[Cases Analysis of Hemoglobin H Disease Caused by HBA2:c.2T>C and HBA2:c.2delT Mutations].

OBJECTIVE: To investigate two cases of rare pathogenic genes, initiation codon mutations in HBA2 gene, combined with Southeast Asian deletion and their family members to understand the relationship of HBA2:c.2T>C and HBA2:c.2delT mutations with clinical phenotype. METHODS: The peripheral blood of family members was obtained for blood cell analysis and capillary electrophoresis hemoglobin analysis. Gap-PCR and reverse dot blotting (RDB) were used to detect common types of mutations in ɑ-thalassaemia gene. Sanger sequencing was used to analyze HBA1 and HBA2 gene sequence. RESULTS: Two proband genotypes were identified as --SEA/αα with HBA2:c.2T>C and --SEA/αα with HBA2:c.2delT. HBA2:c.2T>C/WT and HBA2:c.2delT/WT was detected in family members. They all presented with microcytic hypochromic anemia. CONCLUSION: When HBA2:c.2T>C and HBA2:c.2delT are heterozygous that can lead to static α-thalassemia phenotype, and when combined with mild α-thalassemia, they can lead to the clinical manifestations of hemoglobin H disease. This study provides a basis for genetic counseling.

Hb H disease associated with compound heterozygosity for --SEA deletion and a novel alpha globin chain variant (HBA2:c.175C>A) on the distal histidine in a Chinese family.

OBJECTIVES: In clinical practice, the majority of α-thalassaemia cases arise from deletions of the α-globin genes. However, a subset of cases is attributed to rare haemoglobin variants, which can manifest with borderline or normal screening results, potentially leading to missed diagnoses in clinical practice. METHODS: Blood samples were collected from family members and underwent haematological, DNA and RNA analysis. RESULTS: The five-month-old proband presented a haematological phenotype consistent with Hb H disease. The mother's haematology profile was consistent with an α-thalassaemia carrier, while the father exhibited a borderline reduction in MCV and MCH. MALDI-TOF identified an abnormal α-chain in the proband. DNA analysis revealed a novel α-globin variant (HBA2:c.175C>A, α58His>Asn, Hb DG-Nancheng) affecting the distal histidine in the family. The father and the mother had α-genotype of --SEA/αα and αDG-Nanchengα/αα, respectively; while the proband inherited both mutant alleles (--SEA/αDG-Nanchengα). Sequencing of cDNA from HBA2 gene identified an equal ratio of normal and mutant alleles. CONCLUSION: This rare case highlighted the importance of identifying rare haemoglobin variant during prenatal screening. The clinical and genetic data provides useful information on the pathogenicity of this variant and further insight into the role of distal histidine residue of α-globin.

SUPT5H mutations associated with elevation of Hb A2 level: Identification of two novel variants and literature review.

ß-thalassemia is one of the most common monogenic disorders in areas of the tropics and subtropics, which represents a major familial and social burden to local people. The elevated Hb A2 level, generally specified as greater than 3.5 %, is commonly used as a high efficiency index for screening of ß-thalassemia carriers. However, mutations in other genes such as GATA1 and KLF1, could also result in increased Hb A2 level. In this study, we identified two novel variants in the SUPT5H gene: a frameshift mutation (SUPT5H: c.3032_3033delTG, p.M1011Mfs*9) and a nonsense mutation (SUPT5H: c.397C > T, p.Arg133*) in two Chinese individuals. Utilizing a combination of phenotype analysis, bioinformatics analysis, and functional analysis, we deduced that these two variants modified the SUPT5H protein's structure, thereby impacting its function and consequently leading to the heightened Hb A2 level phenotype found in the carriers. Furthermore, through a comprehensive literature review, a mutation spectrum was consolidated for SUPT5H, an investigation into the genotype-phenotype correlation was conducted, and factors known to influence Hb A2 levels were identified. Based on this in-depth understanding, clinicians are better equipped to carry out large scale screenings in regions with high prevalence of ß-thalassemia.

Molecular spectrum and prevalence of thalassemia investigated by third-generation sequencing in the Dongguan region of Guangdong Province, Southern China.

