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Conserved Genetic Interactions between Ciliopathy Complexes Cooperatively Support Ciliogenesis and Ciliary Signaling.

Yee LE, Garcia-Gonzalo FR, Bowie RV, Li C, Kennedy JK, Ashrafi K, Blacque OE, Leroux MR, Reiter JF - PLoS Genet. (2015)

Bottom Line: Similarly, disruption of an NPHP complex component and the BBS complex component BBS-5 individually did not compromise ciliary structure, but together did.However, disrupting both Tctn1 and either Nphp1 or Nphp4 exacerbated defects in ciliogenesis and cilia-associated developmental signaling, as did disrupting both Tctn1 and the BBSome component Bbs1.Thus, we demonstrate that ciliary complexes act in parallel to support ciliary function and suggest that human ciliopathy phenotypes are altered by genetic interactions between different ciliary biochemical complexes.

View Article: PubMed Central - PubMed

Affiliation: Department of Biochemistry and Biophysics, University of California, San Francisco, San Francisco, California, United States of America.

ABSTRACT
Mutations in genes encoding cilia proteins cause human ciliopathies, diverse disorders affecting many tissues. Individual genes can be linked to ciliopathies with dramatically different phenotypes, suggesting that genetic modifiers may participate in their pathogenesis. The ciliary transition zone contains two protein complexes affected in the ciliopathies Meckel syndrome (MKS) and nephronophthisis (NPHP). The BBSome is a third protein complex, affected in the ciliopathy Bardet-Biedl syndrome (BBS). We tested whether mutations in MKS, NPHP and BBS complex genes modify the phenotypic consequences of one another in both C. elegans and mice. To this end, we identified TCTN-1, the C. elegans ortholog of vertebrate MKS complex components called Tectonics, as an evolutionarily conserved transition zone protein. Neither disruption of TCTN-1 alone or together with MKS complex components abrogated ciliary structure in C. elegans. In contrast, disruption of TCTN-1 together with either of two NPHP complex components, NPHP-1 or NPHP-4, compromised ciliary structure. Similarly, disruption of an NPHP complex component and the BBS complex component BBS-5 individually did not compromise ciliary structure, but together did. As in nematodes, disrupting two components of the mouse MKS complex did not cause additive phenotypes compared to single mutants. However, disrupting both Tctn1 and either Nphp1 or Nphp4 exacerbated defects in ciliogenesis and cilia-associated developmental signaling, as did disrupting both Tctn1 and the BBSome component Bbs1. Thus, we demonstrate that ciliary complexes act in parallel to support ciliary function and suggest that human ciliopathy phenotypes are altered by genetic interactions between different ciliary biochemical complexes.

No MeSH data available.


Related in: MedlinePlus

C. elegans NPHP genes synthetically interact with bbs-5 to affect ciliary structure.(A) Dye filling of amphid neurons in L4 nematodes in single transition zone mutants (left column) and bbs-5 double mutants (right column). Lateral views, with anterior to the left. Scale bar, 20 μm. (B) Fluorescence intensity of DiI filled amphid neurons relative to wild type. Genotypes including an allele affecting an MKS complex component are indicated in green. Genotypes including an allele affecting an NPHP complex component are indicated in red. Error bars represent the standard deviation. Statistical significance according to unpaired Student’s t-tests (* p<0.001; ** p<0.001 compared to bbs-5). (C) Low and high magnification TEM cross-sections of the distal segment, middle segment, transition zone (TZ), and PCMC of amphid cilia with schematics below (lateral and transverse views). bbs-5 mutants display normal ciliary structures, including intact Y-links (green arrowheads). bbs-5; nphp-4 mutant cilia display open B-tubules (yellow arrowheads), reduced Y-links (red arrowheads) and vesicle accumulation in the PCMC (purple arrows) similar to nphp-4 cilia, but have fewer axonemes that fully extend distally in both pores. Boxed numbers indicate distances (μm) from the distal ciliary tips. Scale bars,100 nm.
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pgen.1005627.g004: C. elegans NPHP genes synthetically interact with bbs-5 to affect ciliary structure.(A) Dye filling of amphid neurons in L4 nematodes in single transition zone mutants (left column) and bbs-5 double mutants (right column). Lateral views, with anterior to the left. Scale bar, 20 μm. (B) Fluorescence intensity of DiI filled amphid neurons relative to wild type. Genotypes including an allele affecting an MKS complex component are indicated in green. Genotypes including an allele affecting an NPHP complex component are indicated in red. Error bars represent the standard deviation. Statistical significance according to unpaired Student’s t-tests (* p<0.001; ** p<0.001 compared to bbs-5). (C) Low and high magnification TEM cross-sections of the distal segment, middle segment, transition zone (TZ), and PCMC of amphid cilia with schematics below (lateral and transverse views). bbs-5 mutants display normal ciliary structures, including intact Y-links (green arrowheads). bbs-5; nphp-4 mutant cilia display open B-tubules (yellow arrowheads), reduced Y-links (red arrowheads) and vesicle accumulation in the PCMC (purple arrows) similar to nphp-4 cilia, but have fewer axonemes that fully extend distally in both pores. Boxed numbers indicate distances (μm) from the distal ciliary tips. Scale bars,100 nm.

