Identification of a recurrent mosaic KRAS variant in brain tissue from an individual with nevus sebaceous syndrome

Nevus sebaceous syndrome (NSS) is a rare multisystem neurocutaneous syndrome, characterised by a congenital nevus, and may include brain malformations such as hemimegalencephaly or focal cortical dysplasia, ocular and skeletal features. It has been associated with several eponyms including Schimmelpenning and Jadassohn. The isolated skin lesion, nevus sebaceous, is associated with post-zygotic variants in HRAS or KRAS in all patients studied. The RAS proteins encode a family of GTPases that form part of the RAS/MAPK signalling pathway, which is critical for cell cycle regulation and differentiation during development. We studied an individual with nevus sebaceous syndrome with an extensive nevus sebaceous, epilepsy, intellectual disability, and hippocampal sclerosis without pathological evidence of a brain malformation. We utilized high depth gene panel sequencing and sensitive droplet digital PCR to detect and quantify RAS/MAPK gene variants in nevus sebaceous and temporal lobe tissue collected during plastic and epilepsy surgery, respectively. A mosaic KRAS c.34G>T; p.(Gly12Cys) variant, also known as G12C, was detected in nevus sebaceous tissue at 25% variant allele fraction (VAF), at the residue most commonly substituted in KRAS. Targeted droplet digital PCR validated the variant and quantified the mosaicism in other tissues. The variant was detected at 33% in temporal lobe tissue, but was absent from blood and healthy skin. We provide molecular confirmation of the clinical diagnosis of NSS. Our data extends the histopathological spectrum of KRAS G12C mosaicism beyond nevus sebaceous to involve brain tissue and more specifically, hippocampal sclerosis.

Filamin A and Parafibromin Expression in Parathyroid Carcinoma

Objective: Parathyroid carcinoma (PC), atypical parathyroid tumors (APT) and parathyroid adenoma (PA) present with hypercalcemia. Diminished calcium-sensing receptor (CaSR) expression is reported in PC but is rare in benign tumours. Filamin A (FLNA) binds to the CaSR and activates the mitogen-activated protein kinase (MAPK) signalling pathway. FLNA is related to tumour aggressiveness in several cancers, but its role in parathyroid neoplasia is unknown. Design: We examined FLNA, CaSR and parafibromin expression in PCs (n = 32), APTs (n = 44) and PAs (n = 77) and investigated their potential as diagnostic and/or prognostic markers. Methods: Tissue microarray slides were immunohistochemically stained with FLNA, CaSR and parafibromin. Staining results were correlated with detailed clinical data. Results: All tumours stained positively for CaSR, with two tumours (one PC and one APT) showing diminished expression. Carcinomas were characterized by increased cytoplasmic FLNA expression compared to APTs and PAs (p = 0.004). FLNA expression was not correlated with Ki-67 proliferation index or loss of parafibromin expression. Cytoplasmic FLNA expression was also associated with higher serum calcium, PTH concentrations and male sex (p = 0.014, p = 0.017 and p = 0.049, respectively). Using a combined marker score, we found that parathyroid tumours with low FLNA expression and positive parafibromin staining were extremely likely to be benign (p < 0.001). Conclusion: Cytoplasmic and membranous FLNA expression is increased in parathyroid carcinomas compared to benign tumours. A combined FLNA and parafibromin expression score shows potential as a prognostic predictor of indolent behaviour in parathyroid neoplasms.

Lymphatic Abnormalities in Noonan Syndrome Spectrum Disorders: A Systematic Review

