Alexander, J. et al. (2017) International Worm Meeting "Understanding the Role of xol-1 in C.briggsae Dosage Compensation."

Haag, E., Lo, T., Lee, J., Alexander, J.

[International Worm Meeting, 2017]

Dosage compensation is an essential process in heterogametic organisms where the number of X chromosomes differs between males (XO/XY) and females/hermaphrodites (XX). Dosage compensation ensures that both sexes have equivalent levels of X-linked gene expression regardless of the number of X chromosomes present. This process is not highly conserved. Flies, mammals, and worms all use different mechanisms, therefore, it is necessary to examine more closely related species, such as C. elegans and C. briggsae, to better understand the evolution of dosage compensation. In C. elegans, dosage compensation is mediated by the developmental master switch gene xol-1. The function of xol-1 is conserved between C. elegans and C. briggsae. In both species, loss of xol-1 results in male specific lethality and overexpression results in hermaphrodite specific lethality. To further understand the evolution of xol-1 function, we are performing a C. briggsae xol-1 suppressor screen. C. briggsae xol-1 suppressors will be identified based on their ability to suppress the xol-1 male lethality phenotype. Currently, we are characterizing to newly identified suppressors. We anticipate that these suppressors will belong to one of two classes: (1) C. briggsae homologs of a known C. elegans dosage compensation pathway component or (2) novel suppressors. Novel suppressors will be further examined for a role in dosage compensation in both species. These data will not only further our understanding of C. briggsae dosage compensation, but also provide insights into the evolution of dosage compensation.

Alexander-Floyd, J. et al. (2017) International Worm Meeting "Natural genetic variation modifies polyglutamine aggregation via an imbalance in autophagy."

Gidalevitz, T., Alexander-Floyd, J., Entezari, A.

[International Worm Meeting, 2017]

Many late-onset neurodegenerative diseases, such as Huntington's disease (HD), are caused by aggregation of misfolded proteins. Individuals stricken with these diseases succumb to the detrimental symptoms associated with them. Discovering the cellular and genetic pathways that are protective against protein aggregation will improve our understanding of potential treatments for these diseases. Huntington's disease is associated with aggregation of mutant huntingtin protein, containing an expanded polyglutamine tract. In HD patients, individual's genetic backgrounds can modulate the severity of the disease. However, the variants responsible for modulating disease phenotypes are not known. To ask what natural variant(s) play a role in modifying protein aggregation, we use a C. elegans polyglutamine model expressing a fluorescent 40-glutamine expansion (Q40-YFP) in muscle cells. We have shown that introduction of Q40-YFP into genetically diverse wild strains of C. elegans results in a wide range of phenotypes, from suppression to strong enhancement of Q40-YFP aggregation and toxicity. Here, we have identified a 400kb genetic interval in the DR1350 strain, containing variants that increase polyglutamine aggregation. An RNAi survey of 24 candidate genes in that interval identified atg-5, an important component of autophagy that, when knocked down, rescued the increased aggregation. Interestingly, genome sequencing identified 2 variants within the 3'UTR of atg-5 in the DR1350-derived interval. Animals carrying this interval have increased ATG-5 expression and deficient autophagosome formation. Because autophagy is important for degradation of protein aggregates, we hypothesize that natural variants in the DR1350 genetic background increase polyglutamine aggregation by causing increased levels of ATG-5 expression and thus misregulating autophagosome formation.

Alexander-Floyd J et al. (2020) BMC Biol "Unexpected cell type-dependent effects of autophagy on polyglutamine aggregation revealed by natural genetic variation in C. elegans."

