[Analysis of a child with developmental disorder and epilepsy due to a homozygous variant of SLC25A12 gene].

OBJECTIVE: To explore the genetic basis for a child featuring global developmental delay and epilepsy. METHODS: A child who had presented at Guangzhou Women and Children's Medical Center Liuzhou Hospital on February 19, 2023 was selected as the study subject. Clinical data of the child was collected. The child was subjected to whole exome sequencing, and candidate variant was validated by Sanger sequencing and bioinformatic analysis. RESULTS: The child, an 8-month-old girl, had manifested with global developmental delay, epilepsy, and hyperlactacidemia. Cranial MRI revealed diverse hypomyelinating leukodystrophies. Electroencephalogram showed slow background activities. Genetic testing revealed that she has harbored a homozygous variant of the SLC25A12 gene, namely c.115T>G (p.Phe39Val), for which both of her parents were heterozygous carriers. Based on the guidelines from the American College of Medical Genetics and Genomics, the variant was predicted to be of uncertain significance (PM2_Supporting+PM3_Supporting+PP3_Moderate+PP4_Moderate). I-Mutant v3.0 software predicted that the variant may affect the stability of protein product. CONCLUSION: The homozygous c.115T>G (p.Phe39Val) variant of the SLC25A12 gene probably underlay the pathogenesis of the disease in this child.

The value of single-molecule real-time technology in the diagnosis of rare thalassemia variants and analysis of phenotype-genotype correlation.

To compare single-molecule real-time technology (SMRT) and conventional genetic diagnostic technology of rare types of thalassemia mutations, and to analyze the molecular characteristics and phenotypes of rare thalassemia gene variants, we used 434 cases with positive hematology screening as the cohort, then used SMRT technology and conventional gene diagnosis technology [(Gap-PCR, multiple ligation probe amplification technology (MLPA), PCR-reverse dot blot (RDB)] for thalassemia gene screening. Among the 434 enrolled cases, conventional technology identified 318 patients with variants (73.27%) and 116 patients without variants (26.73%), SMRT identified 361 patients with variants (83.18%), and 73 patients without variants (16.82%). The positive detection rate of SMRT was 9.91% higher than conventional technology. Combination of the two methods identified 485 positive alleles among 49 types of variant. The genotypes of 354 cases were concordant between the two methods, while 80 cases were discordant. Among the 80 cases, 76 cases had variants only identified in SMRT method, 3 cases had variants only identified in conventional method, and 1 false positive result by the traditional PCR detection technology. Except the three variants in HS40 and HBG1-HBG2 loci, which was beyond the design of SMRT method in this study, all the other discordant variants identified by SMRT were validated by further Sanger sequencing or MLPA. The hematological phenotypic parameters of 80 discordant cases were also analyzed. SMRT technology increased the positive detection rate of thalassemia genes, and detected rare thalassemia cases with variable phenotypes, which had great significance for clinical thalassemia gene screening.

[Analysis of IVD gene variants in four children with isovalerate acidemia].

OBJECTIVE: To detect variants of IVD gene among 4 neonates with suspected isovalerate acidemia in order to provide a guidance for clinical treatment. METHODS: 111 986 newborns and 7461 hospitalized children with suspected metabolic disorders were screened for acyl carnitine by tandem mass spectrometry. Those showing a significant increase in serum isovaleryl carnitine (C5) were analyzed for urinary organic acid and variants of the IVD gene. RESULTS: Four cases of isovalerate acidemia were detected, which included 2 asymptomatic newborns (0.018‰, 2/111 986) and 2 children suspected for metabolic genetic diseases (0.268‰, 2/7461). The formers had no obvious clinical symptoms. Analysis of acyl carnitine has suggested a significant increase in C5, and urinary organic acid analysis has shown an increase in isovaleryl glycine and 3-hydroxyisovalerate. Laboratory tests of the two hospitalized children revealed high blood ammonia, hyperglycemia, decreased red blood cells, white blood cells, platelets and metabolic acidosis. The main clinical manifestations have included sweaty foot-like odor, feeding difficulty, confusion, drowsiness, and coma. Eight variants (5 types) were detected, which included c.158G>A (p.Arg53His), c.214G>A (p.Asp72Asn), c.548C>T (p.Ala183Val), c.757A>G (p.Thr253Ala) and 1208A>G (p.Tyr403Cys). Among these, c.548C>T and c.757A>G were unreported previously. None of the variants was detected by next generation sequencing of 2095 healthy newborns, and all variants were predicted to be likely pathogenic based on the guidelines from the American College of Medical Genetics and Genomics. CONCLUSION: The incidence of isovalerate acidemia in Liuzhou area is quite high. Screening of metabolic genetic diseases is therefore recommended for newborns with abnormal metabolism. The discovery of novel variants has enriched the mutational spectrum of the IVD gene.

