TY - JOUR
T1 - Somatic mosaicism in Fanconi anemia
T2 - Evidence of genotypic reversion in lymphohematopoietic stem cells
AU - Gregory, John J.
AU - Wagner, John E.
AU - Verlander, Peter C.
AU - Levran, Orna
AU - Batish, Sat Dev
AU - Eide, Cindy R.
AU - Steffenhagen, Amy
AU - Hirsch, Betsy
AU - Auerbach, Arleen D.
PY - 2001/2/27
Y1 - 2001/2/27
N2 - Somatic mosaicism has been observed previously in the lymphocyte population of patients with Fanconi anemia (FA). To identify the cellular origin of the genotypic reversion, we examined each lymphohematopoietic and stromal cell lineage in an FA patient with a 2815-2816ins19 mutation in FANCA and known lymphocyte somatic mosaicism. DNA extracted from individually plucked peripheral blood T cell colonies and marrow colony-forming unit granulocyte-macrophage and burst-forming unit erythroid cells revealed absence of the maternal FANCA exon 29 mutation in 74.0%, 80.3%, and 86.2% of colonies, respectively. These data, together with the absence of the FANCA exon 29 mutation in Epstein-Barr virus-transformed B cells and its presence in fibroblasts, indicate that genotypic reversion, most likely because of back mutation, originated in a lymphohematopoietic stem cell and not solely in a lymphocyte population. Contrary to a predicted increase in marrow cellularity resulting from reversion in a hematopoietic stem cell, pancytopenia was progressive. Additional evaluations revealed a partial deletion of 11q in 3 of 20 bone marrow metaphase cells. By using interphase fluorescence in situ hybridization with an MLL gene probe mapped to band 11q23 to identify colony-forming unit granulocyte-macrophage and burst-forming unit erythroid cells with the 11q deletion, the abnormal clone was exclusive to colonies with the FANCA exon 29 mutation. Thus, we demonstrate the spontaneous genotypic reversion in a lymphohematopoietic stem cell. The subsequent development of a clonal cytogenetic abnormality in nonrevertant cells suggests that ex vivo correction of hematopoietic stem cells by gene transfer may not be sufficient for providing life-long stable hematopoiesis in patients with FA.
AB - Somatic mosaicism has been observed previously in the lymphocyte population of patients with Fanconi anemia (FA). To identify the cellular origin of the genotypic reversion, we examined each lymphohematopoietic and stromal cell lineage in an FA patient with a 2815-2816ins19 mutation in FANCA and known lymphocyte somatic mosaicism. DNA extracted from individually plucked peripheral blood T cell colonies and marrow colony-forming unit granulocyte-macrophage and burst-forming unit erythroid cells revealed absence of the maternal FANCA exon 29 mutation in 74.0%, 80.3%, and 86.2% of colonies, respectively. These data, together with the absence of the FANCA exon 29 mutation in Epstein-Barr virus-transformed B cells and its presence in fibroblasts, indicate that genotypic reversion, most likely because of back mutation, originated in a lymphohematopoietic stem cell and not solely in a lymphocyte population. Contrary to a predicted increase in marrow cellularity resulting from reversion in a hematopoietic stem cell, pancytopenia was progressive. Additional evaluations revealed a partial deletion of 11q in 3 of 20 bone marrow metaphase cells. By using interphase fluorescence in situ hybridization with an MLL gene probe mapped to band 11q23 to identify colony-forming unit granulocyte-macrophage and burst-forming unit erythroid cells with the 11q deletion, the abnormal clone was exclusive to colonies with the FANCA exon 29 mutation. Thus, we demonstrate the spontaneous genotypic reversion in a lymphohematopoietic stem cell. The subsequent development of a clonal cytogenetic abnormality in nonrevertant cells suggests that ex vivo correction of hematopoietic stem cells by gene transfer may not be sufficient for providing life-long stable hematopoiesis in patients with FA.
UR - http://www.scopus.com/inward/record.url?scp=0035956959&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=0035956959&partnerID=8YFLogxK
U2 - 10.1073/pnas.051609898
DO - 10.1073/pnas.051609898
M3 - Article
C2 - 11226273
AN - SCOPUS:0035956959
SN - 0027-8424
VL - 98
SP - 2532
EP - 2537
JO - Proceedings of the National Academy of Sciences of the United States of America
JF - Proceedings of the National Academy of Sciences of the United States of America
IS - 5
ER -