Department of Biotechnology Bangladesh Agricultural University Beta(β) Thalassemia. By Syed Raju Ali 15BT-JJ07M Session: 2015-2016 Department of Biotechnology Bangladesh Agricultural University

Introduction Definition: Thalassemia is a blood born inherited disorder, causes by abnormal hemoglobin chains, unable to carry oxygen in red blood cell (RBC).

Changed Shape of Red Blood Cells Red blood cells contains a heme group and four globin chains of α and β-globin. Heme responsible for red color and globin chains provides original shape of RBC. Abnormal RBCs look like crescent or abnormal in shape small in size and different in color.

Causes of thalassemia Error in any step of central dogma. Defective transcription Error in posttranscriptional modification (impure mRNA splicing) Error in translation Defective posttranslational modification (protein imperfect folding) Severe point mutation (SNP) in genes Incretion or deletion of nucleotides Transposable elements in globin gene

Genetic transmission of thalassemia Parents are healthy, so no problem of children One parent is unaffected carrier then 25% possibility to children be carrier Parents are carrier then (100%) every child will be carrier or patient.

World Map of Thlassemia

Types of thalassemia Type-1: Mutant Alpha(α) globin genes responsible for Alpha(α) thalassemia and Type-2: Mutant Beta(β) genes responsible for Beta(β) thalassemia.

Genetic basis of β- thalassemia Disorder in globin genes on chromosome -11 Each cell contains 2 copies of beta globin gene. Suppression of gene more likely than deletion. 2 mutations: β+ thalassemia and β- thal. Loss of one gene a thalassemia minor (β+/β-) Loss of both gene a complex picture 2 beta+ thalassemia major (β++)

Types of β- thalassemia β-thalassemia has main three classes. Beta thalassemia minor: When one gene of β-globin chains is nonfunctional clinically show no symptom Carrier parents have 25% risk at each pregnancy Beta thalassemia intermedia: The middle phase of total thalassemia disease. Occasionally require Blood transfusion may need. Beta-thalassemia major: 2 β globin chains are absence in hemoglobin. From hematopoiesis, and skeletal changes.

Leg ulcer due to Beta thalassemia intermedia

Phenotypic Symptoms of β thalassemia Anemia variable severity Dark urine Enlarged abdomen Enlarged liver and spleen Failure to Feeding (infant) Highly susceptible to infection Jaundice & Pale skin Reduced RBC count & size Retarded growth Shortness of breath

The Genetic Configuration of β- globin gene β-globin genes spanning 70 Kb on the short arm of chromosome 11 (11p15.4). The cluster contains five functional genes, 5’ɛ Gγ-Aγ-ψβ‚ δ-β 3’ Upstream region distributed between 6 Kb and 20 Kb 5’ of the ɛ-gene 3’ UTR at the end of the mRNA sequences. The two extreme HS sites flanking the β-complex. The genomic sequence spans 1.6 kbp and codes for 146 amino acids. The first exon encodes amino acids 1 to 29, exon 2 encodes amino acids 30 to 104, and exon 3, amino acids 105 to 146.

β globin gene orientation TATA box (positions -28 to -31), CCAAT box (positions -72 to -76) and Duplicated CACCC motifs (proximal at positions -86 to -90, and distal at position -101 to -105).

Abnormalities in Beta Globin Genes are: β-Globin coexisting with α-thalassemia mutations Novel mutation in TATA Box of globin genes Silent mutation of β-globin genes Insertion of a transposable element in gene Somatic deletion of β-globin gene HFE gene Mutations β-thalassemia due to trans-acting mutation HBS1L-MYB gene mutations eIF2α kinase modified severity of erythropoiesis

mRNA processing errors in β-thalassemia A single nucleotide substitution in intron 1, a change that creates an alternative RNA acceptor splice site that functions in vitro.

The Molecular Diagnosis of β-thalassemia High-pressure liquid chromatography. Reverse dot-blot hybridization, Restriction fragment length polymorphism Amplification refractory mutation system, Single-stranded conformation polymorphism, Denaturing gradient gel electrophoresis.

Treatments for thalassemia Affected patients of thalassemia, considered ‘Half-Related Quality Of Life (HRQOL). Treatment and care for children and adults suffering from thalassemia diseases are experienced by hematology specialist.

Blood transfusion therapy Genetic counseling Bone marrow transplantation Gene Therapy Bone marrow transplantation Gene Therapy

Conclusion The Patients fall down at early age of life. About 200 point mutations of globin genes in chromosome 11 and 16 are responsible for thalassemia. Gene therapy, Bone marrow transplantation and induced Pluripotent Stem Cell (iPSC) therapy are also going on beside Blood transfusion. To make awareness world widely about thalassemia the World Health Organization (WHO) has declared 8th May as International thalassemia Day since 1994.

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