Varianten im FANCA-Gen bei Fanconi-Anämie-Patienten aus Pakistan im internationalen Vergleich
by David Alexander Ziegler
Date of Examination:2023-07-19
Date of issue:2023-07-12
Advisor:Prof. Dr. Abdul Rahman Asif
Referee:Prof. Dr. Silke Jeannette Pauli
Referee:Prof. Dr. Margarete Schön
Persistent Address:
http://dx.doi.org/10.53846/goediss-9999
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Abstract
English
Fanconi anemia (FA) mostly shows an autosomal recessive inheritance, and in the case of Fanconi Anemia Complementation Group G (FANCG), it is inherited in an X-linked trait, while in Fanconi Anemia Complementation Group R (FANCR), it is inherited through dominant negative inheritance. The disease often manifests clinically in childhood and can be associated with the triad of hematopoietic defects, congenital malformations, and increased tumor prevalence. Among the currently known 22 FA genes, the Fanconi Anemia Complementation Group A (FANCA) gene is the most affected gene, accounting for approximately 60% of cases. However, in certain populations, other FA genes such as Fanconi Anemia Complementation Group C (FANCC) in Ashkenazi Jewish and Brazilian FA patients, or Fanconi Anemia Complementation Group G (FANCG) in Japanese FA patients, may be more frequently involved due to founder variants. The aim of this study was to perform variant analysis in all 43 exons of the FANCA gene for the first time in FA patients from Pakistani population, assess the clinical presentation in these patients, and compare it with other ethnic populations. We utilized genetic material from 24 FA patients aged 6.5 to 20 years, which was provided to us by the Combined Military Hospital and Armed Forces Institute of Pathology in Rawalpindi, Pakistan. Some primers known in the literature were used, and additional primers were newly designed to cover extended exon regions with their respective flanking regions. After primer optimization, all patients' 43 exons of the FA gene were amplified using polymerase chain reaction (PCR), sequenced through Sanger sequencing following purification, and analyzed using software programs such as DNA-Dynamo and BioEdit. The identified variants were compared with known variant databases, and for previously unknown variants, additional laboratory methods such as restriction fragment length polymorphism (RFLP) and allele-specific amplification PCR (ASA-PCR) were used for confirmation. Subsequently, the potential impacts of these new variants were investigated using the MutationTaster software tool (mutationtaster.org). Variants in the FANCA gene were identified in 7 out of 24 patients, with three patients having previously unknown variants. Additionally, we detected several mostly known variants/SNPs without clinical relevance. Clinically, there were some differences compared to previously published data, for example, more than half of the patients showed microcephaly and microphthalmia. This study represents the first investigation of all coding regions of the FANCA gene for variants in a Pakistani patient cohort. In comparison to international data, a significantly lower variant density was observed in the FANCA gene, and the clinical presentation also differed significantly from the international average. As observed in some other ethnic populations, this patient cohort also showed a different distribution of mutated gene loci compared to the international population. A comprehensive investigation of the other FA genes and the establishment of a standardized registry in this population is essential for future screening and therapeutic approaches.
Keywords: Fanconi Anemia; Fanconi; FANCA; FANC; Pakistan
Schlagwörter: Fanconi Anämie; Fanconi; Pakistan; FANCA; FANC