Alexander-Floyd J, Haroon S, Vermulst M, Gidalevitz T, Ying M, Jaeger C, Entezari AA

[BMC Biol, 2020]

BACKGROUND: Monogenic protein aggregation diseases, in addition to cell selectivity, exhibit clinical variation in the age of onset and progression, driven in part by inter-individual genetic variation. While natural genetic variants may pinpoint plastic networks amenable to intervention, the mechanisms by which they impact individual susceptibility to proteotoxicity are still largely unknown. RESULTS: We have previously shown that natural variation modifies polyglutamine (polyQ) aggregation phenotypes in C. elegans muscle cells. Here, we find that a genomic locus from C. elegans wild isolate DR1350 causes two genetically separable aggregation phenotypes, without changing the basal activity of muscle proteostasis pathways known to affect polyQ aggregation. We find that the increased aggregation phenotype was due to regulatory variants in the gene encoding a conserved autophagy protein ATG-5. The atg-5 gene itself conferred dosage-dependent enhancement of aggregation, with the DR1350-derived allele behaving as hypermorph. Surprisingly, increased aggregation in animals carrying the modifier locus was accompanied by enhanced autophagy activation in response to activating treatment. Because autophagy is expected to clear, not increase, protein aggregates, we activated autophagy in three different polyQ models and found a striking tissue-dependent effect: activation of autophagy decreased polyQ aggregation in neurons and intestine, but increased it in the muscle cells. CONCLUSIONS: Our data show that cryptic natural variants in genes encoding proteostasis components, although not causing detectable phenotypes in wild-type individuals, can have profound effects on aggregation-prone proteins. Clinical applications of autophagy activators for aggregation diseases may need to consider the unexpected divergent effects of autophagy in different cell types.

Alexander CC et al. (2021) J Gerontol A Biol Sci Med Sci "HspB1 Overexpression Improves Lifespan and Stress Resistance in an Invertebrate Model."

Lozano D, Fisher AL, Gidalevitz T, Alexander CC, Fraker T, Scheirer J, Holstein D, Munkascy E, Rodriguez KA, Khan M, Tillmon H, Zare H, Lechleiter JD

[J Gerontol A Biol Sci Med Sci, 2021]

To explore the role of the small heat shock protein beta 1 (HspB1, also known as Hsp25 in rodents and Hsp27 in humans) in longevity, we created a Caenorhabiditis elegans model with a high level of ubiquitous expression of the naked mole-rat HspB1 protein. The worms showed increased lifespan under multiple conditions and also increased resistance to heat stress. RNAi experiments suggest that HspB1-induced life extension is dependent on the transcription factors skn-1 (Nrf2) and hsf-1 (Hsf1). RNAseq from HspB1 worms showed an enrichment in several skn-1 target genes, including collagen proteins and lysosomal genes. Expression of HspB1 also improved functional outcomes regulated by SKN-1, specifically oxidative stress resistance and pharyngeal integrity. This work is the first to link a small heat shock protein with collagen function, suggesting a novel role for HspB1 as a hub between canonical heat response signaling and SKN-1 transcription.

McGhee JD (1987) Biochemistry "Purification and characterization of a carboxylesterase from the intestine of the nematode Caenorhabditis elegans."

McGhee JD

[Biochemistry, 1987]

The major intestinal esterase from the nematode Caenorhabditis elegans has been purified to essential homogeneity. Starting from whole worms, the overall purification is 9000-fold with a 10% recovery of activity. The esterase is a single polypeptide chain of Mr 60,000 and is stoichiometrically inhibited by organophosphates. Substrate preferences and inhibition patterns classify the enzyme as a carboxylesterase (EC 3.1.1.1), but the physiological function is unknown. The sequence of 13 amino acid residues at the esterase N- terminus has been determined. This partial sequence shows a surprisingly high degree of similarity to the N-terminal sequence of two carboxylesterases recently isolated from Drosophila mojavensis [Pen, J., van Beeumen, J., & Beintema, J. J. (1986) Biochem. J. 238, 691-699].

Murakami S et al. (1999) Curr Biol "Life extension and stress resistance in Caenorhabditis elegans modulated by the tkr-1 gene."

Johnson TE, Murakami S

[Curr Biol, 1999]

In this Brief Communication, which appeared in the 14 September 1998 issue of Current Biology, the UV dose was reported erroneously. The dose reported was 20 J/m2 but the actual dose used was 0.4 J/cm2. Also, the gene formally referred to as tkr-1 has since been renamed old-1 (overexpression longevity determination).