Mentions: To test for genetic interactions between bbs-5 and transition zone genes, we examined dye filling in double mutants for bbs-5 and MKS complex genes or NPHP complex genes. bbs-5; tctn-1 and bbs-5; mksr-1 double mutants dye filled to the same extent as their single mutant counterparts, revealing no genetic interaction between bbs-5 and MKS complex genes (Fig 4A and 4B). In contrast, dye filling in bbs-5; nphp-4 and bbs-5; nphp-1 double mutants was dramatically decreased compared to their respective single mutants (Fig 4A and 4B). Therefore, BBS-5 and NPHP complex components have overlapping functions in supporting C. elegans ciliary integrity. The finding that bbs-5 synthetically interacts with NPHP complex genes but not MKS complex genes further suggests that the NPHP and MKS complexes perform distinct roles.


Conserved Genetic Interactions between Ciliopathy Complexes Cooperatively Support Ciliogenesis and Ciliary Signaling.

Yee LE, Garcia-Gonzalo FR, Bowie RV, Li C, Kennedy JK, Ashrafi K, Blacque OE, Leroux MR, Reiter JF - PLoS Genet. (2015)

C. elegans NPHP genes synthetically interact with bbs-5 to affect ciliary structure.(A) Dye filling of amphid neurons in L4 nematodes in single transition zone mutants (left column) and bbs-5 double mutants (right column). Lateral views, with anterior to the left. Scale bar, 20 μm. (B) Fluorescence intensity of DiI filled amphid neurons relative to wild type. Genotypes including an allele affecting an MKS complex component are indicated in green. Genotypes including an allele affecting an NPHP complex component are indicated in red. Error bars represent the standard deviation. Statistical significance according to unpaired Student’s t-tests (* p<0.001; ** p<0.001 compared to bbs-5). (C) Low and high magnification TEM cross-sections of the distal segment, middle segment, transition zone (TZ), and PCMC of amphid cilia with schematics below (lateral and transverse views). bbs-5 mutants display normal ciliary structures, including intact Y-links (green arrowheads). bbs-5; nphp-4 mutant cilia display open B-tubules (yellow arrowheads), reduced Y-links (red arrowheads) and vesicle accumulation in the PCMC (purple arrows) similar to nphp-4 cilia, but have fewer axonemes that fully extend distally in both pores. Boxed numbers indicate distances (μm) from the distal ciliary tips. Scale bars,100 nm.
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pgen.1005627.g004: C. elegans NPHP genes synthetically interact with bbs-5 to affect ciliary structure.(A) Dye filling of amphid neurons in L4 nematodes in single transition zone mutants (left column) and bbs-5 double mutants (right column). Lateral views, with anterior to the left. Scale bar, 20 μm. (B) Fluorescence intensity of DiI filled amphid neurons relative to wild type. Genotypes including an allele affecting an MKS complex component are indicated in green. Genotypes including an allele affecting an NPHP complex component are indicated in red. Error bars represent the standard deviation. Statistical significance according to unpaired Student’s t-tests (* p<0.001; ** p<0.001 compared to bbs-5). (C) Low and high magnification TEM cross-sections of the distal segment, middle segment, transition zone (TZ), and PCMC of amphid cilia with schematics below (lateral and transverse views). bbs-5 mutants display normal ciliary structures, including intact Y-links (green arrowheads). bbs-5; nphp-4 mutant cilia display open B-tubules (yellow arrowheads), reduced Y-links (red arrowheads) and vesicle accumulation in the PCMC (purple arrows) similar to nphp-4 cilia, but have fewer axonemes that fully extend distally in both pores. Boxed numbers indicate distances (μm) from the distal ciliary tips. Scale bars,100 nm.
Mentions: To test for genetic interactions between bbs-5 and transition zone genes, we examined dye filling in double mutants for bbs-5 and MKS complex genes or NPHP complex genes. bbs-5; tctn-1 and bbs-5; mksr-1 double mutants dye filled to the same extent as their single mutant counterparts, revealing no genetic interaction between bbs-5 and MKS complex genes (Fig 4A and 4B). In contrast, dye filling in bbs-5; nphp-4 and bbs-5; nphp-1 double mutants was dramatically decreased compared to their respective single mutants (Fig 4A and 4B). Therefore, BBS-5 and NPHP complex components have overlapping functions in supporting C. elegans ciliary integrity. The finding that bbs-5 synthetically interacts with NPHP complex genes but not MKS complex genes further suggests that the NPHP and MKS complexes perform distinct roles.

