Miguel Sena‐Esteves

Huntington's disease (HD) is a neurodegenerative disorder caused by expansion of a CAG repeat in the huntingtin (Htt) gene. HD is autosomal dominant and, in theory, amenable to therapeutic RNA silencing. We introduced cholesterol-conjugated small interfering RNA duplexes (cc-siRNA) targeting human Htt mRNA (siRNA-Htt) into mouse striata that also received adeno-associated virus containing either expanded (100 CAG) or wild-type (18 CAG) Htt cDNA encoding huntingtin (Htt) 1-400. Adeno-associated virus delivery to striatum and overlying cortex of the mutant Htt gene, but not the wild type, produced neuropathology and motor deficits. Treatment with cc-siRNA-Htt in mice with mutant Htt prolonged survival of striatal neurons, reduced neuropil aggregates, diminished inclusion size, and lowered the frequency of clasping and footslips on balance beam. cc-siRNA-Htt was designed to target human wild-type and mutant Htt and decreased levels of both in the striatum. Our findings indicate that a single administration into the adult striatum of an siRNA targeting Htt can silence mutant Htt, attenuate neuronal pathology, and delay the abnormal behavioral phenotype observed in a rapid-onset, viral transgenic mouse model of HD.

Brain-derived neurotrophic factor (BDNF) and its receptor TrkB are expressed in several hypothalamic and hindbrain nuclei involved in regulating energy homeostasis, developmentally and in the adult animal. Their depletion during the fetal or early postnatal periods when developmental processes are still ongoing elicits hyperphagic behavior and obesity in mice. Whether BDNF is a chief element in appetite control in the mature brain remains controversial. The required sources of this neurotrophin are also unknown. We show that glucose administration rapidly induced BDNF mRNA expression, mediated by Bdnf promoter 1, and TrkB transcription in the ventromedial hypothalamus (VMH) of adult mice, consistent with a role of this pathway in satiety. Using viral-mediated selective knock-down of BDNF in the VMH and dorsomedial hypothalamus (DMH) of adult mice, we were able to elucidate the physiological relevance of BDNF in energy balance regulation. Site-specific mutants exhibited hyperphagic behavior and obesity but normal energy expenditure. Furthermore, intracerebroventricular administration of BDNF triggered an immediate neuronal response in multiple hypothalamic nuclei in wild-type mice, suggesting that its anorexigenic actions involve short-term mechanisms. Locomotor, aggressive, and depressive-like behaviors, all of which are associated with neural circuits involving the VMH, were not altered in VMH/DMH-specific BDNF mutants. These findings demonstrate that BDNF is an integral component of central mechanisms mediating satiety in the adult mouse and, moreover, that its synthesis in the VMH and/or DMH is required for the suppression of appetite.

Noninvasive systemic gene delivery to the central nervous system (CNS) has largely been impeded by the blood–brain barrier (BBB). Recent studies documented widespread CNS gene transfer after intravascular delivery of recombinant adeno-associated virus 9 (rAAV9). To investigate alternative and possibly more potent rAAV vectors for systemic gene delivery across the BBB, we systematically evaluated the CNS gene transfer properties of nine different rAAVEGFP vectors after intravascular infusion in neonatal mice. Several rAAVs efficiently transduce neurons, motor neurons, astrocytes, and Purkinje cells; among them, rAAVrh.10 is at least as efficient as rAAV9 in many of the regions examined. Importantly, intravenously delivered rAAVs did not cause abnormal microgliosis in the CNS. The rAAVs that achieve stable widespread gene transfer in the CNS are exceptionally useful platforms for the development of therapeutic approaches for neurological disorders affecting large regions of the CNS as well as convenient biological tools for neuroscience research. Noninvasive systemic gene delivery to the central nervous system (CNS) has largely been impeded by the blood–brain barrier (BBB). Recent studies documented widespread CNS gene transfer after intravascular delivery of recombinant adeno-associated virus 9 (rAAV9). To investigate alternative and possibly more potent rAAV vectors for systemic gene delivery across the BBB, we systematically evaluated the CNS gene transfer properties of nine different rAAVEGFP vectors after intravascular infusion in neonatal mice. Several rAAVs efficiently transduce neurons, motor neurons, astrocytes, and Purkinje cells; among them, rAAVrh.10 is at least as efficient as rAAV9 in many of the regions examined. Importantly, intravenously delivered rAAVs did not cause abnormal microgliosis in the CNS. The rAAVs that achieve stable widespread gene transfer in the CNS are exceptionally useful platforms for the development of therapeutic approaches for neurological disorders affecting large regions of the CNS as well as convenient biological tools for neuroscience research.