Ramos CG et al. (2014) J Bacteriol "Retraction for Ramos et al., MtvR is a global small noncoding regulatory RNA in Burkholderia cenocepacia."

Feliciano JR, da Costa PJ, Ramos CG, Grilo AM, Leitao JH

[J Bacteriol, 2014]

Volume 195, no. 16, p. 35143523, 2013. A number of problems related to images published in this paper have been brought to our attention. Figure 1D contains duplicated images in lanes S and LE, and Fig. 4D and 6B contain images previously published in articles in this journal and in Microbiology and Microbial Pathogenesis, i.e., the following: C. G. Ramos, S. A. Sousa, A. M. Grilo, J. R. Feliciano, and J. H. Leitao, J. Bacteriol. 193:15151526, 2011. doi:10.1128/JB.01374-11. S. A. Sousa, C. G. Ramos, L. M. Moreira, and J. H. Leitao, Microbiology 156:896908, 2010. doi:10.1099/mic.0.035139-0. C. G. Ramos, S. A. Sousa, A. M. Grilo, L. Eberl, and J. H. Leitao, Microb. Pathog. 48:168177, 2010. doi: 10.1016/j.micpath.2010.02.006. Therefore, we retract the paper. We deeply regret this situation and apologize for any inconvenience to the editors and readers of Journal of Bacteriology, Microbial Pathogenesis, and Microbiology.

Nillegoda NB et al. (2015) Nature "Crucial HSP70 co-chaperone complex unlocks metazoan protein disaggregation."

Berynskyy M, Morimoto RI, Bukau B, Stengel F, Kirstein J, Szlachcic A, Arnsburg K, Stank A, Scior A, Nillegoda NB, Gao X, Guilbride DL, Aebersold R, Wade RC, Mayer MP

[Nature, 2015]

Protein aggregates are the hallmark of stressed and ageing cells, and characterize several pathophysiological states. Healthy metazoan cells effectively eliminate intracellular protein aggregates, indicating that efficient disaggregation and/or degradation mechanisms exist. However, metazoans lack the key heat-shock protein disaggregase HSP100 of non-metazoan HSP70-dependent protein disaggregation systems, and the human HSP70 system alone, even with the crucial HSP110 nucleotide exchange factor, has poor disaggregation activity in vitro. This unresolved conundrum is central to protein quality control biology. Here we show that synergic cooperation between complexed J-protein co-chaperones of classes A and B unleashes highly efficient protein disaggregation activity in human and nematode HSP70 systems. Metazoan mixed-class J-protein complexes are transient, involve complementary charged regions conserved in the J-domains and carboxy-terminal domains of each J-protein class, and are flexible with respect to subunit composition. Complex formation allows J-proteins to initiate transient higher order chaperone structures involving HSP70 and interacting nucleotide exchange factors. A network of cooperative class A and B J-protein interactions therefore provides the metazoan HSP70 machinery with powerful, flexible, and finely regulatable disaggregase activity and a further level of regulation crucial for cellular protein quality control.

Miller DM et al. (1992) Worm Breeder's Gazette "unc-4 LacZ Expression in A-Type Motor Neurons"

Miller DM, Niemeyer CJ

[Worm Breeder's Gazette, 1992]

unc-4 LacZ expression in A-type motor neurons David M. Miller and Charles J. Niemeyer, Dept. of Cell Biology, Duke Univ. Medical Ctr, Durham, NC 27710

Sommer RJ et al. (1994) Worm Breeder's Gazette "Evolution of Vulva-Formation: Part II: Species With a Central Vulva"

Sommer RJ, Sternberg PW

[Worm Breeder's Gazette, 1994]

Evolution of vulva-formation: Part II: Species with a central vulva Ralf J. Sommer & Paul W. Sternberg, California Institute of Technology, Division of Biology 156-29, Pasadena, CA 91125