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. 2019 Mar 7;9(3):901-909.
doi: 10.1534/g3.118.200863.

The mir-35 Family Links Maternal Germline Sex to Embryonic Viability in Caenorhabditis elegans

Lars Kristian Benner  1 , Katherine Perkins Prothro  1 , Katherine McJunkin  2
Affiliations

The mir-35 Family Links Maternal Germline Sex to Embryonic Viability in Caenorhabditis elegans

Lars Kristian Benner et al. G3 (Bethesda). .

Abstract

The germline sex determination pathway in C. elegans determines whether germ cells develop as oocytes or sperm, with no previously known effect on viability. The mir-35 family of microRNAs are expressed in the C. elegans germline and embryo and are essential for both viability and normal hermaphroditic sex determination, preventing aberrant male gene expression in XX hermaphrodite embryos. Here we show that combining feminizing mutations with partial loss of function of the mir-35 family results in enhanced penetrance embryonic lethality that preferentially kills XO animals. This lethal phenotype is due to altered signaling through the germline sex determination pathway, and maternal germline feminization is sufficient to induce enhanced lethality. These findings reveal a surprising pleiotropy of sperm-fate promoting pathways on organismal viability. Overall, our results demonstrate an unexpectedly strong link between sex determination and embryonic viability, and suggest that in wild type animals, mir-35 family members buffer against misregulation of pathways outside the sex determination program, allowing for clean sex reversal rather than deleterious effects of perturbing sex determination genes.

Keywords: Genetics of Sex; XO lethality; embryogenesis; germline sex determination; microRNAs; sex determination.

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Figures

Figure 1
Figure 1
SUP-26 promotes embryonic viability in mir-35-41(nDf50). A) A schematic of the principal genetic interactions of sex determination pathway genes in C. elegans. Genes in blue are highly active in the male soma and germline, and the spermatogenic germ cells in hermaphrodites. Genes in red are highly active specifically in the hermaphrodite soma and oogenic germ cells. Germline-specific factors are in boxes. B) Percent lethality at embryonic or early larval stages. sup-26(RNAi) has no effect on wild type, but induces synthetic lethality in mir-35-41(nDf50). C) Percent lethality at embryonic or early larval stages. sup-26(lf) alleles enhance lethality in mir-35-41(nDf50). Mean and standard error for three to four biological replicates are shown.
Figure 2
Figure 2
Feminizing mutations enhance lethality in mir-35-41(nDf50) XX animals. A) Top: schematic of crosses performed to generate progeny scored in graph. All males were XX males generated via null mutations in tra-2 and xol-1. XX males were crossed to XX hermaphrodites or females of the three indicated genotypes. Bottom: percent lethality of progeny of crosses illustrated in schematic. The crosses were conducted on RNAi plates, so RNAi affects the maternal and zygotic contribution of sup-26 in the progeny. Sup-26(RNAi) and tra-2(e2020gf) enhance XX lethality in mir-35-41(nDf50). Alleles used are tra-2(e1095lf), tra-2(e2020gf), xol-1(y9). B-C) Percent lethality in mir-35-41(nDf50) combined with her-1(null) or tra-1 or tra-2 RNAi. Mean and standard error for three to four biological replicates are shown.
Figure 3
Figure 3
Feminizing mutations preferentially enhance mir-35-41(nDf50) lethality in males. A) Percent dead/arrested, male or hermaphrodite progeny in a high-incidence-of-males (him) background. Sup-26(RNAi) reduces the proportion of males among surviving animals. B) Top: Schematic of crosses performed to generate progeny scored in graph. The crosses were conducted on RNAi plates, so RNAi affects the maternal and zygotic contribution of sup-26 in the progeny. Males of the same genotype were used for all crosses in order to compare equal dosage of tra-2(e2020gf) across different mir-35-41 genotypes. Colored text highlights functional genetic differences between genotypes. Sup-26(RNAi) and tra-2(e2020gf) preferentially enhance male lethality in mir-35-41(nDf50). C) Top: Schematic of cross with recessive X-linked marker (lon-2(e678)) to assess potential somatic feminization of XO cross progeny. Bottom: Percent of progeny. The rare Lon hermaphrodites likely represent self-progeny (also see methods). In addition to progeny shown, two males were scored as non-Lon on empty vector RNAi. Sup-26(RNAi) does not increase the apparent proportion of somatically feminized XO animals (Lon hermaphrodites).
Figure 4
Figure 4
XO karyotype underlies preferential death of males in feminized mir-35-41(nDf50) animals. A) Schematic of cross. Males contain a GFP-marked nT1 balancer and an X-linked mCherry transgene which aid in distinguishing fem-3 genotype and number of X chromosomes in progeny. B) Percent of progeny from crosses in each category. Dead/arrested embryos and larvae were not scored for fluorescent markers, and thus are likely a mixture of genotypes. C) XO:XX ratios in populations of progeny from crosses. Corrected values assume that differences in XO:XX ratio in nT1+ and nT1- population in the control mir-35-41(nDf50); fem-3(wild type) cross are due to non-Mendelian segregation of the nT1 balancer.
Figure 5
Figure 5
Feminization of the germline causes preferential death of mir-35-41(nDf50) males, and this is a maternal effect. A) Percent dead/arrested, male or female progeny in a fog-2(q71) background, with wild type or deleted mir-35-41. B) Percent dead/arrested, male or female progeny. Top bar: both parents are mir-35-41(nDf50); fog-2(q71). Bottom bar: mother is mir-35-41(nDf50); fog-2(q71). Father is mir-35-41(nDf50); fog-2(wild type). C) Top: Schematic of cross. Males also contained a GFP integrated transgene to prevent the scoring of self progeny. Bottom: Percent dead/arrested, male or female progeny.
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References

    1. Abbott A. L., Alvarez-Saavedra E., Miska E. A., Lau N. C., Bartel D. P., et al. , 2005. The let-7 MicroRNA family members mir-48, mir-84, and mir-241 function together to regulate developmental timing in Caenorhabditis elegans. Dev. Cell 9: 403–414. 10.1016/j.devcel.2005.07.009 - DOI - PMC - PubMed
    1. Alvarez-Saavedra E., Horvitz H. R., 2010. Many families of C. elegans microRNAs are not essential for development or viability. Curr. Biol. 20: 367–373. 10.1016/j.cub.2009.12.051 - DOI - PMC - PubMed
    1. Aoki S. T., Porter D. F., Prasad A., Wickens M., Bingman C. A., et al. , 2018. An RNA-Binding Multimer Specifies Nematode Sperm Fate. Cell Reports 23: 3769–3775. 10.1016/j.celrep.2018.05.095 - DOI - PMC - PubMed
    1. Bartel D. P., 2009. MicroRNAs: target recognition and regulatory functions. Cell 136: 215–233. 10.1016/j.cell.2009.01.002 - DOI - PMC - PubMed
    1. Bender L. B., Cao R., Zhang Y., Strome S., 2004. The MES-2/MES-3/MES-6 Complex and Regulation of Histone H3 Methylation in C. elegans. Curr. Biol. 14: 1639–1643. 10.1016/j.cub.2004.08.062 - DOI - PubMed

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