Dov Hershkovitz

RASA1 mutations may cause hereditary capillary malformations without arteriovenous malformations

Background  Capillary malformation (CM), a common vascular abnormality, is often present among family members. Recently a rare form of hereditary vascular malformation termed capillary malformation–arteriovenous malformation (CM‐AVM) was shown to be caused by heterozygous mutations in RASA1, encoding RAS p21 protein activator 1. CM‐AVM is characterized by multiple, small CMs associated with either AVM or arteriovenous fistula (AVF) in affected individuals or at least one of their family members.

RIN2 Deficiency Results in Macrocephaly, Alopecia, Cutis Laxa, and Scoliosis: MACS Syndrome

Inherited disorders of elastic tissue represent a complex and heterogeneous group of diseases, characterized often by sagging skin and occasionally by life-threatening visceral complications. In the present study, we report on an autosomal-recessive disorder that we have termed MACS syndrome (macrocephaly, alopecia, cutis laxa, and scoliosis). The disorder was mapped to chromosome 20p11.21-p11.23, and a homozygous frameshift mutation in RIN2 was found to segregate with the disease phenotype in a large consanguineous kindred. The mutation identified results in decreased expression of RIN2, a ubiquitously expressed protein that interacts with Rab5 and is involved in the regulation of endocytic trafficking. RIN2 deficiency was found to be associated with paucity of dermal microfibrils and deficiency of fibulin-5, which may underlie the abnormal skin phenotype displayed by the patients.

A novel mutation in RASA1 causes capillary malformation and limb enlargement

Capillary malformations are common vascular malformations. Several syndromes have been described in which CMs are present in association with limb enlargement, among these are Klippel–Trenaunay syndrome (KTS) and Parkes Weber syndrome (PWS). Mutations in the RASA1 gene have been shown to underlie the capillary malformation–arterio-venous malformation (CM–AVM) syndrome, sometimes presenting with PWS. We identified a family comprising a patient with CMs and limb enlargement and a number of family members with CM/CM–AVM. A novel mutation in RASA1 was found to underlie the disease in this case. The present results illustrate the extensive degree of phenotypic heterogeneity associated with deleterious mutations in RASA1.

Functional Characterization of SAMD9, a Protein Deficient in Normophosphatemic Familial Tumoral Calcinosis

Dystrophic cutaneous calcinosis is associated with disorders as common as autoimmune diseases and cancer. To get insight into the pathogenesis of this poorly understood process, we studied the function of SAMD9, a protein of unknown function, recently shown to be deficient in a hereditary form of dystrophic calcification in the skin, known as normophosphatemic familial tumoral calcinosis (NFTC). Consistent with the fact that in NFTC severe inflammatory manifestations always precede cutaneous calcinosis, we found out that SAMD9 is tightly regulated by interferon-γ (IFN-γ). In addition, the SAMD9 promoter was also found to respond strongly to IFN-γ in a luciferase reporter assay. Of interest, we identified a critical 30-bp fragment upstream to the SAMD9 transcription initiation site responsible for driving most of the gene expression. Bioinformatic analysis suggested that SAMD9 function involves interaction with additional protein(s). Using the Ras recruitment system assay and confirmatory immunoprecipitation, we demonstrated that SAMD9 interacts with RGL2. To study the biological importance of this interaction, we assessed the effect of RNA interference-mediated downregulation of this pair of proteins in various cell lines. We found out that downregulation of any of the two protein partners caused increased expression of EGR1, a transcription factor with a known role in the regulation of tissue calcification, inflammation, and cell migration. Supporting the physiological relevance of these data, EGR1 levels were also upregulated in a fibroblast cell line derived from an NFTC patient. In conclusion, our data indicate that SAMD9, an IFN-γ-responsive protein, interacts with RGL2 to diminish the expression of EGR1, a protein of direct relevance to the pathogenesis of ectopic calcification and inflammation.

Defective Lamellar Granule Secretion in Arthrogryposis, Renal Dysfunction, and Cholestasis Syndrome Caused by a Mutation in VPS33B

BACKGROUND Arthrogryposis, renal dysfunction, and cholestasis (ARC) syndrome is a rare and usually fatal metabolic autosomal recessive disorder, which has recently been shown to result from mutations in VPS33B located on chromosome 15q26.1. Neurological signs and ichthyosis almost invariably accompany the disease. OBSERVATIONS We assessed a consanguineous family with 2 identical twins affected with ARC syndrome. Complete sequencing of the VPS33B gene revealed a homozygous missense mutation (D234H), which segregated with the disease in the affected family. The mutation causes aberrant splicing, resulting in the skipping of exon 9 or exons 9 and 10. VPS33B encodes a homologue of the class C yeast vacuolar protein-sorting molecule, Vps33, which regulates soluble N-ethylmaleimide-sensitive factor attachment protein receptor (SNARE) protein-mediated vesicle-to-target fusion, necessary for secretion to occur. Lamellar granules, forming a specialized vesicular system in the epidermal upper layers, are usually secreted at the boundary between granular and lower cornified cell layers. However, ultrastructural examination of the skin in ARC syndrome revealed many entombed lamellar granules in the cornified cells. CONCLUSIONS The present observations indicate that VPS33B deficiency results in abnormal secretion of lamellar granules, which underlies ichthyosis in ARC syndrome. These data underscore the importance of SNARE-mediated vesicle fusion during normal epidermal differentiation.

