常染色体隐性遗传Alport综合征一家系COL4A3及COL4A4基因突变分析

Screening for the mutations of COL4A3/COL4A4 genes in an autosomal recessive Alport syndrome family

目的通过对有近亲婚配史的Alport综合征一家系Ⅳ型胶原α3和α4链的COL4A3/COL4A4基因分析,明确常染色体隐性遗传Alport综合征的基因突变,为该病的基因诊断和家系遗传咨询提供更为全面的理论基础。方法PCR扩增先证者DNA COL4A3/COL4A4基因的共98个外显子,经直接测序,寻找突变位点,对有意义的突变经限制性内切酶AvaⅡ酶切在家系中分析验证。结果在该患者中共发现1个错义突变和10个序列变异。其中在COL4A3基因上发现一个位于42号外显子上的错义突变G3725A,导致蛋白质Gly1242Asp的突变。错义突变在患者中是纯合子,携带者中是杂合子,其他正常家系成员及筛查100条正常人染色体。未发现该突变。10个序列变异为单核苷酸多态性改变。结论报道了一个国内较少见的常染色体隐性遗传Alport综合征家系,同时经基因突变筛查发现Ⅳ型胶原α3链的一个新的致病性的基因突变。

Objective To screen for the COL4A3 and COL4A4 mutations in a Chinese consanguineous family with autosomal recessive Alport syndrome （ARAS）. Methods Using PCR and direct sequencing, all 52 coding exons of the COL4A3 gene and 46 exons, except exon-1, of the COL4A4 gene were analyzed to detect mutations in the pedigree with ARAS. Furthermore, mutation was identified by restriction endonuclease AvaII in all other 20 members. Results A novel missense mutation （3725 G〉A, G1242D ） in exon 42 of the COL4A3 gene was identified in homozygous form. This pathogenic mutation was demonstrated in heterozygous forms in all carriers in this family, whereas it was detected neither in the other normal members of the family nor in the 50 controls. In addition, 10 polymorphisms, including one nonglycine missense variants and 9 neutral polymorphisms, were detected in COL4A3/COL4A4. Conclusion The novel pathogenic mutation （3725 G〉A, G1242D） of the COL4A3 gene may be the underlying pathogen in this family and it is the first reported case in ARAS.