A Point Mutation in the RNA Recognition Motif of CSTF2 Associated with Intellectual Disability in Humans Causes Defects in 3' End Processing [RNA-seq]

CSTF2 encodes an RNA-binding protein that is essential for mRNA cleavage and polyadenylation (C/P). No disease-associated mutations have been described for this gene. Here, we report a mutation in the RNA recognition motif (RRM) of CSTF2 that changes an aspartic acid at position 50 to alanine (p.D50A), resulting in intellectual disability in male patients. In mice, this mutation was sufficient to alter polyadenylation sites in over 1,300 genes critical for brain development. Using a reporter gene assay, we demonstrated that C/P efficiency of CSTF2D50A was lower than wild type. To account for this, we determined that p.D50A changed locations of amino acid side chains altering RNA binding sites in the RRM. The changes modified the electrostatic potential of the RRM leading to a greater affinity for RNA. These results highlight the significance of 3' end mRNA processing in expression of genes important for brain plasticity and neuronal development. Total brain RNA from three wild type and five Cstf2 mutant mice at 50 days were subjected to RNA-seq using the Illumina protocol.CSTF2编码一种对mRNA剪切与多聚腺苷酸化（C/P）至关重要的RNA结合蛋白。目前尚未见该基因存在疾病相关突变的报道。本研究首次报道了CSTF2的RNA识别基序（RRM）区域存在一处突变，该突变将第50位的天冬氨酸替换为丙氨酸（p.D50A），可导致男性患者出现智力障碍。在小鼠模型中，该突变足以改变超过1300个脑发育关键基因的多聚腺苷酸化位点。通过报告基因检测实验，我们证实CSTF2D50A的C/P效率低于野生型（wild type）。为阐明该现象的机制，我们发现p.D50A突变改变了氨基酸侧链的位置，进而改变了RRM区域的RNA结合位点。该变化改变了RRM区域的静电势，使其对RNA的结合亲和力升高。上述结果凸显了mRNA 3'端加工过程在脑可塑性与神经元发育相关基因表达中的重要意义。我们采集了3只野生型小鼠与5只50日龄Cstf2突变小鼠的全脑RNA，并采用Illumina测序方案开展RNA测序。