Disadhesion of epidermal keratinocytes: A histologic clue to palmoplantar keratodermas caused by DSG1 mutations

BACKGROUND Recent developments in molecular genetics may lead to re-examination of the histopathology of inherited palmoplantar keratodermas (PPKs) based on more precise groupings of the various entities and syndromes. OBJECTIVE We sought to characterize the histopathological findings in PPKs associated with mutations in DSG1, which encodes desmoglein 1. METHODS We studied the histopathology of 3 cases of keratosis palmoplantaris striata type I and one case of diffuse PPK, all associated with autosomal-dominant mutations in DSG1. Our cases for comparison included 4 cases with Mal de Meleda PPK associated with autosomal-recessive SLURP1 mutations, one case with pachyonychia congenita type II PPK associated with an autosomal-dominant KRT17 mutation, and one case with focal PPK associated with an autosomal-dominant KRT16 mutation. RESULTS The distinguishing histopathological features of the 3 keratosis palmoplantaris striata type I cases and the diffuse PPK case associated with DSG1 mutation were: varying degrees of widening of the intercellular spaces and partial disadhesion of keratinocytes in the mid and upper epidermal spinous cell layers, often extending to the granular cell layer. These findings, which are associated with haploinsufficiency of desmoglein 1, were not observed in any of the other 6 PPK cases. Mild perinuclear eosinophilic condensations and cytoplasmic vacuolizations were observed in the spinous cell layer keratinocytes of the pachyonychia congenita type II PPK and the nonspecified focal PPK cases. LIMITATIONS There were a limited number of patients and control patients with hereditary PPKs. CONCLUSION Widening of the intercellular spaces and disadhesion of epidermal keratinocytes may serve as a histologic clue to PPKs caused by DSG1 mutations.

Novel mutations in GALNT3 causing hyperphosphatemic familial tumoral calcinosis

Hyperphosphatemic familial tumoral calcinosis (HFTC) is known to be caused by mutations in at least three genes: FGF23, GALNT3 and KL. Two families with two affected members suffering from HFTC were scrutinized for mutations in these candidate genes. We identified in both families homozygous missense mutations affecting highly conserved amino acids in GALNT3. One of the mutations is a novel mutation, whereas the second mutation was reported before in a compound heterozygous state. Our data expand the spectrum of known mutations in GALNT3 and contribute to a better understanding of the phenotypic manifestations of mutations in this gene.

Buschke-Ollendorff syndrome in a three-generation family: Influence of a novel LEMD3 mutation to tropoelastin expression

Buschke-Ollendorff syndrome refers to the concomitant occurrence of connective tissue nevi, composed of elastic fibers in most cases, with osteopoikilosis. This autosomal dominant inherited disorder is caused by mutations in the gene LEMD3 on chromosome 12q14, which induces a rather heterogeneous clinical phenotype. Here, we report on the most proximal germline mutation found to date in the LEMD3 gene, p.Val94fs, in a three-generation Swiss family. Quantitative RNA analyses in affected and non-affected skin tissue from the proband demonstrate a comparable nonsense-mediated decay of mutant LEMD3 mRNA in both tissues; however, different levels of tropoelastin expression suggest that additional factors are involved in the development of the cutaneous lesions.

Novel mutations in DSG1 causing striate palmoplantar keratoderma.

Background.  Striate palmoplantar keratoderma (SPPK) has been shown to be caused by mutations in at least three genes: DSG1, DSP and KRT1.

Macrophage-Induced Lymphangiogenesis and Metastasis following Paclitaxel Chemotherapy Is Regulated by VEGFR3

Summary While chemotherapy strongly restricts or reverses tumor growth, the response of host tissue to therapy can counteract its anti-tumor activity by promoting tumor re-growth and/or metastases, thus limiting therapeutic efficacy. Here, we show that vascular endothelial growth factor receptor 3 (VEGFR3)-expressing macrophages infiltrating chemotherapy-treated tumors play a significant role in metastasis. They do so in part by inducing lymphangiogenesis as a result of cathepsin release, leading to VEGF-C upregulation by heparanase. We found that macrophages from chemotherapy-treated mice are sufficient to trigger lymphatic vessel activity and structure in naive tumors in a VEGFR3-dependent manner. Blocking VEGF-C/VEGFR3 axis inhibits the activity of chemotherapy-educated macrophages, leading to reduced lymphangiogenesis in treated tumors. Overall, our results suggest that disrupting the VEGF-C/VEGFR3 axis not only directly inhibits lymphangiogenesis but also blocks the pro-metastatic activity of macrophages in chemotherapy-treated mice.