PgmNr W4018: PAM-1, the C. elegans ortholog of the puromycin sensitive aminopeptidase, and autophagy pathways genetically collaborate to regulate gametogenesis.

Authors:
A. Munie; A. Cude; C. Trzepacz


Institutes
Murray State University, Murray, KY.


Keyword: Gametogenesis, Fertilization, Egg-embryo transition

Abstract:

Autophagy, the cell's recycling system, is a highly conserved and regulated biological process. Autophagy normally functions as a housekeeping role and is utilized to remove any damaged, malfunctioning, or unnecessary organelles, but can be stimulated in times of cellular stress. Starvation, hypoxia, and the accumulation of cytotoxic aggregates, such as those linked to neurodegenerative disorders such as Huntington's and Alzheimer's disease, are all remediated by autophagic mechanisms. Studies in a number of model organisms, including mice, fruit flies, and nematodes have identified numerous genes involved in mediating autophagy, including the Puromycin-sensitive aminopeptidase (Psa). The Caenorhabditis elegans orthologue of Psa, pam-1,  governs fertility in the nematode. The gonads of adult worms harboring mutant pam-1 alleles display several pheotypes indicating compromised worm gametogenesis, including a decreased brood size, increased embryonic lethality, and an expansion of the population of immature pachytene stage germinal nuclei toward the proximal end of the gonad. Because PAM-1 also functions in autophagic pathways, we examined the reciprocal involvement of autophagy in gametogenesis.

RNAi was employed to independently inhibit the expression of five conserved C. elegans autophagy genes: ATG5/bec-1, ATG8/lgg-1. ATG7/atg-7, ATG18/atg-18, and VPS-34/vps-34, in both wild-type N2 and pam-1 strains,  and adult animals were examined for changes in pam-1-influenced phenotype metrics. Inhibition of vps-34 in N2 animals had a statistically significant effect on pachytene expansion; RNAi of the remaining autophagy genes had no discernible impact on the N2 aniamls. However, the independent inhibition of each of the autophagy genes in mutant pam-1 animals results in a synergistic exacerbation of multiple fertility metrics, most consistently an expansion of the pachytene population. We are currently employing fluorescently-labelled transgenes to examine the colocalization of PAM-1 and the autophagy machinery in the gonad. Our data suggests a novel collaboration of PAM-1. and autophagy functions in mediating meiotic transitions and fertility in C. elegans.



Wormbase Genetic Index
1. pam-1
2. bec-1
3. lgg-1
4. atg-18
5. atg-7
6. vps-32