molecular analysis revealed a novel amino acid substitution at the beginning of the conserved 1A region of the rod domain (I4N) of K2e, resulting from a T to A transversion in codon 188.

Plasma protein binding of an N-pyrrolyl derivative penicillin in several mammalian species.

The extents of protein binding of an N-pyrrolyl derivative penicillin in plasma of different species were determined in vitro by the equilibrium dialysis technique and spectrophotometry determination. The percentage of binding was determined in cows, sheep, pigs and dogs. The percentage of drug that was protein bound was independent of drug concentration for this penicillin within the range studied (5 to 40 micrograms ml-1). The extent of binding was determined at 20 micrograms ml-1. There was a significant difference in the extent of penicillin binding between species (t test P less than 0.005) except for between cows and dogs (t test P less than 0.05) and sheep and pigs (where it was not significantly different). In the species studied the extent of penicillin binding ranged from 41 to 55 per cent.

The comparative stability of different types of penicillin and cephalosporin N-pyrryl derivatives.

The kinetics of the decomposition of potassium salts of 4-thia-1-azabicyclo[3.2.0.]heptane-3,3-dimethyl-6-amino-7-oxo-N- [2(1H-pyrrolyl)acetyl] -2-carboxylic acid (6R, trans), 4-thia-1-azabicyclo[3.2.0]heptane-3,3-dimethyl-6-amino-7-oxo-N-[2-phenyl - 2(1H-pyrrolyl)acetyl]-2-carboxylic acid (6R, trans), 5-thia-1-azabicyclo[4.2.0.]oct-2-ene-3- [(acetyloxy)methyl]-7-amino-8-oxo-N-[2(1H-pyrrolyl)acetyl]-2-ca rbo xylic acid (6R, trans), 5-thia-1-azabicyclo[4.2.0.]oct-2-ene-3- [(acetyloxy)methyl]-7-amino-8-oxo-N-[2-phenyl-2(1H-pyrrolyl)acetyl ]- 2-carboxylic acid (6R, trans), 5-thia-1-azabicyclo[4.2.0.]oct-2-ene-7-amino-3-methyl-8-oxo-N- [2(1H-pyrrolyl)-acetyl]-2-carboxylic acid (6R, trans) and 5-thia-1-azabicyclo[4.2.0.]oct-2-ene-7-amino-3-methyl-8-oxo- N-[2-phenyl-2(1H-pyrrolyl)acetyl]-2-carboxylic acid (6R, trans), in aqueous solution at 37 degrees C and at ionic strength of 0.5 mol.l-1 have been studied over the 2.3-11.5 pH range. In all cases, the hydrolysis of these compounds is subject to acid-base catalysis and, in some instances, to a general catalysis by various species present in the buffer solutions. The experimental results have been analyzed and discussed in relation to the hydrolytic mechanisms.

Anti-CD20 monoclonal antibody (rituximab) in the treatment of pemphigus.

BACKGROUND: Pemphigus is a severe autoimmune blistering disorder caused by autoantibodies to desmoglein 1 and 3. The disease course is typically severe, thus requiring multiple immunosuppressive agents. The treatment is still challenging and in some patients with recalcitrant disease, therapies fail and therapeutic options are limited. OBJECTIVES: To investigate whether depletion of B lymphocytes that are thought to produce disease-causing autoantibodies shows a long-term benefit in pemphigus. METHODS: Five patients diagnosed as having pemphigus vulgaris and pemphigus foliaceus were treated with the monoclonal antibody rituximab. Rituximab was administered intravenously at a dosage of 375 mg m(-2) once weekly for 4 weeks. RESULTS: The treatment was well tolerated and all patients showed a good response over a follow-up period of up to 3 years, allowing immunosuppressive treatment to be reduced or terminated. B-cell depletion persisted for 6-12 months, and in one patient for almost 3 years. CONCLUSIONS: This study highlights the prolonged effect and disease control after one single course of rituximab and further extends the spectrum of treatments of bullous autoimmune disorders.

Rapid and simple method for the determination of urinary benzoic and phenylacetic acids and their glycine conjugates in ruminants by reversed-phase high-performance liquid chromatography.

