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Rec-8 dimorphism affects longevity, stress resistance and X-chromosome nondisjunction in C. elegans, and replicative lifespan in S. cerevisiae.

Ayyadevara S, Tazearslan C, Alla R, Jiang JC, Jazwinski SM, Shmookler Reis RJ - Front Genet (2014)

Bottom Line: A single gene in this interval is now shown to modulate all lsq4-associated traits.Full-genome analysis of transcript levels indicates that lsq4 contains a dimorphic gene governing the expression of many sperm-specific genes, suggesting an effect on spermatogenesis.Fourteen "dual-candidate" genes, implicated by both position and expression, were tested for RNA-interference effects on QTL-linked traits.

View Article: PubMed Central - PubMed

Affiliation: Central Arkansas Veterans Healthcare System, VA Medical Center Little Rock, AR, USA ; Department of Geriatrics, University of Arkansas for Medical Sciences Little Rock, AR, USA.

ABSTRACT
A quantitative trait locus (QTL) in the nematode C. elegans, "lsq4," was recently implicated by mapping longevity genes. QTLs for lifespan and three stress-resistance traits coincided within a span of <300 kbp, later narrowed to <200 kbp. A single gene in this interval is now shown to modulate all lsq4-associated traits. Full-genome analysis of transcript levels indicates that lsq4 contains a dimorphic gene governing the expression of many sperm-specific genes, suggesting an effect on spermatogenesis. Quantitative analysis of allele-specific transcripts encoded within the lsq4 interval revealed significant, 2- to 15-fold expression differences for 10 of 33 genes. Fourteen "dual-candidate" genes, implicated by both position and expression, were tested for RNA-interference effects on QTL-linked traits. In a strain carrying the shorter-lived allele, knockdown of rec-8 (encoding a meiotic cohesin) reduced its transcripts 4-fold, to a level similar to the longer-lived strain, while extending lifespan 25-26%, whether begun before fertilization or at maturity. The short-lived lsq4 allele also conferred sensitivity to oxidative and thermal stresses, and lower male frequency (reflecting X-chromosome non-disjunction), traits reversed uniquely by rec-8 knockdown. A strain bearing the longer-lived lsq4 allele, differing from the short-lived strain at <0.3% of its genome, derived no lifespan or stress-survival benefit from rec-8 knockdown. We consider two possible explanations: high rec-8 expression may include increased "leaky" expression in mitotic cells, leading to deleterious destabilization of somatic genomes; or REC-8 may act entirely in germ-line meiotic cells to reduce aberrations such as non-disjunction, thereby blunting a stress-resistance response mediated by innate immunity. Replicative lifespan was extended 20% in haploid S. cerevisiae (BY4741) by deletion of REC8, orthologous to nematode rec-8, implying that REC8 disruption of mitotic-cell survival is widespread, exemplifying antagonistic pleiotropy (opposing effects on lifespan vs. reproduction), and/or balancing selection wherein genomic disruption increases genetic variation under harsh conditions.

No MeSH data available.


Related in: MedlinePlus

Rec-8 knockdown extends lifespan, dependent on genetic background in the lsq4 region. Groups of 35 worms were fed on bacteria induced to express the indicated dsRNA (or empty expression vector) continuously from the L4/adult molt (A,B) to avoid possible developmental effects, or initiated with the L4/adult molt of the parents of tested worms (C,D) to maximize knockdown. Lifespan survivals were monitored as described (see Methods). Of the indicated genes targeted by dsRNAs, only K09B11.5 had been found to be expressed at higher levels in CL2a, the longer-lived strain, and thus predicted to possibly reduce CL2a longevity; the other 4 genes were expressed at higher levels in SR708, and thus were predicted to extend survival of treated SR708, if causal to the QTL effect on longevity. (A,C) Lifespan survivals of control vs. dsRNA-treated SR708 adults; (B,D) Lifespan survivals of control and dsRNA-treated CL2a adults.
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Figure 1: Rec-8 knockdown extends lifespan, dependent on genetic background in the lsq4 region. Groups of 35 worms were fed on bacteria induced to express the indicated dsRNA (or empty expression vector) continuously from the L4/adult molt (A,B) to avoid possible developmental effects, or initiated with the L4/adult molt of the parents of tested worms (C,D) to maximize knockdown. Lifespan survivals were monitored as described (see Methods). Of the indicated genes targeted by dsRNAs, only K09B11.5 had been found to be expressed at higher levels in CL2a, the longer-lived strain, and thus predicted to possibly reduce CL2a longevity; the other 4 genes were expressed at higher levels in SR708, and thus were predicted to extend survival of treated SR708, if causal to the QTL effect on longevity. (A,C) Lifespan survivals of control vs. dsRNA-treated SR708 adults; (B,D) Lifespan survivals of control and dsRNA-treated CL2a adults.

