Amelioration of β^(654)-thalassemia in mouse model with the knockdown of aberrantly spliced β-globin mRNA

Large amounts of aberrantly spliced mRNA from the β^654 allele was present in erythroid cells, which might impair the erythropoiesis. A therapeutic strategy for β-thalassemia was explored by knocking down the aberrantly spliced mRNA of β-globin. Lentiviral vector with siRNA fragment targets on the specific portion of β^654-globin aberrantly spliced pre-mRNA was constructed. In HeLa β^654 cells, the siRNA vector could reduce approximately 60% of aberrantly spliced mRNA, which was assessed by RT-PCR and qRT-PCR. Furthermore, a disease model of β^654 thalassemia mice with lentiviral-mediated siRNA was produced by subzonal injection （named Hβi-Hbb^th-4/Hbb^＋ transgenic mice）. Our results showed that the hemotological parameters were improved in Hβi-Hbb^th-4/Hbb^＋ transgenic mice. This study provides a potential way for β^654-thalassemia therapy by knocking down the aberrantly spliced β-globin mRNA, whilst supporting that the aberrantly spliced β-globin mRNA may aggravate the disease.

Detection of rare mutation of β-thalassemia by direct sequence analysis of the PCR products

A technique of direct sequence analysis of β-globin gene with the products of amplifi-cation by polymerase chain reaction (PCR) was reported and a case of β-thalassemia with therare mutation in Chinese,‘codon 14/15 (+G)’ was detected by this method.After the se-quence of the mutation site was determined,an analysis of the restriction map of the gene anddot blot hybridization with radioactive allele specific oligonucleotide probe was designed to con-firm the result of DNA sequencing.

Myeloproliferative neoplasms complicated withβ-thalassemia:Two case report

BACKGROUND BCR-ABL-negative myeloproliferative neoplasms(MPNs)are clonal hematopoietic stem cell disorders characterized by the proliferation of one or more myeloid lineages and by mutually exclusive JAK2 V617F,CALR,and MPL[A1]mutations.The combination of MPN and thalassemia is extremely unusual.Several cases with myeloproliferative neoplasms andβ-thalassemia have been reported.However,these have not been extensively reviewed.The present report describes two cases of myeloproliferative neoplasms complicated withβ-thalassemia and reviews all similar cases reported in the literature.CASE SUMMARY We report two patients who were diagnosed with myeloproliferative neoplasms complicated withβ-thalassemia.Both patients had abnormal increases in platelet counts.Based on bone marrow pathology and molecular biology assessment,we made the diagnosis of myeloproliferative neoplasms complicated withβ-thalassemia.The female patient was given hydroxyurea and interferon,which enabled good control of her blood counts;the male patient was given ruxolitinib tablets,thalidomide tablets,and interferon to control the condition,but the patient poorly responded to drug treatment and died of gastrointestinal bleeding six months later.CONCLUSION Given the findings of our cases and the literature review,we hypothesize that myeloproliferative neoplasms complicated withβ-thalassemia can lead to rapid disease progression and a poor prognosis.

A rapid reverse dot blot assay for all 18 β-thalassemia mutations in Chinese population

A set of allele-specific oligonucleotide (ASO) probes used for detecting all 18 β-tha-lassemia mutations found in Chinese was immobilized on two strips of Biodyne C membrane;one containing 7 pairs of oligonucleotide probes specific for the most commonly found mutant al-leles,and the other containing the remaining 11 pairs of ASO_s specific for the less commonlyfound.The membranes were hybridized with β-globin sequences amplified by polymerase chainreaction (PCR) with biotinylated primers,and then treated with Streptavidin-POD conjugateand substrates for color development.The method has been applied successfully to the detectionof all 18 Chinese β-thalassemia mutations and prenatal diagnosis of two high-risk pregnancies ofβ-thalassemia.Patients with homozygous,heterozygous and compound heterozygous alleles ofthese mutations and normal individuals could be easily distinguished by the present method.Us-ing the immobilized-probe format (reverse dot blot),it was able to screen simultaneously multi-ple β-thalassemia mutations of a DNA sample by performing hybridization only once.This assayis simple,rapid and independent of radio-isotopes and can be appplied for all 18 β-thalassemiamutations so far found in Chinese population.It is considered that this method may be usefulfor gene frequency investigation of large numbers of β-thalassemia DNA samples and used as aroutine method in the clinic laboratory.

