The relative levels of alpha 2-, alpha 1-, and zeta-mRNA in HB H patients with different deletional and nondeletional alpha-thalassemia determinants.
We have analyzed the alpha 2/alpha 1-, alpha/beta-, zeta/(alpha + zeta)-mRNA ratios in the retic-ulocytes of 40 patients with Hb H disease. 21 patients had deletional Hb H disease (- -/- alpha), namely combinations of one of four types of alpha-thal-1 (MED-I, MED-II, -(alpha)20.5, SEA) and one of two types of alpha-thal-2 (-3.7 or -4.2 kb); 13 had Hb H disease because of combinations of one of these alpha-thal-1 deletions with either a 5 nt deletion at the 5' splicing site of IVS-I, or a terminating codon mutation (Hb CS), or a poly(A) mutation, and six were homozygous for either a poly(A) mutation or the 5 nt deletion. Significant differences were observed between the deletional types (- -/- alpha; alpha 2/alpha 1 ratio of zero; alpha/beta ratio of approximately 1) and non-deletional types (- -/alpha T alpha; alpha 2/alpha 1 ratio of 0.05-0.3 for those with T = the 5 nt deletion or the terminating codon mutant, and approximately 1.0 for those with T = a poly(A) mutation; alpha/beta ratio in all types of approximately 0.7). Comparable data were found for the nondeletional alpha-thal-2 homozygotes. The noted differences were highly significant and the determination of the two ratios may be diagnostically of considerable value. The low alpha 2/alpha 1-mRNA ratio in the two patients with - -/alpha-5nt alpha and the one patient with alpha-5nt alpha/alpha-5nt alpha indicates the presence of minute amounts of alpha 2-mRNA; apparently splicing at the donor site is greatly impaired by this deletion but not eliminated. The high alpha 2/alpha 1-mRNA ratio in the four patients with - -/alpha PA-2 alpha and the five patients with alpha PA-1 alpha/ alpha PA-1 alpha (PA-1 and PA-2 are poly(A) mutations) is due to the presence of an elongated alpha 2-mRNA which uses an alternate location as polyadenylation site. The relative levels zeta-mRNA varied considerably; the highest levels were found in patients with the -(alpha)20.5/-alpha or - -SEA/-alpha deletional types but not in those with the -(alpha)20.5/alphaPA-2 alpha, -(alpha)20.5/alpha-5nt alpha, or - -SEA/alphaCS alpha nondeletional types. No definitive explanation can be given for these differences; perhaps certain sequences that are part of some of the alpha-thal-1 deletions are important for the suppression of the zeta-globin gene.
Smetanina
N S
NS
Department of Biochemistry and Molecular Biology, Medical College of Georgia, Augusta 30912-2100, USA.
Oner
C
C
Baysal
E
E
Oner
R
R
Bozkurt
G
G
Altay
C
C
Gürgey
A
A
Adekile
A D
AD
Gu
L H
LH
Huisman
T H
TH
D000293:Adolescent; D000328:Adult; D001483:Base Sequence; D002648:Child; D002675:Child, Preschool; D017931:DNA Primers; D015870:Gene Expression; D005914:Globins / Q000235:genetics*; D006801:Humans; D007223:Infant; D008875:Middle Aged; D008969:Molecular Sequence Data; D012333:RNA, Messenger / Q000235:genetics; D012156:Reticulocytes; D017384:Sequence Deletion; D017085:alpha-Thalassemia / Q000235:genetics*
D017931:DNA Primers; D012333:RNA, Messenger; D005914:Globins