| Objective(s):The clinical and genetic characteristics of a rare genetic disease family with 6 members and 4 patients in 2 generations were studied to deeply analyze the clinical characteristics,genetic characteristics and incidence rules.Using whole exome sequencing,transcriptome and metabolome detection based on high-throughput sequencing technology to find the pathogenic gene of the family,improve the systematic understanding of the rare disease,and provide a theoretical basis for genetic diagnosis and prenatal diagnosis of the disease.Method(s): The data of family history and disease history were investigated and summarized,and the genealogy map was drawn to analyze its genetic characteristics.Blood routine examination,biochemistry,electrocardiogram,nerve conduction velocity,electromyography and medical imaging were carried out to analyze the clinical characteristics of the patients.5-10 m L peripheral blood samples were extracted and whole blood genomic DNA was extracted for mitochondrial genome testing and screening verification of suspected disease-related genes.Chromosome number and large fragment structure abnormalities were diagnosed by chromosome karyotype analysis with G banding.The whole exome sequencing method based on high-throughput sequencing technology was used to sequence the family members.Through data analysis,the genes were screened according to the genetic characteristics and clinical characteristics of the family.Candidate pathogenic genes were identified after co-isolation verified by Sanger sequencing.Linkage analysis was performed using Pedminer based on whole-exome sequencing data,and 4healthy individuals were collected as out-of-family controls for transcriptome and metabolome detection,and further screened candidate pathogenic genes in order to find the pathogenic gene of the rare disease family.Result(s):1.Basic information and genetic characteristics: This study was traced back to 30 family members in 3 generations.This paper mainly studies the pedigree of the proband,her husband and children,including 2 generations,6 people and 4 patients.The proband has 4 children,including 1 girl and 3 boys.The symptoms of the daughter and 2 sons are related to their basic symptoms.Similarly,his youngest son was basically normal without any related symptoms and died of drowning.After drawing the pedigree,the analysis confirmed that the inheritance pattern was autosomal dominant.2.Clinical features: The proband was unable to walk upright,crawling on all fours,poor ability to assist standing and walking on both legs,dysarthria,clear consciousness,poor memory,orientation,comprehension,and calculation,low limb muscle tension,and no left and right tendon reflexes.All 3 affected children had the disease,and the symptoms were basically the same as those of the proband.3.Clinical test results: no obvious abnormality related to clinical symptoms was found in blood routine,biochemistry,electrocardiogram,ultrasound medical imaging and DR examination;nerve conduction velocity and acupuncture ultra-electromyography showed that no neurogenic and myogenic properties were found in the examined muscles However,in the proband,the recorded amplitudes of the distal motor nerve conduction of the peripheral nerves of both lower extremities decreased.The results of MRI showed that the volumes of bilateral cerebellar hemispheres and cerebellar vermis were reduced,and the cerebral sulci were deepened.4.Mitochondrial genomic testing did not reveal pathogenic variants in mitochondrial genes that were associated with the subject’s clinical phenotype.5.According to the analysis of the patient’s genetic characteristics and clinical characteristics,it was suspected of autosomal dominant limb-girdle muscular dystrophy;after verification by Sanger sequencing,limb-girdle muscular dystrophy was ruled out.6.G-banded chromosome karyotype analysis revealed no abnormalities in the number of chromosomes or the structure of large segments in this family.7.After whole-exome gene sequencing,bioinformatic analysis of sequencing data screened out 9 patients with shared heterozygous mutations,including FOPNL,DNAH3,RBBP6,KIAA0895 L,MECOM,ABCA13,OXR1,SHB,ZNF283.Sanger sequencing verified that these genes were in line with the co-segregation phenomenon,and identified as the candidate pathogenic gene of this family.8.Linkage genetic analysis based on whole exome gene sequencing data found no gene linkage.9.Transcriptome detection data were enriched for differential genes including active ligand-receptor interactions,neurodegenerative diseases,and the nervous system.KEGG Pathway enrichment of differential metabolites after metabolome detection revealed 13 significant differential metabolites in different metabolic pathways,but no metabolic pathways or metabolites directly related to the disease of the family members were found.10.Based on the above results,we determined that the OXR1 gene was the most suspected pathogenic gene that caused the disease in this family,and it had a heterozygous mutation c.1096T>A(p.S366T)in exon 9.Conclusion(s):1.This study found the first case of a rare disease family in China.The clinical features are inability to walk upright,crawling on all four limbs,poor standing and walking ability with assisted legs,dysarthria,clear consciousness,poor memory,orientation,comprehension,and calculation ability.The muscle tone was low,and the left and right tendon reflexes were absent.Clinical findings tend to be due to neurological factors such as cerebellar atrophy or dysplasia.2.This rare disease is an autosomal dominant genetic disease.3.The heterozygous mutation c.1096T>A(p.S366T)in the 9th exon of OXR1 gene was the most suspected pathogenic gene causing the disease in this family.4.The other 8 suspected candidate pathogenic genes screened,including FOPNL,DNAH3,RBBP6,KIAA0895 L,MECOM,ABCA13,SHB,ZNF283,may have little relevance to this disease after gene structure and function analysis.5.Mitochondrial inheritance,limb-girdle muscular dystrophy,and abnormalities in chromosome number and structure of large segments were excluded. |
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