Therapeutic Drug Monitoring of Chelating Agent Deferoxamine for <i>β</i>-Thalassemia Major Patients

Therapeutic drug monitoring is used to prevent or decrease the risk associated with the toxic effects of medication. This study aims to evaluate the potential advantages of Therapeutic Drug Monitoring (TDM) of subcutaneous Deferoxamine injection and prevention of clinical problems in β-thalassaemia major patients. Patients & Methods: Fifty-four thalassemia patients were allocated into two groups;missing, and not missing deferoxamine dose. TDM of Deferoxamine injection and it clinical outcomes was critically studied under the following subheadings: assessment of the adequacy of Deferoxamine usage, serum peak and trough concentrations of Deferoxamine and ferroxamine with needed pharmacokinetics, cardiac parameters and biomarkers, biochemical and hematological indices, adverse effects/toxicity, urinary assessment of Fe, Zn, selenium, and copper levels, compliance to treatment, dose adjustment in correlation to therapeutic index and life style. Results: Demographic data showed no significant difference. Peak plasma concentrations were 144.83±69 and 43.54±39.16 μg/L, while trough concentrations were 33±26.32 and 31.13±21.58 μg/L of Deferoxamine and ferroxamine, respectively. The elimination rate constant was 0.0237±0.00029 min-1, half-life was 34 min, and distribution volume was 0.93±0.078. Although cardiac parameters showed no significant differences, there were significant differences in CK-MB, and hsCRP levels;troponin I value could not be detected. Biochemical and hematological studies showed significant differences in Ferritin B, urea, SGPT, SGOT, alkaline phosphatase, serum albumin and serum calcium. Assessment of adverse effects/toxicity showed significant differences. The correlation of serum ferritin to therapeutic index, and the life style including Vitamin C and/or E administration were assessed for the compliance to treatment. Conclusion: Therapeutic monitoring of chelation therapy by Deferoxamine in β-thalassemia patients is necessary to ensure effective treatment, compliance, and to avoid adverse side effects and toxicity.

Direct antiglobulin test-negative autoimmune hemolytic anemia in a patient withβ-thalassemia minor during pregnancy:A case report

BACKGROUND Severe refractory anemia during pregnancy can cause serious maternal and fetal complications.If the cause cannot be identified in time and accurately,blind symptomatic support treatment may cause serious economic burden.Thalassemia minor pregnancy is commonly considered uneventful,and the condition of anemia rarely progresses during pregnancy.Autoimmune hemolytic anemia(AIHA)is rare during pregnancy with no exact incidence available.CASE SUMMARY We report the case of a 30-year-oldβ-thalassemia minor multiparous patient experiencing severe refractory anemia throughout pregnancy.We monitored the patient closely,carried out a full differential diagnosis,made a diagnosis of direct antiglobulin test-negative AIHA,and treated her with prednisone and intravenous immunoglobulin.The patient gave birth to a healthy full-term baby.CONCLUSION Coombs-negative AIHA should be suspected in cases of severe hemolytic anemia in pregnant patients with and without other hematological diseases.

Determination of Iron（Ⅱ）, Iron（Ⅲ） and Total Iron in Some β -Thalassemia Patients Using Different Analytical Techniques

There are many well-known analytical methods for determination of iron（Ⅱ） and iron（Ⅲ）. Among these methods： Gravimetric, titrimetric, potentiometric, conductometric and batch and flow-injection spectrophotometric methods. In present study, two batch spectrophotometric, atomic absorption spectrometric and biolabo kit methods have been used for determination of iron（Ⅱ）, iron（Ⅲ） and total iron. The present methods have the advantages of high sensitivity, low cost reagent, low operation cost, simplicity, speed and their applications for determination of iron（Ⅱ） and iron（Ⅲ） in some serum samples of normal human and fl-thalasemia patients in Erbil city. For the first time especially in Erbil city attempts were made to use zero, first and second derivative spectra to identify the serum samples of some β-thallasemia patients from the normal human serum samples due to the appearance and resolution of peaks in both cases.

