A defined donor activating natural killer cell receptor genotype protects against leukemic relapse after related HLA-identical hematopoietic stem cell transplantation

Killer cell immunoglobulin-like receptors (KIRs) recognize different groups of Human Leukocyte Antigen (HLA) class I alleles and are expressed by natural killer (NK) cells and some T lymphocytes. NK cell cytotoxicity is triggered by failure to recognize the appropriate HLA class I ligand on target cells. Recently, it has been shown that HLA class I ligand incompatibility in the graft-versus-host (GvH) direction is associated with a better outcome in haploidentical hematopoietic stem cell transplantation (HSCT). Since KIR genotypes are very diverse in the population, we explored whether or not the donor KIR genotype could affect the graft-versus-leukemia (GvL) effect in the related HLA-identical HSCT setting. We determined the KIR and HLA genotypes of 65 HLA-identical patient-donor siblings. We found that the presence of two activating KIRs, 2DS1 and 2DS2, in the donor was significantly associated with a decreased leukemic relapse rate (P=0.03; OR=0.18; 95% CI: 0.037-0.88). Moreover, the probability of relapse at 5 years was significantly lower for patients who received a graft from a donor with the 2DS1(+)2DS2(+) genotype than for those who received a transplant from other donors (17 vs 63%, respectively; P=0.018). In conclusion, this study suggests that a joint effect of these two selected activating KIRs in the donor might confer some protection against leukemic relapse.

Ichthyosis bullosa of Siemens: its correct diagnosis facilitated by molecular genetic testing

Ichthyosis bullosa of Siemens (IBS, MIM 146800) is a unique congenital ichthyosis characterized by mild epidermal hyperkeratosis over flexural areas, blister formation and the development of superficially denuded areas of hyperkeratotic skin. It is clinically difficult to distinguish severe IBS from mild bullous congenital ichthyosiform erythroderma (BCIE, MIM 113800). In the current literature, 19 IBS families with keratin 2e (K2e) mutations have been reported, despite only five IBS families having been reported before the first identification of K2e mutation in 1994. We studied four patients from three Japanese IBS families. They had previously been misdiagnosed as having BCIE before the correct diagnosis was made after mutation detection. To detect the pathogenic mutations, we performed direct sequencing of the entire coding regions of KRT2E encoding K2e in the patients and healthy family members. K2e mutations, a 1469T-->C transition (L490P) and a 1477G-->A transition (E493K) within the conserved 2B helix termination motif of the rod domain were detected in the families and the definite diagnosis of IBS was made in the four cases. The present results indicate that IBS is not such a rare entity as was previously thought, and accurate diagnosis is now available by mutation analysis.

Isolation of nucleic acid binding proteins: an approach for isolation of cell surface, nucleic acid binding proteins

An approach for isolation of cell surface, nucleic acid binding proteins is described. This approach relies on affinity modification of the proteins of living cells with reactive oligonucleotides bearing a haptenic group. Covalently modified proteins were isolated by hapten-specific affinity chromatography with subsequent SDS-PAGE. Isolated 68-kDa proteins responsible for the binding of oligonucleotides were MS/MS sequenced and identified as keratin K1, keratin K10, keratin K2e, and albumin.

Cell surface oligonucleotide-binding proteins of human squamous carcinoma A431 cells

Affinity modified with Flu-DAP-p(N)16degU oligonucleotide-binding proteins were isolated by affinity chromatography using Ultrogel A2-anti fluorescein antibodies. After separation by SDS-PAGE the proteins with molecular masses about 68 kDa were MS/MS sequenced and identified as keratin K1, keratin K10, keratin K2e and albumin.

