Eeva-Mari Jouhilahti

Reevaluation of the Normal Epidermal Calcium Gradient, and Analysis of Calcium Levels and ATP Receptors in Hailey–Hailey and Darier Epidermis

Electron probe microanalysis was used to analyze elemental content of human epidermis. The results revealed that the calcium content of the basal keratinocyte layer was higher than that of the lowest spinous cell layer in normal epidermis. This was surprising, as it is generally accepted that the calcium level increases with cellular differentiation from the proliferative basal layer to the stratum corneum. Hailey-Hailey disease (HHD) and Darier disease (DD) are caused by mutations in Ca(2+)-ATPases with the end result of desmosomal disruption and suprabasal acantholysis. The results demonstrated three major aberrations in HHD and DD lesions. First, in HHD and DD lesions the calcium content in the basal layer was lower than in the normal skin. Second, adenosine triphosphate (ATP) receptor P2Y2 was not localized to plasma membrane in acantholytic cells, whereas P2X7 appeared in the plasma membrane, potentially mediating apoptosis. Third, transition of keratin 14 to keratin 10 was abnormal as demonstrated by the presence of keratinocytes expressing both cytokeratins, which are usually exclusive in normal epidermis. Our results provide to our knowledge previously unreported elements for understanding how the disturbed calcium gradient is linked to the alterations in ATP receptors and keratin expression, leading to the clinical findings in HHD and DD.

Class III β-Tubulin Is a Component of the Mitotic Spindle in Multiple Cell Types

The findings of this study show that Class III β-tubulin is a component of the mitotic spindle in multiple cell types. Class III β-tubulin has been widely used as a neuron-specific marker, but it has been detected also in association with breast and pancreatic cancers. In this study, we describe a novel finding of Class III β-tubulin in a subpopulation of cells in malignant peripheral nerve sheath tumor. The findings of this study also show that Class III β-tubulin is expressed by normal mesenchymal and epithelial cells (fibroblasts and keratinocytes), two transitional cell carcinoma cell lines, and neurofibroma Schwann cells, as shown by immunolabeling and Western transfer analysis using two different Tuj-1 antibodies that are specific for Class III β-tubulin. The corresponding mRNA was detected using RT-PCR and whole human genome microarrays. Both antibodies localized Class III β-tubulin to the mitotic spindle and showed a colocalization with α-tubulin. The immuno-reaction became visible in early prophase, and the most intense immunoreaction was detected during metaphase and anaphase when microtubules were connected to the kinetochores on chromosomes. Class III β-tubulin–specific immunoreaction lasted to the point when the midbody of cytokinesis became detectable.

The development of cutaneous neurofibromas.

Cutaneous neurofibromas are the hallmarks of neurofibromatosis type 1 (NF1). They are composed of multiple cell types, and traditionally they are believed to arise from small nerve tributaries of the skin. A key finding in the context of this view has been that subpopulations of tumor Schwann cells harbor biallelic inactivation of the NF1 gene (NF1(-/-)). In the present study, our aim was to clarify further the pathogenesis of cutaneous neurofibromas. First, we detected cells expressing multipotency-associated biomarkers in cutaneous neurofibromas. Second, we developed a method for isolating and expanding multipotent neurofibroma-derived precursor cells (NFPs) from dissociated human cutaneous neurofibromas and used it to analyze their growth and differentiation potential. In analogy to solitary cells resident in neurofibromas, NFPs were found to express nestin and had the potential to differentiate to, at least, Schwann cells, neurons, epithelial cells, and adipocytes. Mutation analysis of the NFPs revealed that their genotype was NF1(+/-). The results led us to speculate that the development of cutaneous neurofibromas includes the recruitment of multipotent NF1(+/-) precursor cells. These cells may be derived from the multipotent cells of the hair roots, which often are intimately associated with microscopic neurofibromas.

