Male reproductive aging arises via multifaceted mating-dependent sperm and seminal proteome declines, but is postponable in Drosophila

I.S. and S.W. were supported by a Biotechnology and Biological Sciences Research Council (BBSRC) Fellowship to S.W. (BB/K014544/1) and S.W. additionally by a Dresden Senior Fellowship. B.M.K., P.D.C., and R.F. were supported by the Kennedy Trust and John Fell Funds. R.D. was supported by Marie Curie Actions (Grant 655392). B.R.H. was funded by the EP Abraham Cephalosporin-Oxford Graduate Scholarship with additional support from the BBSRC Doctoral Training Programme. M.F.W. was supported by a NIH Grant R01HD038921. Work in the J.S. Laboratory was supported by NIH Grant R15HD080511.Declining ejaculate performance with male age is taxonomically widespread and has broad fitness consequences. Ejaculate success requires fully functional germline (sperm) and soma (seminal fluid) components. However, some aging theories predict that resources should be preferentially diverted to the germline at the expense of the soma, suggesting differential impacts of aging on sperm and seminal fluid and trade-offs between them or, more broadly, be-tween reproduction and lifespan. While harmful effects of male age on sperm are well known, we do not know how much seminal fluid deteriorates in comparison. Moreover, given the predicted trade-offs, it remains unclear whether systemic lifespan-extending inter-ventions could ameliorate the declining performance of the ejacu-late as a whole. Here, we address these problems using Drosophila melanogaster. We demonstrate that seminal fluid deterioration con-tributes to male reproductive decline via mating-dependent mech-anisms that include posttranslational modifications to seminal proteins and altered seminal proteome composition and transfer. Additionally, we find that sperm production declines chronologically with age, invariant to mating activity such that older multiply mated males become infertile principally via reduced sperm transfer and viability. Our data, therefore, support the idea that both germline and soma components of the ejaculate contribute to male reproduc-tive aging but reveal a mismatch in their aging patterns. Our data do not generally support the idea that the germline is prioritized over soma, at least, within the ejaculate. Moreover, we find that lifespan-extending systemic down-regulation of insulin signaling re-sults in improved late-life ejaculate performance, indicating simul-taneous amelioration of both somatic and reproductive aging.Publisher PDFPeer reviewe

Using drosophila melanogaster to discover human disease genes: An educational primer for use with amyotrophic lateral sclerosis modifiers in drosophila reveal the phospholipase d pathway as a potential therapeutic target

Since the dawn of the 20th century, the fruit fly Drosophila melanogaster has been used as a model organism to understand the nature of genes and how they control development, behavior, and physiology. One of the most powerful experimental approaches employed in Drosophila is the forward genetic screen. In the 21st century, genome-wide screens have become popular tools for identifying evolutionarily conserved genes involved in complex human diseases. In the accompanying article Amyotrophic Lateral Sclerosis Modifiers in Drosophila Reveal the Phospholipase D Pathway as a Potential Therapeutic Target, Kankel and colleagues describe a forward genetic modifier screen to discover factors that contribute to the severe neurodegenerative disease amyotrophic lateral sclerosis (ALS). This primer briefly traces the history of genetic screens in Drosophila and introduces students to ALS. We then provide a set of guided reading questions to help students work through the data presented in the research article. Finally, several ideas for literature-based research projects are offered as opportunities for students to expand their appreciation of the potential scope of genetic screens. The primer is intended to help students and instructors thoroughly examine a current study that uses forward genetics in Drosophila to identify human disease genes

iPLA2-VIA is Required for Healthy Aging of Neurons, Muscle, and the Female Germline in Drosophila melanogaster

Neurodegenerative disease (ND) is a growing health burden worldwide, but its causes and treatments remain elusive. Although most cases of ND are sporadic, rare familial cases have been attributed to single genes, which can be investigated in animal models. We have generated a new mutation in the calcium-independent phospholipase A2 (iPLA2) VIA gene CG6718, the Drosophila melanogaster ortholog of human PLA2G6/PARK14, mutations in which cause a suite of NDs collectively called PLA2G6-associated neurodegeneration (PLAN). Our mutants display age-related loss of climbing ability, a symptom of neurodegeneration in flies. Although phospholipase activity commonly is presumed to underlie iPLA2VIA function, locomotor decline in our mutants is rescued by a transgene carrying a serine-to-alanine mutation in the catalytic residue, suggesting that important functional aspects are independent of phospholipase activity. Additionally, we find that iPLA2-VIA knockdown in either muscle or neurons phenocopies locomotor decline with age, demonstrating its necessity in both neuronal and non-neuronal tissues. Furthermore, RNA in situ hybridization shows high endogenous iPLA2-VIA mRNA expression in adult germ cells, and transgenic HA-tagged iPLA2-VIA colocalizes with mitochondria there. Mutant males are fertile with normal spermatogenesis, while fertility is reduced in mutant females. Mutant female germ cells display age-related mitochondrial aggregation, loss of mitochondrial potential, and elevated cell death. These results suggest that iPLA2-VIA is critical for mitochondrial integrity in the Drosophila female germline, which may provide a novel context to investigate its functions with parallels to PLAN

Drosophila Lysophospholipid Acyltransferases Are Specifically Required for Germ Cell Development

Enzymes of the membrane-bound O-acyltransferase (MBOAT) family add fatty acyl chains to a diverse range of protein and lipid substrates. A chromosomal translocation disrupting human MBOAT1 results in a novel syndrome characterized by male sterility and brachydactyly. We have found that the Drosophila homologues of MBOAT1, Oysgedart (Oys), Nessy (Nes), and Farjavit (Frj), are lysophospholipid acyltransferases. When expressed in yeast, these MBOATs esterify specific lysophospholipids preferentially with unsaturated fatty acids. Generating null mutations for each gene allowed us to identify redundant functions for Oys and Nes in two distinct aspects of Drosophila germ cell development. Embryos lacking both oys and nes show defects in the ability of germ cells to migrate into the mesoderm, a process guided by lipid signals. In addition, oys nes double mutant adult males are sterile due to specific defects in spermatid individualization. oys nes mutant testes, as well as single, double, and triple mutant whole adult animals, show an increase in the saturated fatty acid content of several phospholipid species. Our findings suggest that lysophospholipid acyltransferase activity is essential for germline development and could provide a mechanistic explanation for the etiology of the human MBOAT1 mutation