Brief Report: Human Pluripotent Stem Cell Models of Fanconi Anemia Deficiency Reveal an Important Role for Fanconi Anemia Proteins in Cellular Reprogramming and Survival of Hematopoietic Progenitors

Abstract

Fanconi anemia (FA) is a genomic instability disorder caused by mutations in genes involved in replicationdependant-repair and removal of DNA cross-links. Mouse models with targeted deletions of FA genes have been developed; however, none of these exhibit the human bone marrow aplasia. Human embryonic stem cell (hESC) differentiation recapitulates many steps of embryonic hematopoietic development and is a useful model system to investigate the early events of hematopoietic progenitor specification. It is now possible to derive patient-specific human-induced pluripotent stem cells (hiPSC); however, this approach has been rather difficult to achieve in FA cells due to a requirement for activation of FA pathway during reprogramming process which can be bypassed either by genetic complementation or reprogramming under hypoxic conditions. In this study, we report that FA-C patient-specific hiPSC lines can be derived under normoxic conditions, albeit at much reduced efficiency. These disease-specific hiPSC lines and hESC with stable knockdown of FANCC display all the in vitro hallmarks of pluripotency. Nevertheless, the diseasespecific hiPSCs show a much higher frequency of chromosomal abnormalities compared to parent fibroblasts and are unable to generate teratoma composed of all three germ layers in vivo, likely due to increased genomic instability. Both FANCC-deficient hESC and hiPSC lines are capable of undergoing hematopoietic differentiation, but the hematopoietic progenitors display an increased apoptosis in culture and reduced clonogenic potential. Together these data highlight the critical requirement for FA proteins in survival of hematopoietic progenitors, cellular reprogramming, and maintenance of genomic stability. STEM CELLS

Biallelic inactivation of REV7 is associated with Fanconi anemia

“…Previous studies have indicated that FA proteins are required for normal hematopoiesis and hematopoietic progenitor cell (HPC) survival (6)(7)(8)18). To evaluate whether REV7 deficiency can affect hematopoiesis, we silenced this gene in mouse HPCs.…”

A human iPSC model of Ligase IV deficiency reveals an important role for NHEJ-mediated-DSB repair in the survival and genomic stability of induced pluripotent stem cells and emerging haematopoietic progenitors

“…46 Although we have not studied in detail whether NHEJ is activated during the reprogramming process; the much lower efficiency of obtaining iPSC from LIG4-NHEJ-deficient fibroblasts together with accumulation of chromosomal abnormalities during the reprogramming of those lines, suggest that activation of NHEJ may also be required in this process. Muller et al 47 have shown that reprogramming induces DNA damage, resulting in upregulation of p53, increased DSBs and senescence.…”

Fanconi anemia: a model disease for studies on human genetics and advanced therapeutics

“…Because FA fibroblasts are difficult to reprogram, this study uncovered a novel role of the FA pathway in cell reprogramming. Consequently, correcting FA genes restores the reprogramming efficiency of FA fibroblasts to IPS cells [93][94][95][96][97][98]. Reprogramming induces the DDR [99] and activates the FA pathway [94], leading to P53-mediated apoptosis and low reprogramming efficiency [96].…”