Objective To analyze the clinical manifestations and genetic etiology of three families with hereditary spastic paraplegia(HSP).Methods Gene analysis was performed on patients of the three HSP families from the Gansu Provincial Maternity and Child-care Hospital.Results The proband of family 1 was autosomal recessive spastic paraplegia type 35 caused by homozygous variant c.159_176delGGCGGGCCAGGACATCAG(p.Arg53_Ser59delinsSer)in FA2H.The proband in family 2 was autosomal recessive spastic paraplegia type 47 caused by homozygous variant c.1399G>T(p.Glu467Ter)in AP4B1,and the proband in family 3 was autosomal recessive spastic paraplegia type 11 caused by homozygous variation c.7023C>G(p.Tyr2341Ter)in SPG11.Among them,the variant c.1399G>T(p.Glu467Ter)of AP4B1 is a novel variant,that has not been reported before,according to the ACMG guidelines,the pathogenicity of this variant is pathogenic.Conclusion This study has expanded the variant spectrum of AP4B1 which provides basic data to improve clinical understanding and diagnostic capabilities of HSP patients.

Objective To analyze the clinical manifestations and genetic etiology of three families with hereditary spastic paraplegia(HSP).Methods Gene analysis was performed on patients of the three HSP families from the Gansu Provincial Maternity and Child-care Hospital.Results The proband of family 1 was autosomal recessive spastic paraplegia type 35 caused by homozygous variant c.159_176delGGCGGGCCAGGACATCAG(p.Arg53_Ser59delinsSer)in FA2H.The proband in family 2 was autosomal recessive spastic paraplegia type 47 caused by homozygous variant c.1399G>T(p.Glu467Ter)in AP4B1,and the proband in family 3 was autosomal recessive spastic paraplegia type 11 caused by homozygous variation c.7023C>G(p.Tyr2341Ter)in SPG11.Among them,the variant c.1399G>T(p.Glu467Ter)of AP4B1 is a novel variant,that has not been reported before,according to the ACMG guidelines,the pathogenicity of this variant is pathogenic.Conclusion This study has expanded the variant spectrum of AP4B1 which provides basic data to improve clinical understanding and diagnostic capabilities of HSP patients.

Objective:To investigate the clinical and genetic characteristics of nonsyndromic sensorineural hearing loss caused by STRC biallelic variation. Methods:A child with hearing impairment who was diagnosed at Gansu Provincial Maternal and Child Health Hospital on May 2022 and was selected as the research object. Peripheral blood of the child and her parents was collected, genomic DNA was extracted. IDT The xGen Exome Research Panel v2.0 whole exome capture chip was used to capture and sequence. Bioinformatics and clinical information analysis technology were used to analyze genetic data. The suspected pathogenic mutations were verified by quantitative polymerase chain reaction(QPCR)and Sanger sequencing.Results:The child had moderate hearing loss at about 1 year and 10 months, and now she is 3 years and 6 months, the hearing loss has not worsened. Whole exome sequencing(WES) testing revealed that the child carried the STRC gene with a deletion in EXON:1-29 and variants c.4561(exon24) _c.4562(exon24)insC, inherited from the mother and father, respectively. According to the relevant guidelines of the American Society for Medical Genetics and Genomics (ACMG), they were determined to be likely pathogenic variant and pathogenic variant. Conclusion:The discovery of c.4561(exon24) _c.4562(exon24)insC enriched the STRC variation spectrum, and provided a theoretical basis for the diagnosis and genetic counseling to the children.

Objective To perform genetic analysis in a family line of a pregnant couple with autosomal reces-sive non-syndromic deafness in order to identify its possible genetic etiology and provide prenatal diagnosis.Methods Whole-exome sequencing(WES)was used to analyze the genes of the proband,and Sanger sequencing was used to verify the suspected pathogenic loci.Prenatal genetic diagnosis was performed after amniotic fluid collection at 18 weeks of pregnancy.Results Autosomal recessive deafness type 3 related gene MYO15A c.10419_10423delCAGCT/c.10294_10308delCCTTGCATCCTTGCC compound heterozygous variant was found in the wife.A compound heterozygous variant of autosomal recessive deafness type 77-related gene LOXHD1:c.6388C＞T/ex-on 33-38 del.Maternal MYO15A c.10294_10308del CCTTGCATCCTTGCC heterozygous variant were detected in the husband and paternal LOXHD1 exon 33-38 del heterozygous variant were detected in the fetus.At the same time,the paternal CDH23 c.6693delT heterozygous mutation and the maternal PCDH15 c.5048_5051dupAGAA heterozygous mutation were detected in the fetus.These two heterozygous mutations lead to the possibility of the fe-tus suffering from ID/F Usher syndrome.Conclusion The deafness of the couple is caused by two different deaf gene mutations,and the probability of the fetus having the same deafness as the couple is very low.However,the fetus has a high possibility of having deafness caused by two gene mutations.Therefore,deafness caused by two gene mutations should be paid attention to in the prenatal diagnosis of families with both deaf parents.

