Article Text
Abstract
Background Exploring the expression of X linked disorders like haemophilia A (HA) in females involves understanding the balance achieved through X chromosome inactivation (XCI). Skewed XCI (SXCI) may be involved in symptomatic HA carriers. We aimed to develop an approach for dissecting the specific cause of SXCI and verify its value in HA.
Methods A family involving three females (two symptomatic with severe/moderate HA: I.2, the mother, and II.1, the daughter; one asymptomatic: II.2) and two related affected males (I.1, the father and I.3, the maternal uncle) was studied. The genetic analysis included F8 mutational screening, multiplex ligation-dependent probe amplification, SNP microarray, whole exome sequencing (WES) and Sanger sequencing. XCI patterns were assessed in ectoderm/endoderm and mesoderm-derived tissues using AR-based and RP2-based systems.
Results The comprehensive family analysis identifies I.2 female patient as a heterozygous carrier of F8:p.(Ser1414Ter) excluding copy number variations. A consistent XCI pattern of 99.5% across various tissues was observed. A comprehensive filtering algorithm for WES data was designed, developed and applied to I.2. A Gly58Arg missense variant in VMA21 was revealed as the cause for SXCI.
Each step of the variant filtering system takes advantage of publicly available genomic databases, non-SXCI controls and case-specific molecular data, and aligns with established concepts in the theoretical background of SXCI.
Conclusion This study acts as a proof of concept for our genomic filtering algorithm’s clinical utility in analysing X linked disorders. Our findings clarify the molecular aspects of SXCI and improve genetic diagnostics and counselling for families with X linked diseases like HA.
- Blood Coagulation Disorders
- Whole Exome Sequencing
- X-Linked Genetic Diseases
- Genetic Carrier Screening
Data availability statement
All data relevant to the study are included in the article or uploaded as supplementary information.
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Data availability statement
All data relevant to the study are included in the article or uploaded as supplementary information.
Footnotes
CDB and CPR are joint senior authors.
X @florgili
Contributors BMZ, CPR and CDB performed the research, designed the study, analysed the data and wrote the paper. MMA, VDM, NL, MML, EM-A, LCR, LE and DN contributed with samples and/or analysed the genetic, clinical and bioinformatic data. FG contributed with control samples. Guarator: CPR. All authors revised and approved the final submitted version of the manuscript, and they agree to be accountable for all aspects of the work.
Funding This study was supported by grants from the National Research Council (CONICET) and the National Agency for Scientific and Technological Promotion (ANPCyT).
Competing interests None declared.
Provenance and peer review Not commissioned; externally peer reviewed.
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