A simple, rapid and reproducible reversed-phase high-performance liquid chromatographic method for the simultaneous determination of benzoic acid (BA), phenylacetic acid (PAA) and their respective glycine conjugates hippuric acid (HA) and phenaceturic acid (PA) in sheep urine is described. The procedure involves only direct injection of a diluted urine sample, thus obviating the need for an extraction step or an internal standard. The compounds were separated on a Nova-Pak C18 column with isocratic elution with acetate buffer (25 mM, pH 4.5)-methanol (95:5). A flow-rate of 1.0 ml/min, a column temperature of 35 degrees C and detection at 230 nm were employed. These conditions were optimized by investigating the effects of pH, molarity, methanol concentration in the mobile phase and column temperature on the resolution of the metabolites. The total analysis time was less than 15 min per sample. At a signal-to-noise ratio of 3 the detection limits for ten-fold diluted urine were 1.0 microgram/ml for BA and HA and 5.0 micrograms/ml for PAA and PA with a 20-microliters injection.

Determination of creatinine and purine derivatives in ruminants' urine by reversed-phase high-performance liquid chromatography.

A procedure is described for the rapid and simultaneous determination of allantoin, creatinine, uric acid, hypoxanthine and xanthine in sheep urine. Separation was achieved on a Novapak C18 column under isocratic conditions. The mobile phase was potassium phosphate buffer (10 mM, pH 4.0). A flow-rate of 0.5 ml/min, detection at 218 nm and a column temperature of 25 degrees C were employed with a total analysis time of less than 15 min. Detection limits for allantoin, creatinine, uric acid, hypoxanthine and xanthine were 1.0, 0.5, 0.5, 0.5 and 0.2 micrograms/ml, respectively, at a signal-to-noise ratio of 3 in a 20-microliters injection volume of tenfold-diluted urine. This sensitivity permits the precise determination of these compounds in ruminants' urine.

Identification of a novel mutation in keratin 1 in a family with epidermolytic hyperkeratosis.

Epidermolytic hyperkeratosis (EHK) is a hereditary skin disorder typified by blistering due to cytolysis. One in 100,000 individuals is affected by this autosomal-dominant disease. The onset of the disease phenotype is typically at birth. Histological and ultrastructural examination of the epidermis shows a thickened stratum corneum and tonofilament clumping around the nucleus of suprabasal keratinocytes. Linkage studies localized the disease genes on chromosomes 12q and 17q which contain the type II and type I keratin gene clusters. Recently, several point mutations in the genes encoding the suprabasal keratins, K1 and K10, have been reported in EHK patients. We have investigated a large kindred affected by EHK and identified a new point mutation in the 2B region of keratin 1 (I107T), resulting from a T to C transition in codon 478.

An asparagine to threonine substitution in the 1A domain of keratin 1: a novel mutation that causes epidermolytic hyperkeratosis.

Epidermolytic hyperkeratosis (EHK) is a congenital, autosomal dominant disorder of cornification characterized by hyperkeratosis and blister formation. The clinical manifestations are heterogeneous, with respect to the extent of body surface involvement, palmar and plantar hyperkeratosis and the presence of erythroderma. Point mutations in the genes encoding the suprabasal-specific keratins, keratins 1 and 10 have been identified in EHK patients. The inappropriate amino acid substitutions cause a collapse of the keratin filament network, resulting in cytolysis of the involved keratinocytes. We report a severe case of EHK with a single base pair mutation that causes a threonine for asparagine substitution in residue 8 (N8T) of the 1A region of the keratin 1 protein. This is the region involved in molecular overlaps between neighboring keratin heterodimers. These findings suggest that even conservative amino acid substitutions in overlap regions can cause tonofilament clumping.

Hot spot mutations in keratin 2e suggest a correlation between genotype and phenotype in patients with ichthyosis bullosa of Siemens.

Ichthyosis bullosa of Siemens (IBS) is a rare disorder of cornification characterized by blister formation in the upper suprabasal layers of the epidermis. Molecular analysis of IBS has identified mutations in the keratin 2e (K2e) gene, which is located in the type II keratin gene cluster on chromosome 12q. We have studied two IBS families and have identified heterozygous point mutations in codon 493 of the K2e gene in both families. Whereas a non-conservative amino acid substitution at position 117 of the 2B region of K2e (E117K) was associated with a severe phenotype in family 1, family 2 showed mild clinical features as a result of a conservative substitution (E117D). These data suggest a phenotype-genotype correlation in these families.