Objective:To explore the genetic basis of eighteen patients with tetrahydrobiopterin deficiency (BH4D) from Gansu Province.Methods:Eighteen patients diagnosed with BH4D at Gansu Provincial Maternal and Child Health Care Hospital from January 2018 to December 2021 were selected as the study subjects. Whole exome sequencing was carried out, and candidate variants were verified by Sanger sequencing.Results:All of the thirty-six alleles of the eighteen patients were successfully determined by molecular genetic testing. Sixteen patients were found to harbor variants of the PTS gene, and two had harbored variants of the QDPR gene. Ten variants were detected in the PTS gene, with the most common ones being c. 259C>T (34.38%) and c. 286G>A (15.63%). Based on the guidelines from the American College of Medical Genetics and Genomics (ACMG), the c. 259C>T was classified as a pathogenic variant, whilst the c. 286G>A, c. 166G>A, c. 200C>T, c. 272A>G, c. 402A>C, c. 421G>T, c. 84-291A>G and c. 317C>T were classified as likely pathogenic variants. A novel c. 289_290insCTT variant was classified as likely pathogenic (PM1+ PM2_Supporting+ PM3+ PP3+ PP4). The two variants (c.478C>T and c. 665C>T) detected in the QDPR gene were both classified as variants of uncertain significance (PM1+ PM2_Supporting+ PP3+ PP4). Conclusion:Genetic testing has clarified the pathogenic variants in these BH4D patients, which has enabled timely and accurate clinical intervention and treatment, and provided a reference for genetic counseling and reproductive guidance for their families.

Objective:To explore the genetic basis for a Chinese pedigree affected with co-morbid Ornithine carbamoyl transferase deficiency (OTCD) and MECP2 duplication syndrome.Methods:A proband who was admitted to the Neonatal Intensive Care Unit of Gansu Provincial Maternal and Child Health Care Hospital on December 19, 2017 was selected as the study subject. High-throughput sequencing and multiplex ligation-dependent probe amplification (MLPA) were carried out for her pedigree, and short tandem repeat-based linkage analysis and chromosome copy number variation sequencing (CNV-seq) were used for the prenatal diagnosis.Results:The proband, a 3-day-old female, was found to harbor heterozygous deletion of exons 7-9 of the OTC gene. Based on the guidelines from the American College of Medical Genetics and Genomics (ACMG), the variant was classified as likely pathogenic (PVS1+ PM2_Supporting+ PP4). The proband was diagnosed with OTCD, which was in keeping with her acute encephalopathy and metabolic abnormalities (manifesting as hyperammonemia, decreased blood citrulline, and increased urine orotic acid). Prenatal diagnosis was carried out for the subsequent pregnancy. The fetus did not harbor the exons 7-9 deletion of the OTC gene, but was found to carry a duplication in Xq28 region (which encompassed the whole region of MECP2 duplication syndrome) and was positive for the SRY sequence. The same duplication was also found in the proband and her mother. Considering the possible existence of X-chromosome inactivation, the proband was diagnosed with two X-linked recessive disorders including OTCD and MECP2 duplication syndrome, and the fetus was determined as a male affected with the MECP2 duplication syndrome. Conclusion:Discoveries of the pathogenic variants underlying the OTCD and MECP2 duplication syndrome have enabled clinical intervention, treatment, genetic counseling and prenatal diagnosis for this pedigree.

Objective:To explore the genetic basis for a patient with autosomal dominant retinitis pigmentosa (RP).Methods:A male patient with RP treated at Gansu Provincial Maternal and Child Health Care Hospital in September 2019 was selected as the study subject. Clinical data was collected. Peripheral blood samples of the patient and his parents were subjected to whole exome sequencing (WES). Candidate variant was validated by Sanger sequencing and bioinformatic analysis.Results:The patient, a 29-year-old male, developed night blindness, amblyopia, visual field defects and optic disc abnormalities since childhood. Gene sequencing revealed that he has harbored a heterozygous c. 942G>C (p.Lys314Asn) variant of the IMPDH1 gene, which was inherited from his mother, whilst his father was of the wild type. Based on the guidelines from the American College of Medical Genetics and Genomics, the c. 942G>C variant was predicted as likely pathogenic (PM1+ PM2_Supporting+ PP3+ PP1). Conclusion:The c. 942G>C (p.Lys314Asn) variant in the IMPDH1 gene probably underlay the RP in this patient.

