Mutational analysis of telomere complex genes in Indian population with acquired aplastic anemia

Background: Acquired aplastic anemia (AAA) is rare disorders caused due to the profound or almost complete bone marrow failure. It is a life threatening hematopoietic stem cells disorder, which is characterized by pancytopenia or complete loss of blood-forming cells. The aim of the present study is to screen for the mutations in telomerase complex genes, and to establish a molecular and hematological profile of Indian sub population.

Methodology: We have conducted a case control study of total 70 participants; 50 patients, who fulfilled the blood count and bone marrow criteria of the International agranulocytosis & AAA, and 20 healthy controls. These samples were selected from hematology clinics at Jaipur, India, during the period of two years (January 2012-December 2013). We screened four telomere complex genes; TERT, DKC1, NOP10 and NHP2 of mutations at single base pair in sampled blood and bone marrows. We have predicated the consequences of mutations on protein structure using 3D multilevel modeling protein structure software Phyre2, PolyPhen2 and YASARA.

Results: The hematological and molecular basis of acquired aplastic anemia was investigated in 50 anemia patients and 20 healthy controls. AAA patients showed hematologic abnormalities (macrocytic anemia, thrombocytopenia, & granulocytopenia) in peripheral blood and severe hypoplastic bone marrows. Screening of telomere complex genes TERT, DKC1, NOP10 and NHP2 in AAA patients and controls revealed; novel and reported mutations in TERT and DKC1, whereas, no pathogenic mutations were observed in NOP10 and NHP2 genes. In TERT gene, one non-synonymous mutation (Chr5: 1287,825 C→T; Arg979Trp) was identified in exon 12 and two heterozygous non-synonymous mutations (Chr X: 153,994,542 T→K; Val105Gly & Chr X: 153,994,591 T→K; Ser121Arg) were found in exon 5 of DKC1 gene. To determine and visualize the possible effect of TERT and DKC1 mutations on protein structure YASARA with FoldX functionality has been used and many structural consequences were found that might destabilize the protein. Predicated structural consequences may destabilize the TERT and DKC1 proteins ultimately causing blood disorders..

Conclusion: The present study indicates the mutation spectrum in the genes implicated in AAA, i.e. TERT, DKC1, NOP10 and NHP2 on small case-control group in an Indian sub population.