Single cell-derived clonal analysis of human glioblastoma links functional and genomic heterogeneity

Meyer M, Reimand J, Lan X, Head R, Zhu X, Kushida M, Bayani J, Pressey JC, Lionel AC, Clarke ID, Cusimano M, Squire JA, Scherer SW, Bernstein M, Woodin MA, Bader GD, Dirks PB

Proc. Natl. Acad. Sci. U.S.A. 2015 Jan;112(3):851-6

PMID: 25561528

Abstract

Glioblastoma (GBM) is a cancer comprised of morphologically, genetically, and phenotypically diverse cells. However, an understanding of the functional significance of intratumoral heterogeneity is lacking. We devised a method to isolate and functionally profile tumorigenic clones from patient glioblastoma samples. Individual clones demonstrated unique proliferation and differentiation abilities. Importantly, naïve patient tumors included clones that were temozolomide resistant, indicating that resistance to conventional GBM therapy can preexist in untreated tumors at a clonal level. Further, candidate therapies for resistant clones were detected with clone-specific drug screening. Genomic analyses revealed genes and pathways that associate with specific functional behavior of single clones. Our results suggest that functional clonal profiling used to identify tumorigenic and drug-resistant tumor clones will lead to the discovery of new GBM clone-specific treatment strategies.

Parvalbumin and GAD65 interneuron inhibition in the ventral hippocampus induces distinct behavioral deficits relevant to schizophrenia

Nguyen R, Morrissey MD, Mahadevan V, Cajanding JD, Woodin MA, Yeomans JS, Takehara-Nishiuchi K, Kim JC

J. Neurosci. 2014 Nov;34(45):14948-60

PMID: 25378161

Abstract

Hyperactivity within the ventral hippocampus (vHPC) has been linked to both psychosis in humans and behavioral deficits in animal models of schizophrenia. A local decrease in GABA-mediated inhibition, particularly involving parvalbumin (PV)-expressing GABA neurons, has been proposed as a key mechanism underlying this hyperactive state. However, direct evidence is lacking for a causal role of vHPC GABA neurons in behaviors associated with schizophrenia. Here, we probed the behavioral function of two different but overlapping populations of vHPC GABA neurons that express either PV or GAD65 by selectively inhibiting these neurons with the pharmacogenetic neuromodulator hM4D. We show that acute inhibition of vHPC GABA neurons in adult mice results in behavioral changes relevant to schizophrenia. Inhibiting either PV or GAD65 neurons produced distinct behavioral deficits. Inhibition of PV neurons, affecting ∼80% of the PV neuron population, robustly impaired prepulse inhibition of the acoustic startle reflex (PPI), startle reactivity, and spontaneous alternation, but did not affect locomotor activity. In contrast, inhibiting a heterogeneous population of GAD65 neurons, affecting ∼40% of PV neurons and 65% of cholecystokinin neurons, increased spontaneous and amphetamine-induced locomotor activity and reduced spontaneous alternation, but did not alter PPI. Inhibition of PV or GAD65 neurons also produced distinct changes in network oscillatory activity in the vHPC in vivo. Together, these findings establish a causal role for vHPC GABA neurons in controlling behaviors relevant to schizophrenia and suggest a functional dissociation between the GABAergic mechanisms involved in hippocampal modulation of sensorimotor processes.

Kainate receptors coexist in a functional complex with KCC2 and regulate chloride homeostasis in hippocampal neurons

Mahadevan V, Pressey JC, Acton BA, Uvarov P, Huang MY, Chevrier J, Puchalski A, Li CM, Ivakine EA, Airaksinen MS, Delpire E, McInnes RR, Woodin MA

Cell Rep 2014 Jun;7(6):1762-70

PMID: 24910435

Abstract

KCC2 is the neuron-specific K+-Cl(-) cotransporter required for maintaining low intracellular Cl(-), which is essential for fast inhibitory synaptic transmission in the mature CNS. Despite the requirement of KCC2 for inhibitory synaptic transmission, understanding of the cellular mechanisms that regulate KCC2 expression and function is rudimentary. We examined KCC2 in its native protein complex in vivo to identify key KCC2-interacting partners that regulate KCC2 function. Using blue native-polyacrylamide gel electrophoresis (BN-PAGE), we determined that native KCC2 exists in a macromolecular complex with kainate-type glutamate receptors (KARs). We found that KAR subunits are required for KCC2 oligomerization and surface expression. In accordance with this finding, acute and chronic genetic deletion of KARs decreased KCC2 function and weakened synaptic inhibition in hippocampal neurons. Our results reveal KARs as regulators of KCC2, significantly advancing our growing understanding of the tight interplay between excitation and inhibition.