MOLECULAR GENETIC
STUDY OF EGYPTIAN HEREDITARY SPHEROCYTOSIS PATIENTS WITH COMBINED
ANKYRIN-SPECTRIN DEFICIENCY
Mostafa A*, Rizk S*,
Fleischacker M***, El-Beshlawy A**, El-Massry M*, Manssour I*, Abdel Ghany
H*, Abou-Elew H*, Kuttob T**, Youssry I**
*Clinical
Pathology&**Pediatrics Departments, Cairo University
***Molecular Biology,
Charice Clinic, Humbldt University, Berlin
Objective: To
demonstrate some of the molecular defects of red cell membrane proteins in
pediatric patients with hereditary spherocytosis (HS)& to clarify the
underlying genetic defect in diagnosed cases with combined deficiency of
spectrin- ankyrin red cell membrane proteins.
Methods: We
studied 20 families (100cases) with HS presenting to the Hematology Clinic
at New Cairo University Children Hospital. All cases were subjected to
routine clinical and laboratory evaluation, as well as acidified glycerol
lysis time test. Red cell membrane proteins were analysed by Sodium
Dodycyle Sulfate Polyacrylamide Gel Electrophoresis (SDS-PAGE), followed by
densitometric quantitation of erythrocyte membrane proteins. The ANK1 gene
was studied in 6 families (31cases) with combined deficiency of spectrin-
ankyrin using single strand conformation polymorphism analysis (SSCP)
followed by nucleotide sequencing.
Results: A
combined deficiency of spectrin-ankyrin was the most frequent abnormality
(85%). Disease severity was positively correlated with total reduction of
protein. An abnormal conformation was detected in 4 cases by SSCP- one in
exon2 and 3 in exon6 of ANK1 gene-. Subsequent nucleotide sequence revealed
no sequence change in exon2. In exon6 there was a heterozygous single base
substitution of G to A at position 681 of ANK1 gene (681CCG →CCA)
(silent mutation). The frequency of the mutant allele was 0.08.
Conclusion:
ankyrin gene mutations are rare in Egyptian HS patients. Subsequent study
of other candidate genes is recommended.