A novel mutation in the 2B domain of keratin 2e causing ichthyosis bullosa of Siemens

Ichthyosis bullosa of Siemens (IBS; MIM: 146800) is an autosomal dominant disorder of keratinization characterized by epidermolytic hyperkeratosis without erythroderma. The clinical features are less marked than those of bullous congenital ichthyosiform erythroderma with relatively mild hyperkeratosis usually limited to the skin flexures. Mutations in the epithelial cytokeratin 2e (K2e), which is expressed in a differentiation-specific fashion in the upper spinous and granular layers of the epidermis, have been shown to cause IBS. We detected a novel mutation in a three generation kindred with IBS (1448T-->A) within exon 7 of the KRT2E gene. This is predictive of an I483N substitution in the 2B domain of K2e. This extends the range of mutations reported to date and illustrates the usefulness of molecular genetics in the diagnosis of this disorder.

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.

A novel asparagine-->aspartic acid mutation in the rod 1A domain in keratin 2e in a Japanese family with ichthyosis bullosa of Siemens

Ichthyosis bullosa of Siemens is a unique type of congenital ichthyosis characterized by mild hyperkeratosis over the flexural areas and blister formation after mechanical trauma and superficial denuded areas in the hyperkeratotic skin. Recently, mutations in the helix initiation or termination motifs of keratin 2e (KRT2E) have been described in ichthyosis bullosa of Siemens patients. The majority of the mutations reported to date lie in the 2B region. We report a novel amino acid substitution mutation (asparagine-->aspartic acid) in codon 192 at the conserved 1A helix initiation site of the rod domain of KRT2E in a Japanese family with ichthyosis bullosa of Siemens. Our data indicate aspartic acid substitution in codon 192 in the 1A helix initiation site is deleterious to keratin filament network integrity and leads to ichthyosis bullosa of Siemens phenotype.

Ichthyosis bullosa of Siemens resulting from a novel missense mutation near the helix termination motif of the keratin 2e gene

Ichthyosis bullosa of Siemens (IBS) is an autosomal dominant disorder of keratinization. It is characterized by a mild epidermolytic ichthyosis which tends to localize to the flexures. Affected individuals are born with widespread blistering, which develops into large hyperkeratotic plaques over the extremities. Mutations in the K2e gene cause epidermolytic hyperkeratosis confined to the upper spinous and granular layers, as observed in IBS. In this report, we describe a novel mutation in the keratin 2e gene in a four-generation IBS kindred of German ancestry. The mutation resides within the 2B helix termination motif of the keratin 2e gene, and extends the body of evidence implicating keratin 2e gene mutations in IBS.

Ichthyosis bullosa of Siemens: report of a family with evidence of a keratin 2e mutation, and a review of the literature

We report a large family with ichthyosis bullosa of Siemens (IBS) including eight affected members spanning three generations. The classical features of the disease were consistently observed with blistering, superficial peeling of the skin, and localized lichenified hyperkeratosis mainly confined to the limbs. Phenotypic variation, however, was also observed with some individuals exhibiting unusual clinical features. Specifically, the index patient was erythrodermic at birth; she subsequently developed a widespread pustular eruption. Erythroderma is classically absent in IBS and pustulation is very unusual. She also had hypertrichosis of the limbs, as did an affected female first cousin. This has not previously been reported in IBS. Electron microscopy showed complex aggregates of keratin in the spinous and granular layers associated, in places, with remarkably little cell lysis. Sequencing of genomic DNA revealed a mutation (E493K) in keratin 2e. A review of the literature on IBS indicates that E493K is the most commonly reported mutation to date and might represent a mutational hotspot for this disease.

Ontogeny and regional variability of keratin 2e (K2e) in developing human fetal skin: a unique spatial and temporal pattern of keratin expression in development