The relationship between the minor allele content and Alzheimer's disease.

Alzheimer's disease (AD) is a chronic neurodegenerative disease. The genetic risk factors of AD remain better understood. Using previously published dataset of common single nucleotide polymorphisms (SNPs), we studied the association between the minor allele content (MAC) in an individual and AD. We found that AD patients have higher average MAC values than matched controls. We identified a risk prediction model that could predict 2.19% of AD cases. We also identified 49 genes whose expression levels correlated with both MAC and AD. By pathway and process enrichment analyses, these genes were found in pathways or processes closely related to AD. Our study suggests that AD may be linked with too many genetic variations over a threshold. The method of correlations with both MAC and traits appears to be effective in high efficiency identification of target genes for complex traits.

Application of Copy Number Variation Sequencing in Genetic Analysis of Miscarriages in Early and Middle Pregnancy.

High-throughput sequencing based on copy number variation (CNV-seq) is commonly used to detect chromosomal abnormalities. This study identifies chromosomal abnormalities in aborted embryos/fetuses in early and middle pregnancy and explores the application value of CNV-seq in determining the causes of pregnancy termination. High-throughput sequencing was used to detect chromosome copy number variations (CNVs) in 116 aborted embryos in early and middle pregnancy. The detection data were compared with the Database of Genomic Variants (DGV), the Database of Chromosomal Imbalance and Phenotype in Humans using Ensemble Resources (DECIPHER), and the Online Mendelian Inheritance in Man (OMIM) database to determine the CNV type and the clinical significance. High-throughput sequencing results were successfully obtained in 109 out of 116 specimens, with a detection success rate of 93.97%. In brief, there were 64 cases with abnormal chromosome numbers and 23 cases with CNVs, in which 10 were pathogenic mutations and 13 were variants of uncertain significance. An abnormal chromosome number is the most important reason for embryo termination in early and middle pregnancy, followed by pathogenic chromosome CNVs. CNV-seq can quickly and accurately detect chromosome abnormalities and identify microdeletion and microduplication CNVs that cannot be detected by conventional chromosome analysis, which is convenient and efficient for genetic etiology diagnosis in miscarriage.

Diagnosis and Prenatal Diagnosis in a Chinese Family Carrying the Rare α-Thalassemia Gene HBA2: c.1A>G Mutation.

The aim of this study was to identify the rare thalassemia genotype in a family and perform prenatal diagnosis (PND) on the proband's unborn child. Peripheral blood was collected from the family members for hematology analysis and capillary electrophoresis (CE) analysis. Peripheral blood and cord blood were analyzed by gap-polymerase chain reaction (gap-PCR), reverse dot-blot and Sanger sequencing for genotypes of α-thalassemia (α-thal). A heterozygous mutation, HBA2: c.1A>G, was identified in the proband and his father. Two compound heterozygous variants, HBA2: c.1A>G and the - -SEA (Southeast Asian) deletion, were revealed in the proband's unborn child. The hemoglobin (Hb) CE result of the fetal cord blood indicated the fetus had Hb H disease. We have identified a rare thalassemia mutation (HBA2: c.1A>G) in a Chinese family and enriched the rare α-thal gene pool in the Chinese population. When the patient's phenotype does not match the genotype detected by thalassemia gene detection kits, further investigation of rare genotypes should be conducted to avoid missed diagnosis or misdiagnosis, which can help guide clinical diagnosis, population screening and genetic counseling.

