Research progress in genetic diagnostic methods of fragile X syndrome

doi:10.3969/j.issn.1673-8640.2024.02.002

Abstract

Abstract:

Fragile X syndrome(FXS) is one of the main monogenic diseases that cause intellectual and developmental disorders，and it shows an X-linked incomplete dominant inheritance. The etiology of FXS is unstable extension of (CGG)n repeat within FMR1 gene and abnormal methylation of its upstream CpG island，which would lead to decreasing or deficiency of fragile X mental retardation protein(FMRP). The level of FMRP is directly related to the severity of clinical phenotype. Clinical manifestation and genetic testing are the main diagnostic criteria for FXS. However，the unique molecular structure and genetic pattern of FMR1 gene pose challenges to the molecular diagnosis and genetic counseling of FXS. Therefore，how to detect FMR1 gene conveniently and accurately has always been a focus of attention. This review focuses on the research progress of FXS genetic diagnostic methods，aiming to promote the standardized diagnosis of FXS and provide assistance for clinic.

Key words: FMR1 gene, (CGG)n repeat, Fragile X syndrome, Genetic diagnosis

CLC Number:

R446.7

JIANG Zhu, TAN Jianxin, TAN Juan, LUO Chunyu, XU Zhengfeng. Research progress in genetic diagnostic methods of fragile X syndrome[J]. Laboratory Medicine, 2024, 39(2): 107-113.

Figures/Tables 3

References 47

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变异	变异类型	临床意义	参考文献
c.52-1_52delinsTA(p.Ala18Leufs*4；p.Ala18_Glu66del)	剪接位点变异	致病	[33]
c.80C>A(p.Ser27*)	无义变异	致病	[34]
c.373delA(p.Thr125Leufs*35)	移码变异	致病	[33]
c.420-8A>G(p.Met140Ilefs*3)	移码变异	致病	[35]
c.881-1G>T	剪接位点变异	致病	[31]
c.911T>A(p.Ile304Asn)	错义变异	致病	[36]
c.990+1G>A(p.Lys295Asnfs*11)	剪接位点变异	致病	[35]
c.1021-1028delinsTATTGG(p.Asn341Tyrfs*7)	移码变异	致病	[31]
c.1611insG(p.Gly538Argfs24)	移码变异	致病	[37]
c.(1737+1_1738-1)_(1_?)del(p.Ile580fs9)	移码变异	致病	[35]
c.879A>C	剪接位点变异	致病	[38]

变异	变异类型	临床意义	参考文献
c.52-1_52delinsTA(p.Ala18Leufs*4；p.Ala18_Glu66del)	剪接位点变异	致病	[33]
c.80C>A(p.Ser27*)	无义变异	致病	[34]
c.373delA(p.Thr125Leufs*35)	移码变异	致病	[33]
c.420-8A>G(p.Met140Ilefs*3)	移码变异	致病	[35]
c.881-1G>T	剪接位点变异	致病	[31]
c.911T>A(p.Ile304Asn)	错义变异	致病	[36]
c.990+1G>A(p.Lys295Asnfs*11)	剪接位点变异	致病	[35]
c.1021-1028delinsTATTGG(p.Asn341Tyrfs*7)	移码变异	致病	[31]
c.1611insG(p.Gly538Argfs24)	移码变异	致病	[37]
c.(1737+1_1738-1)_(1_?)del(p.Ile580fs9)	移码变异	致病	[35]
c.879A>C	剪接位点变异	致病	[38]

项目	(CGG)n重复数识别能力		女性杂合子/纯合子判断	评估甲基化状态	分辨低比例嵌合体	检测AGG嵌入数	检测前突变	检测SNV/InDel
模型分析	不能		分辨率低	不能	分辨率低	不能	不能	不能
DNA印迹杂交法	偏低，无法精准确定CGG的重复次数		分辨率低	能	分辨率低	不能	能	不能
MS-PCR	偏低		不能	能	不能	不能	不能	不能
TP-PCR	中等，对于较大重复数不能进行精确定量分析，存在一定错判全突变型和前突变型的概率		分辨率高	不能	分辨率较高	可识别AGG插入有限(不能识别女性杂合和嵌合等位基因中的AGG)	能	不能
RT-PCR	不能		不能	不能	不能	不能	不能	不能
NGS	不能		不能	不能	不能	不能	不能	能
TGS	高		分辨率高	能	分辨率高	可识别AGG插入数量和位置(包括杂合和嵌合等位基因中的AGG)	能	能
项目	检测mRNA	样本需要量	检测时间	检测灵敏度	检测特异性	操作复杂程度
模型分析	不能	高(外周血细胞)	7 d	低	低	复杂
DNA印迹杂交法	不能	高(5~10 μg)	3 d	低(嵌合体影响灵敏度)	低	复杂
MS-PCR	不能	较高(2 μg)	>1 d	高	高	简单
TP-PCR	不能	低(5~100 ng)	<24 h	高	高	简单
RT-PCR	能	低(5~100 ng)	<24 h	高	高	简单
NGS	不能	中(500 ng)	>24 h	高	高	相对复杂
TGS	不能	中(500 ng)	12~24 h	高	高	相对复杂

项目	(CGG)n重复数识别能力		女性杂合子/纯合子判断	评估甲基化状态	分辨低比例嵌合体	检测AGG嵌入数	检测前突变	检测SNV/InDel
模型分析	不能		分辨率低	不能	分辨率低	不能	不能	不能
DNA印迹杂交法	偏低，无法精准确定CGG的重复次数		分辨率低	能	分辨率低	不能	能	不能
MS-PCR	偏低		不能	能	不能	不能	不能	不能
TP-PCR	中等，对于较大重复数不能进行精确定量分析，存在一定错判全突变型和前突变型的概率		分辨率高	不能	分辨率较高	可识别AGG插入有限(不能识别女性杂合和嵌合等位基因中的AGG)	能	不能
RT-PCR	不能		不能	不能	不能	不能	不能	不能
NGS	不能		不能	不能	不能	不能	不能	能
TGS	高		分辨率高	能	分辨率高	可识别AGG插入数量和位置(包括杂合和嵌合等位基因中的AGG)	能	能
项目	检测mRNA	样本需要量	检测时间	检测灵敏度	检测特异性	操作复杂程度
模型分析	不能	高(外周血细胞)	7 d	低	低	复杂
DNA印迹杂交法	不能	高(5~10 μg)	3 d	低(嵌合体影响灵敏度)	低	复杂
MS-PCR	不能	较高(2 μg)	>1 d	高	高	简单
TP-PCR	不能	低(5~100 ng)	<24 h	高	高	简单
RT-PCR	能	低(5~100 ng)	<24 h	高	高	简单
NGS	不能	中(500 ng)	>24 h	高	高	相对复杂
TGS	不能	中(500 ng)	12~24 h	高	高	相对复杂