Generation and phenotype of a transgenic knockout mouse lacking the mercurial-insensitive water channel aquaporin-4.
Aquaporin-4 (AQP4) is a mercurial-insensitive, water-selective channel that is expressed in astroglia and basolateral plasma membranes of epithelia in the kidney collecting duct, airways, stomach, and colon. A targeting vector for homologous recombination was constructed using a 7-kb SacI AQP4 genomic fragment in which part of the exon 1 coding sequence was deleted. Analysis of 164 live births from AQP4[+/-] matings showed 41 [+/+], 83 [+/-], and 40 [-/-] genotypes. The [-/-] mice expressed small amounts of a truncated AQP4 transcript and lacked detectable AQP4 protein by immunoblot analysis and immunocytochemistry. Water permeability in an AQP4-enriched brain vesicle fraction in [+/+] mice was high and mercurial insensitive, and was decreased by 14-fold in [-/-] mice. AQP4 deletion did not affect growth or tissue morphology at the light microscopic level. Northern blot analysis showed that tissue-specific expression of AQPs 1, 2, 3, and 5 was not affected by AQP4 deletion. Maximum urine osmolality after a 36-h water deprivation was (in mosM, n = 15) [+/+] 3,342+/-209, [+/-] 3, 225+/-167, and [-/-] 2,616+/-229 (P < 0.025), whereas urine osmolalities before water deprivation did not differ among the genotypes. Rotorod analysis of 35- 38-d-old mice revealed no differences in neuromuscular function (performance time in s, n = 8): [+/+] 297+/-25, [+/-] 322+/-28, [-/-] 288+/-37. These results indicate that AQP4 deletion in CD1 mice has little or no effect on development, survival, growth, and neuromuscular function, but produces a small defect in urinary concentrating ability consistent with its expression in the medullary collecting duct.
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T
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Department of Medicine, Cardiovascular Research Institute, University of California, San Francisco, California 94143-0521, USA.
Yang
B
B
Gillespie
A
A
Carlson
E J
EJ
Epstein
C J
CJ
Verkman
A S
AS
D000818:Animals; D051399:Aquaporin 2; D051401:Aquaporin 4; D051403:Aquaporin 6; D020346:Aquaporins; D005260:Female; D007473:Ion Channels / Q000235:genetics / Q000502:physiology*; D007671:Kidney Concentrating Ability; D008297:Male; D008628:Mercury / Q000494:pharmacology*; D051379:Mice; D018345:Mice, Knockout; D010641:Phenotype; D012333:RNA, Messenger / Q000032:analysis; D014882:Water-Electrolyte Balance
C496024:Aqp2 protein, mouse; C496031:Aqp4 protein, mouse; D051399:Aquaporin 2; D051401:Aquaporin 4; D051403:Aquaporin 6; D020346:Aquaporins; D007473:Ion Channels; D012333:RNA, Messenger; D008628:Mercury