de Brouwer Arjan P M, Nabuurs Sander B, Verhaart Ingrid E C, Oudakker Astrid R, Hordijk Roel, Yntema Helger G, Hordijk-Hos Jannet M, Voesenek Krysta, de Vries Bert B A, van Essen Ton, Chen Wei, Hu Hao, Chelly Jamel, den Dunnen Johan T, Kalscheuer Vera M, Aartsma-Rus Annemieke M, Hamel Ben C J, van Bokhoven Hans, Kleefstra Tjitske
1] Department of Human Genetics, Nijmegen Centre for Molecular Life Sciences, Radboud University Nijmegen Medical Centre, Nijmegen, The Netherlands [2] Institute of Genetic and Metabolic Disease, Radboud University Nijmegen Medical Centre, Nijmegen, The Netherlands [3] Department of Cognitive Neuroscience, Donders Institute for Brain, Cognition and Behaviour, Radboud University Nijmegen, Nijmegen, The Netherlands.
Centre for Molecular and Biomolecular Informatics, Nijmegen Centre for Molecular Life Sciences, Radboud University Nijmegen, Nijmegen, The Netherlands.
Eur J Hum Genet. 2014 Apr;22(4):480-5. doi: 10.1038/ejhg.2013.169. Epub 2013 Jul 31.
We have identified a deletion of 3 base pairs in the dystrophin gene (DMD), c.9711_9713del, in a family with nonspecific X-linked intellectual disability (ID) by sequencing of the exons of 86 known X-linked ID genes. This in-frame deletion results in the deletion of a single-amino-acid residue, Leu3238, in the brain-specific isoform Dp71 of dystrophin. Linkage analysis supported causality as the mutation was present in the 7.6 cM linkage interval on Xp22.11-Xp21.1 with a maximum positive LOD score of 2.41 (MRX85 locus). Molecular modeling predicts that the p.(Leu3238del) deletion results in the destabilization of the C-terminal domain of dystrophin and hence reduces the ability to interact with β-dystroglycan. Correspondingly, Dp71 protein levels in lymphoblastoid cells from the index patient are 6.7-fold lower than those in control cell lines (P=0.08). Subsequent determination of the creatine kinase levels in blood of the index patient showed a mild but significant elevation in serum creatine kinase, which is in line with impaired dystrophin function. In conclusion, we have identified the first DMD mutation in Dp71 that results in ID without muscular dystrophy.
通过对86个已知的X连锁智力障碍（ID）基因的外显子进行测序，我们在一个患有非特异性X连锁智力障碍的家族中，发现了肌营养不良蛋白基因（DMD）中的一个3个碱基对的缺失，即c.9711_9713del。这种框内缺失导致肌营养不良蛋白的脑特异性异构体Dp71中一个单氨基酸残基Leu3238缺失。连锁分析支持该突变具有因果关系，因为该突变存在于Xp22.11 - Xp21.1上7.6 cM的连锁区间内，最大正向LOD分数为2.41（MRX85位点）。分子建模预测，p.(Leu3238del)缺失会导致肌营养不良蛋白C末端结构域不稳定，从而降低其与β - 肌营养不良聚糖相互作用的能力。相应地，先证者淋巴母细胞系中的Dp71蛋白水平比对照细胞系低6.7倍（P = 0.08）。随后对先证者血液中的肌酸激酶水平进行测定，结果显示血清肌酸激酶有轻度但显著的升高，这与肌营养不良蛋白功能受损一致。总之，我们鉴定出了首个Dp71中的DMD突变，该突变导致智力障碍但无肌肉营养不良。
