Evolutionarily conserved genetic interactions between nphp-4 and bbs-5 mutations exacerbate ciliopathy phenotypes.

Area of Science:

• Cell Biology
• Genetics
• Developmental Biology

Background:

• Primary cilia act as sensory and signaling hubs, with distinct protein compositions due to the transition zone (TZ) barrier.
• The BBSome complex facilitates protein transport across the TZ, and mutations in TZ or BBSome proteins cause human ciliopathies.
• Phenotypic variability in ciliopathies, even with identical genetic variants, suggests the influence of modifier genes.

Purpose of the Study:

• To identify potential modifier genes for ciliopathies by screening for novel alleles in Caenorhabditis elegans.
• To investigate the conserved genetic interaction between NPHP4 and BBS5 in various model organisms.

Main Methods:

• Performed a mutagenesis screen in nphp-4 mutant Caenorhabditis elegans to identify novel alleles.
• Generated and analyzed nphp-4;bbs-5 double mutant worms, zebrafish, and mice.
• Utilized conditional alleles to assess the impact of postnatal gene loss in mice.

Main Results:

• A novel allele of bbs-5 was identified, and nphp-4;bbs-5 double mutants exhibited phenotypes not seen in single mutants.
• Genetic interactions between NPHP4 and BBS5 were conserved across C. elegans, zebrafish, and mice.
• Nphp4;bbs-5 double mutant mice showed reduced viability and survival, indicating a synergistic genetic interaction.

Conclusions:

• BBS5 acts as a modifier of NPHP4, and this genetic interaction is evolutionarily conserved.
• Disruption of the NPHP4-BBS5 interaction likely exacerbates ciliopathy phenotypes through compromised ciliary signaling.
• These findings provide insights into the genetic basis of phenotypic variability observed in human ciliopathies.