A Spontaneous Missense Mutation in Branched Chain Keto Acid Dehydrogenase Kinase in the Rat Affects Both the Central and Peripheral Nervous Systems.
A Spontaneous Missense Mutation in Branched Chain Keto Acid Dehydrogenase Kinase in the Rat Affects Both the Central and Peripheral Nervous Systems.
复制标题
DOI：
10.1371/journal.pone.0160447
复制
发表时间：
2016
期刊：
影响因子：
3.7
通讯作者：
Sinha D
中科院分区：
文献类型：
--
作者：
Zigler JS Jr;Hodgkinson CA;Wright M;Klise A;Sundin O;Broman KW;Hejtmancik F;Huang H;Patek B;Sergeev Y;Hose S;Brayton C;Xaiodong J;Vasquez D;Maragakis N;Mori S;Goldman D;Hoke A;Sinha D
一种新的突变，由于其最明显的特征是后肢严重张开，导致一种表型，我们将其命名为弗罗格腿，它自发地出现在一群Spraogue-Dawley大鼠中。FROGLEG是一种复杂的表型，包括后肢功能异常、脑重量减轻并伴有脑室扩张和不孕症。利用覆盖整个大鼠基因组的微卫星标记，突变被定位在大鼠1号染色体D1Rat131和D1Rat287之间的区域。对连锁区间内的全基因组测序数据进行分析，发现支链α-酮基脱氢酶激酶(Bck-Dk)基因存在错义突变。Bockdk编码的蛋白质是位于许多组织线粒体基质中的酶复合体的组成部分，它调节支链氨基酸(BCAA)、亮氨酸、异亮氨酸和缬氨酸的水平。支链氨基酸是必需的氨基酸(不是由身体合成的)，循环中的水平必须受到严格的控制；水平太高或太低都是有害的。BCKDK使BCKDH蛋白的E1α亚基的Ser293磷酸化，从而催化BCKDH分解代谢的限速步骤，抑制BCKDH，从而限制BCAA的分解。相反，当Ser293没有被磷酸化时，BCKDH的活性就不受抑制，支链氨基酸的水平将急剧下降。该突变位于Bockdk的激活域内，并被预测为具有破坏性。与此一致，我们发现，在突变纯合子的大鼠中，与野生型或杂合子相比，大脑中BCKDH的磷酸化水平显著降低。此外，在突变纯合子的动物中，循环中的支链氨基酸水平降低了70%-80%。Fogue Leg表型与先前描述的Backdk基因敲除小鼠和具有Bockdk突变的人类受试者有重要特征。此外，我们还报道了有关后肢周围神经病变的新数据。
A novel mutation, causing a phenotype we named frogleg because its most obvious characteristic is a severe splaying of the hind limbs, arose spontaneously in a colony of Sprague-Dawley rats. Frogleg is a complex phenotype that includes abnormalities in hind limb function, reduced brain weight with dilated ventricles and infertility. Using micro-satellite markers spanning the entire rat genome, the mutation was mapped to a region of rat chromosome 1 between D1Rat131 and D1Rat287. Analysis of whole genome sequencing data within the linkage interval, identified a missense mutation in the branched-chain alpha-keto dehydrogenase kinase (Bckdk) gene. The protein encoded by Bckdk is an integral part of an enzyme complex located in the mitochondrial matrix of many tissues which regulates the levels of the branched-chain amino acids (BCAAs), leucine, isoleucine and valine. BCAAs are essential amino acids (not synthesized by the body), and circulating levels must be tightly regulated; levels that are too high or too low are both deleterious. BCKDK phosphorylates Ser293 of the E1α subunit of the BCKDH protein, which catalyzes the rate-limiting step in the catabolism of the BCAAs, inhibiting BCKDH and thereby, limiting breakdown of the BCAAs. In contrast, when Ser293 is not phosphorylated, BCKDH activity is unchecked and the levels of the BCAAs will decrease dramatically. The mutation is located within the kinase domain of Bckdk and is predicted to be damaging. Consistent with this, we show that in rats homozygous for the mutation, phosphorylation of BCKDH in the brain is markedly decreased relative to wild type or heterozygous littermates. Further, circulating levels of the BCAAs are reduced by 70–80% in animals homozygous for the mutation. The frogleg phenotype shares important characteristics with a previously described Bckdk knockout mouse and with human subjects with Bckdk mutations. In addition, we report novel data regarding peripheral neuropathy of the hind limbs.