Local knockdown of genes in the brain using small interfering RNA: a phenotypic comparison with knockout animals.
BACKGROUND
Recent reports have suggested effectiveness of RNA interference (RNAi) for the analysis of gene functions in the brain. This study sought to determine the efficiency of local small interfering RNA (siRNA) injections, comparing this approach with animals generated through classical gene targeting.


METHODS
Small interfering RNA against dopamine transporter (DAT) (35 microg/14 days) or tyrosine hydroxylase (TH) (15 microg/3 days) was injected into the ventral tegmental/substantia nigra areas of the brain of adult wildtype or DAT-knockout mice, respectively.


RESULTS
Local injections of siRNA resulted in a 35% to 40% reduction of DAT and TH protein levels in the striatum, respectively. Despite negligible effect of DAT knockdown on novelty-induced locomotion, the locomotor response of DAT siRNA treated animals to amphetamine was blunted similar to what is observed in the DAT heterozygote animals. Since incomplete reduction of TH levels in normal mice does not produce behavioral effects, TH siRNA experiments were carried out in DAT-knockout animals that show increased dependence on newly synthesized dopamine. Knockdown of TH in these animals resulted in reduced basal locomotion.


CONCLUSIONS
Local injection of siRNA in the brain reduced gene expression by 40% to 50%, suggesting that siRNA-mediated knockdown of genes in the brain can be a complementary tool to classical transgenesis for the analysis of gene functions.
Salahpour
Ali
A
Department of Cell Biology, Duke University Medical Center, Durham, North Carolina 27710, USA.
Medvedev
Ivan O
IO
Beaulieu
Jean-Martin
JM
Gainetdinov
Raul R
RR
Caron
Marc G
MG
D000818:Animals; D001522:Behavior, Animal / Q000187:drug effects / Q000502:physiology; D015153:Blotting, Western / Q000379:methods; D001921:Brain / Q000187:drug effects* / Q000378:metabolism*; D050483:Dopamine Plasma Membrane Transport Proteins / Q000235:genetics / Q000378:metabolism; D004333:Drug Administration Routes; D005106:Exploratory Behavior / Q000187:drug effects / Q000502:physiology; D005786:Gene Expression Regulation / Q000187:drug effects / Q000235:genetics; D007150:Immunohistochemistry / Q000379:methods; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout / Q000502:physiology*; D010641:Phenotype; D034741:RNA, Small Interfering / Q000494:pharmacology*; D013997:Time Factors; D014446:Tyrosine 3-Monooxygenase / Q000235:genetics / Q000378:metabolism
D050483:Dopamine Plasma Membrane Transport Proteins; D034741:RNA, Small Interfering; D014446:Tyrosine 3-Monooxygenase