RBR-2 is a histone 3 lysine 4 demethylase whose mammalian homolog is expressed in regenerative tissues and exhibits dynamic changes at gene promoters during stem cell differentiation [Christensen et al. 2007; Dey et al. 2008]. The C.elegans deletion allele
rbr-2(
tm1231) results in increased H3K4me3 and H3K4me2, but inconsistent
rbr-2 phenotypes have been reported: RNAi knockdown of
rbr-2 can extend lifespan [Lee et al. 2003], as can overexpression of
rbr-2 in germ cells, whereas
rbr-2(
tm1231) results in decreased lifespan [Greer et al. 2010]. Moreover,
rbr-2(
tm1231) has low brood size and weakly penetrant multivulval phenotypes, the latter possibly being consistent with a role for
rbr-2 in the SynMuv histone modification pathway [Christensen et al. 2007]. Based on the role of mammalian RBR-2 in stem cell maintenance,
rbr-2(
tm1231) was examined for germ cell maintenance phenotypes.
rbr-2(
tm1231) animals appear smaller than wild-type and show a progressively sterile (Mortal Germline) phenotype when reared at 25 deg C. Outcrosses confirmed that these phenotypes are tightly linked to
rbr-2(
tm1231). However, a second allele of
rbr-2,
ok2544, did not become progressively sterile at 25 deg C and did not confer small or multivulval phenotypes. Thus, some phenotypes observed for
tm1231 are either allele specific or due to a tightly linked additional mutation(s).