[Analysis of PLA2G6 gene variant in a family affected with infantile neuroaxonal dystrophy].

OBJECTIVE: To identify potential variant in a child diagnosed as infantile neuroaxonal dystrophy. METHODS: Genomic DNA was extracted from peripheral blood samples from the patient and his parents and subjected to next generation sequencing. Suspected variant was verified by PCR and Sanger sequencing. Pathogenicity of the mutation was predicted by using bioinformatic software including SIFT and PolyPhen-2. RESULTS: The child was found to carry compound heterozygous variations c.668C>A (p.Pro223Gln) and c.2266C>T (p.Gln756Ter) of the PLA2G6 gene, which were respectively inherited from his father and mother. c.2266C>T has changed codon 756 (glutamine) into a stop codon, resulting premature termination of peptide chain synthesis. c.2266C>T has not been reported previously and was predicted to be harmful. CONCLUSION: The compound variants of c.668C>A (p.Pro223Gln) and c.2266C>T (p.Gln756Ter) of the PLA2G6 gene probably underlies the disease in the child. Above finding has enriched the variant spectrum of the PLA2G6 gene.

[SLC22A5 gene mutation analysis and prenatal diagnosis for a family with primary carnitine deficiency].

OBJECTIVE: To carry out mutation analysis and prenatal diagnosis for a family affected with primary carnitine deficiency. METHODS: Genomic DNA of the proband was extracted from peripheral blood sample 10 days after birth. The 10 exons and intron/exon boundaries of the SLC22A5 gene were subjected to PCR amplification and Sanger sequencing. The proband's mother was pregnant again two years after his birth. Fetal DNA was extracted from amniocytes and subjected to PCR and Sanger sequencing. RESULTS: Tandem mass spectrometric analysis of the proband revealed low level of plasma-free carnitine whilst organic acids in urine was normal. Compound heterozygous SLC22A5 mutations c.1195C>T (inherited from his father) and c.517delC (inherited from his mother) were detected in the proband. Prenatal diagnosis has detected no mutation in the fetus. The plasma-free carnitine was normal after birth. CONCLUSION: Appropriate genetic testing and prenatal diagnosis can prevent further child with carnitine deficiency. The identification of c.517delC, a novel mutation, enriched the spectrum of SLC22A5 mutations.

[Analysis of P gene variations among fourteen patients with oculocutaneous albinism type II].

OBJECTIVE: To analyze variations of TYR and P genes among 14 patients with clinically diagnosed oculocutaneous albinism. METHODS: Potential variations of the TYR and P genes were detected by Sanger sequencing. Novel variations were predicted with bioinformatics software including SIFT and PolyPhen-2. RESULTS: No variation was found in the TYR gene, while 9 types of variations were found in the P gene among the 14 patients, which included c.803-3C>G (7/26), c.1327G>A (p.Val443Ile) (5/26), c.632C>T (p.Pro211Leu) (4/26), c.1832T>C (p.Leu611Pro) (3/26), c.1349C>A (p.Thr450Lys) (2/26), c.2363C>T (p.Ser788Leu) (2/26), c.2228C>T (p.Pro743Leu) (1/26), c.1525A>G (p.Thr509Ala) (1/26), and c.1349C>T (p.Thr450Met) (1/26). Only 1 heterozygous variation was detected in 2 families. c.2363C>T (p.Ser788Leu), c.1832T>C (p.Leu611Pro) and c.1525A>G (p.Thr509Ala) were not reported previously and predicted as "harmful" to the protein function. CONCLUSION: The main type of ocular albinism is oculocutaneous albinism type II in Liuzhou region, where the most common variations of the P gene were c.803-3C>G and c.1327G>A (p.Val443Ile). Above finding has enriched the variation spectrum of the P gene.