Ischemia Modified Albumin and C-Reactive Protein in Children with β-Thalassemia Major

Background: Beta-thalassemia is a hereditary haemoglobinopathy caused by defective hemoglobin (Hb) β-globin synthesis, leading to excess α-globin chains that cause hemolysis and impair erythropoiesis. Ischemia modified albumin (IMA) is not a signal protein and not generated in pro-inflammatory state alone but rather an end product of oxidative stress. Objectives: The aim of the study was to evaluate ischemia modified albumin (IMA) and C-reactive protein (CRP) in children with β-thalassemia major and its relation to different iron chelators. Patients and Methods: The study was carried on 40 children diagnosed as beta-thalassemia major recruited from the outpatient clinic and the pediatric department, at Al-Zahraa University Hospital, Faculty of medicine for Girls, Al-Azhar University and EL Minia Insurance Hospital. They were 20 male and 20 female, aged from 4 - 11 years. Another 40 apparently healthy children age and sex matched as control group. CRP and IMA were determined for all participants. Results: There were significant increases in serum CRP, IMA and ferritin levels in patients group compared to control group. There were significant decreases of IMA and CRP levels of thalassemic patients on chelation deferiprone (DFP) compared to deferasirox (DFX) P-value (<0.01) for each. There was a significant positive correlation between serum ferritin and both CRP and IMA levels in thalassemic children (r = 0.40, p < 0.01), (r = 0.44, p < 0.01) respectively. There was a significant positive correlation between IMA and CRP in beta-thalassemic patients (r = 0.31, p = 0.02). Conclusion: IMA, CRP and Serum ferritin were higher in children with β-thalassemia major than controls. Moreover, IMA and CRP levels in thalassemic children on deferiprone (DFP) were significantly lower compared with children on deferasirox (DFX). So it could be considered as useful markers in the follow up assessment of thalassemic patients for early detection of complications.

Co-Inheritance of Beta &Delta-Globin Gene (HbYialousa) Mutations in an Iranian <i>β</i>-Thalassemia Carrier

Introduction: Beta-thalassemia is characterized by absence or reduced synthesis of the β-globin. Carriers of β-thalas- semia, typically have microcytic hypochromic anemia and elevated hemoglobin HbA2 and normal HbF level. On the other hand carriers of severe alpha-thalassemia also have similar CBC parameters to that of β-thalassemia with normal HbA2 level. Co-presence of mutations in the β-globin and delta-globin genes (point mutations or deletions) usually give normal HbA2 and elevated HbF level. We report a β-thal carrier with normal level of HbA2 and increased level of HbF who had a point mutation in CD39 on the beta-globin gene and a point mutation in CD27 on the δ-globin gene named Hb-Yialousa. Materials & Methods: An individual with low hematological indices, normal HbA2 and elevated HbF was referred to our center as routine premarital screening program. Mutations in the β-globin and δ-globin genes were screened using ARMS and sequencing methods. Results: The mutation in β- and δ-globin genes were identified as CD39 and CD27 (HbYialousa) respectively. No point mutation or deletion in α-globin gene was identified. Discussion: We showed that normal HBA2 with elevated HbF level is due to co-inheritance of delta-globin gene mutation with mutation in the β-globin gene. When screening for β-thalassemia, one has to either rule out presence of α-globin gene mutation of mutation in the delta-globin gene.

Impact of Ferritin Load on Gonadal Reserve among Regular Transfused β-Thalassemia

Background: Iron overload in association with persistent anemia is responsible for endocrine dysfunction in β-thalassemia patients, blood transfusion combined with iron-chelation can modify life quality in these children, but they tend to suffer from delayed maturity and endocrine dysfunction. Aim: This study aims to correlate degree of hypogonadism to ferritin load in regular transfused β-thalassemia patients. Methods: It was carried out on 30 β-thalassemia major (TM) patients aged 12 to 18 years, puberty was assessed clinically, blood picture on Cell-Dyne 2700, ferritin level and pattern of FSH, LH, testosterone and estradiol before and after gonadotropin (GnRH) analogue stimulation test, they were determined on ARCHITECT ABBOTT system. Results: Twenty patients had not yet achieved puberty, FSH level was 1.45 ± 1.88 mIU/ml before (GnRH) analogue and 3.78 ± 4.19 mIU/ml after 4 hours of injection. LH level was 1.91 ± 4.79 mIU/ml before (GnRH) test, while after 4 hours it was 6.52 ± 7.50 mIU/ml, 88.24% of males had low serum testosterone level, 84.6% of girls had low serum estradiol level, FSH, LH, estradiol, testosterone before and after GNRH analogue were statistically insignificant, mean ferritin level was 3344.32 ± 1142.142 ng/ml, with insignificant correlation to hormonal pattern before and after GnRH therapy. Conclusion: Iron overload and hypogonadism are the presenting data in this study, insignificant correlation between ferritin level and hormonal reserve pattern, there may be another etiology in pathophysiology of low gonadal reserve such as severe anemia, chronic disease and may be genetic predisposition underlying susceptibility to iron toxicity, which need further investigations.

