Further studies of the frequency and significance of the Tgamma-chain of human fetal hemoglobin.

Analysis of the <i>γ</i> Chains in a Homozygote for HPFH Negro Type and in Three Related Heterozygotes

“…While the ry detection on finger prints of the total Hb F may be uncertain when this chain is present in low percentage [14], the quantitation of Ty chain in puri fied Ay chain is much more reliable; the ab sence of ry chain in our cases confirms the previous data by Schroeder et al [ 18] who could not show this type of chain in a wide series of carriers of HPFH Negro type. The fact that all the subjects up to now exam ined are negative for Ty chain might be re lated to the low incidence of this chain in black people [10,18]. Even if the cases up to now examined are still limited, these data suggest that the t 7 gene is never linked to the HPFH deter minant and seem to exclude a y-chain pro duction in 'trans'.…”

“…As reported by Schroeder et al [18], the Ty chain seems to be ab sent both in homozygous and in heterozy gous HPFH Negro type.…”

“…In 1975 a new y variant (Hb F Sardinia) [6], carrying threonine instead of isoleucine in position 75, was described; subsequently, the same y chain (Ty chain) was found in a high percentage of Caucasian subjects [14], and with lower incidence also in Negro peo ple [10,18], Recently, the Ty chain has , suggest that the Ty gene is never linked with been documented to be an allelic variant of the Ay chain, both by means of statistical analysis of a wide series of samples [18] and by direct examination of fingerprints of pur ified Ay chains [16]. As reported by Schroeder et al [18], the Ty chain seems to be ab sent both in homozygous and in heterozy gous HPFH Negro type.…”

Polymorphism of Foetal Haemoglobin in the Sardinian β⁺-Thalassaemia

“…These data suggest the presence of at least 2 /(+-thalassaemic chrom osom es in Sardinians, one associated with the variant AyT allele and one asso ciated with the norm al Ay*. The latter is prevalent am ong adult patients showing the interm ediate form of the thalassaem ic disease, which is not transfusion-dependent.The observation of the occurrence of the mutated Ay chain, known as the AyT chain, present in the socalled Hb F Sardinia (a 2A/ 275 lle-Thr) [3,5,13] in the foetal haem oglobin has been dem onstrated to be very im portant for our knowledge o f the genetics o f the ft gene cluster [5][6][7]14], The high incidence of the AyT al lele in various haematological disorders makes its product a m arker to be used for the evaluation o f the y chain production being in cis or in trans o f a particu lar gene [5], M oreover, a num ber of /) thalassaemia m utations have been found in chromosomes contain ing the AyT gene [2,4,9,16,18].In Sardinia, at least 2 main /(-thalassaemic genes coexist: the most com m on and widespread gene, characterized by a non-sense m utation at residue 39 [17], and the gene, present in the N orthern area of the island [8], not yet characterized at a m olecular lev el. It has already been described that the Sardinian fi°- , The linkage be tween the p° and the AyT genes has also been described in homozygous patients from the M editerranean and other areas [2, 5-7, 11, 14], Similarly, a strong linkage has been observed between the P+ and the Ay' genes in homozygous thalassaemic patients of intermediate severity from Algeria, Sicily, Tunisia and Portugal [2,16,18], The aim o f this work was to study the y chain com position of the foetal haemoglobin of Sardinian P+ -thalassaem ic patients in order to establish the pos sible linkage between the /J+ and the AyT genes in this population.…”

Identification and quantitation of embryonic and three types of fetal hemoglobin produced on induction of the human pluripotent leukemia cell line K‐562 with hemin

“…Two of these which occur in all human populations differ only at position 136 of the y chain, which may be occupied by a glycyl residue in "y chains or by an alanyl residue in chains [22]. Furthermore, the Ay chains are polymorphic at position 75, which is usually occupied by an isoleucyl residue in the chain [23,24]. During the developmental transition from fetal to adult types of hemoglobin synthesis, the proportion of "y chains declines from 70% in cord blood to about 40% in adult peripheral blood [25].…”