Collective effects of common SNPs and risk prediction in lung cancer.

Lung cancer is the leading cause of cancer deaths in both men and women in the US. While most sporadic lung cancer cases are related to environmental factors such as smoking, genetic susceptibility may also play an important role and a number of lung cancer associated single-nucleotide polymorphisms (SNPs) have been identified although many remain to be found. The collective effects of genome-wide minor alleles of common SNPs, or the minor allele content (MAC) in an individual, have been linked with quantitative variations of complex traits and diseases. Here we studied MAC in lung cancer using previously published SNPs data sets (US and Finland samples) and found higher MAC in cases relative to matched controls. A set of 5400 SNPs with MA (MAF < 0.5) more common in cases (P < 0.08) and linkage disequilibrium (LD) r2 = 0.3 was found to have the best predictive accuracy. These results identify higher MAC in lung cancer susceptibility and provide a meaningful genetic method to identify those at risk of lung cancer.

Genetic equidistance at nucleotide level.

The genetic equidistance phenomenon shows complex taxa to be all approximately equidistant to a less complex species in amino acid percentage identity. The overlooked mystery was re-interpreted by the maximum genetic diversity hypothesis (MGD). Here, we studied 14 proteomes and their coding DNA sequences (CDS) to see if the equidistance phenomenon also holds at the CDS level. We found that the outgroup taxon was equidistant to the two more complex taxa species. When two sister taxa were compared to human as the outgroup, the more complex taxon was closer to human, confirming species complexity to be the primary determinant of MGD. Finally, we found the fraction of overlap sites to be inversely correlated with CDS conservation, indicating saturation to be more common in less conserved DNAs. These results establish the genetic equidistance phenomenon to be universal at the DNA level and provide additional evidence for the MGD theory.

Close genetic relationships between a spousal pair with autism-affected children and high minor allele content in cases in autism-associated SNPs.

Parents of children affected with autism spectrum disorders (ASD) often have mild forms of autistic-like characteristics. Past studies have focused on searching for individual genetic risk loci of ASD. Here we studied the overall properties of the genomes of ASD trios by using previously published genome-wide data for common SNPs. The pairwise genetic distance (PGD) between a spousal pair with ASD-affected children was found smaller than that of a random pair selected among the spouses in the ASD trios, and spousal relatedness correlated with severe forms of ASD. Furthermore, for a set of 970 ASD associated SNPs, cases showed higher homozygous minor allele content than parents. These results indicate new genetic elements in the broad phenotypes of parents with ASD-affected offspring and in ASD pathogenesis.

[Clinical and cytogenetic study in a child with de novo chromosome 9 abnormality].

This study aimed to analyze the clinical phenotype of chromosome 9p deletion or duplication and its relationship with karyotype. A patient, female, aged 6 months, visited the hospital due to motor developmental delay. Karyotype analysis identified abnormalities of chromosome 9 short arm, and high-throughput sequencing found 9p24.3-9p23 deletion and 9p23-9p13.1 duplication. Her parents had a normal karyotype. Karyotype analysis combined with high-throughput sequencing is of great significance for improving the efficiency of etiological diagnosis in children with motor developmental delay or multiple congenital deformities and mental retardation.

Collective effects of SNPs on transgenerational inheritance in Caenorhabditis elegans and budding yeast.

We studied the collective effects of single nucleotide polymorphisms (SNPs) on transgenerational inheritance in Caenorhabditis elegans recombinant inbred advanced intercross lines (RIAILs) and yeast segregants. We divided the RIAILs and segregants into two groups of high and low minor allele content (MAC). RIAILs with higher MAC needed less generations of benzaldehyde training to gain a stable olfactory imprint and showed a greater change from normal after benzaldehyde training. Yeast segregants with higher MAC showed a more dramatic shortening of the lag phase length after ethanol exposure. The short lag phase as acquired by ethanol training was more dramatically lost after recovery in ethanol free medium for the high MAC group. We also found a preferential association between MAC and traits linked with higher number of additive QTLs. These results suggest a role for the collective effects of SNPs in transgenerational inheritance, and may help explain human variations in disease susceptibility.

