Clinical features and GCDH gene variants in three Chinese families with glutaric aciduria type 1: A case series and literature review.

Aim: To analyze the clinical phenotype and genetic etiology of three cases of glutaric aciduria type 1 (GA1) in Chinese children. Methods: We performed genetic and metabolic testing using tandem mass spectrometry (MS/MS) and gas chromatography-mass spectrometry (GC/MS), followed by trio whole-exome sequencing (trio-WES) and Sanger sequencing. A literature review on glutaric aciduria type 1 (GA1) in Chinese patients was also conducted. Results: Sequencing results showed each case had compound heterozygous variants in GCDH(NM_000159.4): c.214C > G (p.Arg72Gly) and c.411C > G (p.Tyr137Term) (Case 1), c.214C > G (p.Arg72Gly) and c.1204C > T (p.Arg402Trp) (Case 2), and c.1228G > T (p.Val410Leu) and c.395G > A (p.Arg132Gln) (Case 3). These variants were inherited from their respective parents. Notably, the c.214C > G variant found in two children was a novel variant not previously reported. A review of the literature revealed that, clinically, the majority of patients experienced onset in infancy and early childhood (82%). Additionally, 38.36% were diagnosed through newborn screening, with the primary reasons for the initial visit being delayed development (32.43%) and infections (21.61%). The most common clinical manifestations included increased head circumference (77.19%) and motor developmental delay (65.15%). Biochemically, patients exhibited significant elevations in C5DC (98.51%) and C5DC/C8 (94.87%) in blood, as well as GA (94.37%) and 3OHGA (69.39%) in urine. Radiographically, patients showed a high prevalence of abnormalities in cranial MRI (86.15%) and EEG (73.33%). Genetically, 67 distinct GCDH gene variants were identified among 73 patients, with missense variants being the most prevalent type (73.97%). The most frequent variant was c.1244-2 A > C, observed in 17.12% of cases. Additionally, the majority of variant sites were located in exons 11 (25.37%) and 6 (22.39%). Conclusion: GCDH variants were identified as the causative factors in the three children. The discovery of the novel variant (c.214C > G) expands the spectrum of pathogenic GCDH variants. These findings facilitate the diagnosis and treatment of affected children and provide a basis for genetic counseling and prenatal diagnosis for their families.

[Clinical and molecular genetic analysis of a child with comorbid 16p11.2 microdeletion syndrome and Rett syndrome].

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. RESULTS: 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.

[Clinical features and genetic analysis of a child with 3-methylglutenedioic aciduria type VII due to novel variants of CLPB gene].

OBJECTIVE: To explore the clinical features and genetic basis for a child with 3-methylglutaconic aciduria type VII. METHODS: A child who was diagnosed at the Gansu Provincial Maternity and Child Health Care Hospital on August 9, 2019 was selected as the study subject. Clinical data of the child, including urine gas chromatography and mass spectrometry, were collected. The child and her parents were subjected to whole exome sequencing. RESULTS: The child, a female neonate, had presented mainly with intermittent skin cyanosis, convulsions, hypomagnesemia, apnea, neutropenia after birth. Her urine 3-methylpentenedioic acid has increased to 17.53 µmol/L. DNA sequencing revealed that she has harbored compound heterozygous variants of the CLPB gene, namely c.1016delT (p.L339Rfs*5) and c.1087A>G (p.R363G), which were respectively inherited from her mother and father. Both variants were unreported previously. Based on the standards from the American College of Medical Genetics and Genomics (ACMG), the variants were respectively predicted to be pathogenic and likely pathogenic. CONCLUSION: The child was diagnosed with 3-methylglutenedioic aciduria type VII. Discovery of the c.1016delT and c.1087A>G variants has enriched the mutational spectrum of the CLPB gene.

Evaluation of the clinical effects of non-invasive prenatal screening for diseases associated with aneuploidy and copy number variation.

