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.

Unilateral Coats'-like disease and an intragenic deletion in the TERC gene: A case report

We report a case of a 25-year-old woman with unilateral Coats'-like disease. Her brother was previously diagnosed with an autosomal dominant form of dyskeratosis congenita. Genetic testing was performed by screening the TERC gene for mutations and identified heterozygosity for the n.68_124del mutation. Our case demonstrates that the exudative retinopathy seen in Coats'-like disease can be caused by mutations in a telomere-capping gene TERC as a part of the dyskeratosis congenita spectrum without other systemic involvement. This is an interesting case that illustrates that retinal Coats'-like involvement can be the first manifestation of dyskeratosis congenita.