Studying the pathogenicity of 26 variants characterized in the first molecular analyses of Egyptian aplastic anemia patients

BACKGROUND

Aplastic anemia (AA) is a bone marrow disorder characterized by peripheral pancytopenia and marrow hypoplasia which can lead to life-threatening complications. Our objective was to study the telomerase genes (TERT and TERC) variants, explore their relationship to telomere shortening and TERT gene expression, and to identify variants in the MPL gene within Egyptian AA patients.

METHODS

Forty AA patients and 40 sex- and age-matched healthy individuals as the control group were studied through sequencing of TERT, TERC, and MPL genes. Quantitative real-time PCR (qRT-PCR) was used for measuring TERT gene expression. Telomere length (TL) was measured using the Quantitative Fluorescence In Situ Hybridization (Q-FISH) technique. In silico analysis was performed for the prediction of the pathogenicity of resultant variants.

RESULTS

Sequencing of MPL, TERT, and TERC genes identified 26 variants. Eleven variants were identified in the MPL gene. Three of them are pathogenic: two missense [c.305 G>A, c.1589 C>T] and one splice site [g.9130T>G]. TERT gene sequencing showed thirteen variants, among them, four novel [c.484G>A, c.499G>A, c.512G>A, c.3164C>G] and two previously reported [c.835G>A, c.2031C>T] were predicted to be pathogenic. Two variants were characterized within the TERC gene; n.514A>G and n.463 C>T. TERT gene expression was downregulated in 70% of studied patients and the Q-FISH technique detected telomere shortening in 82.5% of patients.

CONCLUSIONS

Twenty-six pathogenic and benign variants within the TERC, TERT, and MPL genes were identified among the studied AA patients that were in several cases associated with shortened telomeres and/or lower TERT gene expression. Genotype/phenotype correlation in AA patients is of great importance in explaining the disease severity and guiding therapeutic decisions.

MBL2 gene variants and susceptibility to meningitis in Egyptian patients

BACKGROUND

Meningitis is inflammation of the membranes enclosing the brain and spinal cord. It is a fatal disease with severe morbidity and mortality. Mannose binding lectin (MBL) encoded by MBL2 gene activates complement system through lectin pathway in innate immunity to defense against the infections.

OBJECTIVE

the current study aimed to investigate the promoter and exon 1 variants of MBL2 gene among Egyptian patients having meningitis to explore their role in disease susceptibility.

PATIENTS AND METHODS

This case-control study, included 53 patients and 50 sex and age matched controls. MBL2 genotyping was done using Sanger sequencing.

RESULTS

The frequency of one promoter (c.-290C>G) and four in exon 1 (c.161G>A, c.170G>A, c.154C>T and c.132C>T) as well as another one located in its 5'utranslated part (c.-66C>T) variants were estimated. The incidence of the four individual exonic variants was not significantly different between cases and healthy individuals (all P> 0.05). The promoter variant, c.-290C>G was found in all examined patients (84.9% of the patients in homozygote state and 15.1% of patients in heterozygous state) with a highly significant variance in the prevalence of this variant between cases and control group (p=0.0001). Additionally, UTR variant (c.-66C>T) was also significantly higher in patients than controls (P=0.033).In comparison with clinical outcome, it was found that c.170G>A variant named C allele was associated with favorable outcome in the studied patients (P=0.025).

CONCLUSION

The results obtained showed that the Promoter (c.-290C>G) and UTR (c.-66 C>T) variants of MBL2 gene may be potential risk factors for disease susceptibility in Egyptian cases with meningitis. Our results also proposed that c.170G>A (C allele and CC genotype) could affect the severity and play a protective role in these patients. The other genetic variants of MBL2 gene, including c.132C>T, c.161G>A (A>B), and c.154C>T (A>D) that were investigated, did not show any association with susceptibility or severity of meningitis.

Dynamic disequilibrium-based pathogenicity model in mutated pyrin’s B30.2 domain—Casp1/p20 complex

Background

The B30.2 variants lead to most relevant severity forms of familial Mediterranean fever (FMF) manifestations. The B30.2 domain plays a key role in protein-protein interaction (PPI) of pyrin with other apoptosis proteins and in regulation the cascade of inflammatory reactions. Pyrin-casp1 interaction is mainly responsible for the dysregulation of the inflammatory responses in FMF. Lower binding affinity was observed between the mutant B30.2 pyrin and casp1 without the release of the complete pathogenicity mechanism. The aim of this study was to identify the possible effects of the interface pocked residues in B30.2/SPRY-Casp1/p20 complex using molecular mechanics simulation and in silico analysis.

Results

It was found that Lys671Met, Ser703Ile, and Ala744Ser variants led mainly to shift of the binding affinity (∆G), dissociation constant (K_d), and root mean square deviation (RMSD) in B30.2/SPRY-Casp1/p20 complex leading to dynamic disequilibrium of the p20-B30.2/SPRY complex toward its complex form. The current pathogenicity model and its predicted implementation in the relevant colchicine dosage were delineated.

Conclusion

The molecular mechanics analysis of B30.2/SPRY-p20 complex harboring Lys671Met, Ser703Ile, and Ala744Ser variants showed dynamic disequilibrium of B30.2/SPRY-casp1/p20complex in context of the studied variants that could be a new computational model for FMF pathogenicity. This study also highlighted the specific biochemical markers that could be useful to adjust the colchicine dose in FMF patients.