The Association Between Variants Of APOL1 Gene And Chinese FSGS

Focal segmental glomerulosclerosis(FSGS)is one of the most common causes of refractory nephrotic syndrome and end-stage renal disease.Genetic factors play an important role in the pathogenesis and progression of this disease.Previous studies have shown that G1 and G2 variants of APOL1 are closely associated with the pathogenesis and progression of FSGS.But the results were not well replicated in Chinese population.It is suggested that there were other APOL1 variants in Chinese FSGS patients.This study included:(1)To analyze the polymorphism and haplotype of APOL1 gene and explore the susceptibility of APOL1 haplotypes to disease in different populations.(2)To detect the copy number of APOL1 gene in FSGS patients and normal control group,and to explore the possible significance of APOL1 gene copy number variation in clinical treatment and prognosis of Chinese patients with FSGS(3)To investigate the effect of APOL1 novel mutation on podocytes,including changes in cell marker protein,cytoskeleton and ion channel.To explore the possible mechanism of APOL1 new mutations involved in FSGS podocyte injury.Our methods of research are included(1)Filtering APOL1 gene single nucleotide polymorphism sites from the 1000 Genome Project database.Divided APOL1 gene into 5’untranslated region,coding region and 3’untranslated region.Statistically analyzed the distribution of APOL1 haplotypes in different regions and in different populations.(2)Screening qualified DNA samples of FSGS patients;Taqman copy number variation experiments were performed by designing APOL1 primers and probes.Using the Copy Caller software to calculate the copy number,SPSS analysis the differences of copy number distribution in FSGS patients and normal controls.(3)Dynamically tracked the morphological change of podocytes by electron microscope.Detected the expression of podocyte markers proteins,autophagy markers proteins and signal transduction protein by western blot.Podocyte cytoskelet and mitochondrial damage were detected by laser confocal microscopy.Patch clamp technology to measure the change of podocyte membrane ion channel.The research results showed(1)The haplotype frequencies of APOL1 gene was significantly different in the four populations.Most of the haplotype frequencies were relatively high in the mixed population and the European population,two haplotypes distributed more frequently in the Asian population than in other populations.(2)The distribution of APOL1 gene copy number between FSGS patients and normal group was not statistically significant.There was no significant difference in the treatment effect of FSGS patients between the high copy number and the low copy number.(3)Podocyte cytoskeleton protein disorder after transfected with mutant APOL1 gene,cell cytoplasm was dissolved and the intercellular gap became increased.The level of podocyte marker proteins was reduced,the signal pathway proteins of P38 MAPK,SAPKs and JNK was activated,in addition,the new mutation of APOL1 may affect the chloride ion channel protein.In this study,we analyzed the possible relationship between the variants of APOL1 gene and FSGS.The results showed that the distribution of single nucleotide polymorphisms of APOL1 gene were significantly different in different populations.The copy number variation of APOL1 was not closely associated with the susceptibility to FSGS in China.But the APOL1 mutation affected the morphology and function of podocyte in different pathways.These results suggest that APOL1 gene mutation may be involved in the pathogenesis of Chinese FSGS,and its pathogenic mechanism needs further exploration.