ef f iciencies ( 8 ) . 
Gene transfer has also been achieved in a number 
of large animal bone marrow transplantation models (7) 
Bone marrow stem cells of rhesus monkeys have been 
successfully transduced by two groups (9 - 11) . 
Multilineage reconstitution of transduced cells was 
reported and long-term expression of the foreign gene 
achieved (10) . For example, rhesus CD34+ cells have 
been transduced with the bacterial neomycin 
phosphotransf erase (Neo'^) gene; autologous 
transplantation with these marked cells led to long- 
term reconstitution (11) . Similar results have been 
obtained transducing rhesus CD34+ cells with a vector 
carrying the adenosine deaminase (ADA) gene (D. Bodine, 
personal communication) . Hematopoietic stem cells from 
dogs (12) and cats (13) have also been successfully 
transduced with retroviral vectors. 
Retroviral mediated transfer of FACC into FA(C) 
lymphoblasts 
Transformed lymphoblast cell lines have been 
established from FA patients bearing mutations in FACC 
alleles. These mutations include a point 
transition (3 ) , a nucleotide deletion(4), and a nonsense 
mutation (14) . We tested the ability of our FACC 
retrovirus to transduce all three types of mutant 
lines. As expected, all lines were extremely sensitive 
to the cross-linking agent MMC. Cell lines transduced 
by the FACC retrovirus were able to proliferate at 
concentrations of MMC several orders of magnitude 
higher than parental controls (and equivalent to a line 
established from a normal individual) . One genetically 
corrected cell line was tested for susceptibility to 
MMC- induced chromosomal breakage and was found to have 
been normalized on cytogenetic analysis. Southern 
analysis confirmed successful transduction of the 
normal FACC gene in these defective lines. 
Retroviral mediated transfer of FACC into FA(C) CD34+ 
hematopoietic progenitors 
We next analyzed the ability of the vectors to correct 
the functional growth defect in hematopoietic 
progenitor cells from a patient bearing a splice donor 
mutation in FACC. Progenitor cells were obtained by 
peripheral blood leukapheresis and purified by an 
immunoaf f inity column to enrich for CD34 expression. 
As for lymphoid cell lines, these CD34 -enriched cells 
were extremely sensitive to MMC. After infection with 
the FACC vector, these progenitors gave rise to 
markedly increased numbers of colonies both in the 
absence and presence of <5 nM MMC, whereas no colonies 
formed from control cells, even in the absence of MMC. 
PCR analysis confirmed the presence of proviral DNA in 
colonies derived from these CD34+ progenitors. Besides 
directly confirming the ability of our FACC virus to 
transduce target cells from a FA(C) patient, these 
studies suggest that FA stem cells can be rescued by 
gene therapy. The infection procedure is exactly 
Recombinant DNA Research, Volume 19 
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