Noninvasive prenatal diagnosis of hemophilia A by a haplotype-based approach using cell-free fetal DNA

Targeted Linked-Read Sequencing for Direct Haplotype Phasing of Parental GJB2/SLC26A4 Alleles: A Universal and Dependable Noninvasive Prenatal Diagnosis Method Applied to Autosomal Recessive Nonsyndromic Hearing Loss in At-Risk Families

Noninvasive prenatal diagnosis (NIPD) for autosomal recessive nonsyndromic hearing loss (ARNSHL) has been rarely reported until recent years. Additionally, the existing method can not be used for challenging genome loci (eg, copy number variations, deletions, inversions, or gene recombinants) or on families without proband genotype. This study assessed the performance of relative haplotype dosage analysis (RHDO)-based NIPD for identifying fetal genotyping in pregnancies at risk of ARNSHL. Fifty couples carrying pathogenic variants associated with ARNSHL in either GJB2 or SLC26A4 were recruited. The RHDO-based targeted linked-read sequencing combined with whole gene coverage probes was used to genotype the fetal cell-free DNA of 49 families who met the quality control standard. Fetal amniocyte samples were genotyped using invasive prenatal diagnosis (IPD) to assess the performance of NIPD. The NIPD results showed 100% (49/49) concordance with those obtained through IPD. Two families with copy number variation and recombination were also successfully identified. Sufficient specific informative single-nucleotide polymorphisms for haplotyping, as well as the fetal cell-free DNA concentration and sequencing depth, are prerequisites for RHDO-based NIPD. This method has the merits of covering the entire genes of GJB2 and SLC26A4, qualifying for copy number variation and recombination analysis with remarkable sensitivity and specificity. Therefore, it has clinical potential as an alternative to traditional IPD for ARNSHL.

Gender equity in hemophilia: need for healthcare, familial, and societal advocacy

Hemophilia is a rare bleeding disorder caused by a genetic defect on chromosome X. It is inherited as an X-linked trait, and hence, it is more frequently diagnosed in males, whereas women have been traditionally considered only as carriers of the disease. However, the role of women in families of patients with hemophilia is pivotal. As mothers, sisters, daughters, and female partners of patients with hemophilia, they play a central role in the management of the patient, considering healthcare, social, and familial aspects, but they might be affected by the disease as well, particularly in regions where consanguinity is frequent. This paper aims to explore the involvement of women in hemophilia, including their carrier status, bleeding symptoms, treatment challenges, and psychosocial impact not only related to male patients, but also as patients affected with hemophilia themselves. We advocate health equity, equal access to healthcare for men and women with hemophilia and dedicated resources to improve the unique needs of the women dealing with hemophilia, ultimately leading to improved care and quality of life.

Exploring factors impacting haplotype-based noninvasive prenatal diagnosis for single-gene recessive disorders

Haplotype-based noninvasive prenatal diagnosis (NIPD) is applicable for various recessive single-gene disorders in proband families. However, a comprehensive exploration of critical factors influencing the assay performance, such as fetal fraction, informative single nucleotide polymorphism (SNP) count, and recombination events, has yet to be performed. It is critical to identify key factors affecting NIPD performance, including its accuracy and success rate, and their impact on clinical diagnostics to guide clinical practice. We conducted a prospective study, recruiting 219 proband families with singleton pregnancies at risk for eight recessive single-gene disorders (Duchenne muscular dystrophy, spinal muscular atrophy, phenylketonuria, methylmalonic acidemia, hemophilia A, hemophilia B, non-syndromic hearing loss, and congenital adrenal hyperplasia) at 7-14 weeks of gestation. Haplotype-based NIPD was performed by evaluating the relative haplotype dosage (RHDO) in maternal circulation, and the results were validated via invasive prenatal diagnosis or newborn follow-ups. Among the 219 families, the median gestational age at first blood draw was 8+5 weeks. Initial testing succeeded for 190 families and failed for 29 due to low fetal fraction (16), insufficient informative SNPs (9), and homologous recombination near pathogenic variation (4). Among low fetal fraction families, successful testing was achieved for 11 cases after a redraw, while 5 remained inconclusive. Test failures linked to insufficient informative SNPs correlated with linkage disequilibrium near the genes, with F8 and MMUT exhibiting the highest associated failure rates (14.3% and 25%, respectively). Homologous recombination was relatively frequent around the DMD and SMN1 genes (8.8% and 4.8%, respectively) but led to detection failure in only 44.4% (4/9) of such cases. All NIPD results from the 201 successful families were consistent with invasive diagnostic findings or newborn follow-up. Fetal fraction, informative SNPs count, and homologous recombination are pivotal to NIPD performance. Redrawing blood effectively improves the success rate for low fetal fraction samples. However, informative SNPs count and homologous recombination rates vary significantly across genes, necessitating careful consideration in clinical practice. We have designed an in silico method based on linkage disequilibrium data to predict the number of informative SNPs. This can identify genomic regions where there might be an insufficient number of SNPs, thereby guiding panel design. With these factors properly accounted for, NIPD is highly accurate and reliable.