Noonan syndrome spectrum disorders are a group of phenotypically related conditions, resembling Noonan syndrome, caused by germline pathogenic variants in genes within the Ras/mitogen-activated protein kinase (Ras/MAPK) signalling pathway. Lymphatic dysplasia with a clinical lymphatic abnormality is one of the major features. We performed a systematic review to get more insight in (1) the prevalence of clinically lymphatic abnormalities in patients with a genetically proven Noonan syndrome spectrum disorder, (2) if a genotype-lymphatic phenotype relation can be found and describe the clinical presentation and course of the lymphatic abnormality. Most studies report patients with Noonan syndrome. Prenatally, the prevalence of increased nuchal translucency differs from 7% in patients with pathogenic <i>PTPN11</i> variant<i>s</i> to 38% in patients with pathogenic <i>RIT1</i> variants, and the prevalence of pleural effusions differed from 7% in patients with pathogenic <i>SOS1</i> to 29% in patients with pathogenic <i>RIT1</i> variants. Postnatally, the prevalence of lymphedema differs from 16% in patients with pathogenic <i>PTPN11</i> variants to 44% in patients with pathogenic <i>SOS1</i> variants, and the prevalence of acquired chylothorax is 4% in patients with pathogenic <i>RIT1</i> variants. Lymphatic abnormalities do occur in patients with cardiofaciocutaneous syndrome and Costello syndrome. In conclusion, Noonan syndrome spectrum disorders, Noonan syndrome in particular, are associated with lymphatic abnormalities. Combining the available published literature about genetically proven Noonan syndrome spectrum disorders, it appears likely that the lifetime prevalence of these abnormalities in Noonan syndrome is higher than the 20% that were generally accepted so far. This is increasingly important, because the activation of the RAS/MAPK pathway can be inhibited by RAS/MAPK inhibitors, and clinically severe lymphatic abnormalities may improve.

RNA-Seq, physiological, and biochemical analysis of burley tobacco response to nitrogen deficiency

To explore the effects of nitrogen deficiency in burley tobacco, two varieties were cultivated and subjected to conditions of sufficient and deficient nitrogen. The natural characteristics of varieties TN90 and TN86 during tobacco cultivation were similar for nitrogen metabolism. Both carbon and nitrogen metabolism were significantly affected by reducing amounts of applied nitrogen. Under nitrogen-deficient conditions, average leaf biomass, root weight, photosynthetic rate (Pn), pigment levels, total nitrogen, and nitrate content of TN86 and TN90 were significantly decreased by 52.88%, 69.19%, 22.65%, 46.80%, 37.42%, and 79.15%, respectively (p < 0.01). Nicotine and soluble reducing sugar contents were significantly decreased by 96.67% and 95.12%, respectively, in TN86 roots (p < 0.01), which was consistent with the reductions in root surf area, average diameter, and root volume. Nitrogen deficiency induced 6318 differentially expressed genes in both TN90 and TN86, which were highly expressed. In total, 428 upregulated genes were analysed and found to be mainly enriched in the MAPK signalling pathway, sesquiterpenoid and triterpenoid biosynthesis, and arginine and proline metabolism. Meanwhile, 213 downregulated genes were analysed and found to be mainly enriched in photosynthesis, nitrogen metabolism, and amino acid biosynthesis. Reduced pigment content and Pn may result in low carbohydrate formation and decreased leaf biomass in burley tobacco under nitrogen-deficient conditions.

Role of Exosomal microRNAs and lncRNAs in the Follicular Fluid of Women With Polycystic Ovary Syndrome

Polycystic ovary syndrome (PCOS) is a complex class of endocrine disorders with insulin resistance, compensatory hyperinsulinaemia and obesity. However, the pathogenesis and therapies of PCOS have not been fully elucidated. Exosomal miRNAs have the potential to serve as biomarkers and therapies for a wide range of medical conditions. In this study, we isolated exosomes from follicular fluid collected from 5 PCOS patients and 5 non-PCOS patients. miRNA cDNA library sequencing identified 124 miRNAs that were significantly upregulated nearly twofold, while 33 miRNAs were significantly downregulated nearly twofold in PCOS follicular fluid exosomes. These miRNA target genes were mainly involved in metabolic pathways, pathways in cancer, the PI3K-Akt signalling pathway, the MAPK signalling pathway, endocytosis, the Ras signalling pathway, the Hippo signalling pathway, and cellular senescence. According to the previously reported exosomal lncRNA data of PCOS follicular fluid, a miRNA and lncRNA coexpression network developed from data from starBase strictly screened 29 differentially expressed miRNAs. This network also helped to identify miRNA signatures associated with metabolic processes in PCOS. Collectively, these results demonstrate the potential pathogenesis of PCOS, and follicular fluid exosomal miRNAs may be efficient targets for the diagnosis and treatment of PCOS in long-term clinical studies.