Optimizing peripheral blood chromosome analysis: effects of refrigeration time and blood volume.

OBJECTIVE: This study aims to investigate the impact of refrigeration time and blood volume on the success rate of peripheral blood chromosomal analysis using response surface methodology (RSM). METHODS: Peripheral blood samples from 30 volunteers were subjected to chromosomal analysis under different refrigeration duration periods (≤7 days, 8 days, 9 days, 10 days, 11 days, 12 days, 13 days, 14 days) along with different blood volumes (0.2 mL, 0.3 mL, 0.4 mL, 0.5 mL, 0.6 mL, 0.7 mL, and 0.8 mL). The effects of refrigeration time and blood volume on the success rate of peripheral blood chromosomal analysis were determined using the Chi-square test for trend, followed with Spearman's rank correlation coefficient, and RSM analysis to identify the optimal combination of refrigeration time and blood volume. RESULTS: The refrigeration time within 10 days had a minor impact on the success rate, while refrigeration time more than 11 days significantly decreased the success rate. An increase in blood volume slightly improved the success rate. The success rate showed both linear and nonlinear changes with refrigeration time, while the effect of blood volume was primarily linear. The highest success rate was observed at a refrigeration time of ≤7 days and a blood volume of 0.8 mL. The interaction between refrigeration time and blood volume had a significant impact on the success rate. CONCLUSION: It is recommended to keep the refrigeration time of blood samples within 7 days and control the blood volume at 0.8 mL to maximize the success rate of chromosomal analysis.

Improved Genetic Characterization of Congenital Adrenal Hyperplasia by Long-Read Sequencing Compared with Multiplex Ligation-Dependent Probe Amplification Plus Sanger Sequencing.

Genetic analysis of congenital adrenal hyperplasia (CAH) has been challenging because of high homology between CYP21A2 and its pseudogene CYP21A1P. This study aimed to evaluate the clinical utility of long-read sequencing (LRS) in diagnosis of CAH attributable to 21-hydroxylase deficiency by comparing with multiplex ligation-dependent probe amplification plus Sanger sequencing. In this retrospective study, 69 samples, including 49 probands from 47 families with high-risk of CAH, were enrolled and blindly subjected to detection of CAH by LRS. The genotype results were compared with control methods, and discordant samples were validated by additional Sanger sequencing. LRS successfully identified biallelic variants of CYP21A2 in the 39 probands diagnosed as having CAH. The remaining 10 probands were not patients with CAH. Additionally, LRS directly identified two pathogenic single-nucleotide variations (SNVs; c.293-13C/A>G and c.955C>T) in the presence of interference caused by nearby insertions/deletions (indels). The cis-trans configuration of two or more SNVs and indels identified in 18 samples was directly determined by LRS without family analysis. Eight CYP21A1P/A2 or TNXA/B deletion chimeras, composed of five subtypes, were identified; and the junction sites were precisely determined. Moreover, LRS determined the exact genotype in two probands who had three heterozygous SNVs/indels and duplication, which could not be clarified by control methods. These findings highlight that LRS could assist in more accurate genotype imputation and more precise CAH diagnosis.

Prenatal diagnosis of paternal uniparental disomy for chromosome 2 in two fetuses with intrauterine growth restriction.

Uniparental disomy (UPD) is when all or part of the homologous chromosomes are inherited from only one of the two parents. Currently, UPD has been reported to occur for almost all chromosomes. In this study, we report two cases of UPD for chromosome 2 (UPD2) encountered during prenatal diagnosis. The ultrasound findings of the fetuses from two unrelated families showed intrauterine growth restriction. The karyotype analyses were normal. The two fetuses both had complete paternal chromosome 2 uniparental disomy detected by whole-exome sequencing, but their clinical outcomes were significantly different, with fetal arrest in case 1 and birth in case 2. In this report, we analyzed and discussed the phenotypes of the fetuses in these two cases and reviewed the literature on UPD2.