Mentions: In an initial screen for effects of RNA interference on lifespan, genes in the lsq4 interval were selected for RNAi suppression of expression in either parental strain CL2a or the recombinant line SR708 (differing from CL2a by insertion of the Bergerac-BO-derived lsq4 allele); positive or suggestive results were repeated multiple times (Table 4). Significant lifespan extension (P < 0.0006 to P < 4 × 10−5 prior to correction for multiple measures) was seen only for RNA interference targeting rec-8, and only in the SR708 line. Table 4 summarizes data from three independent survivals, in which rec-8 dsRNA treatment increased the longevity of SR708 worms to roughly the same level as CL2a (with or without dsRNA). Two of these survival experiments are illustrated in Figure 1. In Figure 1A, mean adult lifespan at 20°C was extended 26%, from 13.5 ± 0.7 d (mean ± s.e.m.) for SR708 adults fed bacteria carrying an empty dsRNA expression vector, to 17.0 ± 0.9 d for those exposed to rec-8 dsRNA (Cox-Mantel P < 0.0004). Note that inclusion of the period of larval development would add 2.5 days to the adult lifespan for each strain, to obtain the “total lifespan” more commonly shown. In contrast, the mean adult longevity of strain CL2a, 16.2 ± 0.9 d, was not shifted significantly (<3% change) as a result of any dsRNA treatment (Figure 1B and Table 4). In this experiment, RNA interference began at the L4/adult molt to avoid embryonic lethality as reported previously (Pasierbek et al., 2001). A very similar life extension relative to empty-vector control (25%, P < 4 × 10−5), however, was obtained in a second experiment wherein dsRNA treatment began in the parental generation (Figures 1C,D, and Table 4) to maximize the impact of knockdown. This resulted in substantial but transient embryonic lethality (Pasierbek et al., 2001), but no subsequent impairment in worms that completed embryogenesis. A third experiment also confirmed significant life extension by rec-8 (Table 4; P < 0.0006), but calculation of the mean age at death was complicated by censorship of worms lost due to burrowing in the agar. The other genes tested here (described briefly in Table 2 and Discussion) did not significantly affect longevity.


Rec-8 dimorphism affects longevity, stress resistance and X-chromosome nondisjunction in C. elegans, and replicative lifespan in S. cerevisiae.

Ayyadevara S, Tazearslan C, Alla R, Jiang JC, Jazwinski SM, Shmookler Reis RJ - Front Genet (2014)

Rec-8 knockdown extends lifespan, dependent on genetic background in the lsq4 region. Groups of 35 worms were fed on bacteria induced to express the indicated dsRNA (or empty expression vector) continuously from the L4/adult molt (A,B) to avoid possible developmental effects, or initiated with the L4/adult molt of the parents of tested worms (C,D) to maximize knockdown. Lifespan survivals were monitored as described (see Methods). Of the indicated genes targeted by dsRNAs, only K09B11.5 had been found to be expressed at higher levels in CL2a, the longer-lived strain, and thus predicted to possibly reduce CL2a longevity; the other 4 genes were expressed at higher levels in SR708, and thus were predicted to extend survival of treated SR708, if causal to the QTL effect on longevity. (A,C) Lifespan survivals of control vs. dsRNA-treated SR708 adults; (B,D) Lifespan survivals of control and dsRNA-treated CL2a adults.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4120681&req=5