BACKGROUND: PCR, Sanger sequencing and NGS are often employed for carrier screening of thalassemia but all of these methods have limitations. In this study, we evaluated a new third-generation sequencing-based approach termed comprehensive analysis of thalassemia alleles (CATSA) to explore the prevalence of thalassemia in the Dongguan region of southern China. METHODS: 19,932 subjects were recruited for thalassemia screening and hemoglobin testing was performed for each of them. Routine PCR was performed for all the hemoglobin testing-positive subjects and CATSA was conducted for randomly selected subjects from hemoglobin testing-positive and negative subjects. RESULTS: In the 2716 subjects tested both by PCR and CATSA, 2569 had the same results and 147 had discordant results between the two methods. Sanger sequencing, specially designed PCR and MLPA confirmed the results of CATSA were all correct. In total, CATSA correctly detected 787 subjects with variants while routine PCR correctly detected 640 subjects with variants. CATSA yielded a 5.42% (147 of 2716) increment compared with routine PCR. In the 447 hemoglobin testing-negative subjects, CATSA identified pathogenic variants in 12 subjects. Moreover, CATSA identified a novel deletion (chr16:171262-202032) in the α-globin gene cluster. As a result, the deduced carrier frequency of α-thalassemia,ß-thalassemia and α-/ß-thalassemia was 5.62%, 3.85% and 0.93%, respectively. CONCLUSIONS: Our study demonstrated CATSA was a more comprehensive and precise approach than the routine PCR in a large scale of samples, which is highly beneficial for carrier screening of thalassemia. It provided a broader molecular spectrum of hemoglobinopathies and a better basis for a control program in Dongguan region.

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.

Distribution characteristics and clinical phenotype analyses of hemoglobin variants in the Z region of Central Guangxi, Southern China.

OBJECTIVE: To investigate the molecular diagnosis of hemoglobin variants in Z region by Capillary electrophoresis in Central Guangxi, Southern China, and analyze their distribution and phenotypic characteristics, to provide a reference for clinical consultation and prenatal diagnosis for couples. METHODS: A total of 23,709 subjects were collected for blood routine analysis, hemoglobin analysis, and common α- and ß-globin gene loci in Chinese population. The hemoglobin electrophoresis components were divided into Zone 1-Zone 15 (Z1-Z15) by Capillary zone electrophoresis (CE). For samples not clearly detected by the conventional technology, Sanger sequencing, and multiplex ligation-dependent probe amplification (MLPA) were used. Single-molecule real-time (SMRT) sequencing technology was used to analyze rare-type genes in a sample with a structural variation. RESULTS: Ten rare hemoglobin variants distributed in Z region were detected in 23,709 samples, including Hb Cibeles, which was reported for the first time in Asia; Hb J-Broussais, Hb G-Honolulu and J-Wenchang-Wuming, they were first reported in Guangxi; 1 case of Hb Anti-Lepore Liuzhou, which was a newly discovered hemoglobin variant; hemoglobin variants Hb G-Siriraj, Hb Handsworth, Hb Q-Thailand, Hb Ube-2, Hb NewYork were also detected. CONCLUSION: There are a few studies on rare hemoglobin variants in Z region in Southern China. Ten rare hemoglobin variants were found in this study. The hematological phenotype and component content of hemoglobin variants are related to the occurrence of thalassemia. This study enriched the data of rare hemoglobin variants in Southern China and provided a comprehensive data basis for prenatal diagnosis of hemoglobin variants in this area.

MALDI-TOF-MS for Rapid Screening and Typing of ß-Globin Variant and ß-Thalassemia through Direct Measurements of Intact Globin Chains.

BACKGROUND: Traditional phenotype-based screening for ß-globin variant and ß-thalassemia using hematological parameters is time-consuming with low-resolution detection. Development of a MALDI-TOF-MS assay using alternative markers is needed. METHODS: We constructed a MALDI-TOF-MS-based approach for identifying various ß-globin disorders and classifying thalassemia major (TM) and thalassemia intermedia (TI) patients using 901 training samples with known HBB/HBA genotypes. We then validated the accuracy of population screening and clinical classification in 2 separate cohorts consisting of 16 172 participants and 201 ß-thalassemia patients. Traditional methods were used as controls. Genetic tests were considered the gold standard for testing positive specimens. RESULTS: We established a prediction model for identifying different forms of ß-globin disorders in a single MALDI-TOF-MS test based on δ- to ß-globin, γ- to α-globin, γ- to ß-globin ratios, and/or the abnormal globin-chain patterns. Our validation study yielded comparable results of clinical specificity (99.89% vs 99.71%), and accuracy (99.78% vs 99.16%) between the new assay and traditional methods but higher clinical sensitivity for the new method (97.52% vs 88.01%). The new assay identified 22 additional abnormal hemoglobins in 69 individuals including 9 novel ones, and accurately screened for 9 carriers of deletional hereditary persistence of fetal hemoglobin or δß-thalassemia. TM and TI were well classified in 178 samples out of 201 ß-thalassemia patients. CONCLUSIONS: MALDI-TOF-MS is a highly accurate, predictive tool that could be suitable for large-scale screening and clinical classification of ß-globin disorders.