Objective:To analyze the clinical phenotype and genotypes of two children with Carnitine-acylcarnitine translocase deficiency (CACTD).Methods:Two children diagnosed with CACTD at the Gansu Provincial Maternal and Child Health Care Hospital respectively on January 3 and November 19, 2018 were selected as the study subjects. Trio-whole exome sequencing (trio-WES) was carried out, and candidate variants were validated through Sanger sequencing and pathogenicity analysis.Results:Both children were males and had manifested mainly with hypoglycemia. Trio-WES and Sanger sequencing showed that child 1 had harbored compound heterozygous variants of the SLC25A20 gene, namely c. 49G>C (p.Gly17Arg) and c. 106-2A>G, which were inherited from his father and mother, respectively. Child 2 had harbored homozygous c. 199-10T>G variants of the SLC25A20 gene, which were inherited from both of his parents. Among these, the c. 106-2A>G and c. 49G>C variants were unreported previously. Based on the guidelines from the American College of Medical Genetics and Genomics (ACMG), the c. 49G>C (p.Gly17Arg), c. 106-2A>G, and c. 199-10T>G variants were classified as likely pathogenic (PM2_supporting+ PP3+ PM3_strong+ PP4), pathogenic (PVS1+ PM2_supporting+ PM5+ PP3), and pathogenic (PVS1+ PM2_supporting+ PP3+ PP5), respectively. Conclusion:Combined with their clinical phenotype and genetic analysis, both children were diagnosed with CACTD. Above finding has provided a basis for their treatment as well as genetic counseling and prenatal diagnosis for their families.

Objective:To explore the genetic characteristics of a child with comorbid 16p11.2 microdeletion syndrome and Rett syndrome (RTT).Methods:A male infant who was admitted to Gansu Provincial Maternity and Child Health Care Hospital in May 2020 was selected as the study subject. Clinical data of the infant was collected. Genomic DNA was extracted from peripheral blood samples from the infant and his parents, and subjected to whole exome sequencing (WES). Candidate variant was verified by Sanger sequencing.Result:The patient, a 4-day-old male infant, had presented with poor response, poor intake, feeding difficulties, and deceased at 8 months after birth. WES revealed that he has harbored a 0.643 Mb deletion in the 16p11.2 region, which encompassed key genes of the 16p11.2 microdeletion syndrome such as ALDOA, CORO1A, KIFF22, PRRT2 and TBX6. His father has carried the same deletion, but was phenotypically normal. The deletion was predicted to be pathogenic. The child was also found to harbor a maternally derived c. 763C>T (p.R255X) hemizygous variant of the MECP2 gene, which was also predicted to be pathogenic (PVS1+ PS4+ PM2_Supporting). Conclusion:The 16p11.2 deletion and the MECP2: c.763C>T (p.R255X) variant probably underlay the pathogenesis in this infant.

Objective:To investigate the clinical and genetic characteristics of nonsyndromic sensorineural hearing loss caused by STRC biallelic variation. Methods:A child with hearing impairment who was diagnosed at Gansu Provincial Maternal and Child Health Hospital on May 2022 and was selected as the research object. Peripheral blood of the child and her parents was collected, genomic DNA was extracted. IDT The xGen Exome Research Panel v2.0 whole exome capture chip was used to capture and sequence. Bioinformatics and clinical information analysis technology were used to analyze genetic data. The suspected pathogenic mutations were verified by quantitative polymerase chain reaction(QPCR)and Sanger sequencing.Results:The child had moderate hearing loss at about 1 year and 10 months, and now she is 3 years and 6 months, the hearing loss has not worsened. Whole exome sequencing(WES) testing revealed that the child carried the STRC gene with a deletion in EXON:1-29 and variants c.4561(exon24) _c.4562(exon24)insC, inherited from the mother and father, respectively. According to the relevant guidelines of the American Society for Medical Genetics and Genomics (ACMG), they were determined to be likely pathogenic variant and pathogenic variant. Conclusion:The discovery of c.4561(exon24) _c.4562(exon24)insC enriched the STRC variation spectrum, and provided a theoretical basis for the diagnosis and genetic counseling to the children.