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Nearly half of severe Hemophilia A (HA) cases are caused by F8 intron 22 inversion (Inv22). This 0.6-Mb inversion splits the 186-kb F8 into two parts with opposite transcription directions. The inverted 5′ part (141 kb) preserves the first 22 exons that are driven by the intrinsic F8 promoter, leading to a truncated F8 transcript due to the lack of the last 627 bp coding sequence of exons 23–26. Here we describe an in situ genetic correction of Inv22 in patient-specific induced pluripotent stem cells (iPSCs). By using TALENs, the 627 bp sequence plus a polyA signal was precisely targeted at the junction of exon 22 and intron 22 via homologous recombination (HR) with high targeting efficiencies of 62.5% and 52.9%. The gene-corrected iPSCs retained a normal karyotype following removal of drug selection cassette using a Cre-LoxP system. Importantly, both F8 transcription and FVIII secretion were rescued in the candidate cell types for HA gene therapy including endothelial cells (ECs) and mesenchymal stem cells (MSCs) derived from the gene-corrected iPSCs. This is the first report of an efficient in situ genetic correction of the large inversion mutation using a strategy of targeted gene addition.

Objective To evaluate the clinical feasibility of noninvasive prenatal diagnosis (NIPD) for b-thalassaemia using circulating single molecule amplification and re-sequencing technology (cSMART). Design zThrough carrier screening, 102 pregnant Chinese couples carrying pathogenic HBB gene variants were recruited to the study. Pregnancies were managed using traditional invasive prenatal diagnosis (IPD). Retrospectively, we evaluated the archived pregnancy plasma DNA by NIPD to evaluate the performance of our cSMART assay for fetal genotyping. Setting Chinese prenatal diagnostic centres specialising in thalassaemia testing. Population Chinese carrier couples at high genetic risk for bthalassaemia. Methods Fetal cell sampling was performed by amniocentesis and HBB genotypes were determined by reverse dot blot. NIPD was performed by a newly designed HBB cSMART assay and fetal genotypes were called by measuring the allelic ratios in the maternal cell-free DNA. Main outcome measures Concordance of HBB fetal genotyping between IPD and NIPD and the sensitivity and specificity of NIPD. Results Invasive prenatal diagnosis identified 29 affected homozygotes or compound heterozygotes, 54 heterozygotes and 19 normal homozygotes. Compared with IPD results, 99 of 102 fetuses (97%) were correctly genotyped by our NIPD assay. Two of three discordant samples were false positives and the other sample involved an incorrect call of a heterozygote carrier as a homozygote normal. Overall, the sensitivity and specificity of our NIPD assay was 100% (95% CI 88.06-100.00%) and 97.26% (95% CI 90.45-99.67%), respectively. Conclusions This study demonstrates that our cSMART-based NIPD assay for b-thalassaemia has potential clinical utility as an alternative to IPD for pregnant HBB carrier couples.

There are many inherited disorders associated with thoracic aortic aneurysms and dissections (TAADs), like Marfan syndrome and Loeys-Dietz syndrome (LDS). The 4 patients in this study all had TAADs and were initially diagnosed with suspected Marfan syndrome. We collected peripheral blood samples from the patients and their family members and then attempted to identify the causal mutation using different methods including PCR, Sanger sequencing, and next generation sequencing. We identified 3 novel heterozygous mutations including 2 splicing mutations of FBN1 and 1 missense mutation of TGFBR2 in our patients. Although these mutation sites have been reported in the Human Gene Mutation Database, the nucleotide changes are different. All novel mutations found in this study were confirmed to be absent in 50 unrelated normal individuals of the same ethnic background. The RT-PCR results of 2 splicing mutations verified that the mutations can lead to the skipping of exons. The RT-qPCR results indicated that FBN1 mRNA levels were nearly 50 percent lower in the patients than in normal controls, indicating that there is almost no expression of truncated fibrillin-1 because of the nonsense-mediated mRNA decay (NMD) mechanism. To the best of our knowledge, we are the first to report these 3 novel mutations. However, the pathogenicity of these mutations still needs further confirmation. Our study has confirmed or corrected the clinical diagnosis, and enlarged the mutation spectrum of FBN1 and TGFBR2. The results should be helpful for prenatal diagnosis and genetic counseling.

3-hydroxyisobutryl-CoA hydrolase (HIBCH) deficiency is a rare inborn error of valine metabolism characterized by neurodegenerative symptoms and caused by recessive mutations in the HIBCH gene. In this study, utilizing whole exome sequencing, we identified two novel splicing mutations of HIBCH (c.304+3A>G; c.1010_1011+3delTGGTA) in a Chinese patient with characterized neurodegenerative features of HIBCH deficiency and bilateral syndactyly which was not reported in previous studies. Functional tests showed that both of these two mutations destroyed the normal splicing and reduced the expression of HIBCH protein. Through a literature review, a potential phenotype-genotype correlation was found that patients carrying truncating mutations tended to have more severe phenotypes compared with those with missense mutations. Our findings would widen the mutation spectrum of HIBCH causing HIBCH deficiency and the phenotypic spectrum of the disease. The potential genotype-phenotype correlation would be profitable for the treatment and management of patients with HIBCH deficiency.