Sohal D S, Nghiem M, Crackower M A, Witt S A, Kimball T R, Tymitz K M, Penninger J M, Molkentin J D
Department of Pediatrics, University of Cincinnati, Children's Hospital Medical Center, Division of Molecular Cardiovascular Biology, Cincinnati, Ohio, USA.
Circ Res. 2001 Jul 6;89(1):20-5. doi: 10.1161/hh1301.092687.
The advent of conditional and tissue-specific recombination systems in gene-targeted or transgenic mice has permitted an assessment of single gene function in a temporally regulated and cell-specific manner. Here we generated transgenic mice expressing a tamoxifen-inducible Cre recombinase protein fused to two mutant estrogen-receptor ligand-binding domains (MerCreMer) under the control of the alpha-myosin heavy chain promoter. These transgenic mice were crossed with the ROSA26 lacZ-flox-targeted mice to examine Cre recombinase activity and the fidelity of the system. The data demonstrate essentially no Cre-mediated recombination in the embryonic, neonatal, or adult heart in the absence of inducing agent but >80% recombination after only four tamoxifen injections. Expression of the MerCreMer fusion protein within the adult heart did not affect cardiac performance, cellular architecture, or expression of hypertrophic marker genes, demonstrating that the transgene-encoded protein is relatively innocuous. In summary, MerCreMer transgenic mice represent a tool for temporally regulated inactivation of any loxP-targeted gene within the developing and adult heart or for specifically directing recombination and expression of a loxP-inactivated cardiac transgene in the heart.
条件性和组织特异性重组系统在基因靶向或转基因小鼠中的出现，使得人们能够以时间调控和细胞特异性的方式评估单个基因的功能。在此，我们构建了转基因小鼠，其在α-肌球蛋白重链启动子的控制下表达与两个突变雌激素受体配体结合域融合的他莫昔芬诱导型Cre重组酶蛋白（MerCreMer）。这些转基因小鼠与ROSA26 lacZ-侧翼靶向小鼠杂交，以检测Cre重组酶活性和系统的保真度。数据表明，在没有诱导剂的情况下，胚胎、新生或成年心脏中基本没有Cre介导的重组，但仅注射四次他莫昔芬后重组率就超过80%。MerCreMer融合蛋白在成年心脏中的表达不影响心脏功能、细胞结构或肥大标记基因的表达，表明转基因编码的蛋白相对无害。总之，MerCreMer转基因小鼠是一种工具，可用于在发育中的和成年心脏中对任何loxP靶向基因进行时间调控的失活，或用于在心脏中特异性地指导loxP失活的心脏转基因的重组和表达。
