A critical developmental role for tgfbr2 in myogenic cell lineages is revealed in mice expressing SM22-Cre, not SMMHC-Cre.
Smooth muscle cell (SMC)-specific deletion of transforming growth factor beta (TGF-beta) signaling would help elucidate the mechanisms through which TGF-beta signaling contributes to vascular development and disease. We attempted to generate mice with SMC-specific deletion of TGF-beta signaling by mating mice with a conditional ("floxed") allele for the type II TGF-beta receptor (tgfbr2flox) to mice with SMC-targeted expression of Cre recombinase. We bred male mice transgenic for smooth muscle myosin heavy chain (SMMHC)-Cre with females carrying tgfbr2flox. Surprisingly, SMMHC-Cre mice recombined tgfbr2flox at low levels in SMC and at high levels in the testis. Recombination of tgfbr2flox in testis correlated with high-level expression of SMMHC-Cre in testis and germline transmission of tgfbr2null. In contrast, mice expressing Cre from a SM22alpha promoter (SM22-Cre) efficiently recombined tgfbr2flox in vascular and visceral SMC and the heart, but not in testis. Use of the R26R reporter allele confirmed that Cre-mediated recombination in vascular SMC was inefficient for SMMHC-Cre mice and highly efficient for SM22-Cre mice. Breedings that introduced the SM22-Cre allele into tgfbr2flox/flox zygotes in order to generate adult mice that are hemizygous for SM22-Cre and homozygous for tgfbr2flox- and would have conversion of tgfbr2flox/flox to tgfbr2null/null in SMC-produced no live SM22-Cre : tgfbr2flox/flox pups (P<0.001). We conclude: (1) "SMC-targeted" Cre lines vary significantly in specificity and efficiency of Cre expression; (2) TGF-beta signaling in the subset of cells that express SM22alpha is required for normal development; (3) generation of adult mice with absent TGF-beta signaling in SMC remains a challenge.
Frutkin
Andrew D
AD
Department of Medicine, University of Washington Box 357710, 1959 NE Pacific Street, Seattle, WA 98195-7710, USA.
Shi
Haikun
H
Otsuka
Goro
G
Levéen
Per
P
Karlsson
Stefan
S
Dichek
David A
DA
D000483:Alleles; D000818:Animals; D019070:Cell Lineage; D003433:Crosses, Genetic; D005260:Female; D018507:Gene Expression Regulation, Developmental; D006720:Homozygote; D019426:Integrases / Q000235:genetics; D008297:Male; D051379:Mice; D008822:Mice, Transgenic; D008840:Microfilament Proteins / Q000235:genetics / Q000378:metabolism*; D009124:Muscle Proteins / Q000235:genetics / Q000378:metabolism*; D009131:Muscle, Smooth, Vascular / Q000098:blood supply / Q000196:embryology / Q000378:metabolism*; D032389:Myocytes, Smooth Muscle / Q000378:metabolism*; D018995:Myosin Heavy Chains / Q000235:genetics / Q000378:metabolism*; D018125:Receptors, Transforming Growth Factor beta / Q000235:genetics / Q000502:physiology*; D011995:Recombination, Genetic; D015398:Signal Transduction; D013737:Testis / Q000196:embryology / Q000378:metabolism
D008840:Microfilament Proteins; D009124:Muscle Proteins; D018125:Receptors, Transforming Growth Factor beta; C051615:transgelin; C045073:Cre recombinase; D019426:Integrases; D018995:Myosin Heavy Chains