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Mosaic KRAS variants and other RASopathy genes cause oculoectodermal, encephalo-cranio-cutaneous lipomatosis, and Schimmelpenning-Feuerstein-Mims syndromes, and a spectrum of vascular malformations, overgrowth and other associated anomalies, the latter of which are only recently being characterized. We describe eight individuals in total (six unreported cases and two previously reported cases) with somatic KRAS variants and variably associated features. Given the findings of somatic overgrowth (in seven individuals) and vascular or lymphatic malformations (in eight individuals), we suggest mosaic RASopathies (mosaic KRAS variants) be considered in the differential diagnosis for individuals presenting with asymmetric overgrowth and lymphatic or vascular anomalies. We expand the association with embryonal tumors, including the third report of embryonal rhabdomyosarcoma, as well as novel findings of Wilms tumor and nephroblastomatosis in two individuals. Rare or novel findings in our series include the presence of epilepsy, polycystic kidneys, and T-cell deficiency in one individual, and multifocal lytic bone lesions in two individuals. Finally, we describe the first use of targeted therapy with a MEK inhibitor for an individual with a mosaic KRAS variant. The purposes of this report are to expand the phenotypic spectrum of mosaic KRAS-related disorders, and to propose possible mechanisms of pathogenesis, and surveillance of its associated findings.

RASopathies are a group of genetic disorders that are caused by genes that affect the canonical Ras/mitogen-activated protein kinase (MAPK) signaling pathway. Despite tremendous progress in understanding the molecular consequences of these genetic anomalies, little movement has been made in translating these findings to the clinic. This year, the seventh International RASopathies Symposium focused on expanding the research knowledge that we have gained over the years to enhance new discoveries in the field, ones that we hope can lead to effective therapeutic treatments. Indeed, for the first time, research efforts are finally being translated to the clinic, with compassionate use of Ras/MAPK pathway inhibitors for the treatment of RASopathies. This biannual meeting, organized by the RASopathies Network, brought together basic scientists, clinicians, clinician scientists, patients, advocates, and their families, as well as representatives from pharmaceutical companies and the National Institutes of Health. A history of RASopathy gene discovery, identification of new disease genes, and the latest research, both at the bench and in the clinic, were discussed.

Congenital hiatal hernia (HH) is a rare congenital defect and is often described on a sporadic basis, but familial cases have also been reported. The mechanism of development is not well understood, and to our knowledge no specific genetic factors have been implicated to date. We report on seven individuals from two families with 9q22 duplication, who have variably associated features including congenital HH in four individuals. One family had an 1.09 Mb 9q22 duplication, and the other family had an overlapping 2.73 Mb 9q22 duplication. We review the genes in this region and discuss BARX1 (BarH-like homeobox gene 1) as a gene of interest.

Mosaic RASopathies are an emerging group of disorders characterized by mosaic or post-zygotic activating mutations in genes of the RAS/MAPKinase signaling pathway. The phenotype is highly variable, ranging from limited or localized forms to cases with a syndromic presentation with extensive or multiorgan involvement, and also overlaps with other mosaic disorders. While there are several reports of malignancies in patients with mosaic RASopathies, specifically rhabdomyosarcoma and transitional urothelial carcinoma, the lifetime risk and molecular mechanisms that lead to the development of malignancies remain unclear. We report a 22-month-old boy with a somatic RASopathy due to an underlying KRAS p.G12D mutation who presented with a large unilateral epidermal nevus, asymmetric lower limb overgrowth with lytic and sclerotic bone lesions, capillary malformation, bilateral nephrogenic rests and Wilms tumors, and a novel complex renal vascular anomaly that resembles Fibro-Adipose Vascular Anomaly (FAVA). This report further expands the phenotypic spectrum of somatic RASopathies, and discusses the potential phenotypic and pathogenetic overlap with PIK3CA-related overgrowth disorders, specifically CLOVES. The occurrence of a secondary cancer hotspot mutation ( FBXW7 p.R479G ) in the Wilms tumor, but not the associated nephrogenic rest, moreover suggests that additional driver mutations are involved in the development of Wilms tumor in somatic overgrowth disorders.

Background Primary open angle glaucoma (POAG) patients have hallmark increases in intraocular pressure (IOP) and noted dysfunction of the trabecular meshwork (TM). Connexin43 (Cx43) is a gap junction widely expressed on the TM that is important for intercellular communication. The human gene is known as gap junction alpha-1 (GJA1). Since the role of Cx43 in the TM is not fully understood, we set out to determine the effect of excess mechanical stretch on cultured human trabecular meshwork cells (hTMCs) and to specifically investigate the effect of stretch on Cx43 expression and function. Methods Primary hTMCs were cultured and subjected to 48 hours of 15% cyclic mechanical stretch at a frequency of 1 Hz. Levels of apoptosis and necrosis secondary to stretch were investigated using colorimetric assays. The effect of stretch on gap junction Cx43 and GJA1 was investigated by RT-PCR, immunoblotting and immunofluorescence. The migration of Lucifer Yellow dye was used to assess intercellular communication. Results Stretch significantly increased the rates of apoptosis and necrosis in hTMCs. The increased rate of injury in stretched hTMCs was further associated with significant upregulation of GJA1 mRNA and Cx43 protein. Upregulation of Cx43 protein was concomitant to increased intercellular communication. Conclusions We have shown stretch to increase GJA1 gene and Cx43 protein expression, as well as intercellular communication. We have further shown stretch to be injurious to hTMCs. Upregulation of Cx43 in the hTM subsequent to stretch is a novel finding, which may be useful in elucidating the mechanism of TM injury in POAG patients.

Background Benzalkonium chloride (BAK) is a controversial ophthalmic preservative because of its prominent side-effect profile. In this study, we examined the mechanism of BAK toxicity in human trabecular meshwork cells (HTMC) and compared the effects of BAK with tafluprost free acid, which is an active form of tafluprost commercially available in a preservative-free formulation. Methods Primary HTMC were treated with different BAK concentrations over various exposure times. Cell viability was quantified using the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenol tetrazolium bromide assay, and apoptosis was measured by enzyme-linked immunosorbent assay. The cell viability of primary HTMC exposed to various concentrations and times of tafluprost free acid was also determined. Cells were treated with BAK and tafluprost free acid for 30 min at 37°C, and cell viability was again assessed. The effect of BAK on the gap junction protein Connexin-43 (Cx43) expression was subsequently examined. Results BAK treatment resulted in a dose- and time-dependent decline in cell viability. Apoptosis increased following BAK treatment. Tafluprost-free acid treatment did not significantly affect cell viability. Tafluprost co-treatment with BAK resulted in an increase in cell viability as compared with BAK treatment alone. BAK treatment upregulated Cx43 expression in HTMC. Conclusions These results demonstrate that BAK is harmful to the health of cultured HTMC. Tafluprost is both safe and cytoprotective against BAK for these HTMC. The effect of tafluprost on the gap junctions of the HTM should be further investigated.