Noninvasive prenatal diagnosis of congenital factor XIII deficiency in Iran

Congenital factor (F) XIII deficiency is a rare coagulation factor deficiency that is inherited in an autosomal recessive manner. FXIII deficiency presents various clinical manifestations, such as intracranial hemorrhage (ICH), which is the most common cause of morbidity and mortality. As ICH can occur in the neonatal period, prenatal diagnosis (PND) is an effective way to reduce neonatal ICH and its associated fatal consequences. In this study, we investigated a noninvasive prenatal diagnosis (NIPD) method, cell-free fetal DNA (cffDNA), for PND in FXIII deficiency. This study was conducted on seven pregnant women in the first trimester. After extraction of cffDNA from maternal plasma, PCR-restriction fragment length polymorphism (PCR-RFLP) was performed to find the underlying F13A gene mutations previously identified in the family members. PCR-RFLP was also performed on postnatal DNA samples. Sanger sequencing was performed to confirm the results. Four cases were heterozygous for F13A gene mutations, whereas three were unaffected. PCR-RFLP results for cffDNA and postnatal DNA samples were identical, and Sanger sequencing confirmed the results. cffDNA is a noninvasive and effective method for PND in congenital FXIII deficiency.

Congenital hemophilia A with low activity of factor XII: a case report and literature review

BACKGROUND

Congenital hemophilia A is a recessive inherited hemorrhagic disorder. According to the activity of functional coagulation factors, the severity of hemophilia A is divided into three levels: mild, moderate and severe. The first bleeding episode in severe and moderate congenital hemophilia A occurs mostly in early childhood and mainly involves soft tissue and joint bleeds. At present, there are limited reports on severe congenital hemophilia A with low factor XII (FXII) activity during the neonatal period.

CASE PRESENTATION

A 13-day-old neonate was admitted to the hospital with hematoma near the joints of both upper arms. Coagulation tests showed he had low activity of factor VIII (FVIII) and FXII. He was diagnosed with congenital hemophilia A and treated with human coagulation factor VIII (recombinant FVIII). Although the hematoma became smaller, FVIII activity was only increased to a certain extent and FXII activity decreased gradually. Unfortunately, the child responded poorly to recombinant human coagulation factor VIII and his guardian rejected prophylactic inhibitors and genetic testing and refused further treatment. Three months later, the child developed intracranial hemorrhage (ICH) due to low FVIII activity.

CONCLUSIONS

In hemophilia A, the presence of FVIII inhibitors, drug concentration and testing are three important aspects that must be considered when FVIII activity does not reach the desired level. Early positive disease treatment and prophylaxis can decrease the frequency of bleeding and improve quality of life. We recommend that pregnant women with a family history of hemophilia A undergo early prenatal and neonatal genetic testing.

Development of a Specific Monoclonal Antibody to Detect Male Cells Expressing the RPS4Y1 Protein

Hemophilia is an X-linked recessive bleeding disorder. In pregnant women carrier of hemophilia, the fetal sex can be determined by non-invasive analysis of fetal DNA circulating in the maternal blood. However, in case of a male fetus, conventional invasive procedures are required for the diagnosis of hemophilia. Fetal cells, circulating in the maternal bloodstream, are an ideal target for a safe non-invasive prenatal diagnosis. Nevertheless, the small number of cells and the lack of specific fetal markers have been the most limiting factors for their isolation. We aimed to develop monoclonal antibodies (mAbs) against the ribosomal protein RPS4Y1 expressed in male cells. By Western blotting, immunoprecipitation and immunofluorescence analyses performed on cell lysates from male human hepatoma (HepG2) and female human embryonic kidney (HEK293) we developed and characterized a specific monoclonal antibody against the native form of the male RPS4Y1 protein that can distinguish male from female cells. The availability of the RPS4Y1-targeting monoclonal antibody should facilitate the development of novel methods for the reliable isolation of male fetal cells from the maternal blood and their future use for non-invasive prenatal diagnosis of X-linked inherited disease such as hemophilia.