Investigation of the mechanism of copy number variations involving the α-globin gene cluster on chromosome 16: two case reports and literature review.

Thalassemia is one of the most common single-gene disorder worldwide. An important genetic cause of thalassemia is copy number variations (CNVs) in the α-globin gene cluster. However, there is no unified summary and discussion on the detailed information and mechanisms of these CNVs. In this study, two novel CNVs, a tandem duplication (αααα159) and deletion (--259), were identified in two Chinese families with thalassemia patients, according to the results of hematologic analysis, routine genetic testing for thalassemia, multiplex ligation-dependent probe amplification (MLPA), next-generation sequencing (NGS) and other molecular methods. Co-inherited with ßCD41-42 mutation and --SEA deletion separately, αααα159 and --259 resulted in a patient with ß-thalassemia intermedia and a lethal fetus with Hb Bart's hydrops fetalis syndrome, respectively. Next, a literature review was performed to summarize all known CNVs involving the α-globin gene cluster. The molecular structure characteristics of these CNVs were analyzed and the possible mechanism was explored. It is the first time to analyze the generation mechanism of genome arrangements in the α-globin gene cluster systematically.

A Rare Hb H Hydrops Fetalis Syndrome Caused by the - -SEA Deletion in Combination with the Rare Hb Hirosaki Mutation in a Chinese Patient.

Despite the milder clinical severity of Hb H patients compared with those of Hb Bart's hydrops fetalis or patients with ß-thalassemia major (ß-TM), a few cases of Hb H hydrops fetalis syndrome have been reported so far. Here, we describe, for the first time in the Chinese population, one case of a neonate with Hb H hydrops fetalis syndrome caused by the - -SEA (Southeast Asian) deletion in combination with the Hb Hirosaki (HBA2: c.132C>G, p.Phe43Leu) mutation. Our study highlights the importance of continuous fetal monitoring using ultrasonography and blood screening studies of fetuses. Appropriate genetic counseling and comprehensive clinical follow-up should be performed on a pregnant woman who carried an α0-thalassemia (α0-thal) deletion and had a Hb H or Hb Bart's hydrops fetalis offspring, especially if the woman's partner also carried a hemoglobinopathy.

[The value of MCV, MCH and HbA(2) in laboratory screening of thalassemia].

OBJECTIVES: To explore the roles of mean corpuscular volume (MCV), mean corpuscular hemoglobin (MCH) and hemoglobin A(2) (HbA(2)) in the laboratory screening of thalassemia, and to find optimal screening modality for different conditions. METHODS: From September 2008 to May 2011, 1384 subjects underwent thalassemia screening at Department of Obstetrics and Gynecology of Nanfang Hospital. Of them, 1036 cases were diagnosed with thalassemia (408 α-thalassemia, 608 ß-thalassemia, and 20 αß compound thalassemia, thalassemia group) and 348 without thalassemia, non-thalassemia group. All subjects were screened respectively for MCV, MCH and HbA(2). Analyses were performed in all subjects to assess the sensitivity, specificity, positive predictive value, negative predictive value and diagnostic accuracy respectively associated with MCV, MCH and HbA(2) alone, combination of MCV and MCH, and combination of MCV, MCH and HbA(2). RESULTS: (1) In the thalassemia group, the sensitivity of MCV alone was 92.9% (379/408) for α thalassemia, 99.3% (604/608) for ß thalassemia and 100.0% (20/20) for αß compound thalassemia. In the non-thalassemia group, the specificity of MCV alone was 75.0% (261/348). (2) In the thalassemia group, the sensitivity of MCH alone was 92.9% (379/408) in α thalassemia, 99.0% (602/608) in ß thalassemia and 100.0% (20/20) in αß compound thalassemia. In the non-thalassemia group, the specificity of MCH alone was 72.7% (253/348). (3) The sensitivity of Hb A(2) alone was 67.4% (275/408) for α thalassemia, 97.5% (593/608) for ß thalassemia, and 100% (20/20) for αß compound thalassemia while it's specificity was 72.4% (252/348) in the non-thalassemia group. (4) With positive indexes of MCV, MCH and MCV + MCH, when HbA(2) > 3.5% it had a high value in ß-thalassemia screening, but when HbA(2) < 2.5% it had little value in α-thalassemia screening. (5) As a single marker, MCV and MCH had better sensitivity, specificity, positive predictive value, negative predictive value and diagnosis accuracy than HbA(2). MCV + MCH was the best for overall screening, but for ß thalassemia screening, MCV + MCH + HbA(2) was the best. CONCLUSIONS: MCV and MCH are suitable for epidemic screening in a large population, physical examination and premarital check-up. Hb electrophoresis and thalassemia gene diagnosis are recommended for subjects with positive MCV and MCH indexes. Diagnoses of α and ß-thalassemia gene are recommended for pregnant women with positive MCV and MCH indexes.

The spectrum of FVIII gene variants detected by next generation sequencing in 236 Chinese non-inversion hemophilia A pedigrees.