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.

WDR62 variants contribute to congenital heart disease by inhibiting cardiomyocyte proliferation.

BACKGROUND: Congenital heart disease (CHD) is the most common birth defect and has high heritability. Although some susceptibility genes have been identified, the genetic basis underlying the majority of CHD cases is still undefined. METHODS: A total of 1320 unrelated CHD patients were enrolled in our study. Exome-wide association analysis between 37 tetralogy of Fallot (TOF) patients and 208 Han Chinese controls from the 1000 Genomes Project was performed to identify the novel candidate gene WD repeat-containing protein 62 (WDR62). WDR62 variants were searched in another expanded set of 200 TOF patients by Sanger sequencing. Rescue experiments in zebrafish were conducted to observe the effects of WDR62 variants. The roles of WDR62 in heart development were examined in mouse models with Wdr62 deficiency. WDR62 variants were investigated in an additional 1083 CHD patients with similar heart phenotypes to knockout mice by multiplex PCR-targeting sequencing. The cellular phenotypes of WDR62 deficiency and variants were tested in cardiomyocytes, and the molecular mechanisms were preliminarily explored by RNA-seq and co-immunoprecipitation. RESULTS: Seven WDR62 coding variants were identified in the 237 TOF patients and all were indicated to be loss of function variants. A total of 25 coding and 22 non-coding WDR62 variants were identified in 80 (6%) of the 1320 CHD cases sequenced, with a higher proportion of WDR62 variation (8%) found in the ventricular septal defect (VSD) cohort. WDR62 deficiency resulted in a series of heart defects affecting the outflow tract and right ventricle in mouse models, including VSD as the major abnormality. Cell cycle arrest and an increased number of cells with multipolar spindles that inhibited proliferation were observed in cardiomyocytes with variants or knockdown of WDR62. WDR62 deficiency weakened the association between WDR62 and the cell cycle-regulated kinase AURKA on spindle poles, reduced the phosphorylation of AURKA, and decreased expression of target genes related to cell cycle and spindle assembly shared by WDR62 and AURKA. CONCLUSIONS: WDR62 was identified as a novel susceptibility gene for CHD with high variant frequency. WDR62 was shown to participate in the cardiac development by affecting spindle assembly and cell cycle pathway in cardiomyocytes.

Analysis of complex chromosomal rearrangements using a combination of current molecular cytogenetic techniques.

BACKGROUND: Using combined fluorescence in situ hybridization (FISH) and high-throughput whole-genome sequencing (WGS) molecular cytogenetic technology, we aim to analyze the junction breakpoints of complex chromosome rearrangements (CCR) that were difficult to identify by conventional karyotyping analysis and further characterize the genetic causes of recurrent spontaneous abortion. RESULTS: By leveraging a combination of current molecular techniques, including chromosome karyotype analysis, FISH, and WGS, we comprehensively characterized the extremely complex chromosomal abnormalities in this patient with recurrent spontaneous abortions. Here, we demonstrated that combining these current established molecular techniques is an effective and efficient workflow to identify the structural abnormalities of complex chromosomes and locate the rearrangement of DNA fragments. CONCLUSIONS: In conclusion, leveraging results from multiple molecular and cytogenetic techniques can provide the most comprehensive genetic analysis for genetic etiology research, diagnosis, and genetic counseling for patients with recurrent spontaneous abortion and embryonic abortion.

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 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.

Concurrent Newborn Hearing and Genetic Screening in a Multi-Ethnic Population in South China.

Hearing loss is a common sensory deficit in humans with intricate genomic landscape and mutational signature. Approximately 1-3 out of 1,000 newborns have hearing loss and up to 60% of these cases have a genetic etiology. In this study, we conducted the concurrent newborn hearing and genetic screening in 20 mutations (18 pathogenic variants in GJB2, SLC26A4, and MT-RNR1 and 2 uncertain clinical significance variants in GJB3) for 9,506 normal newborns (4,977 [52.4%] males) from 22 ethnic population in South China. A total of 1,079 (11.4%) newborns failed to pass the initial hearing screening; 160 (1.7%) infants failed to pass the re-screening, and 135 (1.4%) infants presented the diagnostic hearing loss. For the genetic screening, 220 (2.3%) newborns who presented at least one of the screened mutations were more likely to fail the hearing screening and have diagnostic hearing loss than mutation-negative newborns. In comparison to the differences of distribution of mutations, we did not identify any significant difference in the prevalence of screened mutations between Han group (n = 5,265) and Zhuang group (n = 3,464), despite the lack of number of minority ethnic groups. Studies including larger number of minority ethnic populations are needed in the future.

