Characterization of nurf-1 mutation in suppressing of top-2-induced embryonic lethality in C. elegans
Date
2022-05
Authors
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Publisher
University of Delaware
Abstract
The nurf-1 gene in Caenorhabditis elegans is a Nucleosome Remodeling
Factor (NURF) subunit that has crucial roles in chromatin remodeling and
transcription regulation. nurf-1 null mutations cause severe defects in germline cells
and lead to embryonic lethality. However, a previous study from our lab showed that
nurf-1 with a single missense mutation that changes the glutamate on position 1954 to
a lysine [E1954K] was involved in rescuing embryonic lethality induced by a mutation
of the topoisomerase II enzyme [top-2(it7)]. Here, top-2(it7) is a temperature-sensitive
allele, which contains a single missense mutation [R828C] that causes severe defects
in chromosomal segregation during spermatogenesis. In fact, nurf-1[E1954K] was
found to suppress the top-2-induced embryonic lethality only in conjunction with
another mutation in a gene called mep-1, which encodes a zinc-finger protein that is a
part of chromatin remodeling complex. Bhandari et. al., 2020 found that the
suppressing mutation mep-1(ude14) is a single missense mutation [G57D]. In order to
begin to elucidate the mechanism of this co-suppression, I started this study by
characterizing two nurf-1 mutants, which includes a deletion allele (n4293) and
through the recreation of the single missense mutation [E1952K] (1954 to 1952
change is due to a different nurf-1 isoform). The suppressor mutation was recreated in
a wild-type background using the CRISPR-Cas9 genome editing technique [nurf-1(ude34)]. The percent embryonic viability in each genotype was determined through
an embryonic viability assay. In addition, the gonads in both hermaphrodites and males in each genotype were observed using whole-mount DAPI staining. We
confirmed the severe defects and sterility of the homozygous nurf-1 deletion in
hermaphrodites. However, no germ line defects were observed in the nurf-1(ude34)
[E1952K] hermaphrodites or males. Also, the suppressor allele nurf-1(ude34)
[E1952K] showed no significant difference in the percent embryonic viability
compared to the wild-type control group. These results indicate that this single
missense mutation of nurf-1(ude34) [E1952K] does not have meiotic phenotype when
in isolation. The mechanism of co-suppression of nurf-1 and mep-1 on the top-2-
induced embryonic lethality might be direct or indirect. A combination of the induced
single missense mutation of both nurf-1 and mep-1 will be analyzed in future studies.
Moreover, further structure-function analyses will help elucidate details of the roles of
both nurf-1 and mep-1 during meiosis as well as their co-suppression mechanism at a
molecular level.
Description
Keywords
Mutation, Gene, Embryonic viability