BACKGROUND: To explore and compare the clinical effects of high-resolution non-invasive prenatal screening (NIPS-Plus) for common/uncommon chromosomal aneuploidy and microdeletion/microduplication syndromes (MMS). METHODS: The current prospective study included a total of 25,380 pregnant women who performed NIPS-Plus, and amniocentesis was performed on women with MMS with the screening results to diagnose patients with suspected MMS. RESULTS: There were 415 samples with positive results for NIPS-Plus, included 275 with aneuploidy and 140 with MMS. After diagnosis by amniocentesis, 188 cases were confirmed as true positive, included46 cases of T21, 9 cases of T18, 1 case of T13, 34 cases of SCA, 41 cases of other chromosomal euploidy and 57 cases of MMS. In addition, no false negative cases were found, MMS was classified with 5 Mb with the cutoff value, and the PPV of different fragment size was counted, respectively. CONCLUSION: We found that the corresponding PPV was 44.66% with the fragment of copy number variation (CNV) being less than or equal to 5 Mb, and when it was greater than 5 Mb, the PPV was 29.73%, which suggested that NIPS-Plus was more suitable for screening the PPV of small fragment abnormalities. NIPS-Plus has a good application effect in routine aneuploidy screening and had the best detection effect for T21; moreover, it performed well in screening of MMS and had better detection effect on MMS with CNV fragment length less than 5 Mb. Based on the current results, we suggested that NIPS-Plus should be used as a comprehensive elementary prenatal screening method for all pregnant women, but for MMS caused by abnormal large fragment CNV, the detection method and efficiency still need to be improved.

[Phylogenetic and genetic heterogeneity of 23 Acidithiobacillus strains isolated from different geographical locations].

Objective: To study the phylogenetic and genetic heterogeneity of 23 Acidithiobacillus strains from various geographical locations, as well as the relationship between the DNA fingerprinting classification and geographical origin of Acidithiobacillus. Methods: Partial 16S-23S rRNA gene intergenic spacer (ITS) was used to construct corresponding phylogenetic trees based on the sequence homology. rus gene amplification and rep-PCR assay with two different primers (BOXAIR and ERIC) were performed to analyze genetic heterogeneity of Acidithiobacillus strains from diverse environment. Results: Acidithiobacillus revealed a great genetic heterogeneity. The whole isolates were classified into five groups by ITS sequence analysis. This result was similar with that obtained by rep-PCR. Acidithiobacillus ferrooxidans strains were always divided into two groups of phylogenetic and BOXAIR fingerprinting cluster analysis. However, these were clustered one group in the ERIC dendrogram. Genotypic analysis of the rus gene suggested that different iron oxidation pathways have been evolved in these closely related bacteria. Taken together, the iron oxidation pathway of Acidithiobacillus and phylogenetic groups have no obvious correlation. ITS gene has been proven very useful in distinguishing closely related species or subspecies of Acidithiobacillus, to BOXAIR-PCR, which has been recommended as reliable tool for genetic heterogeneity analysis of Acidithiobacillus.

[Phylogenetic and diversity analysis of Acidithiobacillus spp. based on 16S rRNA and RubisCO genes homologues].

Objective: The purpose of the study was to reveal geographic region-related Acidithiobacillus spp. distribution and allopatric speciation. Phylogenetic and diversity analysis was done to expand our knowledge on microbial phylogeography, diversity-maintaining mechanisms and molecular biogeography. Methods: We amplified 16S rRNA gene and RubisCO genes to construct corresponding phylogenetic trees based on the sequence homology and analyzed genetic diversity of Acidithiobacillus spp.. Results: Thirty-five strains were isolated from three different regions in China (Yunnan, Hubei, Xinjiang). The whole isolates were classified into five groups. Four strains were identified as A. ferrivorans, six as A. ferridurans, YNTR4-15 Leptspirillum ferrooxidans and HBDY3-31 as Leptospirillum ferrodiazotrophum. The remaining strains were identified as A. ferrooxidans. Analysis of cbbL and cbbM genes sequences of representative 26 strains indicated that cbbL gene of 19 were two copies (cbbL1 and cbbL2) and 7 possessed only cbbL1. cbbM gene was single copy. In nucleotide-based trees, cbbL1 gene sequences of strains were separated into three sequence types, and the cbbL2 was similar to cbbL1 with three types. Codon bias of RubisCO genes was not obvious in Acidithiobacillus spp.. Conclusion: Strains isolated from three different regions in China indicated a great genetic diversity in Acidithiobacillus spp. and their 16S rRNA/RubisCO genes sequence was of significant difference. Phylogenetic tree based on 16S rRNA genes and RubisCO genes was different in Acidithiobacillus spp..