Institute of Molecular Biology and Biotechnology (IMBB), Centre for Research in Molecular Medicine (CRiMM), The University of Lahore, Lahore, Pakistan.
Faculty of Life Sciences, University of Central Punjab (UCP), Lahore, Pakistan.
Mol Genet Genomic Med. 2019 Sep;7(9):e902. doi: 10.1002/mgg3.902. Epub 2019 Jul 25.
Jalili syndrome (JS) is a rare cone-rod dystrophy (CRD) associated with amelogenesis imperfecta (AI). The first clinical presentation of JS patients was published in 1988 by Jalili and Smith. Pathogenic mutations in the Cyclin and CBS Domain Divalent Metal Cation Transport Mediator 4 (CNNM4) magnesium transporter protein have been reported as the leading cause of this anomaly.
In the present study, a clinical and genetic investigation was performed in a consanguineous family of Pakistani origin, showing characteristic features of JS. Sanger sequencing was successfully used to identify the causative variant in CNNM4. Molecular dynamics (MD) simulations were performed to study the effect of amino acid change over CNNM4 protein.
Sequence analysis of CNNM4 revealed a novel missense variant (c.1220G>T, p.Arg407Leu) in exon-1 encoding cystathionine-β-synthase (CBS) domain. To comprehend the mutational consequences in the structure, the mutant p.Arg407Leu was modeled together with a previously reported variant (c.1484C>T, p.Thr495Ile) in the same domain. Additionally, docking analysis deciphered the binding mode of the adenosine triphosphate (ATP) cofactor. Furthermore, 60ns MD simulations were carried out on wild type (p.Arg407/p.Thr495) and mutants (p.Arg407Leu/p.Thr495Ile) to understand the structural and energetic changes in protein structure and its dynamic behavior. An evident conformational shift of ATP in the binding site was observed in simulated mutants disrupting the native ATP-binding mode.
The novel identified variant in CNNM4 is the first report from the Pakistani population. Overall, the study is valuable and may give a novel insight into metal transport in visual function and biomineralization.
Jalili 综合征（JS）是一种与釉质不全（AI）相关的罕见的锥-杆营养不良（CRD）。JS 患者的首次临床表现在 1988 年由 Jalili 和 Smith 发表。现已报道，细胞周期蛋白和 CBS 域二价金属阳离子转运介质 4（CNNM4）镁转运蛋白中的致病变异是导致这种异常的主要原因。
本研究对一个具有巴基斯坦血统的近亲家庭进行了临床和遗传研究，该家庭表现出 JS 的典型特征。成功使用 Sanger 测序鉴定了 CNNM4 中的致病变异。进行分子动力学（MD）模拟以研究氨基酸变化对 CNNM4 蛋白的影响。
对 CNNM4 的序列分析显示，外显子 1 中编码半胱氨酸-β-合酶（CBS）域的新型错义变异（c.1220G>T，p.Arg407Leu）。为了了解结构中的突变后果，将突变体 p.Arg407Leu 与同一结构域中先前报道的变异体（c.1484C>T，p.Thr495Ile）一起建模。此外，对接分析揭示了三磷酸腺苷（ATP）辅因子的结合模式。此外，对野生型（p.Arg407/p.Thr495）和突变体（p.Arg407Leu/p.Thr495Ile）进行了 60ns MD 模拟，以了解蛋白质结构的结构和能量变化及其动态行为。在模拟的突变体中观察到结合部位的 ATP 明显构象变化，破坏了天然的 ATP 结合模式。
在 CNNM4 中鉴定的新型变异是来自巴基斯坦人群的首次报道。总的来说，这项研究具有价值，可能为视觉功能和生物矿化中的金属转运提供新的见解。
