Further characterization of Hb Henri Mondor or alpha 2 beta 2(26)(B8)Glu----Val

Two New β Chain Variants: Hb Tripoli [β26(B8)Glu→Ala] and Hb Tizi‐Ouzou [β29(B11)Gly→Ser]

Two new beta-globin chain variants: Hb Tripoli: codon 26, GAG-->GCG [beta26(B8)Glu-->Ala] and Hb Tizi-Ouzou: codon 29, GGC-->AGC [beta29(B11)Gly-->Ser] are described on the first exon of the beta-globin gene. The two variants are characterized by DNA sequencing and mass spectrometry (MS). Hematological abnormalities were found in the two carriers. The presence of microcytosis and hypochromia is explained by an additional homozygous 3.7 kb alpha(+) thalassemic deletion for the carrier of Hb Tizi-Ouzou. Hb Tizi-Ouzou showed a slight instability in vitro. The same hematological abnormalities associated with anemia are difficult to explain for Hb Tripoli's carrier in the absence of an alpha-globin genes abnormality and could suggest a possible abnormal splicing.

Hb Aubenas [beta 62(B8)Glu-->Gly]: a new variant normally synthesized, affecting the same codon as in Hb E

Hb Aubenas [beta 26(B8)Glu-->Gly] is a mildly unstable variant that was found in a French family without hematological or clinical features. The structural abnormality was determined by protein chemistry methods, including tandem mass spectrometry, and was confirmed by Apa I digestion of a polymerase chain reaction-amplified DNA fragment. Although the substitution involves the same residue as in Hb E, the new nucleotide sequence does not create an additional out-of-frame splice site. The mutated chain is therefore normally synthesized.

Mouse alpha chains inhibit polymerization of hemoglobin induced by human beta S or beta S Antilles chains

A murine model of sickle cell disease was tested by studying the polymerization of hybrid hemoglobin tetramers between alpha mouse and human beta S or beta S Antilles chains were prepared from Hb S Antilles, which was a new sickling hemoglobin inducing a sickle cell syndrome more severe than Hb S. The hybrid molecules did not polymerize in solution, indicating that the mouse alpha chains inhibited fiber formation. Consequently, a mouse model for sickle cell disease requires the transfer and expression of both alpha and beta S or beta S Antilles genes.