INTRODUCTION: The reported variants of hemophilia A are mainly from European subjects and American subjects of European descent, and limited data are available from more diverse ethnic backgrounds. This study was performed to identify the causative variants in a large HA cohort from Chinese population. MATERIALS AND METHODS: A total of 236 HA pedigrees were included. Molecular analysis of F8 gene was performed using next-generation sequencing (NGS) and then validated by Sanger sequencing and multiplex ligation probe amplification (MLPA) results. Variants were classified as pathogenic, likely pathogenic, variant of unknown significance, likely benign, and benign according to the American College of Medical Genetics and Genomics guidelines. RESULTS: A total of 186 F8 variants were identified, with 139 (139/186, 74.73%) point mutations, 44 (44/186, 23.66%) small insertions/deletions (InDels), and 3 (3/186, 1.61%) large deletions, they included 80 pathogenic and 84 likely pathogenic variants. Of these variants, 119 had been reported previously, and 67 were novel. No potentially causative mutations were found in the targeted F8 region in seventeen HA pedigrees. CONCLUSIONS: The spectrum of F8 variants identified in this study provides additional information about HA and enriches our knowledge of the variant spectrum in a wider range of ethnic backgrounds.

Correction to: Genetic and evolutionary analysis of enterovirus 71 base dinucleotide.

[This corrects the article DOI: 10.1007/s13337-019-00564-z.].

Genetic and evolutionary analysis of enterovirus 71 base dinucleotide.

In this paper, a comprehensive analysis of genome sequences of 99 EV71 virus isolates base dinucleotide odds ratio was conducted to explore the potential mechanisms of its evolution. The general correlation of dinucleotides at different sites of the codons reveals that mutational pressure is the main factor determining EV 71 evolution. Furthermore, the apparent geographic segmentation of isolates before 2008 and low-frequency appearance of TpA and CpG also suggest that the geographic and host factors play important roles in the evolution of the virus. Finally, obvious fluctuation and divergence of the dinucleotide usage pattern was observed in the EV71 isolated in China after 2008, which might reveal that the virus entered a rapid evolution period, especially after 2010. These results indicate that EV71 has more initiative and adaptability under external pressures.

Molecular analysis of 76 Chinese hemophilia B pedigrees and the identification of 10 novel mutations.

BACKGROUND: Hemophilia B (HB) is an X-linked recessive inherited bleeding disorder caused by mutations in the F9 gene that lead to plasma factor IX deficiency. To identify the causative mutations in HB, a molecular analysis of HB pedigrees in China was performed. METHODS: Using next-generation sequencing (NGS) and an in-house bioinformatics pipeline, 76 unrelated HB pedigrees were analyzed. The mutations identified were validated by comparison with the results of Sanger sequencing or Multiplex Ligation-dependent Probe Amplification assays. The pathogenicity of the causative mutations was classified following the American College of Medical Genetics and Genomics guidelines. RESULTS: The mutation detection rate was 94.74% (72/76) using NGS. Of the 76 HB pedigrees analyzed, 59 causative variants were found in 72 pedigrees, with 38 (64.41%) missense mutations, 9 (15.25%) nonsense mutations, 2 (3.39%) splicing mutations, 5 (8.47%) small deletions, 4 (6.78%) large deletions, and 1 intronic mutation (1.69%). Of the 59 different F9 mutations, 10 were novel: c.190T>G, c.199G>T, c.290G>C, c.322T>A, c.350_351insACAATAATTCCTA, c.391+5delG, c.416G>T, c.618_627delAGCTGAAACC, c.863delA, and c.1024_1027delACGA. Of these 10 novel mutations, a mosaic mutation, c.199G>T(p.Glu67Ter), was identified in a sporadic HB pedigree. Using in-silico analysis, these novel variants were predicted to be disease-causing. However, no potentially causative mutations were found in the F9 coding sequences of the four remaining HB pedigrees. In addition, two HB pedigrees carrying additional F8/F9 mutations were discovered. CONCLUSION: The identification of these mutations enriches the spectrum of F9 mutations and provides further insights into the pathogenesis of HB in the Chinese population.

Different Clinical Phenotypes Caused by Three F8 Missense Mutations in Three Chinese Families with Moderate Hemophilia A.

In families with a monogenic disorder, the causal mutation usually cosegregates with the disease phenotype. In rare cases, however, individuals carrying the same mutation within a family may show various phenotypes. This study aimed to analyze the discrepancy between genotype and phenotype in three families with moderate hemophilia A (HA) caused by missense mutation in the F8 gene. Among the 67 noninversion moderate HA families in our cohort, incomplete penetrance was found in three families. In these three families, the grandfathers were asymptomatic, whereas the probands had different clinical phenotypes. Apart from one mutation in the VWF gene (c.1330 G>A) found in one grandfather, only one missense mutation (c.5837A>T, c.6679G>A, and c.6506G>A, in the respective families) in the F8 gene was identified in each proband and their grandfathers. Subsequent Sanger sequencing results combined with bioinformatic analysis indicated that the three missense mutations in the F8 gene were the causative mutations. Our study demonstrated incomplete penetrance of missense mutation within HA families in China. Therefore, genetic counseling and management of such cases need to be reappraised.