Dose-dependent action of the RNA binding protein FOX-1 to relay X-chromosome number and determine C. elegans sex

  1. Behnom Farboud
  2. Catherine S Novak
  3. Monique Nicoll
  4. Alyssa Quiogue
  5. Barbara J Meyer  Is a corresponding author
  1. Howard Hughes Medical Institute, University of California at Berkeley, United States
  2. Department of Molecular and Cell Biology, University of California at Berkeley, United States
8 figures and 5 additional files

Figures

Overview of the X:A signal and regulatory hierarchy that control sex determination and X-chromosome dosage compensation.

The X:A signal includes a set of genes on X called X-signal elements (XSEs) that repress their direct target gene xol-1 (XO lethal) in a cumulative dose-dependent manner via transcriptional and …

Intron VI is essential for repression of xol-1 by FOX-1.

(A–E) Assays of wild-type xol-1 transgenes and deletion derivatives with different combinations of introns show that removal of intron VI prevents FOX-1 from repressing xol-1. Diagrams on the left …

Figure 2—source data 1

xol-1 transcription is not repressed by high levels of FOX-1.

https://cdn.elifesciences.org/articles/62963/elife-62963-fig2-data1-v3.docx
Figure 3 with 1 supplement
FOX-1 inhibits formation of the active 2.2 kb xol-1 transcript by promoting intron retention and alternative 3' splice acceptor selection.

(A) RNase protection assays show that FOX-1 causes intron VI retention. Shown on the left are diagrams of relevant splice junctions for exon 6 (grey) and coding sequences of exon 7 (blue) that …

Figure 3—figure supplement 1
RNase protection experiments show that FOX-1 promotes intron VI retention and partial exon 7 deletion to inhibit formation of the functional 2.2 kb xol-1 transcript.

(A) Diagram (top) shows the intron and exon structure of xol-1 and the alternative splicing patterns that produce the active 2.2 kb transcript (red dashed line indicating intron VI removal), the …

Intron VI of xol-1 is sufficient to confer FOX-1 repression.

(A) The promoter and 3' UTR of xol-1 are not sufficient for FOX-1 to repress xol-1. Below the diagram of the Pxol-1::lacZ::xol-1 3' UTR reporter transgene (pMN27) are sections of adult gonads from …

Figure 5 with 1 supplement
Purified FOX-1 protein binds in vitro to multiple sites in intron VI using motifs GCAUG and GCACG.

(A) The diagram of intron VI shows the intron VI fragments (A–E) and smaller regions (RNA oligonucleotides B-45 to E-25) tested for direct FOX-1 binding in vitro. Only RNAs from fragments B, C, and …

Figure 5—figure supplement 1
Cross-linking experiments show that FOX-1 binds directly to multiple sites in intron VI.

(A) Graphs show cross-linking experiments comparing binding to 32P-labeled RNA probes of intact intron VI or intron III with different concentrations of purified FOX-1 protein and different cold RNA …

Figure 6 with 2 supplements
FOX-1 binds in vivo to multiple binding sites in xol-1 intron VI using both GCAUG and GCACG motifs to regulate alternative splicing.

The diagram of intron VI (top left) shows locations of the three regions (blue, yellow, and green) shown to exhibit FOX-1 binding in vitro. RNA sequences corresponding to each color-coded region are …

Figure 6—source data 1

Overexpression of ASD-1 kills both XO males and XX hermaphrodites.

https://cdn.elifesciences.org/articles/62963/elife-62963-fig6-data1-v3.docx
Figure 6—figure supplement 1
Brood sizes of XX animals with cis-acting xol-1 mutations in intron VI are consistent with the strain viability.

(A–L) The values in this supplemental figure expand upon the viability information for the same XX genotypes provided in Figure 6. Shown are the average brood sizes and SEM (right side) of xol-1 XX …

Figure 6—figure supplement 2
High FOX-1 levels in XX animals repress xol-1 with multiple low-affinity GCUUG motifs in intron VI.

Diagrams on the left show the configurations of wild-type and mutant motifs in intron VI of XX animals with either two doses of fox-1 (A) or high doses of fox-1 supplied by an integrated array (yIs44

FOX-1 acts in a dose-dependent manner to regulate xol-1 splicing in XX animals and thereby determine sex.

(A–F) Diagrams on the left show sequences for the two different xol-1 intron VI combinations assayed in each cohort of sex-1(RNAi) XX animals to assess the dose-dependence of FOX-1 action in …

Summary of xol-1 splicing regulation by FOX-1 and model for X:A signal assessment.

(A) Summary of xol-1 splicing regulation by FOX-1. Through binding to multiple GCAUG and GCACG motifs in intron VI of xol-1, FOX-1 reduces formation of the male-determining 2.2 kb transcript by …

Additional files

Supplementary file 1

List of primers.

This table includes a complete list of primers.

https://cdn.elifesciences.org/articles/62963/elife-62963-supp1-v3.docx
Supplementary file 2

List of target-specific sequences for guide RNAs used in CriSPR/Cas9 genome editing experiments.

This table lists the gene targets, the target-specific sequence for each Cas9 guide RNA, the figure in which the results are presented, the genomic coordinates corresponding to each guide RNA, and the reference name of each guide. Two guides were used together to delete the fox-1 gene, and two guides were used together to replace sequences within intron VI of xol-1. Coordinates are based on Wbcel235/c11 version of the C. elegans genome.

https://cdn.elifesciences.org/articles/62963/elife-62963-supp2-v3.docx
Supplementary file 3

DNA sequences of repair templates used for CRISPR/Cas9 genome editing experiments.

This table presents information for CRISPR/Cas9 genome editing experiments involving HDR using single-stranded repair templates. The table lists the gene targets that were edited, the figure in which the results are presented, the DNA sequences of the repair template, with SNPs highlighted in red letters and deletion junctions highlighted in blue letters, the reference names of related guides, and the reference names of the oligonucleotide repair template. Two guide RNAs were used together in combination with the repair template to delete the endogenous fox-1 gene, resulting in the allele fox-1(y793). The double-stranded repair templates used for inducing mutations in the DNA encoding intron VI of endogenous xol-1 are available upon request but are too long to include in this table.

https://cdn.elifesciences.org/articles/62963/elife-62963-supp3-v3.docx
Supplementary file 4

List of oligonucleotides used to screen for CRISPR/Cas9 induced mutations and to determine sequences of resulting mutations.

The table lists the gene targets, the figure or table in which the results are presented, the sequences of oligonucleotides used to screen for CRISPR/Cas9 induced mutations or to determine sequences of resulting mutations, the reference name of each oligonucleotide, and the function of each oligonucleotide. For asd-1, the oligos were used to verify the construction of strains built with a pre-existing asd-1 mutation, not for identifying new mutations made using Cas9. The oligonucleotides BF-2507 and BF-2508 were used to synthesize xol-1 repair templates rather than to identify Cas9-induced mutations in intron VI.

https://cdn.elifesciences.org/articles/62963/elife-62963-supp4-v3.docx
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