[Methodological Evaluation of Microarray in the Detection of α-Thalassemia].

OBJECTIVE: To proceed the clinical evaluation of DNA microarray for thalassemia gene detection. METHODS: Peripheral blood samples of 166 thalassemia gene test subjects were collected and tested for thalassemia genes by microarray chip method and Gap-PCR method combined with PCR-reverse dot blot hybridization method according to double-blind control test. The specificity, sensitivity, positive predictive value, negative predictive value, and total coincidence rate of the microarray chip method were evaluated. When the two methods were inconsistent, multiplex ligation dependent probe amplification (MLPA) was used to verify the deletional α-thalassemia. RESULTS: Compared with Gap-PCR method, specificity, sensitivity, positive predictive value, negative predictive value, Youden index, and total coincidence rate of microarray chip method was 100% (70/70), 96.88% (93/96), 100% (93/93), 95.89% (70/73), 0.969, and 97.59% (162/166), respectively, while compared with PCR-reverse dot blot hybridization method was 100% (125/125), 100% (41/41), 100% (41/41), 100% (125/125), 1, and 100% (166/166), respectively. CONCLUSION: The microarray chip method for α-thalassemia gene detection shows the advantages of high specificity, sensitivity, and throughput.

Identification and Functional Characterization of a Novel Nonsense Variant in ARR3 in a Southern Chinese Family With High Myopia.

ARR3 has been associated with X-linked, female-limited, high myopia. However, using exome sequencing (ES), we identified the first high myopia case with hemizygous ARR3-related mutation in a male patient in a Southern Chinese family. This novel truncated mutation (ARR3: c.569C>G, p.S190*) co-segregated with the disease phenotype in affected family members and demonstrated that high myopia caused by ARR3 is not X-linked, female-limited, where a complicated X-linked inheritance pattern may exist. Thus, our case expanded the variant spectrum in ARR3 and provided additional information for genetic counseling, prenatal testing, and diagnosis. Moreover, we characterized the nonsense-mediated decay of the ARR3 mutant mRNA and discussed the possible underlying pathogenic mechanisms.

[Application of DNA Microarray in Genetic Mutation Detection in Patients with Thalassemia].

OBJECTIVE: To perform dried blood spots thalassemia gene detection in patients with positive blood phenotypes by microarray technology, and evaluate its value in clinical detection. METHODS: DNA samples were extracted from dried blood spots of 410 patients. Microarray technology was used to detect 3 deletion and 3 non-deletion types of α-thalassemia and 19 ß-thalassemia point mutations which were common gene mutions in China. RESULTS: There were 357 positive cases in all the 410 tested samples with the positive rate 87.07%, among which 299 cases (72.93%) carried deletion or point mutations of α-thalassemia, 29 cases (7.07%) carried point mutations of ß-thalassemia and 29 cases (7.07%) carried gene mutations of complex αß-thalassemia syndrome. The mutations of α-thalassemia were involved with --SEA heterozygous deletion (177 cases, 59.2%), αCS heterozygote (60 cases, 20.07%) and several other genotypes. The common mutations of ß- thalassemia were involved with ßCD41-42 heterozygote (10 cases, 34.48%) and ßCD17 heterozygote (9 cases, 31.03%). The mutations of complex αß-thalassemia syndrome were mainly involved with --SEA/αα+ßCD17/ßN (7 cases, 24.14%), αCSα/αα + ßCD41-42/ßN (3 cases, 10.34%) and -α4.2/αα + ßCD17/ßN (3 cases, 10.34%). CONCLUSION: The most common genetic mutations are --SEA for α-thalassemia and CD41-42 for ß-thalassemia in Liuzhou, Guangxi Zhuang Autonomous Region. A and ß-thalassemia can be detected at the same time by microarray chip technology in a high throughput manner.

A Novel Multi-Exon Deletion of PACS1 in a Three-Generation Pedigree: Supplements to PACS1 Neurodevelopmental Disorder Spectrum.

