Cells become progressively committed towards a specific identity during embryonic development. Techniques such as transdifferentiation by overexpressing of a cell fate-inducing factor or reprogramming to induced pluripotent stem cells (iPSC) proved that differentiated cell fates are not fixed but reversible. Cell fate conversion strategies provide a great promise for cell therapy. However, direct cell reprogramming by transdifferentiation, which can be performed in vivo in contrast to the iPSC procedure, proved to be difficult since most differentiated cells display resistance once terminal differentiation occurs. The molecular mechanisms preventing differentiated cells to be converted by a cell fate-inducing factor remain elusive. We devised a non-biased approach to recover genetic backgrounds that overcome the molecular barrier for cell reprogramming. Our screen identified 17 mutant backgrounds, where ectopic overexpression of the ASE neuron-inducing factor CHE-1 leads to induction of ASE-specific cell fate markers in germ cells and/or epidermal cells. For example, once
che-1 mis-expression is broadly induced, a number of mutants including
bar1,
bar2,
bar4,
bar6 and
bar13 start to express the ASE cell fate marker
gcy-5::gfp in the epidermis. while
bar1,
bar9,
bar10 and
bar11 allow induction of ASE cell fate markers in germ cells. We have mapped the relative position of mutations and identified the responsible genes in a number of mutants using the SNP strategy paired with next-generation sequencing technologies. For example,
bar1 and
bar2 are alleles of
usp-48 encoding a conserved ubiquitin specific peptidase and was proposed to act as a chromatin eraser for a number of histone marks (1). Presently, we are in the process of characterizing and mapping other bar mutants. Reference:1- X Ji, DB Dadon, BJ Abraham, TI Lee et al (2015),Chromatin proteomic profiling reveals novel proteins associated with histone-marked genomic regions, PNAS, 3841-3846, doi: 10.1073/pnas.1502971112.