Improved tools for providing specific intraoperative diagnoses could improve patient care. In neurosurgery, intraoperatively differentiating non-operative lesions such as CNS B-cell lymphoma from operative lesions can be challenging, often necessitating immunohistochemical (IHC) procedures which require up to 24-48 hours. Here, we evaluate the feasibility of generating rapid ex vivo specific labeling using a novel lymphoma-specific fluorescent switchable aptamer. Our B-cell lymphoma-specific switchable aptamer produced only low-level fluorescence in its unbound conformation and generated an 8-fold increase in fluorescence once bound to its target on CD20-positive lymphoma cells. The aptamer demonstrated strong binding to B-cell lymphoma cells within 15 minutes of incubation as observed by flow cytometry. We applied the switchable aptamer to ex vivo xenograft tissue harboring B-cell lymphoma and astrocytoma, and within one hour specific visual identification of lymphoma was routinely possible. In this proof-of-concept study in human cell culture and orthotopic xenografts, we conclude that a fluorescent switchable aptamer can provide rapid and specific labeling of B-cell lymphoma, and that developing aptamer-based labeling approaches could simplify tissue staining and drastically reduce time to histopathological diagnoses compared with IHC-based methods. We propose that switchable aptamers could enhance expeditious, accurate intraoperative decision-making.
Here, I show that a Noonan Syndrome-linked gain-of-function mutation Raf1L613V, drives modest changes in astrocyte and oligodendrocyte progenitor cell (OPC) density in the mouse cortex and hippocampus. Raf1L613V mutant mice exhibited enhanced performance in hippocampal-dependent spatial reference and working memory and amygdala-dependent fear learning tasks. However, we observed normal perineuronal net (PNN) accumulation around mutant parvalbumin-expressing (PV) interneurons. Though PV-interneurons were minimally affected by the Raf1L613V mutation, other RASopathy mutations converge on aberrant GABAergic development as a mediator of neurological dysfunction.
I therefore hypothesized interneuron expression of the constitutively active Mek1S217/221E (caMek1) mutation would be sufficient to perturb GABAergic circuit development. Interestingly, the caMek1 mutation selectively disrupted crucial PV-interneuron developmental processes. During embryogenesis, I detected expression of cleaved-caspase 3 (CC3) in the medial ganglionic eminence (MGE). Interestingly, adult mutant cortices displayed a selective 50% reduction in PV-expressing interneurons, but not other interneuron subtypes. PV-interneuron loss was associated with seizure-like activity in mutants and coincided with reduced perisomatic synapses. Mature mutant PV-interneurons exhibited somal hypertrophy and a substantial increase in PNN accumulation. Aberrant GABAergic development culminated in reduced behavioral response inhibition, a process linked to ADHD-like behaviors. Collectively, these data provide insight into the mechanistic underpinnings of RASopathy neuropathology and suggest that modulation of GABAergic circuits may be an effective therapeutic option for RASopathy individuals.