Keratin 2e (K2e) is expressed in the upper spinous and granular cells of adult epidermis. A highly specific polyclonal antibody was made against a C-terminal peptide of K2e and used to observe K2e expression at different developmental stages. At 12.5 weeks estimated gestational age (EGA) K2e was detected in trunk skin in scattered cells in the intermediate layer. At 13.5 weeks EGA, greater numbers of intermediate cells were stained with variable intensity, and staining in this pattern increased with age. Epidermal sheets from 14 weeks EGA showed that K2e + cells were excluded from developing hair follicles. At 135 days EGA, the following regional patterns were observed: in cheek, trunk, dorsal and ventral knee, elbow and dorsal hand there was moderate to intense staining of upper intermediate keratinocytes excluding cells of the hair canals and sweat ducts. The periumbilical region distinctly lacked K2e staining, while more distal areas showed increasing numbers of K2e + cells. The earliest expression of K2e was at 10 weeks EGA in the presumptive nail bed of developing digits. By 13.5 weeks EGA this pattern had shifted to the proximal nail fold, and K2e was absent in the nail bed. K2e was excluded from developing sweat glands and ducts and from developing hair follicles at the hair germ and early peg stages. By 15 weeks EGA in the fetal hair follicle small groups of cells were K2e + and by 19 weeks K2e + cells were seen at the level of the matrix. Some overlap in staining was detected for K2e with K10, and in palmar skin with K9; however, mostly the filamentous staining patterns for these keratins were distinctive. This study shows that the complex patterns of temporal and regional expression of K2e differ from known patterns for other epidermal keratins and suggest different regulation and function for this epidermal keratin.

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.

Genomic organization and fine mapping of the keratin 2e gene (KRT2E): K2e V1 domain polymorphism and novel mutations in ichthyosis bullosa of Siemens

We and others have previously shown that ichthyosis bullosa of Siemens, an autosomal dominant disorder characterized by epidermal thickening and blistering, is caused by mutations in the late-differentiation keratin K2e. Here, we have determined the genomic organization and complete sequence of the KRT2E gene, which consists of nine exons, spanning 7634 bp of DNA. The gene was mapped by high-resolution radiation-hybrid mapping to the interval between microsatellite markers D12S368 and CHLC.GATA11B02.1112. Several intragenic polymorphisms were detected, including an 18 bp duplication in exon 1, corresponding to the V1 domain of the K2e polypeptide. Genomic polymerase chain reaction conditions were optimized for all exons, and two novel mutations, N192Y in the 1A domain and E482K in the 2B domain of K2e, were found in ichthyosis bullosa of Siemens families. Mutations were excluded from 50 normal unrelated individuals by restriction analysis. These results emphasize that mutations in K2e underlie ichthyosis bullosa of Siemens and provide a comprehensive mutation detection strategy for ongoing studies of keratinizing disorders.

A glutamate to lysine mutation at the end of 2B rod domain of keratin 2e gene in ichthyosis bullosa of Siemens

Ichthyosis bullosa of Siemens is a rare autosomal dominant skin disorder whose clinical findings are quite similar to those of epidermolytic hyperkeratosis. The differences between those two diseases include absence of erythroderma and different distributions in the skin in ichthyosis bullosa of Siemens. Recent studies have confirmed that ichthyosis bullosa of Siemens is caused by the mutation in the keratin 2e (K2e) gene, which is expressed in the upper spinous and granular layers. We have identified a sporadic case of ichthyosis bullosa of Siemens; based on diagnosis by histopathological findings, the K2e gene of the patient was analysed. Direct sequencing of PCR products revealed a single base change in sequences encoding the highly conserved end of the 2B rod domain segment of the K2e gene. This mutation results in substitution of the codon for glutamic acid by a codon for lysine in position 493 in K2e (E493K). Mutations of the K2e gene involving five different residue positions (Q187P, T485P, L490P, E493D, E493K and E494K) are known to cause ichthyosis bullosa of Siemens. Of these sites, E493, which is conserved in type I and type II keratin genes, is the most frequently altered amino acid in the K2e gene. These data together suggest that this codon constitutes a hot spot for mutations in the K2e gene.