Clinical Efficacy and Molecular Mechanism of Nourishing Shen and Supplementing Marrow Principle in Treating β Thalassemia

Objective: To explore the possibility of using traditional Chinese medicine (TCM) in treating β thalassemia, its clinical effect and molecular mechanism of the action.Methods: According to the TCM theory of“Shen producing marrow”, the composite recipe, Yisui Shenxueling Granule (YSSXL), consisting of Chinese drugs for nourishing Shen and supplementing marrow (NS&SM) was given orally to 7 8 patients with β thalassemia (49 of the severe type and 29 of moderate type ), 3 times a day, 10 g each time (for children, the dose would be reduced proper ly), with 3 months as one therapeutic course, and no blood transfusion used in t he course. The clinical therapeutic efficacy and hematologic parameters in patie nts were observed, and systemic gene analysis was conducted with PAGE, PCR, PCR SSCP, RT PCR and DNA sequences analysis and mRNA detection, in order to s tudy the molecular mechanism from the relationships between genetic mutation and clinical efficacy, gene expression and its regulation. Results: YSSXL showed obvious therapeutic effect in treating β thalassemia. Gene analysis revealed that it did not change the genetic mutatio n type, but could obviously increase hemoglobin, fetal hemoglobin (HbF), γ/(β+ γ) globin ratio, γ globin mRNA expression and GM CSF mRNA expression in patients, as well as the GM CSFmRMA in marrow of mice after 60 Co radia tion. Conclusion: YSSXL has a remarkable therapeutic effect on β tha lassemia, and its possible mechanism is its action in unlocking γ gene, in creasing the γ globin expression and enhancing HbF synthesis so as to compe nsate for the gene defect. This study has opened a new path for the treatment of β thalassemia with TCM.

THE EFFECT OF SOME MEDICAL TREATMENTS ON THE RED BLOOD CELLS IN THE PATIENTS WITH THALASSEMIA

The Mossbauer spectroscopy and circular dichroism measurements have been used to investigate the effect of some medical treatments on the red blood cells (RBCs) of the patients with HbH disease and β-thalassemia major, respectively. The results indicate that both splenectomy and treatment with myleran are effective to alleviate the symptoms of anemia for some patients, but both of them are different in the effect on the RBCs of the patients. On the basis of the results, a hypothesis on the course of denaturation in hemoglobin of the patients is proposed.

Iron-chelating and anti-lipid peroxidation properties of 1-(N-acetyl-6-aminohexyl)-3-hydroxy-2-methylpyridin-4-one(CM1)in longterm iron loading β-thalassemic mice

Objective:To evaluate the iron—chelating properties and free—radical scavenging activities of1-(N-acetyl-6-aminohexyl)-3-hydroxy-2-methyIpyridin—4-one(CM1) treatment in chronic iron-loaded β-thalassemic(BKO) mice.Methods:The BKO mice were fed with a ferrocene-rich diet and were orally administered with CM1|50 mg/(kg·day)| for 6 months.Blood levels of non-transferrin hound iron,labile plasma iron.ferritin(Ft) and malondialdehyde were determined.Results:The BKO mice were fed with an iron diet for 8 months which resulted in iron overload.Interestingly,the mice showed a decrease in the non—transferrin bound iron,labile plasma iron and malondialdehyde levels,but not the Ft levels after continuous CM1 treatment.Conclusions:CM1 could be an effective oral iron chelator that can reduce iron overload and lipid peroxidation in chronic iron overload β—thalassemic mice.