Oral soft tissue alterations in patients with neurofibromatosis

Our aim was to characterize the type and frequency of oral soft tissue alterations in neurofibromatosis. A total of 103 patients with neurofibromatosis 1 (NF1) and three patients with neurofibromatosis 2 (NF2) were clinically evaluated for their oral soft tissue alterations. Disturbing growths were removed from nine patients with NF1 and from one patient with NF2. The specimens were analyzed using routine histological methods and with immunohistochemistry using antibodies to S100, type IV collagen, CD34, neurofilament, and neuron-specific tubulin (TUBB3). Alterations including oral tumors, overgrowths of gingival soft tissue, and enlarged papillae of the tongue were discovered in 74% of NF1 patients. The results showed that three tumors clinically classified as plexiform neurofibromas and five out of six discrete mucosal tumors displayed histology and immunohistology consistent with that of neurofibroma. The histology of one palatal lesion resembled that of a scar, and the lesion removed from the patient with NF2 was classified as an amyloid tumor. To conclude, oral soft tissue growths are common findings in NF1, but most lesions do not require treatment and the patients may even not be aware of these alterations. Collagen IV, S100, and CD34 are useful biomarkers in the analysis of NF1-related oral soft tissue tumors. The clinicians should recognize that oral soft tissue alterations are relatively common in NF1. Some of the growths are disturbing, and plexiform neurofibromas may bear a risk of malignant transformation.

Neurofibromatosis Type 1 Gene Mutation Analysis Using Sequence Capture and High-throughput Sequencing

Neurofibromatosis type 1 syndrome (NF1) is caused by mutations in the NF1 gene. Availability of new sequencing technology prompted us to search for an alternative method for NF1 mutation analysis. Genomic DNA was isolated from saliva avoiding invasive sampling. The NF1 exons with an additional 50bp of flanking intronic sequences were captured and enriched using the SeqCap EZ Choice Library protocol. The captured DNA was sequenced with the Roche/454 GS Junior system. The mean coverages of the targeted regions were 41x and 74x in 2 separate sets of samples. An NF1 mutation was discovered in 10 out of 16 separate patient samples. Our study provides proof of principle that the sequence capture methodology combined with high-throughput sequencing is applicable to NF1 mutation analysis. Deep intronic mutations may however remain undetectable, and change at the DNA level may not predict the outcome at the mRNA or protein levels.

Hypoxic conditions stimulate the release of B-type natriuretic peptide from human retinal pigment epithelium cell culture

A‐type peptide, a natriuretic peptide belonging to the natriuretic peptide family, has been shown to be increased in the vitreous of patients suffering from diabetic retinopathy and that human retina has a well‐developed natriuretic peptide system. The stimulus to which the synthesis of natriuretic peptides responded in these patients has, however, remained unknown. As the natriuretic peptides have recently been shown to respond to hypoxic conditions, the genes of both A‐type and B‐type have a hypoxia‐response element (HRE) in their promoter sequence, we therefore hypothesized that hypoxia in the human retinal pigment epithelium will increase the secretion of NT‐proBNP, the most common natriuretic peptide monitored in clinical medicine.

An approach to comprehensive genome and proteome expression analyses in Schwann cells and neurons during peripheral nerve myelin formation.

Peripheral nerve myelination is a complex event resulting from spatially and temporally regulated reciprocal interactions between the neuron and myelin‐forming Schwann cells. The dynamic process and the protein functional modules and networks that operate throughout the myelination process are poorly understood because of a lack of methodologies suitable for observing specific changes in the Schwann cell/neuron‐unit. The identification of the precise roles for the proteins participating in the functional modules and networks that participate in the myelination process is hindered by the cellular and molecular complexity of the nervous tissue itself. We have developed an approach based on a myelinating dorsal root ganglion explant model that allows distinguishing clear, reproducible and predictable differences between the biochemical properties and the genomic and proteomic expression profiles of both cellular components of the Schwann cell/neuron unit at different stages of the myelination process. This model, derived from E13.5 C57BL/6J mouse embryos, is sufficiently robust for use in identifying the protein functional networks and modules related to peripheral nerve myelin formation. The genomic expression profiles of the selected neuronal, Schwann cell and myelin‐specific proteins in the cultures reflect in vivo profiles reported in the literature, and the structural and ultrastructural properties of the myelin, as well as the myelination schedule of the cultures, closely resemble those observed in peripheral nerves in situ. The RNA expression data set is available through NCBI gene expression omnibus accession GSE60345.

Molecular and Cellular Basis of Human Cutaneous Neurofibromas and Their Development

Multiple cutaneous neurofibromas are one of the two most classical characteristics of neurofibromatosis 1. Cutaneous neurofibromas are benign tumors which never undergo malignant transformation but create the main disease burden in most adult patients with NF1. Cutaneous neurofibromas most commonly begin to grow during puberty, and they increase in number throughout life so that eventually the number of these tumors may reach thousands. Cutaneous neurofibromas have a limited growth potential allowing the final size of tumors to seldom exceed 2–3 cm.