Out of balance: consequences of a partial keratin 10 knockout

Recently we generated keratin 10 knockout mice which provided a valuable model for the dominantly inherited skin disorder epidermolytic hyperkeratosis. Here we investigated the molecular basis for their phenotype. Hetero- and homozygotes expressed a truncated keratin 10 peptide which has been identified directly by microsequencing. Epitope mapping of monoclonal antibodies to keratin 10T enabled us to study its distribution relative to keratin 6, which is highly expressed in keratin 10 knockout mice, by double-immunogold electron microscopy. This revealed that keratin 10T was restricted to complexes with keratin 1 but did not mix with keratin 6. The latter did not form extended filaments with keratins 16/17 but aggregates. Keratins 6/16 were unable to compensate for the lack of normal keratin 1/10 filaments. Remarkably keratin 6 aggregates strictly colocalized with keratohyalin granules. Residual keratin 1/10T clumps were located in the cell periphery and at desmosomes which maintained a normal architecture. Surprisingly keratin 2e, a keratin tailored to sustain mechanical stress, was completely lost in paw sole epidermis of homozygous keratin 10 knockout mice, pointing to keratin 10 as its partner. The selective pairing of keratin 10T and the loss of keratin 2e indicate that in vivo keratins are less promiscuous than in vitro. Skin fragility in keratin 10 knockout mice and in epidermolytic hyperkeratosis is probably the consequence of two complementing mechanisms namely a decrease of normal keratin 1/10 filaments and an increase in keratins 6/16 with a poor filament-forming capacity.

Ichthyosis bullosa of Siemens--a disease involving keratin 2e

Ichthyosis bullosa of Siemens (IBS) is a congenital bullous ichthyosis without erythroderma. In contrast to bullous congenital ichthyosiform erythroderma (BCIE), there is a relatively mild involvement of the skin and epidermolytic hyperkeratosis (EHK) is restricted to the upper suprabasal layers of the epidermis. Tonofilament aggregation was observed by EM in suprabasal cells from affected patients in the two families under study, indicative of a keratin abnormality. Keratin 2e is a differentiation specific type II keratin expressed suprabasally in the epidermis. Part of the K2e gene was amplified by polymerase chain reaction using genomic DNA from affected and unaffected individuals from two IBS families. Direct sequencing of polymerase chain reaction products revealed a point mutation in the highly conserved helix termination motif, producing the protein sequence change LLEGEE-LLEGKE. This mutation was found in all affected members of a five-generation kindred and also in a sporadic case in a second unrelated family. No mutation was seen in unaffected individuals. The mutation destroys a MnlI restriction site, which allowed exclusion of the mutation from a population of 50 unaffected unrelated individuals by restriction fragment analysis of K2e PCR products. This is the sixth keratin gene found to be involved in an inherited epidermal disorder.

Genetic linkage of the keratin type II gene cluster with ichthyosis bullosa of Siemens and with autosomal dominant ichthyosis exfoliativa

Ichthyosis bullosa of Siemens is an autosomal dominant disease characterized by mild hyperkeratosis and blistering. Autosomal dominant ichthyosis exfoliativa is a recently described disease with clinical features similar to ichthyosis bullosa of Siemens, but in contrast to ichthyosis bullosa of Siemens no histologic signs typical for epidermolytic hyperkeratosis are observed. We used linkage analysis to test whether keratin gene mutations might underlie both diseases. This analysis showed linkage of both disorders with the region of chromosome 12 in which the keratin type II gene cluster is located. The keratin type I gene cluster on chromosome 17 is excluded. These data, combined with clinical observations, strongly suggest that the genes coding for keratin 1 or keratin 2e, both expressed in the suprabasal compartment of the epidermis and located in the type II gene cluster, are candidate genes for ichthyosis bullosa of Siemens and ichthyosis exfoliativa.

Mutations in the rod domain of keratin 2e in patients with ichthyosis bullosa of Siemens

Ichthyosis bullosa of Siemens (IBS) is an autosomal dominant skin disorder that resembles epidermolytic hyperkeratosis (EHK). We have identified mutations in two families originally diagnosed with EHK and in four families diagnosed with IBS at the same codon in the highly conserved carboxy terminal of the rod domain of keratin 2e, thus revealing a mutational hot spot. Our results allow a differential diagnosis to be made between IBS and EHK at the genetic level and we suggest that patients diagnosed with EHK, but lacking keratin K1 or K10 mutations, should be re-examined for mutations in their K2e genes.