家族性局灶节段性肾小球硬化3家系临床表型与相关基因连锁分析

Clinical phenotype and linkage analysis in three Chinese kindreds of familial focal segmental glomerulosclerosis

目的分析家族性局灶节段性肾小球硬化(FFSGS)3个家系的临床表型,并通过连锁分析方法进行已知基因的排除性定位研究。方法对3个家系中的所有患者进行临床检查。应用等位基因共享分析和两点连锁分析的方法,在已知的FFSGS相关基因NPHS1、NPHS2、ACTN4、TRPC6、CD2AP和WT1所在染色体区域,选取14个微卫星遗传标记(STR)进行连锁分析研究。结果FFSGS3个家系的遗传方式均为常染色体显性遗传,54名家系成员中有16例患者,其临床表型不同,2个家系(家系A和家系B)的起病年龄相对较大,在青少年期发病,家系A中有3例患者发病年龄偏小,最小者1岁发病,家系A中其他患者都是25岁以后发病。3个家系中有4例因尿毒症死亡,另2例尿毒症行肾移植治疗,还有2例出现肾功能不全。家系A的先证者14岁即出现了Cr增高。应用D19S191、D19S220、D19S224、D1S215、D1S416、D1S466、D11S1391、D11S1986和D11S2000等STR对家系A进行NPHS1、NPHS2、ACTN4和TRPC6基因的两点连锁分析,测得各个标记位点在重组率θ=0时,最大的LOD值为0·18(D11S1391);在θ=0·1时,最大的LOD值为0·18(D11S1986);在θ=0·2时,得到本组最大的LOD值为0·47(D19S220),均不支持连锁。提示家系A与所检测的9个DNASTR位点无共分离。用上述STR以及ACTN4基因内的STRD19S422、CD2AP基因所在位点的STRD6S936、D6S1566、D6S1651和WT1基因所在位点的STRD11S2370对家系A进行等位基因共享分析,结果提示该家系致病基因与ACTN4、NPHS1、NPHS2、TRPC6、CD2AP和WT1等基因所在位点不连锁。应用D19S191、D19S220、D19S224、D19S422、D1S215、D1S416、D1S466、D11S1391、D11S1986、D11S2000、D6S936和D6S1566等STR对家系B和C进行等位基因共享分析,结果这2个家系的致病基因与ACTN4、NPHS1、NPHS2、TRPC6和CD2AP等基因所在位点均不连锁。结论3个中国人常染色体显性遗传型FFSGS家系,具有明显的临床异质性。已知基因NPHS1、NPHS2、ACTN4、TRPC6、CD2AP和WT1不是家系A的致病基因;NPHS1、NPHS2、ACTN4、TRPC6和CD2AP不是家系B和C的致病基因。

Objective To analyze the clinical phenotype in three Chinese kindreds of familial focal segmental glomerulosclerosis （ FFSGS）, and to perform the exclusive gene mapping around six known genes associated with FFSGS. Methods The clinical features of all affected members in three families were analyzed. Fourteen microsatellite markers around NPHS1, NPHS2, ACTN4, TRPC6, CD2AP and WT1 loci were selected and applied to analyze the linkage in the available family members by PCR, non-denatured polyacrylamide gel electrophoresis and silver staining. By two-point linkage analysis and allele sharing analysis, exclusive gene mapping on NPHS1, NPHS2, ACTN4, TRPC6, CD2AP and WT1 were carried out in three FFSGS kindreds. Results The phenotypes of three autosomal dominant FSGS families were diverse. The onset ages of disease were at adolescence in two kindreds. However, there were two children with a very early onset of the disease in family A, the youngest age of onset was 1 year old, and the onset ages of other family members were after 25 years old. Four patients were died of uremia in three kindreds. Three other patients with uremia accepted renal transplantations. Another three patients presented renal insufficiency. The proband of family A presented high serum creatinine at 14 years old. With microsatellite markers of D19S191, D19S220, D19S224, D1S215, D1S416, D1S466, D11S1391, D11S1986 and D11S2000, two-point linkage analysis was performed in family A. The maximum two-point LOD score, 0. 18 at θ=0 was obtained for the marker D11S1391 ; 0. 18 at θ =0. 1 was obtained for the marker D11S1986; 0. 47 at θ = 0. 2 was obtained for the marker D19S220. These markers were not cosegregated with the disease loci in all affected members, indicating that there was no linkage between these markers and four FFSGS related genes （ACTN4, NPHS1, NPHS2 and TRPC6 ） in the kindreds. In family A, allele sharing analysis was performed using over nine microsatellite markers as well as some other markers （D19S422, D6S1657, D6S1566, D6S936 and D11S2370）. There was no linkage between these markers and ACTN4, NPHS1, NPHS2, TRPC6, CD2AP and WT1 genes. In family B and C, allele sharing analysis was performed with 12 microsatellite markers （D19S191, D19S220, D19S224, D19S422, D1S215, D1S416, D1S466, D11S1391, D11S1986, D11S2000, D6S936 and D6S1566）. There was no linkage between these markers and ACTN4, NPHS1, NPHS2, TRPC6 and CD2AP genes. Conclusions There was significant clinical heterogeneity in the three Chinese families with autosomal dominant FFSGS. NPHS1, NPHS2, ACTN4, TRPC6, CD2Ap and WT1 were not the disease-causing genes for family A ; and NPHS1, NPHS2, ACTN4, TRPC6 and CD2AP were not the disease-causing genes for family B and C. This study implied that there may be other new locus or other genes leading to autosomal dominant FSGS.