Correction of β-thalassemia mutant by base editor in human embryos

β-Thalassemia is a global health issue, caused by mutations in the HBB gene. Among these mutations, HBB -28 （A〉G） mutations is one of the three most common mutations in China and Southeast Asia patients with β-thalassemia. Correcting this mutation in human embryos may prevent the disease being passed onto future generations and cure anemia. Here we report the first study using base editor （BE） system to correct disease mutant in human embryos. Firstly, we produced a 293T cell line with an exogenous HBB -28 （A〉G） mutant fragment for gRNAs and targeting efficiency evaluation. Then we collected primary skin fibroblast cells from a β-thalassemia patient with HBB -28 （A〉G） homozygous mutation. Data showed that base editor could precisely correct HBB -28 （A〉G） mutation in the patient＇s primary cells. To model homozygous mutation disease embryos, we consb＇ucted nuclear transfer embryos by fusing the lymphocyte or skin fibroblast cells with enucleated in vitro matured （IVM） oocytes.Notably, the gene correction efficiency was over 23.0% in these embryos by base editor. Although these embryos were still mosaic, the percentage of repaired blastomeres was over 20.0%. In addition, we found that base editor variants, with narrowed deamination window, could promote G-to-A conversion at HBB -28 site precisely in human embryos. Collectively, this study demonstrated the feasibility of curing genetic disease in human somatic cells and embryos by base editor system.

Hematopoietic stem cell transplantation for children with β-thalassemia major: multicenter experience in China

Backgroundβ-Thalassemia major (β-TM) has become a public health problem in China's Mainland. Hematopoietic stem cell transplantation (HSCT) has remained the only cure forβ-TM in China's Mainland since 1998. Methods This multicenter retrospective study provides a comprehensive review of the outcomes of 50 pediatric patients withβ-TM who received HSCT between 1998 and 2009 at five centers in China's Mainland. Both related (n = 35) and unrelated donors (n = 15) with complete human leukocyte antigen matches were included. The stem cell sources included bone mar-row (BM), peripheral blood stem cells, umbilical cord blood (UCB) and a combination of BM and UCB or a combination of BM and peripheral blood stem cells from a single sibling donor. Results The probabilities of 5-year overall survival (OS) and thalassemia-free survival (TFS) after the first HSCT were 83.1 and 67.3%, respectively. Graft failure (GF) occurred in 17 patients. Univariate analyses showed that umbilical cord blood transplantation (UCBT) was one of the potential risk factors for decreased OS (P = 0.051), and that UCBT (P = 0.002) was potentially related to TFS. GF incidence was distinct between the UCBT and non-UCBT groups (P = 0.004). Four cases of UCB-BM combined transplantation led to decreased risks of mortality and recurrence. In the UCBT group, related donor transplantation produced more favorable results than unrelated donor transplantation in OS (P = 0.009) but not in TFS (P = 0.217). Conclusions GF was the primary cause of UCBT failure. Though UCBT from related donors was not favorable, the combined transplantation of UCB and BM could improve the prognosis of UCBT.

Reverse Dot Blot Analysis: A Rapid Prenatal Diagnostic Approach for β-thalassemia Mutations in Chinese

The recently developed method of in vitro DNA amplification by PCR coupled with radioactive or nonradioactive ASO probe detection provides a simple approach to the prenatal diagnosis of β-thalassemia. However, the DNA diagnosis of β-thalassemia has remained a complicated problem,because β-thalassemia

Changes in IncRNAs and related genes in β-thalassemia minor and β-thalassemia major

β-thalassemia is caused by β-globin gene mutations. However, heterogeneous phenotypes were found in individuals with same genotype, and still undescribed mechanism underlies such variation. We collected blood samples from 30 β-thalassemia major, 30 β-thalassemia minor patients, and 30 matched normal controls. Human lncRNA Array v2.0 （8 × 60 K, Arraystar） was used to detect changes in long non-coding RNAs （lncRNAs） and mRNAs in three samples each from β-thalassemia major, β-thalassemia minor, and control groups. Compared with normal controls, 1424 and 2045 lncRNAs were up- and downregulated, respectively, in β-thalassemia major patients, whereas 623 and 349 lncRNAs were up- and downregulated, respectively, in β-thalassemia minor patients. Compared with β-thalassemia minor group, 1367 and 2356 lncRNAs were up- and downregulated, respectively, in β-thalassemia major group. We selected five lncRNAs that displayed altered expressions （DQ583499, X-inactive specific transcript （Xist）, IincRNA-TPM1, MRFS16P, and lincRNA-RUNX2-2） and confirmed their expression levels in all samples using real-time polymerase chain reaction. Based on coding-non-coding gene co-expression network and gene ontology biological process analyses, several signaling pathways were associated with three common organ systems exhibiting β-thalassemia phenotypes： hematologic, skeletal, and hepatic systems. This study implicates that abnormal expression levels of lncRNAs and mRNA in β-thalassemia cases may be correlated with its various clinical phenotypes.

