Project description:The mantle is a thin tissue from which proteins are secreted dictating the mollusk shell construction. As a conserved organ involved in shell formation throughout mollusks, the mantle is an excellent foundation from which to study biomineralization. A P. maxima mantle tissue specific cDNA microarray, termed PmaxArray 1.0, has been developed comprising 5000 cDNA transcripts derived from the mantle tissue of P. maxima. This tool has been used to investigate the spatial functional dynamics of the mantle tissue identifying over 2000 PmaxArray 1.0 spots as differentially expressed spatially within this organ. Gene expression profiles observed for these transcripts indicated 5 major spatial functions for the mantle, 3 of which have been putatively attributed to shell formation roles associated with nacre microstructure, calcite prismatic microstructure and periostracum. These transcripts are further examined with in situ expression localization and comparative sequence analyses in reference to potential shell formation roles. This spatial investigation has expedited the elucidation of functions within the dynamic mantle organ, paying particular attention to of shell biomineralization. Keywords: Spatial expression profiling by array
Project description:The appearance of hard mineralized exoskeletons is a critical leap for animal evolution and partially lead to the explosion of diverse animals during the Cambrian, for example, molluscs. A majority of molluscs have mineralized shells to protect themselves. Despite numerous studies that have studied the remarkable mechanical properties of shells, the origin of shell formation is still elusive. Hence, this study investigated the overlooked shell proteome of chitons, which belong to polyplacophoran, Aculifera of Mollusca. By comparing the shell proteome to well-studied Conchifera groups, we inferred possible ancestral biomineralization toolkits of stem-group Mollusca. Taking advantage of the recently sequenced chiton mantle transcriptome and genome, eight core biomineralization proteins were identified by proteomics. Surprisingly, in contrast to previous thought that shell formation is convergently evolved, two important shell matrix proteins, Nacrein-like and Pif-like proteins were found to be conserved among Aculifera and Conchifera groups. Our findings identify a missed link of mineralized shell evolution in Mollusca and pose a hypothesis that stem-group molluscs have already evolved core biomineralization toolkits, which likely facilitate the formation of mineralized shells for protection that partially leads to their explosion.
Project description:The mantle is a thin tissue from which proteins are secreted dictating the mollusk shell construction. As a conserved organ involved in shell formation throughout mollusks, the mantle is an excellent foundation from which to study biomineralization. A P. maxima mantle tissue specific cDNA microarray, termed PmaxArray 1.0, has been developed comprising 5000 cDNA transcripts derived from the mantle tissue of P. maxima. This tool has been used to investigate the spatial functional dynamics of the mantle tissue identifying over 2000 PmaxArray 1.0 spots as differentially expressed spatially within this organ. Gene expression profiles observed for these transcripts indicated 5 major spatial functions for the mantle, 3 of which have been putatively attributed to shell formation roles associated with nacre microstructure, calcite prismatic microstructure and periostracum. These transcripts are further examined with in situ expression localization and comparative sequence analyses in reference to potential shell formation roles. This spatial investigation has expedited the elucidation of functions within the dynamic mantle organ, paying particular attention to of shell biomineralization. Keywords: Spatial expression profiling by array The mantle tissue from 9 animals was dissected into 5 separate sections: outer fold (OF), middle fold (MF), inner fold (IF), ventral mantle tissue (VM) and dorsal mantle tissue (DM). Total RNA was extracted from these tissues and pooled across subjects in order to reduce the effect of biological variation; such that 3 individuals were pooled together totaling 3 pooled replicate samples for each tissue. All the biologically pooled tissue types were compared against a common reference in which total RNA from all tissues types and all nine animals was equally pooled. A total of 30 dual channel microarrays hybridizations were performed and analyzed.
Project description:Circulating hemocytes in the hemolymph represent the backbone of innate immunity in bivalves. Hemocytes are also found in the extrapallial fluid (EPF), the space delimited between the shell and the mantle, which is the site of shell biomineralization. This study investigated the transcriptome, proteome, and function of hemocytes found in the EPF and hemolymph in the hard clam Mercenaria mercenaria. Total and differential hemocyte counts were similar between EPF and hemolymph. Overexpressed genes in the EPF were found to have domains previously identified as being part of the biomineralization toolkit and involved in bivalve shell formation. Biomineralization related genes included chitin-metabolism genes, carbonic anhydrase, perlucin, and insoluble shell matrix protein genes. Overexpressed genes in the EPF encoded proteins present at higher abundances in the EPF proteome, specifically those related to shell formation such as carbonic anhydrase and insoluble shell matrix proteins. Genes coding for bicarbonate and ion transporters were also overexpressed, suggesting that EPF hemocytes are involved in regulating the availability of ions critical for biomineralization. Functional assays also showed that Ca2+ content of hemocytes in the EPF were significantly higher than those in hemolymph, supporting the idea that hemocytes serve as a source of Ca2+ during biomineralization. Overexpressed genes and proteins also contained domains such as C1q that have dual functions in biomineralization and immune response. The percent of phagocytic granulocytes was not significantly different between EPF and hemolymph. Together, these findings suggest that hemocytes in EPF have dual functions of biomineralization and immunity.
Project description:Various modes of DNA repair counteract genotoxic DNA double-strand breaks (DSBs) to maintain genome stability. Recent findings suggest that the human DNA damage response (DDR) utilises damage-induced small RNA for efficient repair of DSBs. However, production and processing of RNA is poorly understood. Here we show that localised induction of DSBs triggers phosphorylation of RNA polymerase II (RNAPII) on carboxy-terminal domain (CTD) residue tyrosine-1 in an Mre11-Rad50-Nbs1 (MRN) complex-dependent manner. CTD Tyr1-phosphorylated RNAPII synthetises, strand-specific, damage-responsive transcripts (DARTs). DART synthesis occurs via formation of transient RNA-DNA hybrid (R-loop) intermediates. Impaired R-loop formation attenuates DART synthesis, impairs recruitment of repair factors and delays the DDR. Collectively, we provide mechanistic insight in RNA-dependent DSB repair.
Project description:Biomimetics present useful ideas for various product designs. However, most biomimetics only mimic the features of living organisms. It has not been clarified how a given shape is attained through natural selection. This paper presents the design factors that optimize the radula shape of Euhadra peliomphala. Clarifying the important design factors would help designers in solving several problems simultaneously in order to adapt to complicated and multi-functionalized design mechanisms. We measured the radula of Euhadra peliomphala by using a microscope and modeled the grinding/cutting force using the finite element analysis (FEA). We reproduced the natural selection using multi-objective genetic algorithm (MOGA). We compared the solutions when optimizing the radula shape using objective functions of each combination of stress, cutting force, abrasion, or volume. The results show that the solution obtained through two-objective optimization with stress and cutting force was the closest to the actual radula shape.