Genomic DNA α-thalassemia αα/--SEA Std

Product Overview

The Genomic DNA α-thalassemia αα/--SEA Std is a highly characterized reference material designed for validating genetic testing workflows for α-thalassemia, a common inherited hemoglobin disorder. This standard contains genomic DNA with the αα/--SEA genotype, representing the most prevalent α-thalassemia trait in Southeast Asian populations, where carrier frequencies can exceed 15% in high-risk groups. Engineered to mimic clinical specimens, this standard enables accurate calibration of diagnostic assays for detecting the Southeast Asian (SEA) deletion, a critical genetic alteration responsible for approximately 70% of α-thalassemia cases in endemic regions. It serves as an essential quality control tool for laboratories performing carrier screening, prenatal diagnosis, and newborn testing for hemoglobinopathies .

Product Features

Clinically Relevant Genotype

The standard carries the αα/--SEA deletion genotype, consisting of two normal α-globin genes (αα) on one chromosome 16 and a complete deletion of both α-globin genes (--SEA) on the homologous chromosome. This genotype represents the most common α-thalassemia trait, associated with reduced α-globin chain production and mild microcytic anemia. The deletion breakpoint (chr16:134361-201044) is precisely mapped using high-resolution array CGH .

Orthogonally Validated

The SEA deletion status is verified by multiple complementary methods:

• Gap-PCR with allele-specific primers (>99% specificity)

• Next-generation sequencing (>300x coverage across α-globin locus)

• Digital droplet PCR (ddPCR) quantification showing 2 copies of α-globin genes (normal = 4 copies)

• Southern blot analysis confirming deletion junction fragment size (1.9 kb)

Matrix Compatibility

Purified from whole blood using standardized protocols to maintain native DNA characteristics, including:

• High molecular weight (>20 kb) genomic DNA

• A260/A280 ratio of 1.8-2.0 (pure DNA)

• <0.1 ng/μL residual RNA contamination

• Compatible with all common DNA extraction and amplification methods

Usage

Sample Preparation

Reconstitute lyophilized standard in 200 μL TE buffer (pH 8.0) to achieve a working concentration of 50 ng/μL. Allow to rehydrate at room temperature for 20 minutes with gentle mixing. Prepare serial dilutions (1-100 ng/μL) to establish assay linearity and limit of detection.

Assay Validation

Incorporate into validation runs to:

• Verify SEA deletion detection accuracy across platforms

• Establish optimal PCR cycling conditions for gap-PCR assays

• Validate NGS panel performance for α-globin locus coverage

• Monitor inter-run variability in genotype calling

Recommended input: 50-100 ng DNA per reaction for PCR-based methods.

Storage and Handling

Store unopened vials at -20°C for up to 36 months from manufacture date. After reconstitution, aliquot into single-use volumes (20 μL) and store at -20°C to prevent freeze-thaw cycles. Avoid vortexing to preserve DNA integrity. Thawed aliquots remain stable at 4°C for up to 72 hours.

FAQ

What makes the SEA deletion clinically significant?

The --SEA deletion removes both α-globin genes from one chromosome, reducing total α-globin production by 50% in carriers (αα/--SEA). While carriers are typically asymptomatic, couples with both partners carrying α-thalassemia traits have a 25% risk of having a child with severe hemoglobin H disease or hydrops fetalis .

How does this standard improve assay validation?

It provides a well-characterized reference with known genotype, enabling laboratories to verify their ability to correctly identify the SEA deletion and distinguish it from other α-thalassemia mutations (3.7 kb, 4.2 kb deletions). This is critical for accurate carrier screening and prenatal diagnosis .

Can it be used with NGS panels?

Yes, the standard is optimized for use with hemoglobinopathy NGS panels, providing uniform coverage across the α-globin gene cluster (HBZ, HBA2, HBA1). It includes a coverage validation report for common commercial panels (Illumina TruSight Hemato, Thermo Fisher Oncomine Myeloid Assay) .

Is a wild-type control included?

Each lot includes a matched wild-type genomic DNA control (αα/αα genotype) from the same ethnic background, allowing simultaneous validation of assay specificity and differentiation between normal and carrier genotypes.