Novel germline MET pathogenic variants in French patients with papillary renal cell carcinomas type I

Hereditary papillary renal cell carcinoma (HPRC) is a rare inherited renal cancer syndrome characterized by bilateral and multifocal papillary type 1 renal tumors (PRCC1). Activating germline pathogenic variants of MET gene were identified in HPRC families. We reviewed the medical and molecular records of a large French series of 158 patients screened for MET oncogenic variants. MET pathogenic and likely pathogenic variants rate was 12.4% with 40.6% among patients with familial PRCC1 and 5% among patients with sporadic PRCC1. The phenotype in cases with MET pathogenic and likely pathogenic variants was characteristic: PRCC1 tumors were mainly bilateral (84.3%) and multifocal (87.5%). Histologically, six out of seven patients with MET pathogenic variant harboured biphasic squamoid alveolar PRCC. Genetic screening identified one novel pathogenic variant MET c.3389T>C, p.(Leu1130Ser) and three novel likely pathogenic variants: MET c.3257A>T, p.(His1086Leu); MET c.3305T>C, p.(Ile1102Thr) and MET c.3373T>G, p.(Cys1125Gly). Functional assay confirmed their oncogenic effect as they induced an abnormal focus formation. The genotype-phenotype correlation between MET pathogenic variants and PRCC1 presentation should encourage to widen the screening, especially toward non-familial PRCC1. This precise phenotype also constitutes a strong argument for the classification of novel missense variants within the tyrosine kinase domain when functional assays aren't accessible. This article is protected by copyright. All rights reserved.

Indirect application of near infrared light induces neuroprotection in a mouse model of parkinsonism - an abscopal neuroprotective effect

We have previously shown near infrared light (NIr), directed transcranially, mitigates the loss of dopaminergic cells in MPTP (1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine)-treated mice, a model of parkinsonism. These findings complement others suggesting NIr treatment protects against damage from various insults. However one puzzling feature of NIr treatment is that unilateral exposure can lead to a bilateral healing response, suggesting NIr may have 'indirect' protective effects. We investigated whether remote NIr treatment is neuroprotective by administering different MPTP doses (50-, 75-, 100-mg/kg) to mice and treating with 670-nm light directed specifically at either the head or body. Our results show that, despite no direct irradiation of the damaged tissue, remote NIr treatment produces a significant rescue of tyrosine hydroxylase-positive cells in the substantia nigra pars compacta at the milder MPTP dose of 50-mg/kg (∼30% increase vs sham-treated MPTP mice, p<0.05). However this protection did not appear as robust as that achieved by direct irradiation of the head (∼50% increase vs sham-treated MPTP mice, p<0.001). There was no quantifiable protective effect of NIr at higher MPTP doses, irrespective of the delivery mode. Astrocyte and microglia cell numbers in substantia nigra pars compacta were not influenced by either mode of NIr treatment. In summary, the findings suggest that treatment of a remote tissue with NIr is sufficient to induce protection of the brain, reminiscent of the 'abscopal effect' sometimes observed in radiation treatment of metastatic cancer. This discovery has implications for the clinical translation of light-based therapies, providing an improved mode of delivery over transcranial irradiation.

Convergence of apical and basolateral endocytic pathways at apical late endosomes in absorptive cells of suckling rat ileum in vivo

Absorptive cells of the intestinal epithelium endocytose proteins from both apical and basolateral membrane domains. In absorptive cells of suckling rat ileum, luminal protein tracers first enter an apical tubulovesicular endosomal system, then enter larger apical endosomal vesicles and multivesicular bodies (MVB), and finally are delivered to a giant supranuclear lysosomal vacuole. To determine whether proteins endocytosed from the basolateral domain in vivo enter the same endosomal or lysosomal compartments as those taken up from the apical side, we simultaneously applied cationized ferritin (CF) apically (by intra-luminal injection) and horseradish peroxidase (HRP) basally (by intravenous injection), and examined absorptive cells after 3 min to 60 min using light, electron and fluorescence microscopy. At early times, CF and HRP entered separate endosomal compartments at apical and basolateral poles. At no time did HRP enter the apical tubulovesicular system, and CF never entered early basolateral endosomes. After 15 min, however, both tracers appeared together in large late endosomes and MVB located apically, above the giant vacuole. From 15 to 60 min both tracers accumulated in the giant vacuole. Membranes of some apical late endosomes, all apical MVB, the giant vacuole, and occasional sub-nuclear vesicles contained immunoreactive Igp120, a glycoprotein specific to late compartments of the endosome-lysosome system. These results show that highly polarized intestinal epithelial cells have separate apical and basolateral early endosomal compartments, presumably to maintain distinct membrane domains while allowing endocytosis and recycling of membrane from both surfaces. Apical and basolateral endocytic pathways, and presumably vesicles delivering hydrolytic enzymes and lysosomal membrane components, converge at the apical late endosome.