Analysis of a family with mitochondrial trifunctional protein deficiency caused by HADHA gene mutations.

Mitochondrial trifunctional protein (MTP) deficiency (MTPD; MIM 609015) is a metabolic disease of fatty acid oxidation. MTPD is an autosomal recessive disorder caused by mutations in the HADHA gene, encoding the α­subunit of a trifunctional protease, or in the HADHB gene, encoding the ß­subunit of a trifunctional protease. To the best of our knowledge, only two cases of families with MTPD due to HADHB gene mutations have been reported in China, and the HADHA gene mutation has not been reported in a Chinese family with MTPD. The present study reported the clinical characteristics and compound heterozygous HADHA gene mutations of two patients with MTPD in the Chinese population. The medical history, routine examination data, blood acyl­carnitine analysis results, results of pathological examination after autopsy and family pedigree map were collected for patients with MTPD. The HADHA gene was analyzed by Sanger sequencing or high­throughput sequencing, the pathogenicity of the newly discovered variant was interpreted by bioinformatics analysis, and the function of the mutated protein was modeled and analyzed according to 3D structure. The two patients with MTPD experienced metabolic crises and died following an infectious disease. Lactate dehydrogenase, creatine kinase (CK), CK­MB and liver enzyme abnormalities were observed in routine examinations. Tandem mass spectrometry revealed that long­chain acyl­carnitine was markedly elevated in blood samples from the patients with MTPD. The autopsy results for one child revealed fat accumulation in the liver and heart. Next­generation sequencing detected compound heterozygous c.703C>T (p.R235W) and c.2107G>A (p.G703R) mutations in the HADHA gene. The mother did not have acute fatty liver during pregnancy with the two patients. Using amniotic fluid prenatal diagnostic testing, the unborn child was confirmed to carry only c.2107G>A (p.G703R). Molecular mechanistic analysis indicated that the two variants affected the conformation of the α­subunit of the MTP enzyme complex, and consequently affected the stability and function of the enzyme complex. The present study comprehensively analyzed the cases, including exome sequencing and protein structure analysis and, to the best of our knowledge, describes the first observation of compound heterozygous mutations in the HADHA gene underlying this disorder in China. The clinical phenotypes of the two heterozygous variants of the HADHA gene are non­lethal. The present study may improve understanding of the HADHA gene mutation spectrum and clinical phenotype in the Chinese population.

Detection of four rare thalassemia variants using Single-molecule realtime sequencing.

Conventional methods for the diagnosis of thalassemia include gap polymerase chain reaction (Gap-PCR), reverse membrane hybridization (RDB), multiplex ligation-dependent probe amplification (MLPA) and Sanger sequencing. In this study, we used single molecule real-time technology (SMRT) sequencing and discovered four rare variants that have not been identified by conventional diagnostic methods for thalassemia. We also performed genotype and phenotype analyses on family members of thalassemia patients. The SMRT technology detected five cases in which the proband had abnormal results by conventional diagnostic methods or inconsistencies between the genotype and phenotype. The variants included two cases of an α-globin gene cluster 27,311 bp deletion, --27.3/αα (hg38 chr16:158664-185974), one case of an HS-40 region 16,079 bp deletion (hg38 chr16:100600-116678), one case of a rearrangement of -α3.7α1α2 on one allele and one case of a ß-globin gene cluster HBG1-HBG2 4,924 bp deletion (hg38 chr11:5249345-5254268). This study clarified the hematological phenotypes of four rare variants and indicated the application value of SMRT in the diagnosis of rare α-globin and ß-globin gene cluster deletions, gene recombination and deletion breakpoints. The SMRT method is a comprehensive one-step technology for the genetic diagnosis of thalassemia and is particularly suitable for the diagnosis of thalassemia with rare deletions or genetic recombination.