Biology subjects

Vo, A. A.

Publications and source records attributed to Vo, A. A..

5 recordsLinked to original sources

bioRxiv2022

Experimental considerations for study of C. elegans lysosomal proteins

Lysosomes are an important organelle required for the degradation of a range of cellular components. Lysosome function is critical for development and homeostasis as dysfunction can lead to inherited genetic disorders, cancer, and neurodegenerative and metabolic disease. The acidic and protease-rich environment of lysosomes poses experimental challenges. Many fluorescent proteins are quenched or degraded, while specific red fluorescent proteins can be cleaved from translational fusion partners and accumulate. While studying MLT-11, a C. elegans molting factor that localizes to lysosomes and the cuticle, we sought to optimize several experimental parameters. We found that, in contrast to mNeonGreen fusions, mScarlet fusions to MLT-11 missed cuticular and rectal epithelial localization. Rapid sample lysis and denaturation was critical for preventing MLT-11 fragmentation while preparing lysates for western blots. Using a model lysosomal substrate (NUC-1) we found that rigid polyproline linkers and truncated mCherry constructs do not prevent cleavage of mCherry from NUC-1. We provide evidence that extended localization in lysosomal environments prevents the detection of FLAG epitopes in western blots. Finally, we optimize an acid-tolerant green fluorescent protein (Gamillus) for use in C. elegans. These experiments provide important experimental considerations and new reagents for the study of C. elegans lysosomal proteins.

molecular biology↗

bioRxiv2022

The conserved, secreted protease inhibitor MLT-11 is necessary for C. elegans molting and embryogenesis

Apical extracellular matrices (aECMs) are associated with all epithelia and form a protective layer against biotic and abiotic threats in the environment. C. elegans molting offers a powerful entry point to understanding developmentally programmed aECM remodeling. Several protease inhibitors are implicated in molting, but their functions remain poorly understood. Here we characterize mlt-11, an unusual protease inhibitor with 10 conserved Kunitz domains. MLT-11 oscillates and is localized in the cuticle and in lysosomes in larvae and in the embryonic sheath starting at the 3-fold embryo stage. mlt-11 (RNAi) produced a developmental delay, motility defects, failed apolysis, and a defective cuticle barrier. mlt-11 null and C-terminal Kunitz domain deletion mutants are embryonic lethal while N-terminal deletions cause a rolling phenotype indicative of cuticle structure abnormalities. mlt-11 activity is primarily necessary in seam and hypodermal cells and accordingly mlt-11 (RNAi) causes defects in localization of the collagens ROL-6 and BLI-1 over the cuticle. mlt-11 (RNAi) molting phenotypes can be suppressed by genetically inhibiting endocytosis. Our model is that MLT-11 is acting in the aECM to coordinate remodeling and timely ecdysis.

developmental biology↗

bioRxiv2022

NHR-23 and SPE-44 regulate distinct sets of genes during C. elegans spermatogenesis

Spermatogenesis is the process through which mature male gametes are formed and is necessary for transmission of genetic information. While much work has established how sperm fate is promoted and maintained, less is known about how the sperm morphogenesis program is executed. We previously identified a novel role for the nuclear hormone receptor transcription factor, NHR-23, in promoting C. elegans spermatogenesis. Depletion of NHR-23 along with SPE-44, another transcription factor that promotes spermatogenesis, caused additive phenotypes. Through RNA-seq, we determined that NHR-23 and SPE-44 regulate distinct sets of genes. Depletion of both NHR-23 and SPE-44 produced yet another set of differentially regulated genes. NHR-23- regulated genes are enriched in phosphatases, consistent with the switch in spermatids to post-translational regulation following genome quiescence. In the parasitic nematode Ascaris suum, MFP1 and MFP2 control the polymerization of Major Sperm Protein, the molecule that drives sperm motility and serves as a signal to promote ovulation. NHR-23 and SPE-44 regulate a number of MFP2 paralogs, and NHR-23 depletion caused defective localization of MSD/MFP1 and NSPH-2/MFP2. Although NHR-23 and SPE-44 do not transcriptionally regulate the casein kinase gene spe-6, a key regulator of sperm development, SPE-6 protein is lost following NHR-23+SPE-44 depletion. Together, these experiments provide the first mechanistic insight into how NHR-23 promotes spermatogenesis and an entry point to understanding the synthetic genetic interaction between nhr-23 and spe-44.

genetics↗

bioRxiv2022

The mIAA7 degron improves auxin-mediated degradation in C. elegans

Auxin-inducible degradation (AID) is a powerful tool for the targeted degradation of proteins with spatiotemporal control. One limitation of the AID system is that not all proteins are degraded efficiently. Here, we demonstrate that an alternative degron sequence, termed mIAA7, improves the efficiency of degradation in C. elegans, as previously reported in human cells. We tested depletion of a series of proteins with various sub-cellular localizations in different tissue types and found that the use of the mIAA7 degron resulted in faster depletion kinetics for five out of six proteins tested. The exception was the nuclear protein HIS-72, which was depleted with similar efficiency as with the conventional AID* degron sequence. The mIAA7 degron also increased the leaky degradation for two of the tested proteins. To overcome this problem, we combined the mIAA7 degron with the C. elegans AID2 system (C.e.AID2), which resulted in complete protein depletion without detectable leaky degradation. Finally, we show that degradation of ERM-1, a highly stable protein that is challenging to deplete, could be improved further by using multiple mIAA7 degrons. Taken together, the mIAA7 degron further increases the power and applicability of the AID system. To facilitate the generation of mIAA7-tagged proteins using CRISPR/Cas9 genome engineering, we generated a toolkit of plasmids for the generation of dsDNA repair templates by PCR.

molecular biology↗

bioRxiv2021

Conditional depletion reveals temporal requirements for the oscillating transcription factor NHR-23/NR1F1 in C. elegans larval progression

SUMMARY STATEMENTThis work shows how a C. elegans transcription factor controls remodeling of the apical extracellular matrix during development and in which tissues it acts. ABSTRACTNematode molting is a remarkable process where animals must repeatedly build a new apical extracellular matrix (aECM) beneath a previously built aECM that is subsequently shed. The nuclear hormone receptor NHR-23/NR1F1 is an important regulator of C. elegans molting. NHR-23 expression oscillates in the epidermal epithelium, and soma-specific NHR-23 depletion causes severe developmental delay and death. Tissue-specific RNAi suggests that nhr-23 acts primarily in seam and hypodermal cells. NHR-23 coordinates the expression of factors involved in molting, lipid transport/metabolism, and remodeling of the aECM. NHR-23 depletion causes dampened expression of a nas-37 promoter reporter and a loss of reporter oscillation. The cuticle collagen ROL-6 and zona pellucida protein NOAH-1 display aberrant annular localization and severe disorganization over the seam cells following NHR-23 depletion, while the expression of the adult-specific cuticle collagen BLI-1 is diminished and frequently found in patches. Consistent with these localization defects, the cuticle barrier is severely compromised when NHR-23 is depleted. Together, this work provides insight into how NHR-23 acts in the seam and hypodermal cells to coordinate aECM regeneration during development.

molecular biology↗