Figure 1: Rec-8 knockdown extends lifespan, dependent on genetic background in the lsq4 region. Groups of 35 worms were fed on bacteria induced to express the indicated dsRNA (or empty expression vector) continuously from the L4/adult molt (A,B) to avoid possible developmental effects, or initiated with the L4/adult molt of the parents of tested worms (C,D) to maximize knockdown. Lifespan survivals were monitored as described (see Methods). Of the indicated genes targeted by dsRNAs, only K09B11.5 had been found to be expressed at higher levels in CL2a, the longer-lived strain, and thus predicted to possibly reduce CL2a longevity; the other 4 genes were expressed at higher levels in SR708, and thus were predicted to extend survival of treated SR708, if causal to the QTL effect on longevity. (A,C) Lifespan survivals of control vs. dsRNA-treated SR708 adults; (B,D) Lifespan survivals of control and dsRNA-treated CL2a adults.
Mentions: In an initial screen for effects of RNA interference on lifespan, genes in the lsq4 interval were selected for RNAi suppression of expression in either parental strain CL2a or the recombinant line SR708 (differing from CL2a by insertion of the Bergerac-BO-derived lsq4 allele); positive or suggestive results were repeated multiple times (Table 4). Significant lifespan extension (P < 0.0006 to P < 4 × 10−5 prior to correction for multiple measures) was seen only for RNA interference targeting rec-8, and only in the SR708 line. Table 4 summarizes data from three independent survivals, in which rec-8 dsRNA treatment increased the longevity of SR708 worms to roughly the same level as CL2a (with or without dsRNA). Two of these survival experiments are illustrated in Figure 1. In Figure 1A, mean adult lifespan at 20°C was extended 26%, from 13.5 ± 0.7 d (mean ± s.e.m.) for SR708 adults fed bacteria carrying an empty dsRNA expression vector, to 17.0 ± 0.9 d for those exposed to rec-8 dsRNA (Cox-Mantel P < 0.0004). Note that inclusion of the period of larval development would add 2.5 days to the adult lifespan for each strain, to obtain the “total lifespan” more commonly shown. In contrast, the mean adult longevity of strain CL2a, 16.2 ± 0.9 d, was not shifted significantly (<3% change) as a result of any dsRNA treatment (Figure 1B and Table 4). In this experiment, RNA interference began at the L4/adult molt to avoid embryonic lethality as reported previously (Pasierbek et al., 2001). A very similar life extension relative to empty-vector control (25%, P < 4 × 10−5), however, was obtained in a second experiment wherein dsRNA treatment began in the parental generation (Figures 1C,D, and Table 4) to maximize the impact of knockdown. This resulted in substantial but transient embryonic lethality (Pasierbek et al., 2001), but no subsequent impairment in worms that completed embryogenesis. A third experiment also confirmed significant life extension by rec-8 (Table 4; P < 0.0006), but calculation of the mean age at death was complicated by censorship of worms lost due to burrowing in the agar. The other genes tested here (described briefly in Table 2 and Discussion) did not significantly affect longevity.

Bottom Line: A single gene in this interval is now shown to modulate all lsq4-associated traits.Full-genome analysis of transcript levels indicates that lsq4 contains a dimorphic gene governing the expression of many sperm-specific genes, suggesting an effect on spermatogenesis.Fourteen "dual-candidate" genes, implicated by both position and expression, were tested for RNA-interference effects on QTL-linked traits.

View Article: PubMed Central - PubMed

Affiliation: Central Arkansas Veterans Healthcare System, VA Medical Center Little Rock, AR, USA ; Department of Geriatrics, University of Arkansas for Medical Sciences Little Rock, AR, USA.

ABSTRACT
A quantitative trait locus (QTL) in the nematode C. elegans, "lsq4," was recently implicated by mapping longevity genes. QTLs for lifespan and three stress-resistance traits coincided within a span of <300 kbp, later narrowed to <200 kbp. A single gene in this interval is now shown to modulate all lsq4-associated traits. Full-genome analysis of transcript levels indicates that lsq4 contains a dimorphic gene governing the expression of many sperm-specific genes, suggesting an effect on spermatogenesis. Quantitative analysis of allele-specific transcripts encoded within the lsq4 interval revealed significant, 2- to 15-fold expression differences for 10 of 33 genes. Fourteen "dual-candidate" genes, implicated by both position and expression, were tested for RNA-interference effects on QTL-linked traits. In a strain carrying the shorter-lived allele, knockdown of rec-8 (encoding a meiotic cohesin) reduced its transcripts 4-fold, to a level similar to the longer-lived strain, while extending lifespan 25-26%, whether begun before fertilization or at maturity. The short-lived lsq4 allele also conferred sensitivity to oxidative and thermal stresses, and lower male frequency (reflecting X-chromosome non-disjunction), traits reversed uniquely by rec-8 knockdown. A strain bearing the longer-lived lsq4 allele, differing from the short-lived strain at <0.3% of its genome, derived no lifespan or stress-survival benefit from rec-8 knockdown. We consider two possible explanations: high rec-8 expression may include increased "leaky" expression in mitotic cells, leading to deleterious destabilization of somatic genomes; or REC-8 may act entirely in germ-line meiotic cells to reduce aberrations such as non-disjunction, thereby blunting a stress-resistance response mediated by innate immunity. Replicative lifespan was extended 20% in haploid S. cerevisiae (BY4741) by deletion of REC8, orthologous to nematode rec-8, implying that REC8 disruption of mitotic-cell survival is widespread, exemplifying antagonistic pleiotropy (opposing effects on lifespan vs. reproduction), and/or balancing selection wherein genomic disruption increases genetic variation under harsh conditions.

No MeSH data available.


Related in: MedlinePlus