Genomewide DNA Methylation Responses in Patients with β-Thalassemia Treated with Yisui Shengxue Granules (益髓生血颗粒)

Objective: To examine the clinical effects of Yisui Shengxue Granules(益髓生血颗粒) in the treatment of β-thalassemia and explore its mechanism on DNA methylation levels. Methods: A randomized placebo-controlled double-blinded trial was conducted. Forty patients with β-thalassemia were recruited and distributed randomly by envelope method into an experimental group and a control group, 20 patients in each group. The patients were given Yisui Shengxue Granules in the experimental group and placebo in the control group(12 g/bag, 3 times a day) during a 3-month intervention. Before and after 1, 2, and 3 months of treatment, peripheral intravenous blood was sampled, and blood parameters such as hemoglobin(Hb), red blood cells(RBCs), reticulocytes(Ret), and fetal hemoglobin(HbF) were analyzed. Mononuclear cells from 5 patients, who showed an obvious treatment effect, were isolated by density gradient centrifugation. DNA methylation was analyzed using an Affymetrix USA GeneChip Human Promoter 1.0 Array and Input-promoter 1.0. Results: Compared with pre-treatment, there was an obvious increase in Hb and RBCs counts after 1, 2, and 3 months in the experiment group(P<0.01 or P<0.05). Meanwhile, HbF increased from the 2 nd to the 3 rd month(P<0.05). In the control group, Hb and RBCs showed no obvioas change. After 3-month treatment, DNA methylation results from 5 patients revealed that there were 24 hypomethylated genes and 3,685 hypermethylated genes compared with pre-treatment. Genes of insulin-like growth factor 1 receptor(IGF1 R) and Janus kinase 3(JAK3) revealed the most relations with other genes(degree: 21) and genes of 1-phosphatidylinositol-4, 5-bisphosphate phosphodiesterase gamma 2(PLCG2) and mitogen-activated protein kinase 10(MAPK10) showed a stronger intermediary role(betweenness centrality=0.04). Conclusions: JAK3 and MAPK10 are two key genes in bone marrow and the lymphatic system, and JAK3 is likely to be related to hematopoietic cytokines in the process of early hematopoiesis.(Registration No. NCT01549080).

Treatment of β-Thalassemia With Hydroxyurea (HU)——Effects of HU on Globin Gene Expression

A newly developed method of RT-PCR/competitive PCR for measuring the relative and ab-solute content of globin mRNAs as well as micro-globin chain biosynthetic assay have been used to study thealterations of globin gene expressions in the patients with β-thalassemia pre-and post-hydroxyurea(HU)treatment.It was found for the first time that HU had the effect of enhancing β-globin gene expression insome patients.Two cases with β-thalassemia who were subjected to HU treatment for over two years showeda marked increase in β-globin mRNA level and β-globin chain synthesis,resulting in more effective erythro-poiesis and the alleviation of clinical symptoms.

CRISPR/Cas9-mediated gene editing in human tripronuclear zygotes

Genome editing tools such as the clustered regularly interspaced short palindromic repeat （CRISPR）-associated system （Cas） have been widely used to modify genes in model systems including animal zygotes and human cells, and hold tremendous promise for both basic research and clinical applications. To date, a serious knowledge gap remains in our understanding of DNA repair mechanisms in human early embryos, and in the efficiency and potential off-target effects of using technologies such as CRISPR/Cas9 in human pre-implantation embryos. In this report, we used tripronuclear （3PN） zygotes to further investigate CRISPR/Cas9-mediated gene editing in human cells. We found that CRISPR/Cas9 could effectively cleave the endogenous β-globin gene （HBB）. However, the efficiency of homologous recombination directed repair （HDR） of HBB was low and the edited embryos were mosaic. Off-target cleavage was also apparent in these 3PN zygotes as revealed by the T7E1 assay and whole-exome sequencing. Furthermore, the endogenous delta-globin gene （HBD）, which is homologous to HBB, competed with exogenous donor oligos to act as the repair template, leading to untoward mutations. Our data also indicated that repair of the HBB locus in these embryos occurred preferentially through the non-crossover HDR pathway. Taken together, our work highlights the pressing need to further improve the fidelity and specificity of the CRISPR/Cas9 platform, a prerequisite for any clinical applications of CRSIPR/Cas9-mediated editing.