Red cell dimorphism in a young man with a constitutional chromosomal translocation t(11;22)(p15.5;q11.21).
A constitutional, balanced chromosomal translocation t(11;22)(p15.5;q11.21) was discovered in a tall young man during investigation of a red cell dimorphism. The red cells are predominantly normochromic and normocytic with a small population of hypochromic, microcytic cells. Contained within the regions involved in the translocation are determinants of height (IGF2:11p15.5), red cell haemoglobinization (non-alpha globin gene complex: 11p15.5) and oncogenesis (cHa-Ras-1, Beckwith-Wiedemann syndrome: 11p15.5; BCR, Burkitts lymphoma, Ewings sarcoma: 22q11.21). To map these regions in the patient, somatic cell hybrids were generated and cell lines that segregated the chromosomes 11, 22 and 22q- were obtained. All 11p15.5 sequences investigated, in particular the whole of the non-alpha globin gene complex including its 5' and 3' regulatory sequences, were found to be translocated to 22q-. All chromosome 22 sequences studied were missing from the 22q- cell lines, including the proximal anonymous marker D22S24, and therefore assumed to be translocated to 11p+. These results suggest that the non-alpha globin gene complex has been moved close to the centromeric region of chromosome 22q-. It is postulated that such a positioning subjects the complex to a variegated position-effect bringing about a clonal exclusion of the complex and thus producing a beta-thalassaemia trait mosaic.
Rees
M I
MI
Department of Haematology, University of Wales College of Medicine, Cardiff.
Worwood
M
M
Thompson
P W
PW
Gilbertson
C
C
May
A
A
D000293:Adolescent; D002874:Chromosome Mapping / Q000379:methods; D002880:Chromosomes, Human, Pair 11; D002892:Chromosomes, Human, Pair 22; D004913:Erythrocytes, Abnormal / Q000473:pathology*; D005914:Globins / Q000235:genetics; D006130:Growth Disorders / Q000235:genetics*; D006454:Hemoglobins / Q000032:analysis; D006801:Humans; D007621:Karyotyping; D008297:Male; D014178:Translocation, Genetic / Q000502:physiology*
D006454:Hemoglobins; D005914:Globins