Expression of mutant human cystathionine β-synthase rescues neonatal lethality but not homocystinuria in a mouse model
Expression of mutant human cystathionine β-synthase rescues neonatal lethality but not homocystinuria in a mouse model
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DOI：
10.1093/hmg/ddi224
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发表时间：
2005-08-01
影响因子：
3.5
通讯作者：
Kruger, WD
中科院分区：
文献类型：
--
作者：
Wang, LQ;Chen, XL;Kruger, WD
胱硫醚β-合酶（CBS）缺乏症是一种隐性遗传疾病，其特征是总血浆同型半胱氨酸（tHcy）水平升高和人类频繁血栓形成。I278 T突变是人类CBS缺陷患者中最常见的突变。T424 N突变被鉴定为人CBS中的突变，其可以恢复酿酒酵母中I278 T的功能。在这份报告中，我们已经改造小鼠表达人类I278 T和I278 T/T424 N蛋白从金属蛋白酶驱动的转基因。然后将这些含有转基因的小鼠与CBS敲除动物（Cbs（-））交配以产生仅表达人I278 T或I278 T/T424 N蛋白的小鼠。I278 T和I278 T/T424 N转基因都能够完全挽救先前描述的新生儿死亡表型，尽管动物的平均tHcy为250 μ m。转基因Cb（-/-）动物表现出面部脱毛，具有中度肝脏脂肪变性，并且比杂合同窝出生的动物略小。与人CBS缺乏相反，这些小鼠不表现出极端的甲硫氨酸血症。突变蛋白在肝脏、肾脏和结肠中是稳定的，并且肝脏提取物仅具有在野生型小鼠中发现的CBS酶活性的2-3%。令人惊讶的是，I278 T/T424 N酶具有与I278 T酶完全相同的活性，表明T424 N不能抑制小鼠中的I278 T。我们的研究结果表明，升高的tHcy本身是不负责的新生儿死亡率观察到的CBS（-/-）的动物，并表明CBS蛋白可能有一个功能，除了它的作用，同型半胱氨酸催化剂。这些转基因动物在研究同型半胱氨酸相关的人类疾病中将是有用的。
Cystathionine beta-synthase (CBS) deficiency is a recessive genetic disorder in humans characterized by elevated levels of total plasma homocysteine (tHcy) and frequent thrombosis in humans. The I278T mutation is the most common mutation found in human CBS-deficient patients. The T424N mutation was identified as a mutation in human CBS that could restore function to I278T in Saccharomyces cerevisiae. In this report, we have engineered mice that express human I278T and I278T/T424N proteins from a metallotheinein-driven transgene. These transgene-containing mice were then bred to CBS knockout animals (Cbs(-)) to generate mice that express only human I278T or I278T/T424N protein. Both the I278T and the I278T/T424N transgenes are able to entirely rescue the previously described neonatal mortality phenotype despite the animals having a mean tHcy of 250 mu m. The transgenic Cbs(-/-) animals exhibit facial alopecia, have moderate liver steatosis and are slightly smaller than heterozygous littermates. In contrast to human CBS deficiency, these mice do not exhibit extreme methioninemia. The mutant proteins are stable in the liver, kidney and colon, and liver extracts have only 2-3% of the CBS enzyme activity found in wild-type mice. Surprisingly, the I278T/T424N enzyme had exactly the same activity as the I278T enzyme indicating that T424N is unable to suppress I278T in mice. Our results show that elevated tHcy per se is not responsible for the neonatal lethality observed in Cbs(-/-) animals and suggests that CBS protein may have a function in addition to its role in homocysteine catabolism. These transgenic animals should be useful in the study of homocysteine related human disease.