New mutations in the BTK gene in Russian patients with X-linked agammaglobulinemia
AbstractIntroduction. X-linked agammaglobulinemia (XLA) refers to primary immunodeficiencies (PIDs) with a defect in humoral immunity. This disease manifests mainly in patients with mutations in the BTK gene and is characterized by an inability to develop mature B-lymphocytes. Differentiating XLA from other PIDs with similar symptoms is essential for choosing the best treatment strategy as well as for genetic counseling of families, given the sex-linked inheritance of the disease. Currently, the most effective genetic screening approach is next-generation sequencing (NGS).
Aim – to confirm the diagnosis of XLA using a proprietary test system for preparing NGS libraries of BTK gene and characterize the clinical, immunological, and genetic traits of patients with XLA.
Material and methods. We developed a reagent kit to obtain a cDNA covering all 19 exons of the BTK gene and suitable for sequencing on the Ion PGM platform to confirm the diagnosis of XLA made according to ESID criteria. The study included 14 patients with unverified agammagolobulinemia from Russia from different families aged 9 to 40 years.
Results. BTK gene sequence analysis revealed 3 new putatively pathogenic mutations: 2 deletions NP_000052.1:p.Met570del/NM_000061.2:c.1708_1710delATG and p.Cys145Alafs*31/NM_000061.2:c.433delT, and 1 single-nucleotide polymorphism (SNP), NM_000061.2:c.1909-1G>A. 2 patients had no mutations in the BTK gene despite classic XLA symptoms. Most patients showed no significant association between genotype and phenotype, which is consistent with most of the literature.
Conclusion. This study confirms the effectiveness of NGS in assessing the mutational profile of the BTK gene and offers an accurate method for genetic confirmation of XLA diagnosis. Patients with an unconfirmed genetic diagnosis by genetic testing will be further investigated by other methods to identify autosomal mutations associated with the development of PID and to refine the diagnosis.
Keywords:primary immunodeficiency; X-linked agammaglobulinemia; targeted sequencing; NGS; Next Generation Sequencing
For citation: Ivanova S.D., Bulusheva I.A., Latysheva E.A., Manto I.A., Nikiforova A.I., Kazakova A.A., Latysheva T.V., Khaitov M.R., Kofiadi I.A. New mutations in the BTK gene in Russian patients with X-linked agammaglobulinemia. Immunologiya. 2022; 43 (1): 33–43. DOI: https://doi.org/10.33029/0206-4952-2022-43-1-33-43 (in Russian)
Funding. This study was supported by the RFBR within the framework of the scientific project No. 20-34-90030 «Graduate Students».
Conflict of interests. The authors declare no conflict of interests.
Authors’ contributions. Study concept and design – Kofiadi I.A.; test system development – Nikiforova A.I.; material collection and processing – Ivanova S.D., Latysheva E.A., Manto I.A., Latysheva T.V.; software data processing – Ivanova S.D., Bulusheva I.A.; text writing – Ivanova S.D., Bulusheva I.A., Kazakova A.A.; editing – Khaitov M.R.