PACS1 neurodevelopmental disorder (PACS1-NDD) is a category of rare disorder characterized by intellectual disability, speech delay, dysmorphic facial features, and developmental delay. Other various physical abnormalities of PACS1-NDD might involve all organs and systems. Notably, there were only two unique missense mutations [c.607C > T (p.Arg203Trp) and c.608G > A (p.Arg203Gln)] in PACS1 that had been identified as pathogenic variants for PACS1-NDD or Schuurs-Hoeijmakers syndrome (SHMS). Previous reports suggested that these common missense variants were likely to act through dominant-negative or gain-of-function effects manner. It is still uncertain whether the intragenic deletion or duplication in PACS1 will be disease-causing. By using whole-exome sequencing, we first identified a novel heterozygous multi-exon deletion covering exons 12-24 in PACS1 (NM_018026) in four individuals (two brothers and their father and grandfather) in a three-generation family. The younger brother was referred to our center prenatally and was evaluated before and after the birth. Unlike SHMS, no typical dysmorphic facial features, intellectual problems, and structural brain anomalies were observed among these four individuals. The brothers showed a mild hypermyotonia of their extremities at the age of 3 months old and recovered over time. Mild speech and cognitive delay were also noticed in the two brothers at the age of 13 and 27 months old, respectively. However, their father and grandfather showed normal language and cognitive competence. This study might supplement the spectrum of PACS1-NDD and demonstrates that the loss of function variation in PACS1 displays no contributions to the typical SHMS which is caused by the recurrent c.607C > T (p.Arg203Trp) variant.

Tandem Mass Spectrometry Screening for Inborn Errors of Metabolism in Newborns and High-Risk Infants in Southern China: Disease Spectrum and Genetic Characteristics in a Chinese Population.

Inborn errors of metabolism (IEMs) often causing progressive and irreversible neurological damage, physical and intellectual development lag or even death, and serious harm to the family and society. The screening of neonatal IEMs by tandem mass spectrometry (MS/MS) is an effective method for early diagnosis and presymptomatic treatment to prevent severe permanent sequelae and death. A total of 111,986 healthy newborns and 7,461 hospitalized high-risk infants were screened for IEMs using MS/MS to understand the characteristics of IEMs and related gene mutations in newborns and high-risk infants in Liuzhou. Positive samples were analyzed by Sanger sequencing or next-generation sequencing. The results showed that the incidence of IEMs in newborns in the Liuzhou area was 1/3,733, and the incidence of IEMs in high-risk infants was 1/393. Primary carnitine deficiency (1/9,332), phenylketonuria (1/18,664), and isovaleric acidemia (1/37,329) ranked the highest in neonates, while citrullinemia type II ranked the highest in high-risk infants (1/1,865). Further, 56 mutations of 17 IEMs-related genes were found in 49 diagnosed children. Among these, HPD c.941T > C, CBS c.1465C > T, ACADS c.337G > A, c.1195C > T, ETFA c.737G > T, MMACHC 1076bp deletion, PCCB c.132-134delGACinsAT, IVD c.548C > T, c.757A > G, GCDH c.1060G > T, and HMGCL c.501C > G were all unreported variants. Some related hotspot mutations were found, including SLC22A5 c.51C > G, PAH c.1223G > A, IVD c.1208A > G, ACADS c.625G > A, and GCDH c.532G > A. These results show that the overall incidence of IEMs in the Liuzhou area is high. Hence, the scope of IEMs screening and publicity and education should be expanded for a clear diagnosis in the early stage of the disease.

A natural DNMT1 mutation elevates the fetal hemoglobin level via epigenetic derepression of the γ-globin gene in ß-thalassemia.

DNA methyltransferase 1 (DNMT1) is a major epigenetic regulator of the formation of large macromolecular complexes that repress human γ-globin expression by maintaining DNA methylation. However, very little is known about the association of DNMT1 variants with ß-thalassemia phenotypes. We systematically investigated associations between variants in DNMT1 and phenotypes in 1142 ß-thalassemia subjects and identified a novel missense mutation (c.2633G>A, S878F) in the DNMT1 bromo-adjacent homology-1 (BAH1) domain. We functionally characterized this mutation in CD34+ cells from patients and engineered HuDEP-2 mutant cells. Our results demonstrate that DNMT1 phosphorylation is abrogated by substituting serine with phenylalanine at position 878, resulting in lower stability and catalytic activity loss. S878F mutation also attenuated DNMT1 interactions with BCL11A, GATA1, and HDAC1/2, and reduced recruitment of DNMT1 to the γ-globin (HBG) promoters, leading to epigenetic derepression of γ-globin expression. By analyzing the F-cell pattern, we demonstrated that the effect of DNMT1 mutation on increased fetal hemoglobin (HbF) is heterocellular. Furthermore, introduction of S878F mutation into erythroid cells by clustered regularly interspaced short palindromic repeats (CRISPR)-CRISPR-associated protein 9 (Cas9) recapitulated γ-globin reactivation. Thus, the natural S878F DNMT1 mutation is a novel modulator of HbF synthesis and represents a potential new therapeutic target for ß-hemoglobinopathies.