摘要
目的 :研究1例具有非典型临床特征的进行性骨化性纤维增殖不良症(fibrodysplasia ossificans progressiva,FOP)患者,并对其致病基因人活化蛋白/促激蛋白A受体1(activin A type 1 receptor,ACVR1)进行突变分析。方法:根据患者大踇趾轻微畸形和进行性异位骨化等临床表现,结合骨骼系统放射线检查、骨ECT和相关血液生化检查进行临床诊断。采集患者、患者父母和60位正常人外周血,提取基因组DNA,对ACVR1基因全部外显子进行聚合酶链反应(polymerase chain reaction,PCR)扩增和序列分析;对突变后的蛋白质结构进行分子模拟以便评估其突变后的功能改变。结果:患者具有非典型的临床表现:先天性大踇趾轻微畸形和进行性非经典顺序的异位骨化,其父母无FOP相关临床表现。患者的ACVR1第5外显子存在c.774 G>C(R258S)杂合突变,而其父母和正常对照组均无此杂合突变。此外,患者和所有正常人都存在c.690 G>A(E230E),此为无意义突变。三维蛋白质分子模拟发现R258与高度保守的甘氨酸-丝氨酸(glycine-serine,GS)活化区邻近,该突变可能导致ACVR1与ACVR1的抑制蛋白FK506结合蛋白12(FK506 binding protein 12,FKBP12)结合的亲和力降低,进而对ACVR1抑制作用降低。结论:典型FOP均在ACVR1之GS区发生突变,而本例FOP在ACVR1激酶区发生突变,这可能是该患者在临床表现呈非典型的原因。该结果有助于我们更好地去理解FOP表型和基因型之间的关系。
Objective:Fibrodysplasia ossificans progressiva(FOP) is a rare and disabling genetic condition of congenital skeletal malformations and progressive heterotopic ossification(HO),associated with the mutation in the activin A type 1 receptor / activin-like kinase 2(ACVR1/ALK2) gene.The purpose of this study was to report one FOP patient with atypical clinical findings and to identify the genetic entity.Methods: Clinical diagnosis was based on physical examination,radiological findings and biochemical tests.For mutation detection,the blood samples from the FOP patient,his parents and 60 normal controls were collected with informed consent.Genomic DNA was isolated from peripheral lymphocytes and all the exons of ACVR1 were amplified by PCR.The PCR products sequenced directly with the cycle sequencing methods.Then we generated the three-dimensional model of protein structure for the cytoplasmic domain of the R258S in ACVR1 to evaluate its receptor function.Results: The patient had congenital minimal malformations of the great toes and radiographic evidence of heterotopic ossification at the time of evaluation.The process of heterotopic bone formation was a mild course and did not follow the typical temporal and spatial patterns.Analysis of ACVR1 gene revealed that the patient had a heterozygous missense mutation,c.774 G>C(R258S),which is located in the kinase domain of ACVR1.We also find that all the people,including the patient,the parents and 60 normal controls,occurred nonsense mutation,c.690 G> A(E230E).In the protein modeling,ARG258 and SER194 can form the H-bonds.When the ARG258 is substituted by SER,the H-bonds are lost,so the αGS1 and the αC helix conformations do shift and make ACVR1 into an'open' conformation and constituently activated.Conclusion: Most patients showing typical FOP phenotypes have the heterozygous c.617G>A(R206H) mutation belonging to the GS domain of ACVR1.Our report describes a patient affected with FOP showing mild progressive symptoms,and these atypical FOP phenotypes may associate with a novel mutation(c.774 G>C),affecting a conserved residue of the ACVR1 kinase domain.Our findings make the relations between phenotypes and genotypes of FOP better understood.
出处
《南京医科大学学报（自然科学版）》
CAS
CSCD
北大核心
2012年第1期62-66,共5页
Journal of Nanjing Medical University(Natural Sciences)
基金
医院引进人才基金(303070060NA05)
