Watanabe M, Osada J, Aratani Y, Kluckman K, Reddick R, Malinow M R, Maeda N
Department of Pathology, University of North Carolina, Chapel Hill 27599-7525.
Proc Natl Acad Sci U S A. 1995 Feb 28;92(5):1585-9. doi: 10.1073/pnas.92.5.1585.
Studies by various investigators have indicated that elevated levels of plasma homocyst(e)ine are strongly associated with the occurrence of occlusive vascular diseases. With the eventual aim of determining whether or not elevated plasma homocyst(e)ine concentrations are directly causative of cardiovascular diseases, we have generated mice that are moderately and severely homocyst(e)inemic. Homologous recombination in mouse embryonic stem cells was used to inactivate the cystathionine beta-synthase [L-serine hydrolyase (adding homocysteine), EC 4.2.1.22] gene. Homozygous mutants completely lacking cystathionine beta-synthase were born at the expected frequency from matings of heterozygotes, but they suffered from severe growth retardation and a majority of them died within 5 weeks after birth. Histological examination showed that the hepatocytes of homozygotes were enlarged, multinucleated, and filled with microvesicular lipid droplets. Plasma homocyst(e)ine levels of the homozygotes were approximately 40 times normal. These mice, therefore, represent a model for severe homocyst(e)inemia resulting from the complete lack of cystathionine beta-synthase. Heterozygous mutants have approximately 50% reduction in cystathionine beta-synthase mRNA and enzyme activity in the liver and have twice normal plasma homocyst(e)ine levels. Thus, the heterozygous mutants are promising for studying the in vivo role of elevated levels of homocyst(e)ine in the etiology of cardiovascular diseases.
多位研究者的研究表明，血浆同型半胱氨酸水平升高与闭塞性血管疾病的发生密切相关。为了最终确定血浆同型半胱氨酸浓度升高是否直接导致心血管疾病，我们培育了中度和重度高同型半胱氨酸血症的小鼠。利用小鼠胚胎干细胞中的同源重组技术使胱硫醚β-合酶[L-丝氨酸水解酶（添加同型半胱氨酸），EC 4.2.1.22]基因失活。完全缺乏胱硫醚β-合酶的纯合突变体以预期频率从杂合子交配中出生，但它们生长严重迟缓，大多数在出生后5周内死亡。组织学检查显示，纯合子的肝细胞肿大、多核，并充满微泡脂滴。纯合子的血浆同型半胱氨酸水平约为正常水平的40倍。因此，这些小鼠代表了因完全缺乏胱硫醚β-合酶而导致严重高同型半胱氨酸血症的模型。杂合突变体肝脏中的胱硫醚β-合酶mRNA和酶活性降低约50%，血浆同型半胱氨酸水平是正常水平的两倍。因此，杂合突变体有望用于研究同型半胱氨酸水平升高在心血管疾病病因学中的体内作用。
