Comparative studies on sorting cells from Artemia sinica at different developmental stages for in vitro cell culture

Challenges in cellular agriculture: lessons from Pacific white shrimp, Litopenaeus vannamei

The overall goal of this research was to develop an embryonic stem cell (ESC) line from the Pacific white shrimp, Litopenaeus vannamei, to support production of cell-based cultivated seafood products towards meeting a growing global demand for sustainable seafood. It was hypothesized that characteristics of ESCs, such as high proliferation and pluripotency, would facilitate development of a continuous cell line that could be triggered to differentiate into a muscle cell phenotype. The targeted approach was based on collection of ESCs from fertilized shrimp eggs at the blastomere stage. Various media, supplements, growth factors, and plate coatings were tested to achieve growth of the shrimp ESCs. Although successful in early culture, this manuscript describes substantial challenges encountered as cultures grew over time. The cell cultures were initially dominated by shrimp as indicated by 18S rDNA community analysis, but after multiple passages, thraustochytrids, a common contaminant of invertebrate cell culture, became the predominant cell type. Presence of shrimp cells was confirmed through species-specific primers for the cytochrome C oxidase subunit 1 gene. Presence of thraustochytrids was also confirmed using species-specific primers, morphological features, growth properties, and acriflavine staining. Unsuccessful attempts to eradicate thraustochytrid contamination prevented shrimp cells from thriving. The future of shrimp cell culture depends on eliminating culture contaminants while encouraging growth of shrimp ESCs.

Differential DNA methylation in Pacific oyster reproductive tissue in response to ocean acidification

BACKGROUND

There is a need to investigate mechanisms of phenotypic plasticity in marine invertebrates as negative effects of climate change, like ocean acidification, are experienced by coastal ecosystems. Environmentally-induced changes to the methylome may regulate gene expression, but methylome responses can be species- and tissue-specific. Tissue-specificity has implications for gonad tissue, as gonad-specific methylation patterns may be inherited by offspring. We used the Pacific oyster (Crassostrea gigas) - a model for understanding pH impacts on bivalve molecular physiology due to its genomic resources and importance in global aquaculture- to assess how low pH could impact the gonad methylome. Oysters were exposed to either low pH (7.31 ± 0.02) or ambient pH (7.82 ± 0.02) conditions for 7 weeks. Whole genome bisulfite sequencing was used to identify methylated regions in female oyster gonad samples. C- > T single nucleotide polymorphisms were identified and removed to ensure accurate methylation characterization.

RESULTS

Analysis of gonad methylomes revealed a total of 1284 differentially methylated loci (DML) found primarily in genes, with several genes containing multiple DML. Gene ontologies for genes containing DML were involved in development and stress response, suggesting methylation may promote gonad growth homeostasis in low pH conditions. Additionally, several of these genes were associated with cytoskeletal structure regulation, metabolism, and protein ubiquitination - commonly-observed responses to ocean acidification. Comparison of these DML with other Crassostrea spp. exposed to ocean acidification demonstrates that similar pathways, but not identical genes, are impacted by methylation.

CONCLUSIONS

Our work suggests DNA methylation may have a regulatory role in gonad and larval development, which would shape adult and offspring responses to low pH stress. Combined with existing molluscan methylome research, our work further supports the need for tissue- and species-specific studies to understand the potential regulatory role of DNA methylation.

ArHsp40, a type 1 J-domain protein, is developmentally regulated and stress inducible in post-diapause Artemia franciscana

Upon diapause termination and exposure to favorable environmental conditions, cysts of the crustacean Artemia franciscana reinitiate development, a process dependent on the resumption of metabolic activity and the maintenance of protein homeostasis. The objective of the work described herein was to characterize molecular chaperones during post-diapause growth of A. franciscana. An Hsp40 complementary DNA (cDNA) termed ArHsp40 was cloned and shown to encode a protein with an amino-terminal J-domain containing a conserved histidine, proline, and aspartic acid (HPD) motif. Following the J-domain was a Gly/Phe (G/F) rich domain, a zinc-binding domain which contained a modified CXXCXGXG motif, and the carboxyl-terminal substrate binding region, all characteristics of type I Hsp40. Multiple alignment and protein modeling showed that ArHsp40 is comparable to Hsp40s from other eukaryotes and likely to be functionally similar. qRT-PCR revealed that during post-diapause development, ArHsp40 messenger RNA (mRNA) varied slightly until the E2/E3 stage and decreased significantly upon hatching. The immunoprobing of Western blots demonstrated that ArHsp40 was also relatively constant until E2/E3 and then declined dramatically. The drop in ArHsp40 when metabolism and protein synthesis were increasing was unexpected and demonstrated developmental regulation. The reduction in ArHsp40 at such an active life history stage indicates, as one possibility, that A. franciscana possesses additional Hsp40s, one or more of which replaces ArHsp40 as development progresses. Increased synthesis upon heat shock established that in addition to being developmentally regulated, ArHsp40 is stress inducible and, because it is found in mature cysts, ArHsp40 has the potential to contribute to stress tolerance during diapause.