Bottom Line: Similarly, disruption of an NPHP complex component and the BBS complex component BBS-5 individually did not compromise ciliary structure, but together did.However, disrupting both Tctn1 and either Nphp1 or Nphp4 exacerbated defects in ciliogenesis and cilia-associated developmental signaling, as did disrupting both Tctn1 and the BBSome component Bbs1.Thus, we demonstrate that ciliary complexes act in parallel to support ciliary function and suggest that human ciliopathy phenotypes are altered by genetic interactions between different ciliary biochemical complexes.

View Article: PubMed Central - PubMed

Affiliation: Department of Biochemistry and Biophysics, University of California, San Francisco, San Francisco, California, United States of America.

ABSTRACT
Mutations in genes encoding cilia proteins cause human ciliopathies, diverse disorders affecting many tissues. Individual genes can be linked to ciliopathies with dramatically different phenotypes, suggesting that genetic modifiers may participate in their pathogenesis. The ciliary transition zone contains two protein complexes affected in the ciliopathies Meckel syndrome (MKS) and nephronophthisis (NPHP). The BBSome is a third protein complex, affected in the ciliopathy Bardet-Biedl syndrome (BBS). We tested whether mutations in MKS, NPHP and BBS complex genes modify the phenotypic consequences of one another in both C. elegans and mice. To this end, we identified TCTN-1, the C. elegans ortholog of vertebrate MKS complex components called Tectonics, as an evolutionarily conserved transition zone protein. Neither disruption of TCTN-1 alone or together with MKS complex components abrogated ciliary structure in C. elegans. In contrast, disruption of TCTN-1 together with either of two NPHP complex components, NPHP-1 or NPHP-4, compromised ciliary structure. Similarly, disruption of an NPHP complex component and the BBS complex component BBS-5 individually did not compromise ciliary structure, but together did. As in nematodes, disrupting two components of the mouse MKS complex did not cause additive phenotypes compared to single mutants. However, disrupting both Tctn1 and either Nphp1 or Nphp4 exacerbated defects in ciliogenesis and cilia-associated developmental signaling, as did disrupting both Tctn1 and the BBSome component Bbs1. Thus, we demonstrate that ciliary complexes act in parallel to support ciliary function and suggest that human ciliopathy phenotypes are altered by genetic interactions between different ciliary biochemical complexes.

No MeSH data available.


Related in: MedlinePlus