A fln-2 mutation affects lethal pathology and lifespan in C. elegans

Abstract

Differences in genetic background in model organisms can have complex effects on phenotypes of interest. We previously reported a difference in hermaphrodite lifespan between two wild-type lines widely used by C. elegans researchers (N2 hermaphrodite and male stocks). Here, using pathology-based approaches and genome sequencing, we identify the cause of this difference as a nonsense mutation in the filamin gene fln-2 in the male stock, which reduces early mortality caused by pharyngeal infection. We show how fln-2 variation explains previous discrepancies involving effects of sir-2.1 (sirtuin deacetylase) on ageing, and show that in a fln-2(+) background, sir-2.1 over-expression causes an FUDR (DNA synthesis inhibitor)-dependent reduction in pharyngeal infection and increase in lifespan. In addition we show how fln-2 variation confounds effects on lifespan of daf-2 (insulin/IGF-1 signalling), daf-12 (steroid hormone signalling), and eat-2 (putative dietary restriction). These findings underscore the importance of identifying and controlling genetic background variation.

Mutation of daf‐2 extends lifespan via tissue‐specific effectors that suppress distinct life‐limiting pathologies

“…Trials were conducted at 15˚C and 20˚C, which are permissive for development, and at 25˚C which induces dauer entry during development and dauer‐like behavior in class 2 daf ‐ 2 mutant adults. All alleles were crossed into a fln ‐ 2( + ) background to avoid the confounding effects of the fln ‐ 2(ot611) mutation, which reduces P frequency (Zhao et al, 2019). The resulting, deconvolved data includes survival data for the whole population, and for P and p subpopulations, plus the proportion of P deaths.…”

“…Trials were performed at 25˚C and the class 1 allele daf ‐ 2(m41) and class 2 allele daf ‐ 2(e1370) were included, to be comparable to the original study in which effects on lifespan of allele class‐specific interactions between daf ‐ 2 and daf ‐ 12 were described (Larsen et al, 1995); we also included an additional class 1 allele, daf ‐ 2(e1368) . We recently reported that, when confounding effects of fln ‐ 2 are excluded, daf ‐ 12(m20) modestly reduces daf ‐ 2(m41) lifespan by increasing P death frequency (Zhao et al, 2019). In the present study, necropsy analysis revealed that daf ‐ 12(m20) increases P frequency in both wild type and class 1 but not class 2 daf ‐ 2 mutant backgrounds (Figure 6a–c).…”

“…This mutation confounded previous comparisons of daf ‐ 2 ; fln ‐ 2 + vs daf ‐ 2 ; + daf ‐ 12 leading to a false impression that daf ‐ 12(m20) can substantially suppress daf ‐ 2 class 1 Age. However, in the absence of fln ‐ 2 , daf ‐ 12 does still increase P frequency to a smaller extent, and by doing this weakly suppresses class 1 daf ‐ 2 Age (Figure 6a,b) (Zhao et al, 2019). Suppression of class 1 daf ‐ 2 Age by daf ‐ 12 due solely to increased P frequency is consistent with neck‐and‐shoulder type survival curves seen previously (Larsen, 1993) (Figure 3b in that study).…”

“…First, as described previously, mortality deconvolution analysis led to the discovery that the widely used N2 male stock (N2M) distributed by the Caenorhabditis Genetics Center, carries an X‐linked fln ‐ 2(ot611) mutation that increases lifespan by reducing P frequency (Zhao et al, 2019). This mutation confounded previous comparisons of daf ‐ 2 ; fln ‐ 2 + vs daf ‐ 2 ; + daf ‐ 12 leading to a false impression that daf ‐ 12(m20) can substantially suppress daf ‐ 2 class 1 Age.…”

Phenotypic Screening in C. elegans as a Tool for the Discovery of New Geroprotective Drugs

“…For example, the Bristol N2 hermaphrodite strain from CGC is generally considered the wild-type (WT) strain, but in 2018 a user reported that this N2 strain contained the alh-2(ot588) mutation ( ). Recently, the Gems lab reported that the Bristol N2 male stock from CGC contains the fln-2(ot611) mutation [ 166 ]. These findings have been confirmed by our lab (unpublished findings).…”