Somatic mosaicism in Fanconi anemia: Evidence of genotypic reversion in lymphohematopoietic stem cells

Citation
Jj. Gregory et al., Somatic mosaicism in Fanconi anemia: Evidence of genotypic reversion in lymphohematopoietic stem cells, P NAS US, 98(5), 2001, pp. 2532-2537
Citations number
34
Categorie Soggetti
Multidisciplinary
Journal title
PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
ISSN journal
00278424 → ACNP
Volume
98
Issue
5
Year of publication
2001
Pages
2532 - 2537
Database
ISI
SICI code
0027-8424(20010227)98:5<2532:SMIFAE>2.0.ZU;2-B
Abstract
Somatic mosaicism has been observed previously in the lymphocyte population of patients with Fanconi anemia (FA). To identify the cellular origin of t he genotypic reversion, we examined each lymphohematopoietic and stromal ce ll lineage in an FA patient with a 2815-2816ins19 mutation in FANCA and kno wn lymphocyte somatic mosaicism. DNA extracted from individually plucked pe ripheral blood T cell colonies and marrow colony-forming unit granulocyte-m acrophage and burst-forming unit erythroid cells revealed absence of the ma ternal FANCA exon 29 mutation in 74.0%, 80.3%, and 86.2% of colonies, respe ctively. These data, together with the absence of the FANCA exon 29 mutatio n 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 lymphocyt e population. Contrary to a predicted increase in marrow cellularity result ing from reversion in a hematopoietic stem cell, pancytopenia was progressi ve. Additional evaluations revealed a partial deletion of 11q in 3 of 20 bo ne marrow metaphase cells. By using interphase fluorescence in situ hybridi zation with an MLL gene probe mapped to band 11q23 to identify colony-formi ng unit granulocyte-macrophage and burst-forming unit erythroid cells with the 11q deletion, the abnormal clone was exclusive to colonies with the FAN CA exon 29 mutation. Thus, we demonstrate the spontaneous genotypic reversi on in a lymphohematopoietic stem cell. The subsequent development of a clon al cytogenetic abnormality in nonrevertant cells suggests that ex vivo corr ection of hematopoietic stem cells by gene transfer may not be sufficient f or providing life-long stable hematopoiesis in patients with FA.